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MIE ewes Tee aye reap ly ey: is he ie i v~ | NG, Te wy Negro ewarety vie M r] vy rt] y = Ei eer ae yee Cnn aty Opes we eee rtaeveey ROLL LL lll a te } 1) ithe 2 a JL ER —_ _ yep UF \) aN o Dahan ele ie) ina isha mou4o | S9200— SarecZ& Abd SCIENTIFIC PROCEEDINGS ROYAL DUBLIN SOCIETY. det Series. VOLUME VIII. he Su > 10 SS [ ae | oO > #ATIONAL We DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY. LONDON: WILLIAMS & NORGATE. 1893-1898, Te Soctirry desires it to be understood that it is not answerable Jor any opimon, representation of facts, or train of reasoning, that may appear in this Volume of its Proceedings. The Authors of the several Memoirs are alone responsible for their contents. Printed at THe UNIvERsITy Press, Dudlzx. CONTENTS. WOE. Vii PART I. PAGE I.—Pogotrichum hibernicum, sp. nu. By T. Jounson, D.Sc., F.L.S., Professor of Botany in the Royal College of Science, and Keeper of the Botanical Collections, Science and Art Museum, Dublin. (Plate I.), : : ¢ 1 II.—Note on the Action of Bhaealitine on Slain Tete. By Sir Cuartzs A. Cameron, M.D., 11 III.—The Use of the Protractor in Field Genloer By kane Aree, MVS AR EGAS ss: 0s : 12 TV.—Reports on the Zaclonical @olleenone sande in homes Straits Oy Professor A. C. Haddon, 1888-1889. Pycnogonida (Supple- ment). By Gzuorce H. Carpenter, B.Sc., Lond., Assistant Naturalist in the Science and Art Museum, Dublin. (Plate II.), 21 V.—On the Germination of Seedlings in the absence of Bacteria. By H. H. Dixon, B.A. (Abstract), . 28 VI.—A List of some of the Rotifera of Ireland. By Miss L. S. Boescern, (Plates III. to VII.), é 29 VII.—On Pitchstone and Andesite from Teor Makes in Deasest. By Proressor W. J. Sotuas, LL.D., D.Sc., F.R.S., . 87 VIII.—On the Variolite and Associated Tiesncow Rocks 3 Rovadeond! Co. Wicklow. By Prorzssor W. J. Sorzas, LL.D., D.8c., 11 RolSe5 : 94 IX. _ eee of some New Cheats: of iglesia coin Memes Serta By Prorsssor A. C. Happon and Atice M.Suacxuzton, B.A., 116 X.—On Hemitrypa hibernica, M‘Coy. By GrenvitiE A. J. thn, F.G.S., Professor of Geology in the nl College of Science for een (Plate VIII.), . 132 X1I.—On the Bright Colours of Alpine alsmere By 7 aie OLY, M. ne D.Sc., F.R.S., 145 XII.—S8ugg atin as to ie Possible eons of ae uerey rend for ime Life of Bacilli, and as to the Cause of their Small Size. By G. Jounstonse Stonzy, M.A., D.Sc., F.R.S., Vice-President, Royal Dublin Society, . . 154 XIII.—On the Law of Gladstone and Dalene as an Open Probe. By Prorsssor W: J. Sortzas, D.Sc., LL.D., F.R.S. (Abstract), 157 A 2 iV Oontents. LevaVendhy iBT XIV.—A Lecture Note on the Relation of the Theorem of Work to the Theorem of Moments. By Tuomas Preston, M.A., F.R.U.1., XV.—Report on Polychets collected during the Royal Dublin Society’s Survey off the West Coast of Ireland. Part I. Deep Water Forms. By Frorunce Bucnanan, B.Sc., Univ. College, Lon- don. (Plates 1X., X., XI.), . XVI.—Notes on Depastrum cy alhiforne By G. We and in Tae, ican XVII.—On the Photographic Method of detecting the Existence of Variable Stars. By J. Jony, M.A., D.Sc., F.R.S., XVIII.—On the Distortion of Bhaieenrp ae Star meee due io Berocuon By Proressor Antuur A. Rampaut, M.A., D.Sc.,. XIX.—On some Pycnogonida from the Irish Coasts. By GEORGE H. Carpenter, B.Sc., Lond., Assistant Naturalist in the Science and Art Museum, Dublin. (Plate XII.), 5 : 3 : XX.—On a Graphitic Schist from Co. ie By Ricuarp J. Moss, HCAS pele Ces : : : : : : PART III. XXI.—Note on the Present Condition of the Water in the Reservoir at Roundwood. By W. EH. Aprney, F.I.C., F.C.8., Curator in the Royal University of Ireland, 0 c , XXII.— Useful Methods in Teaching ie i Digdew By J. Joty, DSC hakveass. F XXIII.—On the Terese of Tecwernnnes upon the Soneineneee of the Photographic Dry Plate. By J. Joty, D. Sc., F.R.S., XXIV.—Notes on the Vartry Water in November, 1393. By Brew ann J. Moss, F.C.8., F.1.C., XXV.—On the Tang of vation ei pneciall ieforones to the iieien of Insects. By G. Jounstone Sronry, M.A., D.Sc., F.R.S., Vice-President, Royal Dublin Society, . : : . . XXVI.—On the Post-Embryonic Development of Fungia. By GiLsErt C. Bourns, M.A., F.L.S., Fellow of New ye Oxford. (Abstract), : : XXVII.—On the Reduction of ames Bees in seas, By W. E. Apvrnegy, Assoc. R.C.Sc.1., F.C.S., F.1.C., Curator in the Royal University of Ir semi XXVIII.—On a New Form of Hguatorial Mounting for Wigner Redectiee Telescopes. By Sir Howarp Gruss, M.A.I., F.R.S., Vice- President, Royal Dublin Society, 9 . 0 - XXIX.—On the Great Meteor of February 8th, 1894. By Prorrssor Artuur A. RamBaut, D.8c., F.R.A.S., XXX.—On a Method for Golounine Rantoen Slides for Spicanae Diae grams and other purposes. By Prorssson J. A. Scorr, M.D., XXXI.—On a Mounting for the Specula of Reflecting Weleneanent Designed to Remove the Impediment to their being Used for Celestial Photography and Spectroscopy. By G. Joun- stonr Stoney, M.A., D.Sc., F.R.S., Vice-President, eis Dublin Society, - PAGE 167 169 180 184 186 195 206 208 215 222 225 228 244 247 252 258 263 266 Contents. PART II1.—continued. XXXII.—On the Selection of Suitable Instruments for Photographing the Solar Corona during Total Solar Eclipses. By ALBERT Taytor, A.R.C.Sc.(Lond.), A.R.S.M., F.R.A.S., XXXIII.—On derived Crystals in the Basaltic cae of Glstiemnann Port, Co. Down. By Grenvitite A. J. Conn, M.R.I.A., F.G.S8., Professor of Geology in the Royal College of Sailer: for Tnelinadl (Abstract), . XXXIV.—On the Fossil Fish-Remains of the Coal MManames ae the Pi fh Islands. Part II.—Acanthodide. By the late James W. Davis, F.G.S., F.L.8., F.S.A., &. (Abstract), . XXXY.—On EHozoonal Geen of the saute Blocks of Monte Sonar By Proressor H. J. Jounston-Lavis and Dr. J.W. GreGory, F.G.8. (Abstract), PART IV. XXXVI.—The Automatic ae By the Rzy. Ricuarp C. Bopxin, XXXVII.—The Occurrence x Siflhas in Talks Dearavaraely Co. West- meath, 1898, 1894. By J. R. H. Mac Fartanz, Staff- Commander R.N. (Retired), XXXVIII.—On Pucksia Mac Henryi, a New Fossil fren ae Gamipren Rocks of Howth. By Prorrssor Soxzas, D.Sc., LL.D., BRE Seal: : XXXIX.—A Colleen of Memid@nters ison Thalkegey West Adrien: By Gzorce H. CarprentER, B.Sc., Assistant Naturalist, Science and Art Museum, Dublin, XL.—On the Gold N ee hitherto found in ‘ihe Gatney Wchlom Thy Wie J Uiaey CIS IUCR Des Mlolvasn | (deleniss DUDES) i XLI.—Survey of Fishing Grounds: West Coast of Ireland, 1890-91. Notes on the Hydroida and Polyzoa. By J. E. Durrpen, AeiRaC asc: (London) ; Curator of the Museum of the Institute of Jamaica. (Plate XIV.), XLII.—On the Chemical Examination of Organic Matters in Te Waters. By W. E. Aprnuy, F.I.C., Associate of the Royal College of Science, Ireland ; Onesie in the Royal University of Ireland, XLIII.—Branched Worm-tubes and Aunommarninng, "By eormscor A.C. Happon, M.A., F.Z.8., Royal College of Science, Dublin, XLIV.—A Method of crane the Bower of Goneinon: ligarenouse Lights. By Joun R. WicHam, M.R.J.A., Member of the Council of the Royal Dublin Society, . XLYV.—Of the Kinetic Theory of Gas, regarded as Tins Nature. By Gzuorcr Jounstonr Sronzy, M.A., D.Sc., F.R.S., Vice-President, Royal Dublin Society, PAGE 272 279 279 280 261 288 297 304 311 325 337 344 347 351 vi Contents. PART V. XLVI.—Some Remarks on Difficulties of Meridian Circle Work. By Arruur E. Lystrr, M.A., . XLVII.—A Method of Using Cosine Beislewin + as the Teeter en Beacons and Buoys by which a Continuous Light may be maintained, Day and Night, for Weeks or Months, without the Necessity for the Attendance of a Light-keeper. By Joun R. Wieuam, M.R.I.A., Member of the Council of the Royal Dublin Society, XLVIII.—On Hamilton’s Singular Poms ane Planes on resales Ware ; Surface. By Prorrssor Witi1am Booru, M.A., Hoogly College, Bengal, . : XLIX.—On the Rotation- Period of the « fe eaaes ie Shs on J amie By Arruur A. Rampaut, M.A., D.Sc., F.R.A.S., L.—Note on Irish Annelids in ‘ine ihereenin of Seigues and Art Dublin.—No. I. By W. C. M‘Invosu, Professor of Natural History in St. Andrew’s University, LI.—The Hydroids of the Irish Coast. By J. E. Cana, A.R. C. Sc. (Lond.) ; Curator of the Museum, Kingston, Jamaica, LII.—The Distribution of Drift in Ireland in its relation to Nena ture. By J. R. Kitroez, (formerly) F.C.S., H. M. Geological Survey (Plate XV.), : LITI.—Note on the Worm askoueededl ain Honhghene prolifera. By FLorencre BucHANAN, . LIV.—On some Dragonflies in the Dublin Wao of isciemee and Art, By Gzorer H. Carprnter, B.Sc. (Lond.), Assistant Natu- ralist in the Science and Art Museum, Dublin. (Plate XVI.), LY.—The Geographical Distribution of Dragonflies. By Gzuorcr H. CarpPEnTER, B.Sc. (Lond.), F.E.8., Assistant Naturalist in the Science and Art Museum, Dublin. (Plate XVII.), . LVI.—Application of the Parallelogram Law in Kinematics. By Tuomas Preston, M.A., F.R.U.1., LV1II.—Report of the (ontmnttes! boneeene of Protsevor W. J. Sollee, LL.D., F.R.S., R. Lloyd Praeger, B.A., B.H., A. F. Dixon, M.B., ‘al Alfred Delap, B.A., B.E., a nomed by the Royal Dublin Society to investigate the recent Bog-flow in Kerry. Drawn up by R. Luoyp PRAEGER and PRorsssor SoLLAS. (Plates XVIII. and XIX.), PAR Eval LVIII.—On the Geological Investigation of Submarine Rocks. By J. Jory, M.A., B.A.I., D.Sc., F.R.S., Hon. Secretary, Royal Dublin Sada (Plate XX.), LIX.—Short Account of an Experlment to Deters the aoa Parton in a Focus Tube from which the X-Rays are emitted. By the Very Rzy. Grratp Moutoy, D.D., D.8c., LX.—A New Method of Conferring Dicinemeeiee Giecremete Appearance upon Illuminated Buoys and Beacons for Har- bours, Estuaries, and Rivers. By J. R. WicHam, M.R.I.A., Member of the Council of the Royal Dublin Society, . PAGE 375 377 381 389 399 405 421 432 434 439 469 475 509 515 519 Contents. PART VI.—continued. LXI.—Notes on a Paper recently Published in the Astrophysical Journal, by Professor E. Hale, of the Yerkes Observatory, Chicago, on “‘the Comparative Values of Refracting and Reflecting Telescopes for Astrophysical Observations.”” By Str Howarp Gruss, F.R.S., Vice-President, Royal Dublin Society, LXII.—A Mechanical Cause e TElamoeeuchie of Sancine and Seraenene Geometrically investigated ; with Special Application to Crys- tals and to Chemical Combination. By Witi1am Bartow, LXIITI.—Arrangement of the Crystals of certain Substances on Solidifica- tion. By Frep. T. Trovuton, D.S8c., F.R.S., : LXIV.—Phellia Sollasi: A New Species of Aetnimian from Ooemnt, By Atrrep C. Happon, M.A., D.8c., Professor of Zoology, Royal College of Science, Deli, LXV.—The Apparent Cometary Nature of the Spiral inonalah in Canes Venatici. By W. E. Witson, F.R.S. (Plate XXI.), . LXVI.—A Theory of Sun-spots. By I. Jory.) MeAR DESCy. WoknGe Hon. Secretary, Royal Dublin Society, Professor of Haney and Mineralogy in the Uuiversity of Dublin, LXVII.—Of Atmospheres upon Planets and Satellites. By G. JouNsTONE Stoney, M.A., D.Sc., F.R.S. (Adstract), LXVIII.—A Aceon ‘Analysts of Iron Meteorites, cidenglited and Meteoric Stones. By W. N. Hanrruzy, F.R.S., and Hueu Ramacez, Assoc. R.C.8ce.1., F.I.C. (Plates XXII., XXIIL., XXIV., LXIX.—On the Mouneiae of the Tiere Rawlend Shawnie & in the Royal University of Ireland. By W. E. Apsnry, D.Sc., F.1.C., Curator in the Royal University, and James Carson, Are OHS (eb aan Onl dep : : : : 5 : 3 LXX.—Notes on certain Actiniaria. By Dr. Karurermne Macurre. (Plate XXIV a.), : ? : ‘ : : LXX1I.—On the Occurrence of Asvoions (Xanthitane ?) and Brookite in the Quartzites of Shankill. By Prorzussor J. P. O’Reriiy, C.E., Royal College of Science, Dublin. (Plate XXY.), LXXII.—On some Minute Organisms found in the Surface-water of Dublin and Killiney Bays. By J. Jouy, D.Sc., F.R.S., Hon. Sec., Royal Dublin Society ; and Henry H. Drxon, D.Sc. (Plates XXVI. and XXVII.), LXXIII.—An improved Form of Hydrometer iy ath ‘hel Speortie Gravis of Liquids may be accurately determined at any Temperature. By the Rey. H. O’Toouz, of Blackrock College, County of Dublin, : : , ; : 3 : : INDEX, List or Screntiric PuBLicaTIons. List or EXCHANGES. Vil PAGE 523 527 691 693 696 697 701 703 711 “lel 732 741 753 757 DATES OF THE PUBLICATION OF THE SEVERAL PARTS OF THIS VOLUME. Part 1.—Containing pages 1 to 166. (April, 1893.) Lahti, i , 167 to 207. (Sept., 1893.) a » 208 to 280. (August, 1894.) 281 to 3874. (Sept., 1895.) 95 » 93875 to 508. (July, 1897.) », 509 to 755. (August, 1898.) PX BR oo ERRATUM. Pages 509, 525, at foot, for Scien. Proc. R.D.S., Vol. VIII., Part V., read Vol. VIII., Part VI. : a , ie ee THE SOTENTIFIC PROCBEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol, VIIT. (N. 8.) APRIL, 1893. Part 1. CONTENTS. PAGE I.—Pogotrichum hibernicum, sp.n. By T. Jounson, D.Sc., F.L.S., Professor of Botany in the Royal College of Science, and Keeper of the Botanical Collections, Science and Art Museum Dublin. (Plate J.), : : 1 II.—Note on the Action of Pee on eelenar Tineide. By Se Cartes A. Cameron, M.D., : 11 III.—The Use of the Protractor in Field- Geology. By ALreEp Hansen, M.A., F.G.S., : 12 VK Herts on the Wonca deltections a in Torres Str oe iy Professor A. C. Haddon, 1888-1889. Pycnogonida (Supple- ment). By Guorex H. Carpenter, B.Sc., Lond., Assistant Naturalist in the Science and Art Museum, Dublin. (Plate 2h Y.—On the Germination of Seedlings in the absence of Bacteria. By H. H. Drxon, B.A. (Abstract), . : . 28 VI.—A List of some of the Rotifera of Ireland. ‘By! Miss co s. Guascotr. (Plates III. to VII.), . 29 ViII.—On Pitchstone and Andesite from Detiory Diykes in Donegal By Proressorn W. J. Sonztas, LL.D., D.Sc., F.R.S., . Debio: VIII.—On the Variolite and Associated irigdtid Rooks of Ranndwead, Co. Wicklow. By Prorsssor W. J. ee h.DsD:8e-.; eS. 94 IX.— Description of some Neg Spscie’ of stint aan ented Straits. By Proressor A.C. Happon and Atice M. Suackteton, B.A., 116 X.—On Hemitrypa hibernica, M‘Coy. By Grenvitte A. J. Cox, F.G.S., Professor of Geology in the poke ae of Science for Ireland. (Plate VIII.), . : 132 _ XI.—On the Bright Colours of ce lowers, By J. J OLY, M. i, D.8c., F.R.S., : 145 “XIL—Suegestion as to a Possible Keiive of the Briere ced fie the Life of Bacilli, and as to the Cause of their Small Size. By G. JoHnstonE Stonzy, M.A., D.Sc., F.R.S., Vice-President, Royal Dublin Society, . é 154 XIII.—On the Law of Gladstone and Tite: as an 7 Oabienl Probe. By Proressor W. J. Sonnas, D.Sc., LL.D., F.R.S. (Abstract), . 157 The Authors alone are responsible for all Opinions expressed in their Communications. DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY. LONDON: WILLIAMS & NORGATE, 14, HENRIETTA-STREET, COVENT GARDEN. 1893. - Price Six Shillings. Ropal Dublin Society, FOUNDED, A.D. 1731. INCORPORATED, 1749. EVENING SCIENTIFIC MEETINGS, Tuer Evening Scientific Meetings of the Society and of the associated bodies (the Royal Geological Society of Ireland and the Dublin Scientific Club) are held on Wednesday Evenings, at 8 o’Clock, during the Session. Authors desiring to read Papers before any of the Sections of the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at deast ten days prior to each Evening Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission to the Editor. THE SCIENTIFIC PROCEEDINGS. OF THE ROYAL DUBLIN SOCIETY. se I. ‘POGOTRICHUM HIBERNICUM, SP. N. By T. JOHNSON, D.Sc., F.L.8., Professor of Botany in the Royal College of Science, and Keeper of the Botanical Collections, Science and Art Museum, Dublin. Puare I. [Read NovemBer 16; Received for publication NovemBer 18, 1892; Published Marcu 25, 1893.] “arabe an algological visit to the west coast of Clare in September, 1891, I found growing on young A/aria plants, at low water on the Duggerna Rocks at Kilkee, brown tufts of filaments, which, on subsequent microscopic examination, appeared to be different from any plant with which I was acquainted. I sent some of the material to Professor Reinke, of Kiel, with an accompanying suggestion that the plant might be Litosiphon Lami- narie, Harv., a suggestion which was not adopted. My plant was, in Reinke’s opinion, a second species of a new genus, Pogotri- chum, of which the other species, P. filiforme,' collected at Heligo- land, had just been described by Reinke for his ‘“‘ Atlas deutscher Meeresalgen.” A proof plate of P. filiforme was kindly sent to me for comparison. The Kilkee plant agrees in so many features with the Heligoland plant that I propose to call it Pogotrichum hibernicum.? Reinke’s diagnosis of his genus Pogotrichum is as follows :— | | “ Unverzweigte, bischelformige, beisammenstehende, fadenfor- 1J. Reinke, ‘‘ Atlas deutscher Meeresalgen,”’ 11. Taf. 41, 1892. 27. Johnson, Irish Naturalist, No. 1, p. 5, 1892 SCIEN. PROC. R.D.S., VOL. VIII., PART I. B 2 Scientific Proceedings, Royal Dublin Society. mige Thallome von radiar gebautem Querschnitt und intercalarem Wachsthum. Vegetations- Faden aus mehreren oder, doch seltener, ans nur einer Langsreihe von Zellen gebildet. Pluriloculare Sporangien intercalar in den Thallus eingesprengt, nur aus einigen der ausseren oder auch aus simmtlichen Zellen eines Querschnitts gebildet ; bei einreihigen Individuen durch Theilung einzelner Gliederzellen in viele kleine Zellen entstanden.” Pogotrichum hibernicum oceurs on the thallus of Alaria esculenta, Grev., in the form of numerous small Edachista-like tufts of fila- ments, radiating from gall-like swellings (fig.1). The individual filaments of a tuft, not more than 1 cm. long, are seen, when examined microscopically, to vary much in thickness, some being only one cell thick, others many. All are provided with the usual pheeosporous hairs, scattered singly over their surface (fig. 3), and all or nearly all the filaments are, judging from my material, fertile, even when uniseriate. Hach filament has at its apex one, and, near its apex, usually several, of the just mentioned hairs. The growth of the filaments is intercalary, trichothallic, as, e. g., in Desmarestia. Each filament, when examined in cross section, shows itself to be radially constructed, solid or sub-solid, and with its axial cells the largest. Further, each filament is unbranched, as in P. filiforme, Reinke (fig. 3). Though the filaments of a tuft are unbranched, and, to this extent, unconnected with one another, they are, at their lower ends, in close contact with one another, and more or less fused into a compact body of a subparenchymatous nature. There are, too, to be observed, growing out from the superficial cells at the base of the filaments rhizoidal septate hyphee which come into contact with the surface of the A/aria thallus, and can, no doubt, give rise to new Pogotrichum filaments. On making a vertical section through the anchorage of Pogotrichum hibernicum it is seen to be not merely applied to the surface of the Alaria, i.e. epi- phytic, as a root-dise of a Fucus is to a stone, on which it grows. The individual filaments of P. hibernicum penetrate into the Alaria tnaiius, creep and ramify between both its cortical and medullary cells, the limiting layer of the A/aria being frequently obliterated during the process. Though I searched with =; mm. objective, I was not able to see a host-cell into the cavity of JoHnson—Pogotrichum hibernicum. 3 which a parasitic hypha had entered. A close examination of the sections gives every indication that these endophytic or intra- cortical hyphe can, after creeping for some distance in the Alaria thallus, emerge at either surface to form new Pogotrichum tufts. This vegetative reproduction by means of stoloniferous endophytic hyphae, though distinctly novel in a brown alga, is not uncommon in parasitic Phanerogams (e. g. Arceuthobium,' Pilostyles”), in which plants their intra-cortical hyphae give rise to new plants at the external surface of their host-plants. Having been familiar for some time with the budding of the intra-cortical hyphae in Arceuthobium and other parasitic Phanerogams, it was not un- natural for me to see in the intra-cortical hyphee of Pogotrichum a similar power of vegetative reproduction. My views were very much strengthened on reading a noteworthy paper by M. C. Sauvageau, which, under the title “Sur quelques algues phéos- porées parasites,’ has appeared this year® in the “Journal de Botanique.” In this paper the few observations hitherto recorded of parasitic brown algze possessed of endophytic hyphe are summarised, and the interesting statement is made that the late Professor Harvey, of Trinity College, Dublin, was the first to record, in 1846, the penetration into the thallus of the host-plant by the filaments of a parasitic brown alga.* In 1850 and 1851 Thuret observed Streblonema investiens, Thur., sending endophytic filaments into the thallus of Gracilaria compressa, an observation repeated by Hauck in 1875. In 1872 Kny, at Heligoland, observed the endophytic filaments of an unidentified sterile brown alga in the thallus of Delesseria sanguinea, Chondrus crispus, Laminaria saccharina, &e. In 1875 Reinsch founded the genus Entonema, to include those microscopic Hetocarpee which grow parasitically on other Pheophycee, and on Rhodophycee, and send endophytic filaments into their thalli. In 1878 the most 17. Johnson, ‘“‘ Annals of Botany,”’ 11. 2 Solms Laubach, Das Haustorium d. Loranthaceen, &c., in Pringsheim’s Jahrb. v1. 3C. Sauvageau, Journ. de Bot., Nos. 1-7, 1892. 4W. H. Harvey, Phyc. Brit., 1846-1851, Pl. 28, B. (The basal joints of the fila- ments of Elachista velutina, Aresch: (Ectocarpus velutinus, Kiitz.), are represented penetrated into the thallus of Himanthalia Lorea, Lyngb.) Hlachista attenuata, Hary. (Uyriactis pulvinata, Kitz) is, more strictly speaking, the first brown alga figured (op. cit. Pl. xxvir., A.) and described as truly parasitic. ae 4 Scientific Proceedings, Royal Dublin Society. distinct advance was made by Dr. Bornet,’ who followed the course of the endophytic filaments of the two species Elachista -elandestina, Crouan, and Elachista stellulata, Griff., and saw them produce, some distance -off, at the surface of the host-plant, daughter tufts identical with the mother plant, from which the endophytic stolons had grown. SBornet compared this develop- ment with that of endophytic Fungi. The name Herponema, proposed in 1880 by J. G. Agardh® for a genus to include three species, H. pulvinatum, H. maculans, H. velutinum (Ectocarpus velu- tinus, Kiitz.), was adopted, with altered diagnosis, by Hauck* in 1885 for a group of species of the genus Eetocarpus, in which group two of the species are Z. investiens and LE. velutinus, provided, as previously mentioned, with endophytic filaments. The last addition to our knowledge of parasitic Pheophycee is that made by J. Reinke‘ in the Sphacelariacee of which the genus Sphacelia, Rke., and five species of Sphacelaria, Liyngb., are described as parasitic. Sauvageau commences an account of his own valuable investigations with a more detailed description of the parasitism of Elachista stellulata, Griff., a species which, in the hands of Dr. Bornet, had, in 1875, been the means of a marked addition to our knowledge of parasitic Pheosporee. Sauvageau describes how the epidermis of the old plant of Dictyota, dichotoma, the host, is destroyed, and how the cushion of £. sted/ulata rests on the medul- lary layer of the host-plant, sending off radiating stoloniferous hyphee which ultimately reach the surface of the host-thallus, and give rise to daughter tufts. The parasitic hyphe penetrate into the cavities of the host-cells without losing their chromatophores or injuring the contents of the host-cells. Similar but less com- plete observations were made on Elachista Areschougu, Crn., a species which is parasitic on Himanthalia Lorea. In Elachista clandestina, Crn., which is considered an Ectocarpus, the endophytic hyphe were readily seen connecting external tufts of filaments 1]. Bornet, “Etudes Phycologiques,’”’ p. 21. It is now known that Elachista Areschougii, Crn., not L. clandestina, Crn., was examined. 2J. G. Agardh, ‘‘ Till Algernes Systematik,’’ p. 55. 3F. Hauck, ‘‘ Die Meeresalgen,’’ 1885, S. 324. 4J. Reinke, ‘‘ Uebersicht der bisher bekannten Sphacelariaceen”’ (Ber. d. deut. bot. Gesellsch. vir1., S. 201-215). Jounson—Pogotrichum hibernicum. as) together. lachista fucicola, Fries., growing on Fucus vesiculosus and Ff. serratus, EH. scutulata, Duby, in the erypts of Himanthalia Lorea, and E. pulvinata, Harv., in the crypts of Cystosira ericoides and C. discors were found by Sauvageau to be epiphytic only. This observer also examined a number of species of Lctocarpus, Myrionema, &e., and found eight species of Eetocarpus penetrating into their hosts, to produce, by means of endophytic hyphe, new tufts or patches of filaments. It would take us too far to give an account of these observations. Suffice it to say that six of the eight species have their diagnoses published for the first time. The species and their hosts are as follows :— Ectocarpus velutinus, . . Himanthalia Lorea. Ectocarpus minimus, . . H. Lorea. Ectocarpus luteolus, . f PEA poral: Fucus vesiculosus. Elachista clandestina, . . Fucus ceranoides. (ictocarpus). Kctocarpus brevis, ‘ . Ascophyllum nodosum. Ketocarpus Valiantei, . . Cystosira ericoides. Taonia atomaria. Dictyopteris polypodioides. Ceramium rubrum. Kictocarpus parasiticus, . ‘ Cystoclonium purpurascens. Gracilaria confervoides. Gracilaria compressa. Gracilaria multipartita. Dictyota dichotoma. Ectocarpus solitarius, A | Kctocarpus investiens, . ‘ To return to Pogotrichum hibernicum, a simple inspection of the infested A/aria is enough to show that where the larger tufts of Pogotrichum hibernicum occur the host thallus has been disturbed, and a wart-like swelling produced. Microscopic examination shows that this swelling is formed partly of Pogotrichum and partly of Alaria, that a gall-like body’ has been formed, just as in the case of the parasitism of Hetocarpus Valiantei on Cystosira 1Gall-like bodies have been described in Rhodymenia palmata, Grev., by Miss Barton (Journ. Bot., 1890), and in this and many other Floridex by F. Schmitz, Bot. Zeit., 1892, No. 38 (Knéllchenartige Auswiichse an den Sprossen einiger Florideen 6 | Scientific Proceedings, Royal Dublin Society. ericoides, and of Streblonemopsis irritans on Cystosira opuntioides. As the tufts of Pogotrichum hibernicum are very numerous, penetrate deeply into the host tissue, and occur, in my material, on very young plants, it would seem that there is a possibility of considerable injury being inflicted on the Alaria. Sauvageau traces in the plants examined by himself a gradation of parasitism, from the more or less symbiotic condition of Streblonemopsis irritans on C. opuntioides, to the well-marked parasitism of Zctocarpus investiens and of E. parasiticus, without seeing much indication of injury to the host-plants, or of degradation of the parasite. Reproductive Organs of P. hibernicum.—As already mentioned every epiphytic or extra-cortical filament is, judging from my material, fertile. One of the features which struck me most on first examining the plant was the very great abundance of the reproductive organs which are confined for the most part to the free (upper) halves of the filaments. In this region the whole of the superficial cells of the thick filaments, or in some cases, the whole of the internal cells also, and all the joint-cells of the uniseriate ones are not at all unfrequently converted into repro- ductive cells. Thus the sporangia stand side by side more or less continuously over the whole of the surface of the upper part of the filaments. One cannot speak of definite sori of sporangia as one does in such a plant as Dictyota. The zoosporangia are of two kinds: unilocular and multisporous (figs. 3, 4) and plurilocular (fig. 5). Both kinds occur in the same tuft, but not, so far as I have seen, on the same filament. Unfortunately I know nothing as to the fate of the zoospores. I hope to have an opportunity of examining them at Kilkee in the coming year. On comparing P. hibernicum with P. filiforme, Rke., it is found as described by Reinke, that P. filiforme, Rke., has no lateral Pheosporean hairs, has plurilocular sporangia only, and is entirely epiphytic on Laminaria saccharina. Its filaments are longer, thinner, and have their plurilocular sporangia more localized than is the case in P. hibernicum. As regards the absence of endophytic organs in P. filiforme, a parallel case is presented by Litosiphon, one species of which, L. pusil/us, is epiphytic, the other, L. Laminaria, 1J. Reinke, ‘‘ Atlas deutscher Meeresalgen,’’ 11. 3, 4; s. 62. JoHnson—Pogotrichum hibernicum. 7 as pointed out by Reinke,’ endophytic also. A more noteworthy example of an apparently important difference of habit in closely allied forms is described* by Sauvageau in Ectocarpus fasciculatus, variety abbreviatus. Two forms of this variety, growing on Laminaria flexicaulis, were examined; one is entirely epiphytic with abundant sporangiferous rhizoids, the other is endophytic also. Affinities of Pogotrichum, Rke.—The affinity of Pogotrichum to Litosiphon, Harv., is so close, that Reinke in writing to me states that had he known of the Kilkee plant he would have hesitated before founding the genus Pogotrichum. In the last number of his ‘‘ Atlas deutscher Meeresalgen,” Reinke compares the four plants Pogotrichum filiforme, P. hibernicum [“the Johnsonian plant” |, Litosiphon pusillus, L. Laminarie. It is stated that— 1. The individuals with plurilocular sporangia, of P. hibernicum, agree with the filamentous specimens of P. filiforme. 2. The individuals with unilocular porate of P. hibernicum, are like those of Z. Laminariae. 3. Before, however, uniting the two genera it will be necessary to find plants of true Zitosiphon species with plurilocular sporangia, like Pogotrichum individuals with plurilocular sporangia. (P. Jiliforme, with its plurilocular sporangia, is not, as one might suppose at first thought, the missing state of Z. pusillus which is known up to the present with unilocular sporangia only). 4. Though the individuals of Poyotrichum consist of uni- seriate as well as multiseriate filaments, those of Lrtosiphon are always multiseriate. I have been enabled to examine dry, authentic material of Litosiphon Laminarie, Harv., from the following sources :— 1. Through the kindness of Dr. E. P. Wright, Dublin, material of the type specimens, preserved in the Trinity College Herbarium, was at my disposal. One specimen was labelled “ Bangia laminarie, Lyngb. [and was collected by] Mr. Moore [the late Dr. D. Moore of Glasnevin] in Co. Antrim”; another “Ball and Thompson, 1834, Arran”; another “ W. Andrews, Inch, Dingle Bay.” 2. A specimen in the late Dr. D. Moore’s own collection of 1J. Reinke, ‘‘ Atlas deutscher Meeresalgen,”’ J. c. *C. Sauvageau, ‘‘Sur quelques algues phéosporées parasites,”’ p. ‘38 (Jovrn. de Bot. v1., 1892). 8 Scientific Proceedings, Royal Dublin Society. Algze of the N.E. coast of Ireland, 1834, for many years past in the Royal College of Science, Stephen’s Green. This specimen was probably part of the same material as that from which Dr. Moore supplied Professor Harvey in the Trinity College Herbarium. 3. A specimen in the Herbarium of the Science and Art Museum, Kildare-street. I think it right to point out, before recording the result of my own examination of this material collected fifty years ago, first that the genus Litosiphon was founded in 1849 by Harvey’ at the suggestion of Dr. Moore, who had noted the affinity of Asperococcus pusillus, Carm., and Bangia Laminarie, Lyngb. ;* secondly, that Harvey in lis description of Lntosiphon Laminarie, states that ‘the [peripheral] cells some- times separate into four smaller cells which occupy the space of one cell.”” This condition is represented in the illustrations of the plant. Lyngbye, under Bangia Laminarie, and J. G. Agardh, under , ¢itrina, Ehr., Bienes) », petromyzon, Ehr., fet Mil ;, Mmegalotrocha, Ehr., .. 35 inflata, sp. noy., Boe Ol », aculeata, Ehr., SAU INOD Buareulanie forficula, Ehr., ba 02 Rotifer vulgaris, Schr., ee aCO an gracilis, Ehr., set Oe »» macroceros, Gosse, Het ake) ae cxca, Gosse, .. 58 »» hapticus, Gosse, Beal yeaa 95 gibba, Ehr., Ses >, Macrurus, Schr., Sroka gerll a ensifera, Gosse, .. 58 phaleratus, sp. noy., .. 38 + marina, Duj., Ae | O63 Gallas elegans, Ehr., let t38 ‘ Boltoni, Gosse, Bee aes: », bidens, Gosse, “oy OS Rs longiseta (Ehr.), .. 655 », bihamata, Gosse, Heh NRO 5 zequalis (Ehr.), ow 08 Adineta vaga, Dav., reeds) He sterea, Gosse, sao) Microcodon clayus, Ehr., eRe OL) tt semisetifera, sp. NOY., 55 », (?) robustus, sp. nov.,.. 40 Dp megalocephala, sp.noy., 56 Sacculus viridis, Gosse, So eae rigida, sp. nov., Bie 9) Syncheta pectinata, Ehr., oy aad Hsohdta aurita (Ehr.), pee 7)// » tremula, Ehr., .. 42 striata, sp. nov., see RO Hydatina senta, Ehr., ee nebne TDAsteae grandis, Ehr., eet 10S Notops hyptopus, Ehr., fa 42 », ‘forcipita, Ehr., vp 08 , (?) quadrangularis, sp. nov., 438 » Circinator, Gosse, poh ah) Taphrocampa annulosa, Gosse, 43 » girafia, Gosse, MeO Saundersiz, Gosse, 44 », caudata, Ehr., gone, Ge Blearatnocha gibba (?), Ehr., .. 44 », permollis, Gosse, igre). Notommata aurita, Ehr., .. 44 », catellina, Ehr., .. 60 ne ansata, Ehr., SO ie nce »» inflata, sp. nov., se GO is cyrtopus, Gosse, .. 45 » revolvens, sp. noy., .. 61 ‘A tripus, Ehr., .. «45 »> ./ elongata, sp. NOV., ..« soll by forcipata, Ehr., -. =46 rugosa, Sp. Nov., Kio we 84 ie brachyota, Ehr., .. 46 Distenme raptor, Gosse, ae a aS: ” saccigera, Ehr., .. 46 » platyceps(?), Gosse .. 63 Guascorr—A List of some of the Rotifera of Ireland. 3l PAGE PAGE: Mastigocerca scipio, Gosse, $92. 3168 Monostyla cornuta, Ehr., son as rattus (Ehr.), $24) (63 2» Lordii, Gosse, ose ill” - bicornis (Ehr.) .. 64 Monostyla quadridentata, Ehr., 73 i bicristata (?),Gosse, 64 Colurus deflexus, Ehr., teh 0S - brachydactyla,sp.nov., 64 », obtusus, Gosse, . 03 Rattulus tigris, Miill., oe yaGe », caudatus, Ehr., ha Th, i helminthodes, Gosse, 65 », pachypodus, sp. noy.,.. 74 a cimolius, Gosse, .. 65 », tessellatus, sp.nov., .. 74 Czlopus porcellus, Gosse, 5 Metopidia lepadella, Ehr., sp de ,», tenuior, Gosse, SOD », Solidus, Gosse, Bea ale », brachyurus, Gosse, .. 66 Fe) oxysternum, Gosse, .. 75 », eavia, Gosse, ay) 66 », triptera, Ehr,, ooh ee >, minutus, Gosse, sal) BO ” bractea (Ehr.), Ba (2 Dinocharis pocillum, Ehr., Bor pr ke ry) ovalis (?) (Ehr.), Boga (ie. s tetractis, Ehr., eS ENTE Monura colurus, Ehr., po romedio Scaridium longicaudum, Ehr., 67 Cochleare turbo, Gosse, be Oe Stephanops lamellaris, Ehr.. .. 67 Pterodina patina, Ehr., a 16 Me unisetatus, Coll, .. 67 », valvata, Huds., Bion ae Diaschiza valga, Goss., He! 68 », Clypeata, Ehr., ae: be exigua, Goss., ae BS Brachionus urceolaris, Ehr., .. 77 FS Hoodii, Gosse, so (ats) » rubens (?), Ehr., .. 77 5 peta, Gosse, a0) 68 » Bakeri, Ehr., pamper ld) » Semiaperta, Gosse, .. 69 » serrulata, Hhr, .. 77 Salpina mucronata, Ehr., sa. GY) Anurea brevispina, Gosse, Soh) es »» Spinigera, Ehr., SYNE Notholca thalassia, Gosse, Bo adie », brevispina, Ehr., vay ohdO Euchlanis dilatata, Ehr., Se n70 Later Appirions. on macrura, Khr., Be ris Notops forcipata, sp. nov. ap. ce “s triquetra, Ehr., He Na Notommata lucens, sp.nov. .. 79 a deflexa, Gosse, Sonate A gigantea, sp.nov... 80 »> pyriformis,Gosse, .. 71 Furcularia micropus (?) Gosse, .. 82 Cathypna luna, Ehr., 3 Saal Diglena Hudsoni, sp. nov. EetaSo », rusticula, Gosse, Bs enril », dromius, sp. nov. 1 Se Distyla flexilis, Gosse, eee », aquila, Gosse, a nod Monostyla lunaris, Ehr., AGA EI »» uncinata (Milne), .. 85 Floscularia regalis, Hudson. [The Rotifera, vol. i. p. 49, Pl. I. fig. 8.] Several of this species occurred attached to the leaflets of Myriophylium and Lemna trisulea, from a marsh drain exposed to the influence of a tidal river and also upon the leaflets of Sphagnum from a bog. In some cases there were two or three eggs adhering to the base of the foot within the tube. The species is said to be not common; the seven knobbed lobes of the corona afford a good specific feature. Habitat.—A. marsh drain, Co. Wexford. 32 - — Setentific Proceedings, Royal Dublin Society. Floscularia ornata, Ehrenberg. [The Rotifera, vol. i. p. 50, Pl. I. fig. 9.] Habitat.—F requent in bogs, ponds, and deep drains, Co. Wexford. Floseularia cornuta, Dobie. [The Rotifera, vol. i. p. 51, Pl. I. fig. 7.] Frequent. The long tapering dorsal lobe is usually curved backward when the coronal cap is expanded. Habitat.—Ponds, bogs, and drains, Co. Wexford. Floseularia campanulata, Dobie. [The Rotifera, vol. 1. p. 52, Pl. I. fig. 1.] Frequent. The voracity of this species fully equals that of Floscu- laria ambigua. On one occasion, as I was watching the struggles of an unfortunate little Colurus obtusa which had been engulfed into the already closely packed stomach, a Diaschiza Hoodii, almost as large as the Floscule itself, came sailing above. Down it rushed headlong into the vortex; but alas! even the throat of a Floscule has its limits, and in spite of every effort made to swallow it, the prize stuck fast, head downward, heels kicking frantically above, until finally it was released, and went on its way rejoicing. Habitat.—Pond and bogs, Co. Wexford. Flosecularia ambigua, Hudson. [The Rotifera, vol. i. p. 53, Pl. I. fig. 2.] Frequent. The lateral lobes in every case reduced to mere undulations. Habitat.—Ponds, bogs, and drains, Cos. Wexford and Waterford. Floscularia algicola, Hudson. [The Rotifera, vol. i. p. 54, Pl. II. fig. 1.] I have found this tiny member of the family several times, attached to small clumps of Gloiotrichia growing upon the stems of water-plants, as described by Dr. Hudson, and also adhering to the leaves of other small aquatic plants, such as Calletricha, Lemna, &¢., but it is by no means common. Habitat.—Bogs and ponds, Co. Wexford; the Canal, Dublin. Griascorr—A List of some of the Rotifera of Ireland. 30 Melicerta ringens, Schrank. [The Rotifera, vol. i. p. 70, Pl. V. fig. 1.] Abundant in ponds, adhering in colonies to the stems of water plants. In one instance I noticed many empty tubes of large size, the recent occupants lying about not far distant, the long wrinkled foot looking so strangely naked without its habitual covering. Whether it is customary with the species thus to forsake their tubes at certain seasons of the year, or whether it was due on that occasion to some discontent with their surroundings, I do not know. The occurrence suggests investigation. Habitat.—A pond, Co. Wexford. Melicerta conifera, Hudson. _ [The Rotifera, VOlsda pa Se NE igen A large specimen seated upon the stem of a plant without a tube, the body so contracted as to entirely conceal the foot. The lobes of the corona were fully expanded, and did not exceed the width of the body; the long pointed chin was likewise observable. At some little distance there was an empty tube of about the same circumference, but of greater length, the long conical pellets of which sufficiently denoted the species to which it belonged. Habitat.—A. pond, Co. Wexford. Limnias annulatus, Bailey. [The Rotifera, vol. i. p. 77, Pl. VI. fig. 2. ] Two of this rare species occurred upon the leaflets of Utricularia oulgaris. I have mounted them in situ in glycerine jelly. The transverse ridges of the tubes show out beautifully ; the head of one of the creatures is bent sideways in the tube, and shows the horny processes. In order to kill them I applied a drop of hot water to the edge of the cover glass, which was laid over the plant on which they were fixed, whereupon they immediately expanded the lobes of the corona, and set the wheels in motion with glorious vigour, which, with a spot-lens, afforded a most interesting sight to the beholder. I subsequently killed them by applying the glyce- _ rine jelly, which at the same time preserved their bodies. Habitat.—A. deep marsh drain, Co. Wexford. SCIEN. PROC. R.D.S., VOL. VIII., PART I. D 34 Scientific Proceedings, Royal Dublin Society. @cistes erystallinus, Ehrenberg. [The Rotifera, vol. i. p. 80, Pl. VII. fig 3.] A very common species. JI have met with large colonies embedded in the gelatinous balls of Gloiotrichia which infests some water-plants; also single specimens in various situations. When they adopt the Gloiotrichia for their dwelling-place the tube is simply continued from the surface of the plant to protect the upper portion of the animal. It is of loose, gray, fluffy texture, and very unsymmetric in shape. Habitat.— Bogs and ponds, Cos. Wexford and Waterford. @cistes longicornis, Davis. [The Rotifera, vol. i. p. 82, Pl. VII. fig. 6. ] The tube of this species was much more compactly built than that given in the description in the Monograph. It was smooth, cylindric, and tapered towards the base, which was attached to a leaflet of Utricularia vulgaris. The body of the animal was half the length and size of the tube, and supported by a slender foot. The antenne were very long, with a small joint at the tip, and spread widely apart; the coronal disc was small and almost circular, with a wide ventral gap; there were two long, oval eggs placed end to end in the lower half of the tube, which were but dimly discernible through the semi-opaque wall, which was of an orange colour. The creature was extremely timid, and retreated within the tube upon the slightest alarm. Habitat.—A. marsh drain, Co. Wexford. @Ecistes brachiatus, Hudson. [The Rotifera, vol. i. p. 83, Pl. IX. fig. 2.] Three of this well-marked species occurred, two among fila- ments, and one attached to a moss leaf. The dark branching ribs, which spread over the walls of the coronal cup, give it a very distinctive appearance. Habitat.—A pond, Co. Wexford. Guascotr—A List of some of the Rotifera of Ireland. 35 dEcistes velatus (Gosse). [The Rotifera, vol. i. p. 83, Pl. D. fig. 8.] I have met with this species, which is noticed as of rare occur- rence by Mr. Gosse, frequently, but in no instance has it attained to any remarkable size or striking beauty. Always wandering, the corona is usually maintained expanded, and is of somewhat square outline. The very opaque back eyes, set widely apart in the neck, close to the corona, arrests the attention at once, as does also the very dark contents of the intestine (?), which seem to be invariably present. The creature in all respects resembled the figure, and in some instances the form of the trophi was quite distinct. Habitat.—A. pond, a bog, Co. Wexford. Philodina erythrophthalma, Ehrenberg. [The Rotifera, vol. i. p. 99. ] Frequent. Cos. Wexford and Waterford. ' Philodina roseola, Ehrenberg. [The Rotifera, vol. i. p. 99, Pl. IX. fig. 4. ] Frequent. Habitat.—Ponds and ditches, Cos. Wexford, Waterford and Kerry. Philodina citrina, Ehrenberg. [The Rotifera, vol. i. p. 100, Pl. IX. fig. 6]. Not uncommon. The truncate body and abrupt foot sufficiently mark off the species from its congener. Cos. Kerry and Wexford. Philodina megalotrocha, Ehrenberg. [The Rotifera, vol. i. p. 101, Pl. IX. fig. 7.] Rare. Habitat.—Ponds and streams, Co. Wexford. Philodina aculeata, Ehrenberg. _ [The Rotifera, vol. i. p. 101, Pl. IX. fig. 5.] This species is apparently subject to great variation with regard to the development of the spines, and also with respect to D2 36 Scientific Proceedings, Royal Dublin Society. colour. I have met with many examples answering to the descrip- tions of each of the authorities quoted in the Monograph. In the long-spined variety (Plate rx. fig. 5) the number varies from two to three in the first row, but the two central spines in the succeeding row are always highly developed. I have seen them moved independently up and down, as though under the control of special muscles. Also in one instance I noticed that the upright lateral spines were not visible, but whilst I watched, the creature suddenly assumed a sitting posture, and the spines, which had lain flat against the sides of the body, were flung upward with a jerk, and after some time were withdrawn entirely into the integument, and I found one example with no spines at all. With regard to the short-spined variety, Dujardin’s description “tout herissé d’épines”’ is most appropriate. At the juncture of every segment there is a closely set row of short, pointed, upright spines, which continue round toward the ventral surface. These cause the body, in many instances, to be so overlaid with sediment that it is difficult to discern them. There is a considerable diffe- rence between these two varieties. In the latter, or short-spined variety, the body is deeply corrugated longitudinally, and though there is a notable swelling in the central segment, the succeeding portion does not terminate abruptly towards the base of the foot as in the former, but descends gradually; the toes are also very small. The colour is sometimes white, but generally shades from light amber to brown. Its manners are slow and timid, as it crawls into the axils of moss leaves, and persistently hides itself therein. Habitat.—Ponds, bogs, and streams, Cos. Wexford and Water- ford. Rotifer vulgaris, Schrank. [The Rotifera, vol. i. p. 104, Pl. X. fig. 2. ] Common everywhere. Rotifer macroceros, Gosse. [The Rotifera, vol. i. p. 105, Pl. X. fig. 5.] Though not common, several fine examples have occurred. The unusual length of the antenna, its forward direction and Giascorr—A List of some of the Rotifera of Ireland. oO” strange wagging movement denote the species unmistakably. It is very timid, and shrinks under cover on the slightest alarm. In one instance it was seated in a little nest in a small heap of flock adhering to the stem of a water-plant, from which it cautiously protruded its head, and wagged the long antenna in a knowing manner. Habitat.—A. bog ; a marsh drain, Co. Wexford. Rotifer hapticus, Gosse. [The Rotifera, vol. i. p. 106, Pl. X. fig. 3.] Only one specimen occurred during a whole summer’s research. Habitat.—A. marsh drain, Co. Wexford. Rotifer macrurus (2), Schrank. [The Rotifera, vol. i. p. 107, Pl. X. fig. 4. ] The body very large, smooth, and colourless, and well marked out from the foot; when extended there was always a waist-like attenuation just under the mastax, as described of Philodina roseola. In the intestine—a large oval chamber—a mass of coloured granules rotated, and close to the foot the beat of the contractile vesicle was plainly visible, occurring at distant intervals. The collar was thick and bulging, the lobes of the corona of splendid size, with a deep V-shaped sulcus between them ; when it was expanded, the column was not visible. The foot—composed of 7 or 8 joints—was stout, and capable of immense extension. The toe and spurs were of moderate length. Its manners were sluggish, remaining for lengthened periods as if asleep, then slowly unfurling the lobes of the corona, it set the cilia in motion for a short time, and then again relapsed into a quiescent state. There were two of this species close together, and in neither could I detect the slightest trace of eyes. Although not agreeing in all particulars with the description of the above-mentioned member of the genus given in the Monograph, it seems to approximate closely to it. Habitat.—A. pond, Co. Wexford. 38 Scientific Proceedings, Royal Dublin Society. Rotifer phaleratus,’ sp. nov. (Pl. III. fig. 1.] Sp. Ch.—Body translucent, tapering gradually from the shoul- ders, which are broad, and ornamented with a conspicuous pear- shaped marking. This species is probably only a variety of R. vulgaris, which it resembles in most particulars, but it is much broader at the . shoulders (or that part of the body immediately behind the neck), which are ornamented with a broad, dark, pear-shaped marking, apparently confined to the outer integument, as it shows no change of position during the movements of the internal organs. As I was obliged to sketch in the head from memory, the details of that part are not reliable. Three of these creatures occurred from the same dip. Habitat.—A stream, Co. Wexford. Callidina elegans, Ehrenberg. [The Rotifera, vol. i. p. 109. ] The hooked proboscis on the tip of the column—a distinctive feature in the species—was not minute, as described in “The Rotifera,” but quite prominent. ‘The body was large and heavy, the central segment greatly swollen, and marked out by deep con- strictions. It was of a dirty white colour; its manners were sluggish, crawling slowly and heavily amongst the rubbish, in which it sought to conceal itself. There were, of course, no eyes— about the most inelegant species I have met with. Habitat.—A. pond, Co. Waterford. Callidina bidens, Gosse. [The Rotifera, vol. i. p. 109, Pl. X. fig. 8.] At my first introduction to this species it was boldly walking across an open space with regular stride, using foot and mouth as does the larva of a Geometra. As soon as it approached a neighbouring cover, however, it was glad enough to take refuge therein, and withdrawing the foot sat comfortably down on a broad base, 1 Phaleratus, ‘‘ with ornaments on the shoulder.” _— Guascorr—A List of some of the Rotifera of Ireland. 39 stretched out the long tapering neck, unfurled the corona, and commenced to resuscitate exhausted nature with an ample meal. In this position the transverse corrugations of the integument were plainly visible, as was also the exceptionally long buccal funnel. The species is said to have no eyes, and certainly none were appa- rent; yet I noticed that as soon as it neared the coloured mass of sediment it altered its course, and made straight for it with evident purpose; the boldness of its stride also seemed hardly that of a creature dependent on the sense of touch alone for guidance. Habitat.—Streams and ponds, Cos. Wexford and Waterford. Callidina bihamata, Gosse. [The Rotifera, vol. 1. p. 111, Pl. X. fig. 7.] Quite a number of these occurred in bog moss from Kerry. The very short dorsal antenna and its backward direction affords a good feature for identification. Habitat.— Bog moss, Co. Kerry ; a pond, Co. Wexford. Adineta vaga (Davis). [The Rotifera, vol. i. p. 112, Pl. X. fig. 10.] Of peculiar interest, there being only two species of the genus. It was busily searching for food, and the strange manners described by Dr. Hudson were in full operation. The clear channel dividing the head into two halves was conspicuous. Habitat.— Amongst Confervee on the walls of a well, Co. Wex- ford. Microcodon clavus, Ehrenberg. [The Rotifera, vol. i. p. 118, Pl. XI. fig. 1.] When I first saw this morsel of exquisite beauty it was swaying about between two leaflets of Myriophyllum, attached, as Dr. Hudson shrewdly guesses, by a slender foot-thread to a tiny heap of flock. As the light was fortuitous, I distinctly saw this line, and furthermore it was clearly demonstrated by tiny atoms of flock which adhered to it in several places throughout its length, all of which responded in concert to the swaying of the animal. The creature remained in the same spot for more than an hour, occasionally changing its point of attachment until there was quite 40 Scientific Proceedings, Royal Dublin Society. a little web spread about, against a bar of which it finally attached itself by the middle of the foot, swung round and round head over heels with great rapidity, a most amusing sight; then a sudden dart of lightning speed, and it was gone. I found it again, but it had grown wild and restless, and we soon bid adieu forever. Since then I have met with numbers of them from two different locali- ties; they bear confinement well, and increased rapidly in a large pan into which I had thrown the water containing them. The re- presentation of the species in the Monograph is so truthful both in form and colouring that it leaves me little to say. The stomach always appeared to be distinctly two-chambered, the lower chamber being about two-thirds the size of the one above it, the line of division marked by a slight constriction, and also by the different condition of the contents. The bright red organ mostly present was even larger than given in the figure alluded to, and unsymmetric in shape, but examples also occurred in which it was absent; and in the latter case the whole body was invariably studded over with globules, some of which were tinged with yellow, and had an oily appearance. The coronal disc, though always open, was rarely ex- panded to the plate-like flatness represented in the above figure. I have seen it suddenly close over an atom within the circle to prevent itsescape. The margin of the disc invariably swept down in an open V-shaped curve to a point upon the breast. Both the under and upper surface of the mastax were deeply tinged with purple, looking like two transverse purple plates, upon the latter of which rested the large purple eye. Occasionally I detected a low dorsal ridge, running from under the dorsal antenna to the base of the foot. The ovary was always of large size, and remarkably clear; the contractile vessel was well defined. Habitat.—A bog, a drain, Co. Wexford. Microcodon (?) robustus, sp. nov. (Pl. III. fig. 2.] Sp. Ch.—Body smooth, cylindric, stout; corona of the same diameter as the trunk; foot almost as long as the body; toe single, stout, and acutely pointed. This species most probably belongs to the family Microcodida, Se Giascorr—A List of some of the Rotifera of Ireland. 4] though quite a giant as compared to its hitherto sole representative M. clavus. We have the same contour of the body, the same long foot continuous with the trunk and terminating in a single acutely pointed toe, the same upright position, hovering motion, and per- manently expanded disc of that species. The latter, however, was: not produced into a flattened rim, but remained always of the same circumference as the body, the margin being interrupted by many depressions and elevations. The interior of the cup also contained some cushion-like prominences, somewhat similar to those of Hy- datina senta. I regret that I can only give a proximate idea of these outlines as the creature disappeared from view before my observations were completed. There were two prominent projec- tions on the margin of the disc toward the centre of the ventral aspect which were most probably the ventral antenne. Depressed at the sides the margin then swept upward in waving curves to a dorsal elevation, at the back of which was seated the tuberculate dorsal antenna. ‘There appeared to be a wide-spread brain, which dipped downward in the middle; and from the centre of the cup there gleamed a large red eye. I could not discern the trophi. An ample stomach was surmounted by two clear globe-shaped gastric glands, which were very conspicuous. The body was smooth, cylin- dric, but somewhat flattened ventrally, and of a dull amber colour. It hovered about in an upright position, and made little jerks for- ward, as though snatching at tiny atoms of food. Length, about =izth of an inch. Habitat.—A. ditch, Co. Wexford. — Sacculus viridis, Gosse. [The Rotifera, vol. i. p. 124, Pl. XI. fig. 2.] Not unfrequent. Trophi often protruded with a snap. Habitat.—Ponds and deep drains, Co. Wexford. Synchata pectinata, Hhrenberg. {The Rotifera, vol. i. p. 125, Pl. XIII. fig. 3.1 Not common. Habitat.—Ponds, Co. Wexford. 42 Scientific Proceedings, Royal Dublin Society. Synchieta tremula, Ehrenberg. [The Rotifera, vol. i. p. 128, Pl. XIII. fig. 2.] Not common. A few examples only occurred. Habitat.—A marsh drain, Co. Wexford; a stream, Co. Waterford. Hydatina senta, Ehrenberg. [The Rotifera, vol. i. p. 9; vol. ii. Pl. XIV. fig. 1.] Crowds of splendid examples of this interesting species occurred in a small duck-pond, in the month of July, in company with Notops hyptopus, many of which (the Hydatina) were affected by the fungoid disease alluded to by Dr. Hudson. ‘The internal parasite also noticed by him seemed quite of common occurrence ; in one specimen, which had been recently killed on the slide by the rays of the sun, there were no less than three of these curious pear-shaped creatures tumbling madly over each other in their desperate efforts to escape from the body of their dead host; they finally effected their escape by making their exit through the mouth. I searched the same pond again in the month of Septem- ber, and there was not one Hydatina to be found: they had en- . tirely disappeared. Habitat.—A duck-pond, Co. Waterford. Notops hyptopus (Ehrenberg). [The Rotifera, vol. ii. p. 18, Pl. XV. fig. 2.] As before stated this species occurred in swarms in a duck-pond in company with Hydatina senta. The wobbling gait, the curved — edges down the dorsal surface, and the truncate corona bulging forward toward the centre, afford satisfactory points for identifi- cation: It also occurred in other localities, but only as isolated specimens. In all cases there were two distinctly separate red eyes (cervical), placed, however, so close together as to appear like one. Their ultimate union would not be improbable. Habitat.—Ponds, bogs, and streams, Cos. Waterford, Wexford, and Kerry. Giascorr—A. List of some of the Rotifera of Ireland. 43 Notops (?) quadrangularis, sp. nov. [ Pl. IIT. fig. 3.] Sp. Ch.—Body quadrangular; head narrow; foot long and non-retractile ; toes nearly as long as the foot, furcate. Approaching JV. brachionus this species still bears too many distinctive characteristics to be confounded with it, the much narrower head, the high shoulders, straight sides of the body, and comparatively long toes being subject to no variation in the many examples which occurred. At the four corners of the trunk there are dark gray or brown patches seemingly spread out upon the ventral floor which, under a high power, appear to be globu- lated, foliaceous expansions, such as we see in Pterodina. ‘The truncate head is simple, and bears no styligerous prominences. A single large red eye is situated close to the frontal margin. The large forcipate (?) trophi reach deep into the neck, from the pos- terior end of which spreads an ample stomach, with wide, flat ovary underneath. The foot is long, round, and non-retractile, the pointed toes being almost of equal length. Length about 5th of an inch. Not unfrequent. Habitat.—Ponds and streams, Cos. Wexford and Waterford. Taphrocampa annulosa, Gosse. [The Rotifera, vol. ii. p. 16, Pl. XVII. fig. 12.] Very common. I have seen it as described and figured in Pl. xvi. fig. 12, of the Monograph, but far more frequently the body presented a depressed and collapsed appearance, with a deep broad groove along the dorsal line, the annular ridges conspicuously raised, and the lateral depressions (Pl. xvi. fig. 120) deeply marked. The sedimentous deposit adhering to the surface of the integu- ment denoted that this appearance was a reality, and not due to an optical delusion. The black brain mass was always conspicuous, but no red eye occurred. The auricles were frequently everted, especially when the animal swam inthe open. ‘The foot, if rightly so called, was mostly crescent-shaped, and in all cases appeared to 44 Scientifie Proceedings, Royal Dublin Society. be but a furcate projection of the ventral integument, and incapable of independent movement, the rounded lobe in the middle of the erescentic fork being situated distinctly above it, and hence to be regarded as a true tail; this was especially evident on one occasion, as the creature curled itself round a slender stem, when the crescent was bent underneath, leaving the tail projecting above ite Habitat.—All fresh waters, Cos. Wexford, Waterford, and Kerry. Taphrocampa Saundersiz, Gosse. [The Rotifera, vol. 11. p. 18, Pl. XVII. fiz. 11.] I had but a moment’s glimpse of this species as it hurried into cover, but the ridged annulations of the body, the lumpish head, narrow neck, and the shape of the toes sufficiently proved its identity. Habitat.—A stream, Co. Wexford. Pleurotrocha gibba (?), Ehrenberg. [The Rotifera, vol. ii. p. 20, Pl. XVIII. fig. 5. ] This is undoubtedly the species figured by Mr. Gosse. The large head curving to the oblique disc, the short body, the single foot-joint stout, but distinct ; toes a trifle longer than the foot: all coincide so as to render its identity indisputable; its manners were slow, as it persistently grubbed amongst the flocose. Habitat.—A. stream, Co. Waterford. Notommata aurita, Ehrenberg. [The Rotifera, vol. i. p. 21, Pl. XVII. fig. 6.] Common. Habitat.—Stream, ponds, Cos. Waterford and Wexford. Notommata ansata, Hhrenberg. [The Rotifera, vol. ii. p. 21, Pl. XVII. fig. 3.] The great rapidity of movement in this species renders it a difficult one to study. I could not detect the eye; but the brain, though clear, was well defined. The contents of the stomach were not of the dark red colour represented in the above figure, but of a Guascott—A List of some of the Rotifera of Ireland. 45 _ yellow tint, this being, of course, dependent upon the nature of the food. The shape of the body, foot, and toes, were all identical with the figure in the Monograph, and its manners completed the picture. After many rapid flights, twists, and turns, it at length dashed into some flock adhering to a stem, contracted its body into a ball, and kicked itself roundand round with great vigour, until weary of watching I dislodged it. A few other examples occurred from different localities, but it is a rare species. Habitat—Streams, Co. Wexford; a bog, Co. Waterford; the Canal, Dublin. Notommata cyrtopus, Gosse. [The Rotifera, vol. ii. p. 22, Pl. XVII. fig. 7. ] Not frequent. The two colourless eyes always apparent. In several examples the auricles, of somewhat oblong shape, were freely everted. Habitat.—Streams, amongst alge, Cos. Wexford and Carlow. N.B.—Hitherto the auricles of this species have not been seen, but I fancy their presence was suspected. Notommata tripus, EKhrenberg. [The Rotifera, vol. ii. p. 22, Pl. XVII. fig. 4.] Although the auricles of this species are somewhat larger and more rounded than represented in the figure in the Monograph, they never could be termed “great globose,” as described of WV. pilarius, and the general contour of the body, together with the thick and deeply incised folds at the neck, approach closely to it. It is a quaint little creature, whose upright tail gives it a marked individuality, and a fairly common species, which seems to take the place in this country of its congener JV. pilarius, which I have not yet seen. I found one specimen whose brain (?) or eyeball (?) had evidently received some injury, for it hung from the back of the red eye as a grey pear-shaped globe, suspended by the stalk, which wobbled about from side to side when the animal moved. The digestive sac seems simple and undivided; I have seen a rotation of granules throughout the entire chamber. Habitat.—Pond, bogs, and streams, Co. Wexford. 46 Scientific Proceedings, Royal Dublin Society. Notommata forcipata, Ehrenberg. [The Rotifera, vol. ii. p. 238, Pl. XVIII. fig. 1.] A dead specimen, from a bog, Co. Wexford. Notommata brachyota, Ehrenberg. [The Rotifera, vol. ii. p. 24, Pl. XVII. fig. 1.] Essentially a scavenger this species has frequently occurred, four or five together, feeding busily within the empty skins ofaquatic larvee and shells of small species of Entomostraca, the very soft pliant nature of the body affording a marked adaptation to the situation. The very large stomach was always filled with a light brown granulated mass as described in the Monograph. The red eye was mostly visible, but only when it swam in the open could the minute auricles be detected. Habitat.—Ponds, bogs, not uncommon, Co. Wexford. Notommata saccigera, Ehrenberg. [The Rotifera, vol. ii. p. 24, Pl. XVII. fig. 2. ] So exactly resembling the figure referred to, as it glided along the slide with auricles extended, that I have little doubt of its identity, though I did not get a glimpse of it from any other point of view; the face was kept flat upon the glass as it moved. Habitat.—A pond, Co. Wexford. Notommata naias (?), Ehrenberg. [The Rotifera, vol. ii. p. 25, Pl. XVII. fig. 2.] About the same size; the shape of the creature did not corre- spond with that of the above figure, the head being very much wider than the body, which latter tapered from it to the foot; perhaps the empty state of the stomach may account for this, but the formation of the head seemed identical with it; the clear brain bore a small eye close to its extremity, which looked black by transmitted light, but was of a deep red colour when viewed Guiascorr—A List of some of the Rotifera of Ireland. 47 with light from above. ‘The foot and toes were exactly as described by Mr. Gosse. th of an inch. Habitat.—A. stream, Co. Wexford. Eosphora aurita (Ehrenberg). [The Rotifera, vol. ii. p. 47, Pl. XVII. fig. 10.] Several of these lively little creature occurred among the leaf- lets of Utricularia; their two bright red eyes draw attention at once; and then deeper toward the centre of the body a dark-looking spot is seen which occasionally gives out a flash of red colour as the creature turns; in all cases the body was filled with bright green food, the extremities being remarkably clear and transparent. The head and auricles were also much broader than represented in the figure in the Monograph. I once met with one of unusually large size, I suppose an ancient dame. Habitat.—Bogs and drains, Co. Wexford. Eosphora striata, sp. nov. [PL IV. fig. 5.] Sp. Ch.—Body sub-cylindric, swollen in the middle, hyaline, fluted ; head dilate; eyes three; foot long ; toes furcate. A large and conspicuous species, particularly clear white throughout. The dilated head is cushioned within the disc, and truncate on the frontal margin, which bears a bright red eye at each extremity ; an ample brain descends to the middle of the neck, _ and near its end another red eye is placed just above and between two black patches which coat its surface at either side. The lower 58 Scientific Proceedings, Royal Dublin Society. half of the brain rests upon an enormous mastax, the square forci- pate trophi reaching close to the disc. The body is of oblong shape slightly swollen in the middle and deeply fluted longitudinally, the circular stomach is situated very low down. ‘The great transparency of the tissues rendered all other organsinvisible. The foot one long and simple joint, the toes two pointed cones, not quite halfits length. Its manners were quiet, gentle, and deliberate when feeding, and it swam in the open with an easy gliding motion. I saw no auricles. Length about ,);th of an inch. ‘Habitat.—On a submerged leaf of Comarum from a bog, Co. Wexford. Diglena grandis, Ehrenberg. [The Rotifera, vol. ii. p. 48, Pl. XIX. fig. 6.] A. splendid specimen amongst the branches of Cladophora from a stream. It was seated toes apart, and fell about awkwardly from side to side as though in a dying state. The contents of the stomach were of a yellow colour. The head was constantly in- verted. The resemblance to the figure in all points was unmis- takable. I found one also among alge from a stream in the Co. Water- ford, in whose body I was surprised to see the gleam of many bright red eyes, but the mystery was almost immediately explained by the birth of three fully formed individuals in uninterrupted suc- cession ; the first and largest measuring 5}, inch in length, includ- ing the toes. After the event the parent, much reduced in girth, swam carelessly away; the babes, I regret to say, drifted under some vegetation, and when trying to bring them into better view I must have killed them by over pressure of the cover glass, for they showed no signs of life. Habitat.—Streams, Cos. Waterford and Wexford. Diglena forcipata, Ehrenberg. [The Rotifera, vol. ii. p. 50, Pl. XIX. fig. 2.] Not uncommon. Habitat.—Streams, ponds, Cos. Waterford and Wexford. Guascorr—A List of some of the Rotifera of Ireland. 09 Diglena circinator, Gosse. [The Rotifera, vol. ii. p. 50, Pl. XIX. fig. 4.] Not common. ‘The peculiar fold at the sides of the neck, seen from the dorsal aspect, was apparent in some, but not in all of them. The gibbous development of the body, and the long narrow neck, together with the widespread crescentic curves of the toes, afford good specific features. Habitat.—Ponds and bogs, Cos. Waterford and Wexford. Diglena giraffa, Gosse. [The Rotifera, vol. ii. p. 51, Pl. XIX. fig. 9.] I have met with but a single example of this rare species. It was stationary, and lifting the long neck and head high above the level of the body, craned it about as though taking stock of its surroundings; both extremities were frequently withdrawn into the tube-like central area of the body in a slow and deliberate manner, then as slowly protruded again. Habitat.—A. stream, Co. Wexford. Diglena caudata, Ehrenberg. [The Rotifera, vol. ii. p. 51, Pl. XIX. fig. 8.] This creature is indeed well described. One might think it had donned a garment at least three times too large for it, which fell into innumerable folds, and greatly impeded all its movements, which were remarkably slow ; when swimming in the open, it occasionally gave a little jump forward, and at intervals withdrew the foot and toes entirely within the body, just as one would draw in a piston through a tube, then pushed them deliberately out again. _ Habitat.—Several occurred from a pool, Co. Wexford. Diglena permollis, Gosse. [The Rotifera, vol. ii. p. 52, Pl. XTX. fig. 11.] Apparently a rare species. I found one within the empty shell of a Daphnia; the body was extremely soft and flexible, and 60 Scientific Proceedings, Royal Dublin Society. as it twisted about I had much difficulty in getting a good view of its shape. The head was broad on the frontal margin, and sometimes contracted into a straight line, over which the soft proboscis was curled ; at times it assumed a conic form and bore little resemblance to the genus to. which it belonged. Another appeared swimming in the open, undoubtedly the same species, bearing all the characteristics portrayed in the figure of the Monograph. From two localities. Habitat.—A. bog, a marsh drain, Co. Wexford. Diglena catellina, Ehrenberg. [The Rotifera, vol. ii. p. 538, Pl. XIX. fig. 10. ] A fine stout example, busily rooting amongst a mass of floccose sediment as it stood upon its toes, which were bent forward under the body. Habitat.—A. pond, Co. Wexford. Diglena inflata, sp. nov. [Pl. IV. fig. 6.] Sp. Ch.—Body gibbous in the middle, flat on the ventral sur- face, white; head long, narrow; no eyes; foot thick, of one or two (?) joints; toes nearly as long as the foot. The body of this species is white throughout; gibbous in the middle, with a strong fold below the central segment into which the lower portion is continually withdrawn ; the long narrow head projects into the usual curved proboscis, the ciliated dise being quite prone and running down nearly the whole length of the neck. The foot, composed of one or two stout joints, bears two short and slightly decurved toes; internal organs normal. Its manners are sluggish ; remaining long in the same spot, it twists and turns incessantly. The extremities exhibit great flexibility, while the - central area preserves a certain rigidity of form. Size about that of D. circinator. Habitat.—One example from a stream, Co. Waterford; several from a pond, Co. Wexford. Guascotr—A List of some of the Rotifera of Ireland. 61 Diglema revolvens, sp. nov. : [Pl. V. fig. 1.] Sp. Ch.—Body long, sunk in the middle ; head arching ; hood broad. The resemblance to D. musteda, Pl. xxx1m1. nie 4, of the “ Supple- ment,” cannot fail to strike the observer, but there are points of difference which cannot be ignored. The gastric glands, which are very conspicuous, are clear and round, and seated directly at the mouth of the large stomach, not pyriform in shape, or attached to it by long stalks as described of that species ; no dorsal antenna was visible; the trophi also differ much in shape, being broad at the top, the semicircular rami curving inward at the tips. The toes, which are always closely adpressed, are nearly three times as long, and the foot glands are remarkably conspicuous. I could see no eyes. Its manners are the very reverse of “fierce and active”’; it glided about with great deliberation, the head turned upward, now and then, and slowly revolved upon its long axis with protraded jaws as though in search of floating atoms. Length about , r o of an inch. Habitat.—Two specimens occurred from a stream, Co. Wexford. Diglena elnneata, Sp. Nov. (Pl. V. fig. 2.] Sp. Ch.—Body long, flat, very flexible, colour white ; head long, broadly truncate on frontal margin ; proboscis triangular ; foot long, narrow, two-jointed; toes short, straight, rod-like, slightly bent at the tips; no eyes. A very distinct species. Head thick, broad, dilated, with a prominent proboscis overhanging the ciliated face; trophi very long, the semicircular rami much projected, and always gaping; no eyes discernible; body long and unusually flat, of a clear white colour; internal organs normal; foot, two long, rounded, narrow joints, and two straight rod-like toes bent slightly down- wards at the tips; the foot glands lie within the body from whence their slender tubes descend to the toes. Its manners are peculiar; it firmly attaches the toes to the slide, stretches out the body to its utmost length, and thus remains for a time with 62 Scientific Proceedings, Royal Dublin Society. distended trophi working the cilia of the disc vigorously, then | rapidly contracting itself, it again flings out the body as before and the same process is repeated, and so on all round the circle, the toes still adhering to the same spot. Though I watched for a considerable time, I did not once see it-either grasp or swallow a single morsel of food. It seems a rare species—only a single example occurred. Length about =: of an inch. Habitat.—A. bog, Co. Wexford. Diglena rugosa, sp. nov. [Pl. V. fig. 3.] Sp. Ch.—Body cylindric, thick at the head, and tapering to the toes, wrinkled; foot long, thick, cylindric; toes short, broad, pointed, and abruptly decurved. ‘This species (if fully grown) is the smallest and most insigni- ficant member of the genus yet discovered, being scarcely half the length of D. caudatus, yet it presents some very striking characteristics. The colourless body is cylindric and vermiform, and tapers gradually from the head to the foot. This latter seems not to be marked off by the usual enfolding of the integument, but is a simple prolongation of the trunk, which terminates abruptly in a thick rounded end; the short, broad, and acutely pointed toes are set on near either side, and directed forward. There is a slight indenture in the middle of the back, and from this point the bodyis closely wrinkled down to the toes, and this wrinkled portion is continually shrunk upward with a jerk as though the creature were stung; the upper half is smooth and of firmer consistence ; the head is thick and round, the proboscis prominent; the ciliary disc quite ventral in position is continued down to near the middle of the body in a straight line; no eyes were apparent. I could not detect the form of the trophi, if they were present ; the stomach is long and narrow, and was filled with a granulated semifluid which -rotated rapidly. The contractile vesicle is of a long, narrow, oval shape, and lies upon the ventral floor. Its manners were very erratic; it made sudden darts from place to place, then stopped and twisted about into all sorts of contortions, as though greatly discontented with its surroundings. Habitat.—A. marsh drain, Co. Wexford. Guiascott—A List of some of the Rotifera of Ireland. 63. Distemma raptor, Gosse. [The Rotifera, vol. ii. p. 54, Pl. XIX. fig. 1.] One fine specimen from a pool which had been formerly exposed to the tide of the river Suir, Co. Waterford. Distemma platyceps (?), Gosse. (The Rotifera, Pl. XXXI. fig. 25, of “ Supplement.” | [Pl. V. fig. 4. ] Though I could see no eyes, this species seems to correspond closely with the description of the above. The head is very broad, . truncate, or even slightly crescentic on the frontal margin, from the centre of which a slender finger-like process was occasionally thrust out, but rapidly retracted again; besides this, there were one ventral and two lateral projections from the face, somewhat similar to what we find in D. raptor. The trophi are large and pear-shaped ; the semicircular rami always held open, and some- times thrust out with rapid motion to the very hilt, snapped, and withdrawn. Below the mastax, at either side, is a small globose bundle of black granules, presumably the gastric glands. This unusual black-spotted appearance of these organs was notable in the three examples which occurred. The rest of the body was identical with Mr. Gosse’s species, the enormous contractile vesicle forming a very prominent feature. I give a sketch of the species for comparison with the above- mentioned figure in the “Supplement.” Habitat.—A. marsh drain, Co. Wexford. LORICATE DIVISION. Mastigocerea scipio, Gosse. {The Rotifera, vol. 11. p. 61, Pl. XX. fig. 11.] A dead specimen, among the branches of Utricularia from a. drain; also a living specimen from a bog. Rare. Co. Wexford. Mastigocerea rattus (Ehrenberg). [The Rotifera, vol. i. p. 62, Pl. XX. fig. 9.] Habitat.—Very common in pond, bog, and stream, Cos. Waterford and Wexford. 64 Scientific Proceedings, Royal Dublin Society. Mastigocerea bicornis (Ehrenberg). [The Rotifera, vol. ii. p. 68, Pl. XX. fig. 5.] One example only occurred. ‘The toe was longer in proportion to the body than given in the figure of the Monograph, and ex- tremely flexible ; it was curled about like the lash of a whip. Habitat.—A. marsh drain, Co. Wexford. Mastigocerea bicristata (?%), Gosse. [The Rotifera, p. 35, Pl. XXXI. fig. 27, of the “ cnppleray sl [Pl. V. fig. 5.] If the outline of the above-named species is persistent in all details, I am hardly justified in supposing my species to be identical with it, as it differs in two prominent features, firstly, in the curve © of the toe, which is of greater length, and sweeps downward con- tinuous with the curve of the dorsal line, not recurved as in the figure given in the “Supplement” (there is also a slender substyle closely adpressed); and, 2ndly, in the termination of the double arine, which, instead of ending abruptly at the neck, sweep down along either side of the face, and from between them the ciliary dise is but slightly protruded. The tips of the trophi are not in- curved but produced into a long narrow pincer-like form. The general contour of the body approaches closely to that of IZ. cari- nata. Habitat—A. marsh drain exposed to high tides of the river Barrow, in which some examples attained to a considerable size : Co. Wexford. Mastigocerea brachydactyla, sp. nov. (Pl. VI. fig. 1.] Sp. Ch.—Body irregularly cone-shaped; head lumpish; toe style-like, short, straight, no substyles, no ridge. Allied to I. séylata, but broadest at-the head ; body an irregu- lar cone, puckered into constrictions, but not gibbous in the middle ; the toe straight and finely-pointed, only one-fourth the length of the body ; no substyles; gait wobbling. Habitat.—A. pond, Co. Wexford. Griascotr—A List of some of the Rotifera of Ireland. 65 Rattulus tigris, Miller. [The Rotifera, vol. ii. p. 65, Pl. XX. fig. 13.] A rare species. One fine example only occurred among the leaflets of Utricularia. Habitat.—A. marsh drain, Co. Wexford. Rattulus helminthodes, Gosse. [The Rotifera, vol. u. p. 65, Pl. XX. fig. 17.] Not frequent. In the few specimens which occurred the head was always of the same width as the body, but possibly in death there would be a slight contraction, more nearly approaching the figure in “ The Rotifera.” Habitat.—A marsh drain, Co. Wexford. Rattulus cimolius, Gosse. [The Rotifera, vol. ii. p. 66, Pl. XX. fig. 14.] One solitary example from a pond. The dark sacculated brain reached almost to the centre of the body. The auricles were occasionally thrust out. Habitat.— A. pond, Co. Wexford. Celopus porcellus, Gosse. [The Rotifera, vol. ii. p. 67, Pl. XX. fig. 18. ] This is a very common species, and occurs in both still and running waters amongst various aquatic plants and alge. The absence of styles at the base of the toes and the plump rounded outline of the body render it easy of recognition. Habitat.—Ponds and streams in the Cos. Waterford and Wexford. Celopus tenuior, Gosse. [The Rotifera, vol. ii. p. 68, Pl. XX. fig. 19.] By no means frequent. A few examples occurred. Habitat.—A. bog and a marsh drain, Co.Wexford ; one amongst bog-moss from Oo. Kerry. , SCIEN. PROC. R.D.S., VOL. VIII., PART I. F 66 Seientific Proceedings, Royal Dublin Society. Ceelopus brachyurus, Gosse. [The Rotifera, vol. ii. p. 69, Pl. XX. fig. 21.] This species is noticed as “rare.” I have found it in abun- dance amongst the leaves of Lemna trisulca and other small plants, in bogs, drains, and ponds. The very short, plump body, the absence of spinous projections towards the head, and the uninter- rupted curving line from the neck to the tip of the strongly- decurved toes defines the species well. Habitat.—Bogs and drains, Co. Wexford ; a marsh drain, Tramore, Co. Waterford. Celopus eavia, Gosse. [The Rotifera, vol. ii. p. 69, Pl. XX. fig. 22.] The short glimpse I had of this queer little creature did not give me an opportunity of naming it with decision, but the gibbous development behind and the position of the toes, which were placed. far inward on the ventral surface, lead me to believe that I have named it correctly. Habitat.—A. stream, Co. Waterford. Celopus minutus, Gosse. [The Rotifera, vol. ii. p. 70, Pl. XX. fig. 20.] This hump-back species was floating about quite dead, and stretched out toitsfull length. I could not detect the slender tubes from the head to the stomach mentioned by Mr. Gosse, but mstead a tangle of shapeless rods just above it, presumably the trophi collapsed by approaching decay ; the toes, two broad decurved blades ewactly alike in size, seemed to spring from the same point just inside the lorica. They were stretched out in a line with the body, the points diverging so as to form a moderate angle. Habitat.—A stream, Co. Wexiord. ‘Dinocharis pocillum, Ehrenberg. {The Rotifera, vol. ii. p. 71, Pl. XI. fig. 1.] Not uncommon. The long-spurred variety predominates. Habitat.—Pond and bogs, Cos* Waterford and Wexford. : agi ie ag ee Giascotr—A List of some of the Rotifera of Ireland. 67 Dinocharis tetractis, Ehrenberg. [The Rotifera, vol. ii. p. 72, Pl. XXI. fig. 2.] This species is rare in comparison to its congener D. pocillum ; in all cases the spurs -were well developed ; the spine between tlie toes of course being absent. Habitat.—A. bog, Co. Wexford. Searidium longicaudum, Ehrenberg. [The Rotifera, vol. 1. p. 73, Pl. XXI. fig. 5. | Noticed as “rare,” I have met with it in great profusion in bogs. Its movements are quiet and deliberate, the long toes are trailed after it, held close together like a tail; the large crimson eye cer- tainly appeared to be seated upon the mastax and partook of all its movements. It lives well in captivity, and outlasted all other species in the tank. Habitat.—Bogs, Co. Wexford. Stephanops lamellaris, Ehrenberg. [The Rotifera, vol. 11. p. 75, Pl. XXI. fig. 7.] Some very fine specimens occurred among waterweed from a marsh drain; in some instances the three posterior spines of the lorica were projected upward ata considerable angle from the body, which gave it quite a bristled appearance. Can it be that they are raised or lowered at the will of the animal? The width of the head and the body were always much broader than given in the figure referred to. From the same dip appeared some others resembling S. muticus, apparently without the posterior spines, but I had not an opportunity of watching them to ascertain this point to a certainty. Habitat.—A. marsh drain, Co. Wexford; a cattle-pond, Co. Waterford. Stephanops unisetatus, Collins. [The Rotifera, vol. ii. p. 76, Pl. X XT. fig. 8.] Not frequent. Habitat.—Ponds and bogs, Cos. Waterford and Wexford. F2 68 Scientific Proceedings, Royal Dublin Society. Diaschiza valga, Gosse. [The Rotifera, vol. u. p. 77, Pl. XXII. fig. 12.1] This species is fairly common. I rely upon the more rounded and tapering form of the toes as the distinguishing feature between it and D. Hoodii which it so closely resembles ; the cleft down the back of the lorica is always apparent as it turns round a stem or filament. Habitat.—-Ponds and bogs, Co. Wexford; a pond, Co. Water- ford. Diaschiza exigua, Gosse. [The Rotifera, vol. ii. p. 78, Pl. XXII. fig. 13. ] This tiny little creature was grubbing in a small heap of flock and by turns exhibited all sides to me. Viewed laterally the body was high, the toes much decurved; viewed dorsally it was very narrow and much pinched in toward the foot; the head was large in proportion ; I could not detect an eye. Rare. Habitat.—A. marsh-drain, Co. Wexford. Diaschiza Hoodii, Gosse. [The Rotifera, vol. 11. p. 79, Pl. XXII. fig. 15. | This species is noticed as ‘‘ rare” by Mr. Gosse. I have found it in great abundance and of various sizes in all fresh waters ; not unlike Notommata lacinulata in general outline it is at once distinguishable by the deep cleft down the back which can be best seen as it creeps round the stems of small plants and alge ; the body is also much more depressed than that species. The margins of the lorica behind are most difficult to discern, as they are laid flat upon the body, which protrudes beyond them, thus hiding their outline. Habitat.—Ponds and streams, Cos. Waterford and Wexford. Diaschiza pzta, Gosse. [The Rotifera, vol. ii. p. 79, Pl. XXII. fig. 11.] Of frequent occurrence. The very large rose-red eye, extending almost wholly across the neck (when seen) denotes the species unmistakably. The toes, in all examples, were shorter, stouter, Giascorr—A List of some of the Rotifera of Ireland. 69 and much less recurved than represented in the figure of the Monograph. The little globular ball noticed by Mr. Gosse was not present, but I have seen it-in Diaschiza semi-aperta, a mere bubble which floated away. | | Habitat.—Amongst algze in ponds and bogs, Co. Waterford. Diaschiza semiaperta, Gosse. [The Rotifera, vol. ii. p. 80, Pl. XXII. fig. 10.] Not so frequent as the foregoing species. It was only after long and careful watching that I was enabled to satisfy myself of this creature’s identity ; for, although agreeing in most particulars with the figure and description in the Monograph, the gape at the lower end of the dorsal cleft was not apparent. This I found to be due to the fact that it was as frequently closed as open. If a good vertical view be obtained, the strange manner of the creature will show this clearly. ‘These manners are so highly characteristic that I wonder they have not received more definite notice: when feeding it incessantly withdraws the foot with a jerk, throwing _ back the long pointed toes on either side of the body, at the same time burying the head far back upon the neck within the lorica, thus assuming an almost spherical shape. When in this position the plates of the lorica are drawn apart to their fullest extent, and a wide gap is seen throughout their entire length; then, as the toes are brought down, and the head again protruded, they are drawn together, and the temporary aperture is closed more or less entirely according to the varying undulations of the body. This practice has, I believe, something to do with the digestive process, for it always occurs when the animal is feeding, and is followed by various evolutions of the internal organs. Habitat.—Bogs, streams, and ponds in Co. Wexford ; bog- moss, Co. Kerry ; a pond, Co. Waterford. Salpina mucronata, Ehrenberg. [The Rotifera, vol. 11. p. 83, Pl. XXII. fig. 1.] A rare species. Habitat.—A pond, a marsh-drain, Co. Wexford. In bog-moss, Co. Kerry. 70 Scientific Proceedings, Royal Dublin Society. Salpina spinigera, Ehrenberg. [The Rotifera, vol. ii. p. 84, Pl. XXII. fig. 2.] A few examples. ‘The lumbar spine was well-developed. Habitat.—A. pond, Cos. Waterford and Wexford. Salpina brevispina, Ehrenberg. [The Rotifera, vol. ii. p. 84, Pl. XXIT. fig. 4.] Very common. Variable in the length of the body, and also in the width of the dorsal cleft, which latter depends upon the internal condition. The stippled markings of the lorica are best seen in dead specimens. Habitat.—A. pond, Cos. Waterford and Wexford. Euchlanis dilatata, Hhrenberg. [The Rotifera, vol. ii. p. 90, Pl. XXIII. fig. 5.] Very common. The parallel lines of the dorsal and ventral flanges, and the pinched appearance of the dorsal posterior notch, mark the species at once. I could detect no seta on the foot. The large amber-coloured stomach, studded with clear globules, is ever rolled from side to side with rhythmical precision. Habitat.—Ponds and streams, Cos. Waterford and Wexford. Euchlanis macrura, Ehrenberg. [The Rotifera, vol. ii. p. 91, Pl. XXIII. fig. 6.] This was a very small specimen, possibly not fully grown. It was dying. The foot was retracted; only half of the toes were visible beyond the lorica. My attention was immediately arrested by the semicircle of very long and coarse cilia revolving at either side of the head, just at the juncture of the lorica. ‘The body was - more depressed than than that of Z. dilatata, the lorica not pinched in, above the foot, but the flanges were almost identical in shape with that species. A. single specimen among the branchlets of Vaucheria. Habitat.—A. stream, Co. Carlow. a bh L q ; } [ p Guascotr—A List of some of the Rotifera of Ireland. 71 Euchlanis triquetra, Ehrenberg. [The Rotifera, vol. i. p. 91, Pl. XXIII. fig. 4.] This splendid species is fairly frequent, the dorsal crest well developed ; the glass-like clearness of the lorica, and the creature’s gentle, quiet way give ample opportuuity to study the internal structure. ‘The muscular bands at the sides of the body, the lateral canals with their vibratile tags, and the digestive system, are all clearly visible. Habitat.—Ponds, drains and streams, Co. Wexford; a stream, Co. Waterford. Euehlanis deflexa, Gosse. [The Rotifera, vol. ii. p. 92, Pl. XXIV. fig. 1.] The formation of the head of this species, which is peculiar and differs much from its congeners, gives it a very definite character. But a few examples occurred. Habitat—Amongst alge in a stream; in a pond, Co. Wex- ford ; a stream, Co. Waterford. Euehlania pyriformis, Gosse.' [The Rotifera, vol. ii. p. 93, Pl. XXIII. fig. 2.] Very scarce. Of singular beauty, the lateral expansions of the lorica being remarkably thin and clear, and the bend of the upper flanges gives a further expression of their tenuity. Habitat.—A bog, a stream, Co. Wexford. Cathypna Tuna (Ehrenberg). [The Rotifera, vol. ii. p. 94, Pl. XXIV. fig. 4.] Common everywhere. Cathypna rusticula, Gosse. [The Rotifera, vol. 1. p. 95, Pl. XXIV. fig. 6.] IT have little hesitation in applying this name to the species in question, although the toes are much more slender and somewhat longer than given in the figure referred to. The narrow and simple frontal aperture is identical with it, as is also the shape of 72 Scientific Proceedings, Royal Dublin Society. the body, the very transparent lorica, and the rose-pink hue of the large eye; the very conspicuous trophi are of an orange brown colour, slightly tinted with pink from their close proximity to the eye. Habitat.—Bogs, drains, streams, Cos. Waterford and Wexford. Distyla flexilis, Gosse. [The Rotifera, vol. ii. p. 97, Pl. XXIV. fig. 7.] This species abounded amongst Conferve growing on the sides of a water-tub placed under a pump in the month of Sep- tember. Earlier in the summer not a single specimen occurred from the same place. The longitudinal flutings of the very flexible lorica were strongly marked ; the eye was conspicuous. Its manners were always slow, creeping lazily among the filaments. Habitat.— Among Conferve in a water-tub, Co. Waterford; a bog, Co. Wexford. Monostyla lunaris, Ehrenberg. [The Rotifera, vol. ii. p. 98, Pl. XXV. fig. 2.] Very common. | Habitat.—In all waters, Cos. Waterford, Carlow, Wexford, and Kerry. Monostyla cornuta, Ehrenberg. [The Rotifera, vol. ii. p. 98, Pl. XXV. fig. 1.] Common. Cos. Wexford, and Waterford. Monostyla Lordii, Gosse. [The Rotifera, vol. 11. p. 99, Pl. XXYV. fig. 5. | This is a fairly common species. ‘The coarse tesselation and crumpled appearance of the lorica affords a satisfactory dis- tinction from its congeners, but invariably the square excavation behind was lacking, a rounded outline taking its place. This variation of form is noticed by Mr. Gosse, who suggests that it may afford sufficient ground for specific rank. Habitat.—Ponds and bogs, Co. Wexford; Vaucheria, from a stream, Co. Carlow. Guascorr—A List of some of the Rotifera of Ireland. 73 Monostyla quadridentata, Ehrenberg. [The Rotifera, vol. ii. p. 100, Pl. XXYV. fig. 3.] The longitudinal striations of the lorica, and its unusual flexibility, together with the V-shaped gape of the frontal margin, denote the species. JI have seen it twice. In the first example, which was dead, the horns were not visible; in the second, they were partially protruded and analy withdrawn while - under observation. Habitat.—Among Wyriophyllum in a bog, Co. Wexford. Colurus deflexus, Ehrenberg. [The Rotifera, vol. ii. p. 102, Pl. XX VI. fig. 1.] Several examples of this rare species occurred in bogs and ditches, and in one locality, a deep drain of a marsh by the sea- side, it was quite frequent. The rounded excavation behind, the much greater plumpness of the body, and its shaded yellow tint form considerable differences between it and C. deflegus ; the ventral cleft seemed always to terminate upon the breast. Its manners were slow and heavy, exactly the reverse of its ea relative. Habitat.—Ponds and ditches, Co. Wexford; a marsh drain Tramore, Co. Waterford; among the stems of Vaucheria, Co. Carlow. Colurus obtusus, Gosse. [The Rotifera, vol. ii. p. 108, Pl. XXVL. fig. 3.] Fairly common. Habitat.—Ponds a streams, Cos. Waterford, Wexford, and Carlow. Colurus caudatus, Ehrenberg. [The Rotifera, vol. i. p. 104, Pl. XXVI. fig. 6.] Hasily recognized by the long toes, which are frequently thrown apart. Not uncommon. Habitat.—Ponds, bogs, and streams, Cos. Waterford, Wexford, and Kerry. 7 74 Scientific Proceedings, Royal Dublin Society. Colurus pachypodus,’ sp. nov. (Pl. VI. fig. 2.] Sp. Oh.—Lorica slants in a straight line from above the foot to the middle of the breast; foot very stout, of several bulging — joints ; toe single, style-like, nearly as long as the foot. Not unlike C. caudatus, when viewed laterally, and of the same size, but the body is deepest in the centre, to which the margin of the lorica sweeps down in a straight line from above the foot. The foot is thick and long, and composed of several bulging joints. The toe is single, style-like, and almost of equal length with the foot. The hood sweeps down in a bold curve to the breast. Habitat.—A tide-pool, River Barrow, Co. Wexford. Colurus tesselatus, sp. nov. [Pl. VI. fig. 3.] Sp. Oh.—Lorica tesselated, raised at the sutures; no dorsal cleft, but a wide curved excavation behind; ventral cleft gaping ; foot stout ; toes spread wide apart. About the same size as O. obtusus ; the lorica of this pretty little species is coarsely tesselated, no cleft behind, but a wide open curving notch ; body deepest toward the head, ventral cleft gaping. The foot is short and stout; the toes, which are almost of equal length with the foot, are always held wide apart. A rare species ; four examples occurred. Habitat.—Bogs, Co. Wexford. Metopidia lepadelia, Khrenberg. (The Rotifera, vol. ii. p. 106, Pl. XXV. fig. 6. ] Habitat.—Common everywhere. Metopidia solidus, Gosse. [The Rotifera, vol. ii. p. 106, Pl. XXYV. fig. 11.] Very rare, a solitary example. Habitat.—A. stream, Co, Wexford. 1 raxus, thick ; wovs, foot. Guascorr—A List of some of the Rotifera of Ireland. 7d Metopidia oxysternum, Gosse. [The Rotifera, vol. i. p. 107, Pl. XXV. fig. 8. ] The dorsal ridge was much higher than in the figure quoted above, but the sternum was not prominent; very rare, only one example occurred. Habitat.—A stream, Co. Waterford; a pond, Co. Wexford. Metopidia triptera, Ehrenberg. [The Rotifera, vol. 11. p. 108, Pl. XXV. fig. 7.] This very interesting form is said to be rare. I have found it frequently in all fresh waters. | Habitat.—Ponds, bogs, and streams, Cos. Kerry, Waterford, Wexford. Metopidia bractea (Ehrenberg). [The Rotifera, vol. i. p. 109]. The largest of the genus. Very common. I have never seen the eyes. Habitat.—In all fresh waters. Metopidia ovalis (?), Ehrenberg. [The Rotifera, Pl. XXXIV. fig. 2, of “ Supplement.” | This not uncommon species answers very closely to HKhrenberg’s figure and description referred to above. It has occurred in several localities. ‘The depressed and oval shape of the lorica, narrowed in front, the dorsal plate truncate at both ends, its margin not excised, are identical, but the frontal excision of the ventral plate is deeply crescent-shaped, not square. The excision behind for the protrusion of the foot is square, not round. ‘The hood is very prominent. Habitat.—Ponds and pools, Co. Wexford. Monura colurus, Ehrenberg. [The Rotifera, vol. ii. p. 109, Pl. XX VI. fig. 7. ] This species is said to be exclusively marine, but I have found it twice in fresh water, among confervoid growth, on an old leaf which had lain in a well; the outstretched hook, the unusual 76 Scientific Proceedings, Royal Dublin Society. length of the body from head to foot, the rounded ends of the lorica, both behind and before, and the long, single, style-like toe correspond exactly with the figure above mentioned. Habitat.—A well, tide-pools, Co. Wexford; a small pond, formerly exposed to the tide, Blenheim, Co. Waterford. Cochleare turbo, Gosse. [The Rotifera, vol. ii. p. 111, Pl. XXVI. fig. 10.] This was evidently avery well grown specimen, the body much more plump and rounded than in the figure referred to, especially over the dorsalarea. I did not perceive it to be “‘ three-sided ”’ but rather of an interrupted rounded outline somewhat flattened on the ventral side. ‘There were two conspicuous globose gastric glands seated near the mouth of the stomach, a large ovary beneath it; the red eye was placed upon the lower end of a semi-globose brain, The face was oblique and just as described in the Monograph, the two lower half-cones being considerably protruded, which produced | a chin-like appearance. The toes were occasionally divided, but more usually pressed together, and upon their points the creature balanced itself as upon a pivot, and swung about in an aimless manner. Habitat.—A marsh drain, Co. Wexford. Pterodina patina, Ehrenberg. [The Rotifera, vol. ii. p. 112, Pl. XXVI. fig. 11.] Frequent. The borders of the dorsal plate widely stippled. Habitat.—Ponds, Cos. Waterford and Wexford. Pterodina valvata, Hudson. [The Rotifera, vol. ii. p. 118, Pl. XXVI. fig. 13.] Rather scarce. Lorica so thin as to be hardly perceptible. Habitat.—Ponds, Co. Wexford. Pterodina clypeata, Ehrenberg. [The Rotifera, vol. ii. p. 114, Pl. XXVI. fig. 14.] This species, agreeing closely with the figure given in the Ro- tifera, is somewhat broader, and not so distinctly truncate behind ; Giascorr—A List of some of the Rotifera of Ireland. ae the margins of the frontal aperture both on the dorsal and ventral sides are exactly similar to the figure referred to. The foliaceous expansions reach to the rounded edges of the lorica and there spread upward; they are always of a dark gray-brown hue. I have seen the sides of the lorica bent downward in some instances, and bent.acutely upward like a pair of wings at other times, when the progress was much like the flight of a bird on a windy day. It is sald to be exclusively marine. I have found it occasionally in bog-waters. | Habitat.—A. bog, a marsh drain exposed to tides, Co. Wexford ; a cattle-pond, formerly exposed to tides, Blenheim, Co. Water- ford. Brachionus urceolaris, Ehrenberg. [The Rotifera, vol. 11. p. 118, Pl. XX VII. fig. 6. ] Numbers of this handsome species occurred in the Cos. Water- ford and Wexford. Habitat.—Ponds. Brachionus rubens (?), Khrenberg. [The Rotifera, vol. ii. p. 119, Pl. XX VII. fig. 5.] With the exception of being much smaller than the foregoing species, the spines on the frontal margin being longer and less bent, the mastax placed more toward the centre of the body, there was little distinction between them. Habitat.—A pond, Co. Waterford. Brachionus Bakeri, Ehrenberg. {The Rotifera, vol. ii. p. 120, Pl. XX VII. fig. 8.| In this species the spines both before and behind are much more developed than in the figure given in the Monograph, and not only is the lorica facetted, but invariably stippled all over ; very handsome and of frequent occurrence. Habitat.—Ponds, Cos. Waterford and Wexford. Anurza serrulata, Ehrenberg. [The Rotifera, vol. ii. p. 124, Pl. XXIX. fig. 8.] Common. | ' Habitat.—Bogs, Co. Wexford. 78 Scientific Proceedings, Royal Dublin Society. Anurza brevispina, var. Gosse. [The Rotifera, vol. ii. p. 124, Pl. XXIX. fig. 5.] Common. Habitat.—In stagnant ponds, Co. Waterford. Notholea thalassia, Gosse. [The Rotifera, vol. 11. p. 127, Pl. XXIX. fig. 2.] Said to be exclusively marine. I have found two specimens among the branchlets of Vaucheria in a small cattle pond, at one time exposed to tides from the river Suir. The water was per- fectly fresh, the pond being fed from a spring. They were fine healthy specimens. Their manners were deliberate, and they continually revolved upon their transverse axis, head backwards. It has also occurred from a mountain stream, but examples from tidal pools always displayed much greater robustness, and more vigour and rapidity of movement. Habitat.—A. cattle-pond, a tide-pool, Co. Waterford ; a stream, a tide-pool, Co. Wexford. | [Pl. VI. fig. 4. ] Three of these singular-looking creatures were attached to the body of a young Nats. ‘The head tapers to a sharp beak which was buried in the soft skin of the worm, upon whose juices they apparently feed. So wide a departure from the usual structure of the mouth of.a Rotifer raises a doubt whether they may be truly classed among the group to which in other respects they seem to bear close affinity. The body is white, smooth, gibbous in the middle, and, curving downwards, tapers at both extremities. A black brain or eye (?) is placed over the mouth of the stomach, which latter occupies almost the entire cavity of the body, and was filled with a light gray granulated substance. Below it, and close to the foot, is a large clear vesicle, probably the contractile vesicle. The foot, one large bulbose joint, bears two slightly decurved blade-like toes of moderate length. There is no trace of mastax or trophi. The creature was singularly stiff in movement, and the foot was evidently non-retractile. Not measured, but about the size of Notommata cyrtopus. Habitat.—A pond, Co. Wexford, August. Guascott—A List of some of the Rotifera of Ireland. (hes The following additional species were found in the summer of 1892 :— Notops forcipita, sp. nov. [Pl. VI. fig 5. ] Sp. Ch.—Body stout; dorsum rounded, ventral surface flat ; head bent downward ; disc an obtuse cone, ciliary wreath simple ; eyes two; trophi forcipate ; foot ventral, withdrawn ; toes two. This species resembles VV. hyptopus both in general outline and in internal structure, but is of much smaller size and is at once: distinguished by the possession of two tiny dark red eyes, which are placed close together in a little socket upon the surface of, and almost in the centre of the disc,.which bulges forward; the great size of the forcipate trophi is also remarkable; they occupy almost half the entire length of the body, their tips approaching the margin of the dise toward the ventral side. The head is con- tinually withdrawn into a stiff fold of the integument, which is deeply and widely scolloped on the margin, these gaps being then closed and their edges brought together. There is a depression at either side of the rounded dorsum from whence the body again bulges out. The foot is quite ventral in position and nearly always withdrawn ; the toes are moderately long, widest from the vertical aspect, straight, and pointed; they are invariably directed forward under the body. Its manners are lively, busily nibbling at everything that comes in its way. Length from 5}, to 74; of an inch. Habitat.—Several from a bog, Co. Wexford. Notommata lucens, sp. nov. [Pl. VI. fig. 6.] Sp. Ch.—Body cylindric, tapering from a broad head to the foot, hyaline; foot conspicuous, of one or two joints; toes slender, pointed, adpressed; head wide, auricles small; brain large; eye conspicuous; trophi forcipate, very large ; disc prone. This very attractive species is at once distinguished by the enormous size of the head and trophi, which together measure fully half its entire length, and from behind which the body » rapidly diminishes to the foot. The disc is quite prone, and 80 Scientific Proceedings, Royal Dublin Society. descends to a considerable distance on the ventral surface; the broad pale yellow brain descends to, and apparently rests upon the forepart of the mastax, and at its extremity are three or four dark grey round cells, upon which is seated anteriorly a lovely rose-red globate eye. A pair of small round auricles are occasion- ally everted almost on a line with the frontal margin. The enormous forcipate trophi spring from the middle of the body and are peculiarly weak and slender in proportion to their length. The stomach is long and narrow, reaching close to the foot; no other organs were visible. ‘The foot, composed of one or two (?) joints is conspicuous and rather flat; the toes, a trifle longer than the foot, are slender, pointed, slightly decurved, and habitually adpressed. Its manners are slow and methodical; it adhered firmly by the toes to a certain spot, and from thence twisted about in all directions, working the cilia vigorously for over an hour; some- times. it lifted the head up, and revolved around, everting the small auricles, then again bent downward. I noticed that the trophi were hardly ever brought into use, and seemed very feeble. In the position of the dise this species closely resembles JV. saccigera, but the shape and size of the head, the conspicuous foot, and slender tapered and pointed toes, are widely different. Length 4, of an inch. Habitat—Amongst Callitrichia verna, from a pond, Oo. Wexford. Notommata gigantea, sp. nov. [Pl. VII. fig. 1.] Sp. Ch.—Body cylindric, stout; head very small, truncate ; no auricles; brain small; eye minute; trophi very small, forci- pate ; foot saccate; toes minute; stomach enormous; ovary very large; contractile vesicle small, globate; tail conspicuous. This is one of the largest of the genus I have yet seen. Its form is a stout cylinder, narrowed at either end. The integu- ment, in fully matured examples, of great transparency, and puffed out from the viscera to a considerable distance, thus affording an excellent view of the internal organs, the minutest details of which can be studied with ease. The head is remarkably small, the dise Guascorr—A List of some of the Rotifera of Ireland. 81 truncate. A small but clearly-defined brain depends from the margin, bearing a tiny red eye-speck a little below the middle. The trophi, situated close to the disc, are short, and describe a square outline. A short fulerum supports two stout, solid-looking rami, upon which the unci appear to be soldered; the manubria are longer than the fulcrum, and curl inward at the base; their action is slow and deliberate. From either side of the upper part - of the head a tiny granulated bag is suspended by a thread; these may be the salivary glands, but their mode of attachment is pecu- liar; delicate muscular bands are visible running down close to the body-wall, to which they are fastened at intervals by slender threads. ‘The vascular system is represented by lateral canals of unequal dimensions, and apparently without tags; they curl in- ward at about two-thirds distance from the head to the small con- tractile vescicle, which lies hidden between the ‘stomach and the ovary. (I found it in a specimen subject to lateral pressure.) From this they seem again to emerge, and run down the centre of the great saccate foot to the toes. A short cesophagus leads to an enormous sacculated alimentary chamber, of a yellow tint, which extends throughout the whole length of the body, and on its shoulders are seated two large pear-shaped, semi-transparent, and nucleated gastric glands, which are attached by their narrow end to the body-wall. The ovary is also of enormous size, with three or four ova in an advanced stage of development. The foot is thick and short, and almost entirely covered “above by a clear finger-like tail. The toes are very minute, sharply pointed, and placed close together in the centre of, and on the lowest level of, the foot. The foot glands are well developed. I found numbers of this fine species within the eggs of the water-snails, upon which they feed, in company with Furcularia micropus (?), and the eggs and the young of both species in every stage surrounded them. As may be anticipated from the habitat, its manners are sluggish, ever rolling about and inverting the extremities to the distraction of the student. I had the good fortune to catch a wanderer between the slide and the cover-glass, which enabled me to study it at leisure. When the species is only half grown it is hardly recognizable, and looks like a shapeless lump of wrinkled SCIEN. PROC. R.D.s., Vol. VIII., PART I. G 82 Scientific Proceedings, Royal Dublin Society. and sometimes mottled skin, revolving and twisting incessantly. In one of the eggs upon which they were feeding I noticed two small apertures, by which no doubt they had epediell an cnn The length in fret individuals varies from =; to 35 of an inch ; the width from ,5 to ~1, of aninch. | Habitat.—In egg-clusters of water-snails. A pond, Co. Wex- ford. Furcularia micropus (?), Gosse. [The Rotifera, vol. 11. p. 46. ] LPlD VIE. fies 2.) Sp. Ch.—Body cylindric, larviform ; head truncate; brain ample, with small red eye-speck near the lower end ; trophi forei- pate, broad ; foot broad; toes two, small, cone-shaped. Owing to its extreme flexibility and unceasing contortions the shape of the creature defies description. It seemed to delight in giving itself temporary waists in impossible places all along the line, and the shape portrayed one moment was wrong the next. "he head is not large, and generally truncate on the margin, but sometimes it is projected forward in the middle, and bent down until the disc is almost prone. There is an ample brain, within which is seated a tiny red eye-speck toward the lower end. The trophi are broad and very conspicuous ; they are situated rather low in the neck, but are brought to the margin by the retraction of the’ head when required. ‘The stomach is large, the contents thickly nucleated. The foot is broad, and rather flat, and indistinctly marked off from the body. The foot glands are well developed. The toes—two small cones—are set close together and diverge. I noticed that at the extremities of the frontal margin there was an appearance of auricles, but a closer scrutiny proved it to be delusive. Iam not certain that the coronal dise was a complete circle; occasionally it appeared to break off ab- ruptly, and run down in a V-shaped slit on the ventral side. The sketch giving a lateral view, represents the animal in its most habitual attitude when feeding, with sunken neck, and head bent backward. When swimming in open space it shrinks up the body into numberless close-set folds, squares the frontal margin, and loses all trace of its former appearance as it wags itself merrily along. Guascorr—A List of some of the Rotifera of Ireland. 83 I found numbers of this species and their eggs within the eggs of water-snails, where they ceaselessly wriggled and twisted about, in company with Votommata gigantea ; and, notwithstanding some points of difference, I think it may yet prove to be identical with Furcularia micropus. The eye-speck, though present in them all, is so small that it might readily be overlooked, and now and then the shape was assumed which is represented in Pl. XIX. fig. 12, in the Monograph. Length variable, from ;4; to 3); of an inch. Habitat.—Within the eggs of water-snails. A pond, Co. Wexford. Diglena Hudsoni, sp. nov. [Pl. VII. fig. 3.] Sp. Ch.—Body cylindric, ventral surface flat, gibbous behind, deeply fluted; head rather broad; hood broad ; trophi forcipate; foot ventral; toes of moderate length, divergent, blade-shaped ; no eyes. When I first saw this creature it was sitting up on end; the head and neck withdrawn into the trunk, and looked so like one of the genus Rotifer that I nearly passed it by ; it began to move, however, when I quickly perceived my mistake. The body, which is remarkably soft and flexible, is deeply fluted longitudinally, rises abruptly behind, and falls into many transverse folds and wrinkles as it descends gradually to a flat and attenuated neck. The head, which slightly dilates, is furnished with a broad hood, in place of the usual pointed proboscis; a good-sized brain descends to the neck. No eyes were visible. The forcipate trophi are remarkably small and simple, and placed low in the neck. The integument was so overlaid with a fine sediment that the internal organs could be but dimly seen ; they appeared to be normal. The short foot is quite ventral in position, and habi- tually withdrawn; the toes are of moderate length, blade-shaped, pointed, and slightly decurved; united at the base they spring widely apart, seem to be immovable, and take no part in locomo- tion. Its manners are most peculiar, sluggish, and vermiform ; it ever makes fruitless efforts to advance by alternate elongation and contraction of the body, and at every movement the whole viscera are forced violently toward the head; at rare intervals it G2 84 Scientific Proceedings, Royal Dublin Society. abandons the crawling motion, and glides onward by means of the cilia, then again resumes it; occasionally it sits up on end, sinks the head and neck into the trunk, and relapses into the quiescent state in which I first found it. ‘The whole animal is of a pale amber-colour. Length about = of an inch, but capable of con- siderable extension. Habitat.—Among Cladophora flavescens, from a tide-pool, river Barrow, Co. Wexford. Diglenma dromius, sp. nov. [Pl. VII. fig. 4.] Sp. Ch.—Body sub-cylindric, long, slender, and slightly gib- bous in the middle; neck long; head long, broadest above, with a tapered proboscis projecting in front; trophi forcipate, broad, and short; foot of one or more (?) joints; toes long, slender, straight; brain ample, narrowing to the extremity; no eyes. This very slender and graceful species is the fleetest of its brethren, and as it glides swiftly and evenly along with head laid flat, the tapered proboscis projected in front, it darts it forth to the right and left with extraordinary rapidity. The long straight toes are finely pointed, and slightly decurved at the tips. They are set close together, and are held a little apart, and when the animal turns are flung wide asunder. A long and well-defined brain depends from the frontal margin; but I could discern no eyes. Its manners amusingly resemble those of some of the predatory beetles, and when alarmed it dashes into cover and there remains motionless until the fancied danger is past. Length, including the toes, =, of an inch. Habitat.—A. pond, Co. Wexford. Diglena aquila, Gosse. [The Rotifera. The Supplement, p. 28, Pl. XXXTI., fig. 20.] In every point similar to the above figure. There was a bunch of black globules situated over the forepart of the stomach ; a large and distinct brain was visible, but no eye. Habitat.—On a submerged leaf in a pond, Co. Wexford. Guascorr—A List of some of the Rotifera of Ireland. 85 Diglena uncinata, Milne. [The Rotifera. The Supplement, p. 30, Pl. XXXIII., fig. 13.) | In this species the very remarkable longitudinal lines dividing the foot into three equal parts strikes the eye at once, and the thickness of the base of the toes is also unusual. The long styles, projecting from under the front of the hood, were swept apart in a curve to either side by pressure when the head was laid on the slide; occasionally the head was raised and flung forward with a jerk and a snap of the jaws. Habitat.—Among Utricularia. A marsh drain, Co. Wexford. EXPLANATION OF PLATES. Prats III. Fia 1. Rotifer phaleratus. 2. Microcodon robustus. 2a. a oe side view. 3. Wotops quadrangularis. 4. Notommata volitans. Ade ss Ns side view. 5. Notommata cylindriformis. 6. Notommata larviformis. 7. Notommata rubra. 7a. bP) 2? 76. ) a side view. Prats IY. F IG. 1. Proales inflata. 2. Furcularia semisetifera. 2a. is : side view. 3. Lurcularia megalocephala. 3a. Kh we head, disc drawn down. 30. is ae », irontal margin. 4. Furcularia rigida. 4a. a » dorsal view. 5. Hosphora striata. 6. Diglena inflata. 86 Scientific Proceedings, Royal Dublin Society. Prate V. Fie. 1. Diglena revolvens. 1G top 9 side view. 2. Diglena elongata. Qa; es, se side view. 3. Diglena rugosa. 3a. ” ” 4. Distemma platyceps (?), Gosse. 4a. “) e side view. 5. Mastigocerca bicristata (?), Gosse Prate VI. Fic. 1. Mastigocerca brachydactyla. 2. Colurus pachypodus. 3. Colurus tesselatus. Soa ne side view. 4. Unknown. ‘4a. oS side view. ADDITIONS. 5. Notops forcipata. 6. Notommata lucens. 6a. on “ side view. Prats VII. Fie. 1. Notommata gigantea, ventral surface, flattened. la. ee He side view. 10. A dorsal view showing gastric glands. 2. Furcularia micropus, Gosse (?). 2a. is 9 side view. 26. a Be when swimming, with body shrunk up to half ; its length. 3. Diglena Hudsont, 4. Diglena dromius. 4a. ;, a side view. ie VII. ON PITCHSTONE AND ANDESITE FROM TERTIARY DYKES IN DONEGAL. By PROFESSOR W. J. SOLLAS, LL.D., D.Sc., F.R.S. [Read DecemBeEr 21; Received for publication DrecemBEr 22, 1892; Published Marcu 26, 1893.] So far back as 1857 Dr. Haughton communicated to the Geo- logical Society of Dublin’ an account of some pitchstone dykes, which traverse the granite of Barnesmore Gap, Co. Donegal. Subsequently they were described by Mr. Kilroe of the Geological Survey,’ who speaks of them as numerous and as graduating from dark bluish grey glossy pitchstone to light pink or flesh-coloured compact felstone. ‘The specimens which furnished the material for Dr. Haughton’s investigations, which include a complete chemical analysis, are preserved in the Collection of the Geological Museum of Trinity College, and my attention being attracted by their remarkably fresh appearance, I had thin slices prepared from them, and these when examined under the microscope reveal a singularly close resemblance in structure and mineral composition to the celebrated pitchstones of Arran. Complete justification is thus afforded for the procedure of Sir Archibald Geikie, who has included these dykes of Donegal in his map of the Tertiary Volcanic areas of the British Isles.* Glossy black and vesicular in hand specimens, with occasional phenocrysts of sanidine and quartz, the pitchstone presents under the microscope (fig. 1) a colourless or brownish glassy base crowded with long slender needles of pyroxene, minute stellate crystallites 1 Journal of the Geological Society of Dublin, vol. viz., p- 196. 2 Memoir to accompany Sheet 24 of H.M. Geological Survey, 1888. 8 Transactions of the Royal Society of Edinburgh, vol. xxxv., p. 184, 1889, 88 Scientific Proceedings, Royal Dublin Society. and dust-like globulites; magnetite occurs in addition, sparingly dispersed in minute grains and octahedra. The pyroxene needles are incomplete hollow prisms, filled with glass; their edges are rarely continuous straight lines, but jagged with projec- tions which frequently develope on each side into secondary prisms, proceeding from the shaft, like the barbs of a feather, and these by continued growth tend to pass into an extended plate. The angle of extinction measured against the length of the primary prisms varies from 27° to 43°. The angle of the prism, owing to the minuteness and incompleteness of the crystals, is difficult to measure, but such observations as I could make sug- gested that of augite rather than hornblende. The colour is faint green, and there is no dichroism. The glass immediately Fie. 1.—Pyroxene and stellate crystallites in a glassy base. surrounding the pyroxene is usually clear and structureless, but at a very little distance away it becomes dark with granules, which under a high magnification are resolved into clusters of stellate crystaliites, wonderfully similar to the minute asters of a sponge such as Astropeplus or Thenea. The rays of these asters vary in number from two to ten or more, and are generally without action on polarized light; when, as in some instances is the case, they are birefringent, extinction is parallel. Some- times within a cluster of asters is seen a clear central space, and lying in this a comparatively large aster, with secondary raylets ; Sottas—On Pitchstone and Andesite. 89 occasionally the rays develope into minute lozenge-shaped plates. From these bodies we pass downward in size to the almost. ultra-microscopic globulites which are isotropic. No crystals that could be mistaken for amphibole occur in any of the slices I have examined. It isin the stellate character of the crystallites. that our pitchstone differs from that of Arran, in which the erystallites are represented by tufts of branching plumose micro- liths. Specimens are in the Museum taken from the very edge of the dyke, where it came in contact with the surrounding granite. — These differ in structure from the rest of the rock; under the microscope they reveal an irregular banded structure due to alter- nations of layers almost colourless, with others rich in brown glass, and dusty with globulites. The feather-lke pyroxene prisms are absent, but their absence is compensated by the excessive development of stellate crystallites which attain a larger size than in the rest of the rock, at the same time remaining isotropic, or rarely appearing feebly birefringent. Phenocrysts of quartz are present, and curious elongated streaks of colourless glass devoid of crystallites and structureless, save for certain problematic spherical and tubular bodies near the edge, which are colourless or faintly bluish and transparent ; around them is an aureole of different refractive index to them- selves, and to the surrounding glass, but also colourless and trans- parent. One of the little spheres gives a black cross between crossed nicols, and it is probable that both spheres and tubes consist of chalcedony. In some cases additional structures are present, such as rhombohedra, apparently of calcite, and long filaments, with an axial row of highly refringent granules, looking very like Oscillatoria. It is possible that these lenticular patches or streaks were formed by a splitting of the pitchstone, while in the viscous state, as a consequence of cooling, the prisms being subsequently filled up with glass and other material. The specific gravity of the central part of the dyke, as deter- mined by a Walker’s balance, was found to be 2°41, of the selvedge, 2°42. . Dr. Haughton’s published analysis is given in Column [.; that by its side in Column II. is of an Arran pitchstone, by M. P. 90 Scientific Proceedings, Royal Dublin Society. Tait ; in Column III. also of an Arran pitchstone, by J. H. Player, taken from Teall’s “ British Petrography,” p. 347. I. IT. III. Silica, 7 : 64:04 66°03 72°6 Alumina, ‘ : 10°40 12°55 12°4 Ferric oxide, : 9°36 2°75 “7 (FeO, 1°1) Lime, we 4-24 2°80 9 Magnesia, . : none 2°33 trace Potash, ‘ ‘ 3°63 4:13 4:7 Soda, . A ; 2°91 5°02 1-7 Loss by ignition, . 5°18 4°30 5:2 99°71 99°81 99°3 Sp. gr., : 2°41 — 2°34 The absence of magnesia from a rock containing so much pyr- oxene is remarkable, but not unique; it would seem to indicate an aluminous hedenbergite as the chief pyroxenic molecule, a sugges- tion supported by the high extinction angles observed under the microscope. From the analysis, Dr. Haughton calculated a possible mineral composition for the rock as follows :— Quartz, ; : j 7°33 Felspar, : : . 62°55 Stilbite, : : : 29°83 99°71 It is interesting as illustrating the aid afforded by the micro- scope in checking calculations from analysis, to point out that in this case, where the mathematical computation takes no account of paste, the microscope proves it to be present in the state of glass as the chief constituent, while in granite, where the equations leave a surplus of material as paste, the microscope shows that paste is altogether absent. The bulk analysis is insufficient for determining the mineral Sottas— On Pitchstone and Andesite. 9] composition of the rock; but it may not be uninstructive to express its results by molecular formulz as follows :— Morecunar Compostrion. Per cent. Hedenbergite, 7°5 (Si0,), CaO FeO, : : ‘ 18 See (Si0,), Al,O; K,0 Sanidine, Or,Ab,, 8 (Si0,), A1,0, Na,0 Water pyroxene (S102)40 (Al,03), eae oa 5 34 Quartz, ‘ ay Magnetite (not eopaited for), ; : - : = 101 The glass probably consists chiefly of the sanidine and what we may term water pyroxene molecules. Had opportunity been afforded it for complete dehydration a considerable quantity of sanidine and quartz in excess of that now present as phenocrysts would have probably crystallized out, and the hypothetical water pyroxene molecules would have broken up, affording free silica, water, and ferro-aluminous pyroxene, which would crystallize together with the hedenbergite molecules as augite. Dr. Haughton mentions the occurrence of another variety of pitchstone, presenting an “ oolitic ”’ appearance, in association with that just described. This is probably spherulitic, but specimens of it are so friable that I haye been unable to prepare thin slices. The Museum Collection contains specimens of another glassy rock, labelled ‘“‘ Barnesmore, from a dyke 9 feet wide in granite.” This proves to be a typical augite andesite, with a structure as much hyalopilitic as intersertal. The felspar occurs in long rect- angular longitudinal and square transverse sections, frequently twinned once or twice, and containing a core of globulitic glass. The extinction angle ranges from 11° to 30°. Lither several varieties of felspar are present, possibly a series extending from oligoclase to labradorite, or more probably the extinctions are obtained in various directions in the zone [001,010]. The pyroxene is a pale green monoclinic variety, with an extinction angle of 40°. It occurs in small, irregular grains, and long, fibrous jointed prisms, approximately square in transverse section (fig. 2). It is frequently penetrated by the felspar, and then 45 92 Scientific Proceedings, Royal Dublin Society. presents a corroded appearance. Small octahedra, grains, and plates of magnetite are abundantly scattered amongst the other er <= a —- sw: | Fie. 2.—Augite Andesite—The Pyroxene is indicated by close parallel fine lines, the Felspar is left white, the Magnetite, cross-hatched, and the Glass dotted (x 225). constituents. The colourless glass is rendered brown by included globulites, and sometimes contains black belonites. Phenocrysts of plagioclase felspar, fragmentary and often highly corroded, lie scattered here and there. One finely twinned example gave a symmetrical ex- tinction of 10°, and is probably therefore. oligoclase. A curious fringe sometimes extends from the margin of the pheno- eryst inwards.. This marks the advanc- ing invasion of the felspar by the glassy Fic. 3.—-Felspar invaded by the ; glassy base (x 187). mesostasis; each fibre of the fringe con- sists of a row of minute granules, resembling globulites (fig. 3). Sortas—On Pitchstone and Andesite. 93 Numerous more or less spherical inclusions occur, which are evidently infilled vesicles. In some cases these are bordered ex- ternally by felspar laths, lying tangentially, an arrangement probably resulting from the expansion of a bubble of steam, driving the glass and included felspar laths before its advancing walls (fig. 4). The infilling material differs in different cases; sometimes it is calcite, sometimes deeply reddish coloured glass, occasionally opal. Fie. 4. The complete absence of even incipient devitrification in these glassy rocks forbids their reference to any earlier date of eruption than the Tertiary; rocks of remarkably fresh appearance are known from much more ancient periods, but these are crystalline —never, so far,as I know, truly vitreous. at VEL. ON THE VARIOLITE AND ASSOCIATED IGNEOUS ROCKS OF ROUNDWOOD, CO. WICKLOW. By PROFESSOR W. J. SOLLAS, LL.D., D.&c., F.B.S. [Read DeceMBER 21; Received for publication DEcemBER 22, 1892; Published Marcu 25, 1893.] In glassy rocks, consolidating under certain conditions, one of which is a somewhat rapid rate of cooling, a radiate growth of erystals about scattered centres is frequently set up, leading in many cases to the formation of crystalline spheres with a radiate structure. In rocks containing a large proportion of silica, such as rhyolites (obsidian), geologists have long been familiar with this spherulitic structure ; but in basic rocks or those poor in silica, such as glassy basalts, its existence has been questioned or denied : and yet under the name of variolite, basic rocks presenting the spherulitic structure in all its details have long been known and frequently described. Their true nature was, however, not at first re- cognized, and itis only in comparatively recent times that they have received a full and complete explanation. A learned account of the views which have from time to time been held on this subject has been given by Professor Cole and Mr. Gregory,! and I need only add to the long list of Papers cited by them one by Dathe,* which is of interest as confirming by anticipation some of their views, and another by Lossen,* whose remarks, though short, are characteristically to the point. Professor Cole has recently added to our knowledge of this subject by Papers read before this Society, 1«On the Variolitic Rocks of Mont Genévre,’’ by G. A. J. Cole and J. W. Gregory, Quart. Journ. Geol. Soc., vol. xlvi., p. 295 (1890) ; and “‘On the Variolitic Diabase of the Fichtelgebirge,”’ by J. W. Gregory, id, vol. xlvii., p. 45 (1891). 2 “ Dathe, Beitrage z. Kenntniss der Diabase-mandelstaine,’’ J. B. d. K. Preussichen geologischen Landesanstalt u. Bergakademie, p. 410 (1884). 3 Lossen, Geologische u. Petrographische Beitrage z. Kembriss des Harzes, ib., p. 7 (1881). Sortas—On the Variolite and Associated Igneous Rocks. 95 one on the variolite of Cerriggwladys, where it was discovered by Professor Blake, and this closely resembles that which we are about to describe; and another on a Tertiary example from Annalong, county Down.! I am glad to be able to add to the list a second Irish variolite possessing the essential characters. of the variolite of the Durance. It occurs at Tougher or Round- wood, near Dublin, where I found it while on an expedition with Professor Cole. The variolite of Roundwood forms part of an igneous complex,. which includes diabase, spilite, and consolidated volcanic tuff. The complex is exposed in a series of isolated hummocks, rising from peaty and marshy ground on each side of the road from Roundwood to Annamoe and Glendalough. The first hummock is met with half-a-mile south of the Roman Catholic chapel of Roundwood, and the series extends a little over half-a-mile in a more or less southerly direction, with a breadth of about 300 yards. Although not represented on the published map of the Geological Survey, this interesting patch of igneous rocks was evidently not unknown to the surveyor. So long ago as 1848 Professor Oldham’ called attention to it ‘‘as a small boss of Serpentine,” for which rock the strikingly green diabase might without microscopical analysis be very well mistaken. Mr. Kinahan subsequently alluded to it as ophite, and with the typical ophite of the Pyrenees it has as much in common as any ophitic diabase necessarily must ; but beyond a general resemblance there seems to be no sufficient justification for the name. Specimens of the diabase had evidently come under the observation of Jukes,’ who with the true petrographical instinct which distinguished him was contented to name them greenstone. It appears further that it is only by some oversight that this area does not appear on the published map. Mr. Watts has kindly allowed me to inspect the 6-inch map on which the surveyor’s work is recorded, and there it is plotted carefully enough, -with the remark that it should be 1 «The Variolite of Annalong,’’ Co. Down, Sci. Proc. Roy. Dublin Soe. (N.S.), vol. vii. p. 115 (1892). 2 Oldham, ‘‘ Notice of the Occurrence of a Small Boss of Serpentine in the County Wicklow,’’ Journ. Geol. Soc. Dublin, vol. iv., p. 202. 3 Jukes, Catalogue of the Collection of the Geological Survey of Ireland, p. 14. 96 Scientific Proceedings, Royal Dublin Society. inserted on the l-inch map. This is only one instance out of many of the rather careless way in which the reductions from the 6-inch map have been effected. It is probable that this is not the only locality in Leinster where variolites are to be found. Thus, DuNoyer' speaks of green- stone near Enniscorthy as weathering “into small rough pimples,” and Jukes sagaciously remarks that ‘this would probably be the variolite of Continental authors.”’ On the coast of Waterford, also in Bonmahon Bay, diabase ‘‘mandelstein” occurs in association with rocks which I have reason to believe are variolitic. The greenstone which lies on the right-hand side of the road going from Roundwood, not far from the church of Raheen, is a holocrystalline ophitie diabase, having a specific gravity of from 2°78 to 3:0. The lower value is exceptional; the mean is 2°97. It is of medium grain, the crystals of plagioclase, felspar, and pyroxene, which are its chief constituents, frequently attaining a length of 7 mm. as seen in thin slices. Plates of altered ilmenite, which are not uncommon, sometimes measure as much as 3 mm. Across. : The felspar affects long, more or less rectangular outlines, is frequently twinned on the albite—sometimes on the Carlsbad plan, and extinguishes at large angles pointing to labradorite and bytownite. The pyroxene occurs in colourless sections with well- ‘developed cleavage; it extinguishes at from 82° to 45°, and is frequently rendered ophitic by included felspar. Of olivine there is no certain trace, but it is by no means impossible that it was originally present. If in its fresh state the rock was an ophitic dolerite, it has since its extension suffered so much mineral change that its pristine character can only be recognized with difficulty. It has yielded both to the weather and to earth pressure, but of pressure the effect has been small compared to that of the weather. Thus, as shown in fig. 1, the augite has been nearly all converted into chlorite, which has eaten into it along numerous irregular cracks, and extending from them has produced a ground- work of chlorite, in which only small isolated fragments of the original mineral remain. These, which still preserve a common ° ‘ Memoirs of the Geological Survey, 167, 168, 178, and 179, p. 13 (1865). Sortas— On the Varioiite and Associated Igneous Rocks. 97 optical orientation, are probably not always of their original com- position, their want of colour suggesting the loss of some ferric constituent. The felspar has also suffered greatly ; chlorite has everywhere invaded it, often forming within it a coarse irregular network which, in general form, sometimes reminds one of that taken by included glass, so as to suggest the original presence of this ‘material. Calcite is not infrequently developed in it; and epidote y a i Su D F oe i A ag aha Hs ATi itn RE Gea Fie. 1.—Au. augite, Ch. chlorite, F. felspar, Il. ilmenite. ! My it | Hi abounds, sometimes penetrating and traversing the felspar, some- times included within it, sometimes bordering its margins, and frequently forming mosaics, when it does not seem to he specially related to one constituent of the rock more than another. In thin SCIEN. PROC. R.D.S., VOL. VIII. PART I. H 98 Scientific Proceedings, Royal Dublin Society. slices the epidote is pale greenish-yellow, with only faint traces of dichroism: it is to this constituent that the rock, as a whole, chiefly owes its strikingly green colour. The ilmenite has undergone complete conversion into leucoxene, so that as a rule skeleton plates of leucoxene, often hexagonal in form, and penetrated by felspar, are all that remain to mark its ~ previous presence. The effects of pressure are seen in the occasional fracturing of the felspar and augite. The hummocks on the right-hand side of the road consist of a dark brownish-red felsitic-looking rock, with a platy or splintery fracture, in this and in its colour closely resembling some of the Cambrian slates of the district; indeed, in the case of the more thoroughly cleaved examples, some doubt may well be felt as to their true nature on first making their acquaintance in the field, a doubt that a glance through the microscope at a thin slice will immediately dispel. In places, spheroidal jointing is seen in the hummocks, the concentric planes of division being crossed by a second set of fissures running radially. Here and there minute vesicles and amygdaloids appear, and at one spot included frag- ments of calcite ; one of these, a rounded block of completely crystalline pinkish-red limestone, measures 6 inches in diameter, and is very unlike a segregation or concretionary product; it looks far more like a derived fragment, caught up by the ascending lava from some underlying stratum. The specific gravity ranges from 2°834 to 3:004; the mean obtained from six specimens is. 291. The most coarsely crystallized example of these rocks I have met with happens to be somewhat vesicular, irregular cavities some half-an-inch in diameter, now filled in with calcite, occurring abundantly dispersed through it. In this, as in all the rocks on the right-hand side of the road, the chief mineral constituent is. felspar, which occurs in lath-shaped crystals, twinned once or twice, generally grouped, as many as six or eight together in stellate clusters. The ends of the crystals are frequently forked and the sides sometimes ragged; a thread of opaque white mate- rial, representing decomposed glass, usually runs through them axially. ‘The same opaque white material occurs between the crystals, and is sometimes distributed in groups of short parallel Sorzas—On the Variolite and Associated Igneous Rocks. 99 lines, which appear to proceed from the side of a felspar lath, diverging from it at angles of about 60°. It thus suggests the reedy form of augite with feathered edges seen in some glassy rocks, but no connexion with augite can now be traced, if any ever existed. The felspar laths are often bent, partly as a consequence of earth pressure, by which they have also frequently been broken across, partly by trichitic growth. Angles of extinction have been measured exceeding 20°; the species is therefore probably andesine. Augite appears to have been originally present in small grains, situated in the interstices left between the felspar; it is now entirely converted into pale-green chlorite. Hpidote is thickly scattered in small crystals through the rock, and calcite, which has replaced much of the felspar, is similarly dispersed. Calcite also fills up the cavities of the vesicles, which, though sometimes more or less oval in outline, are more frequently of quite irregular shape, bridged across by threads of rock, or invaded by promontories. Felspar laths sometimes project into them, forming with their surrounding film of altered glass tent-like eminences. The infilling calcite occurs as a mosaic; its cleavage planes are some- times curved or otherwise distorted; in some cases it presents a fan-shaped radiate structure, but this does not appear to be original, for distorted cleavage planes of earlier calcite grains can be traced across the rays of the fans, which would thus appear to result from the action of pressure on a once existing mosaic: fur- ther illustration of the action of pressure is afforded by lines of typical cataclastic granulation, which cross some of the calcite mosaics, in precisely the same fashion as the familiar crush lines in quartz mosaics of granite. From this rock, with its intersertal structure and slight traces of original glass, up to the completely variolitic modifications, there is every stage of transition, affording a complete passage from the variolites “du Drac” to those ‘‘de la Durance.” The prevalent rock of the area does not differ in general character from the foregoing, but a greater tendency is observable on the part of the felspar'to long curvilinear growths in sheafy aggregates, and in some cases this becomes so clearly expressed that the structure of the rock might properly be described as diffusely spherulitic. The examples in which this is best displayed are very much broken rocks, cracks now filled with calcite traverse them in all directions, H2 100 Scientific Proceedings, Royal Dublin Society. naturally suggestive of a rapid rate of cooling in the outpoured lava. Phenocrysts, much corroded at the time of effusion by the surrounding glass, are also met with, frequently collected together in groups. They now consist of chlorite and other secondary minerals, but were originally composed, in some cases at least, of olivine. The slaty character of the rock results from a kind of “ auswei- chungs-clivage.” In hand specimens the rock is seen to be tra- versed by numerous irregularly curved planes of cleavage, which are usually coated with chlorite and more or less regularly striated. In thin slices, cut transversely to the cleavage, numerous undulating dark lines running in a general direction are seen to divide the slice into lenticular areas. These lines correspond to the cleavage planes, and that gliding has taken place along them is shown very clearly in one instance where a crystal of felspar happening to lie transverse to the cleavage planes has been repeatedly broken and displaced along them (fig. 2). How slight the dislocation has been may be judged from the figure; measure- ments give a maximum displacement for each shear of 0:06 m.m., and a total displacement of twice this (0.12 mm.). ‘The two ends of the crystal have scarcely moved relatively to each other, the greatest displacement being reached in the middle of the erystal. On the other hand, the number of glide-planes is very great. The length of this single crystal (1°2 mm.) is crossed by no less than eight planes, so that the mean distance between them is 0-14 mm. The cleavage thus has evidently been produced by a great number of internal shears, each of very triflimg amount, and, as our crystal of felspar shows, the sum total of the whole, reckoning displace- ments in one direction as negative and in the other as positive, might amount to zero. The whole appearance points to packing under earth-pressure. Save for the presence of minute pheno- crysts the prevalent rock on the right-hand side of the road strongly reminds us of the “Spilite’”’ of Rosenbusch. Near the little cottage opposite the lane leading to Raheen church variolitic streaks appear in the rock running more or less parallel to concentric lines of jointing. They are rendered very distinct by the green colour which many of them present, due to a copious development of epidote. The varioles are seen in hand Sottas—On the Variolite and Associated Igneous Rocks. 101 specimens as little rounded bodies ranging in size from that of a pea downwards (Mr. Watts has since found examples half-an- inch in diameter) ; they are sometimes red, but more usually green in colour and weather to an opaque white powder. Under the Fig. 2. microscope the streaked appearance of the rock is seen to be due to irregularly alternating bands of different colour and compost- tion. Some are clearly divitrified glass traversed by numerous wavy lines of opaque white material giving it a fluxional appear- ance; others are similar, but in addition crowded with spherulites, singly and in groups, while others again are wholly spherulitic, the spherules in this case being more or less devoid of well-defined edges (fig. 3). Superposed upon these structures are crystals of epidote and zoisite collected in bands; these have been developed without completely destroying the structure of the glass, so that 102 Scientific Proceedings, Royal Dublin Society. the fine linear opaque streaks, which seem to be fluidal in origin, run through them undisturbed ; the structure of the spherulites has also, in some cases, survived epidotization. ‘The varioles not only become confluent, but in some cases a larger entirely includes a smaller one. The structure of the varioles is rendered very obvious by the presence of opaque white or brown material similar f YM Lp Mf EAR Me \y 2a ; Rg S SS = z =a = I APs y ses Wiz : « f LZ & A_ Gla eK SE = Li) TN Z CD. esol ae & EE WZ AW, ae = Za ] ees so = y+ Sie! = Ss SS wig @& S awl Z YY} WF See”. ES oe Alu Gas, \ Sse wey MD Wife, = Gs gle> SUD Se yp Opa) UE ERs ie v=; = Wwe , OU] Es PS SW AS aK S Re LZ S Z\_ py Z7, 1 \ NSS Se] SSI Y cae Ze Bese AS lis” m Ds ) GMS a Ss FA ~ Sé : We MZ SO ae AI Been ~ “nye ANS GI. dines. ~~ 7. Fic. 3.—Variolitic structure. G. altered glass, E. Epidote, crossed by cracks filled with calcite (chris-crossed). Magnified about 12 diameters." to that previously alluded to as occurring in the axis of the felspar crystals of the spilite. This borders the rays of felspar, which now chiefly constitute the variole, so that their course may be traced without the aid of polarized light (fig. 4); occasionally, however, it is developed to superabundance, and only serves to obscure: the same material occurs as a definite border about the periphery of the varioles; sometimes it is replaced by a brown translucent substance, which appears illuminated between crossed ! The slices from which these drawings were made have been mislaid, and it is im- possible therefore in all cases to state the amount of magnification. Sonrtas—On the Variolite and Associated Igneous Rocks. 103 nicols, and somewhat resembles leucoxene. Frequently it occurs as long black threads strongly suggestive of trichites. In a great number of cases the nucleus of the variole is fur- nished by a lath-shaped crystal of felspar ; from the ends’ of this delicate rays, also of felspar, repeatedly branching diverge in regular curves towards the margin, leaving at the sides of the nucleus a SN 4 Fic. 5.—Sheaf structure for spherulite. Ch. chlorite. space where but little structure is apparent. When fully deve- loped] the whole appearance of this beautiful growth forcibly re- ealls the distribution of lines of force about a bar magnet (figs. 4 104 Scientific Proceedings, Royal Dublin Society. and 5). Scales of hexagonal outline giving parallel-sided transverse sections, and often of a pale green tint, are thickly disseminated through the varioles and the surrounding matrix; many are, no doubt, chlorite, but some, judging from the brilliancy of their colours, between crossed nicols, are probably secondary mus- covite. No definite pseudomorphs after augite are to be seen, but it is quite possible that this mineral was originally present, and is now represented by decomposition products such as the scattered chlorite. In the larger varioles a distinction into a central clearer region and an outer more granular zone is of Fie. 6.—Confluent varioles with central area and outer zone, the darkly shaded portion indicates the opaque border. LE. epidote, Ch. chlorite (x 19). frequent occurrence (fig. 6). The outer zone retains the structure and general appearance of the substance of the smaller varioles ; the central portion which polarizes in more brilliant colours is poorer in the radiating opaque lines, representing altered glass, and suggests the previous existence of a cavity, which has been since obliterated by a growth inwards from the outer zone that originally formed its walls. But as opposed to this explanation is the apparent existence of traces of a nuclear felspar-lath in some of these central regions, leading one rather to regard the whole Sortas—On the Variolite and Associated Igneous Rocks. 105 variole as centrifugal in its growth from its earliest origin, and careful examination leads me to conclude that this view is correct, and that in this instance the central clearer space which polarizes in more lively tints than the rest of the variole, has been produced by subsequent decomposition, and develop- ment of silica. ‘That bubbles were pre- sent (fig. 7), which might have afforded a surface from which growth could take place both inwards into their cavity and upwards into the surrounding glass, is proved by the occurrence of spheri- cal vesicles, now occupied by chlorite and epidote, within the varioles. But fy¢. 7.—A vesicle filled in with these have been without influence on “blorite (Ch.) and epidote (E.). the variolitic growth. The occurrence of minute phenocrysts, originally consisting of olivine, has already been alluded to in describing the spilite ; it is not, therefore, surprising to find them within the varioles, where they usually occupy an eccentric posi- Fie. 8.—Variole, including minute pseudomorphs after olivine, and traversed by a fissure of retreat. tion, rarely forming the centre and serving as a nucleus. They now consist of chlorite, sometimes with the addition of epidote and calcite (fig. 8). 106 Scientific Proceedings, Royal Dublin Society.” Transverse or tangential cracks, the “fissures of retreat,” of Fonqué and Lévy, are of frequent occurrence in the varioles; in some cases they are traversed not only by the fibres of chloritized felspar, but by the opaque threads which we have regarded as representing decomposed glass (fig. 8). This adds a fresh difficulty in the way of their explanation ; it would appear that their forma- tion occurred while the glass was still viscid. Sometimes they are completely infilled with calcite, which in some cases has extended outwards from them in long prisms into the surrounding substance of the variole (fig. 9.) A chemical analysis was made of the variolitic rock from por- tions presenting a prevalent reddish colour, and another from portions mainly green. The following are the results :— Chemical Analysis of Variolite from Roundwood. Red variety. Green variety. S10,, : : 5 : 42°52 37°97 Ti0,, ; : : ‘ *892 "92 Al,0z, - < 5 5 18-10 19°45 Fe,0s3, : : : ‘ 7°50 7°85 FeO, : : : : 4°12 2°95 CaO, ; : : : 6:07 18°25 MgO, : ‘ : : 8°55 4°58 K,0, 3 : : : 56 trace. Na,0, 5 ‘ é : 4°38 2°90 H,0, : : A : 6°86 2°71 CO,, ‘ ; : : trace 258 99-50 100-16 S]Op HNP ‘ : ; 2°94 3°01 The water was determined by loss on ignition. A qualitative examination of the green variety showed the presence of a con- siderable quantity of manganese and chromium. The average specific gravity of the variolite is 3:05. It is scarcely probable that these analyses make any close approach to the original composition of the rock; and in our un- certainty as to the precise nature of many of the products of decomposition, particularly of the chloritic minerals and the white opaque granular material, we cannot attempt any calculation of its Sorzas—On the Variolite and Associated Igneous Rocks. 107 existing mineral composition. It is clear, however, that the original material was of a very basic character. Disregarding the water, the existing rock contains material which would furnish the following : Molecules. Ilmenite, — ‘ : : ‘ 3 1 Magnetite (and Chromite), : ‘ 2 Olivine (Mg;Fe,Si,), . § s : 4 (of M,8i0,) Anorthite, : : : P ae Alpites 3 : : ; 3 2 Fie. 9.—Part of a variole, showing calcite extending into its substance from a fissure of retreat. This would give us the sum total of molecules (SiO,).,, (Al,Os)<, (Fe,0;), FeO, (CaO),, (MgO), (Na,O),, a very close approximation to the result obtained by analysis, the water, as subsequently acquired, being disregarded. Since, however, silica has certainly been removed in solution, we must add sufficient of this to convert some of the olivine, and probably some of the magnetite also, into augite, which was evidently an original constituent of the rock. Probably: some of the calcium also was present in the form of pyroxene. | 108 Scientific Proceedings, Royal Dublin Society. By subsequent hydration, and exchange of material, the anor- thite has been converted into epidote and zoisite, and the olivine into chlorite; calcite also has been produced probably by the weathering of the anorthite and of the wollastonite molecules in the augite. In connexion with these subsequent changes stand the development of cracks in the highly epidotised portions of the rock and the migration of chlorite from its place of origin to surround- ing minerals. No doubt the cracks associated with epidotisation are best developed in those portions of the rock which were origi- nally in a glassy state, and which might consequently have been expected to undergo considerable contraction in the course of devi- trification ; but at the same time it is clear that where they are most strikingly displayed, the cracks have been produced after the for- mation of epidote, since single cracks may be traced passing con- tinuously through several crystals of this mineral. A slice in which this is conspicuously shown, consisting chiefly of epidote, resembles a diagrammatic section of a country traversed by mineral veins. The fissures, some of which completely cross the slice, vary in breadth in different parts of their course, branch, and reunite, forming “horses,” receive feeders and give off droppers, die out and are replaced by fresh ones running in the same direction. They are now filled with crystalline calcite. It might be conjec- tured that under the earth-pressure which has produced “ auswei- chungs-clivage’’ in the spilite, the hard and resistant epidote became fractured in the direction of the pressure; but even so the cracks are so wide and numerous as to suggest a previously exist- ing want of compactness; and this one would naturally expect to result from the shrinking which it would seem must necessarily occur when anorthite gives rise to epidote. Ii, for simplicity, zoisite, instead of epidote, be compared with anorthite as regards its molecular volume, we obtain the following :— Anorthite. Wollastonite.! Zoisite. : 3(CaA1,8i,0¢) + 8i0,Ca + H,O = H,Ca,A1,Sig02, ar 810, Molecular weight,” 810 116 884 60 1 By wollastonite is to be understood the calcium silicate molecule of pyroxene. 2 The atomic weight of aluminium is taken as 27 in this and subsequent calcu- lations. SotLtas—On the Variolite and Associated Igneous Rocks. 109 : “810 Anorthite (sp. gr. 2°77), a7 300 (molecular volume), dis 884 Zoisite (sp. gr. 3°38), saat 268. E 116 Wollastonite (sp. gr. 2°8), Rar 41. SiicalG@ne er! 2:65) Seer ica (sp. gr. f AGE mt Thus the contraction which anorthite undergoes in passing into zoisite amounts to 10°6 per cent., and the result is similar if epidote be substituted for zoisite, while if the united volume of the anorthite and wollastonite molecules on one side of the equation be compared with that of zoisite and quartz on the other, the con- traction will be found to reach 14°3 per cent. Possibly the strong tendency to idiomorphic outlines displayed by epidote and zoisite is connected with this contraction in volume. The formation of chloritic minerals, on the other hand, is attended on the whole with expansion of volume. In investigating this complex group we may adopt T'schermak’s theory of their constitution, which in any case has the merit of conveniently expressing the facts. From this point of view the members of the chlorite family may be regarded as forming a series, having serpentine at one end, and a hypotheti- cal mineral, amesite, at the other, the intermediate members con- sisting of mixtures or combinations of these two simplest terms in various proportions, as shown in the following table :— Molecular Proportions. Simplest Formula. SPro, . . Si,0,Mg,H,, . : Serpentine. SpAt, - . SigQsALMgiHoo, } ee SpsAts, ; Si,0ic4],MgcH., } Clinochlore. Spat, . . Si05Al,Mg,,H»,, Sp,At;, . : Sip309AL4M eg»; Huo, Prochlonice. Spe Ate, i : Si,O4; Al,M 1 Hy, i c Corundophilite. Atio, 5 ! Si0;AlMeoH, . 4 Amesite. The constitution of amesite may be expressed by the formula:— Si] 0Al(OH),|(0.A10)(OMg0H)>. An actually existing mineral, with a composition closely approach- ing that of the hypothetical amesite, is a chlorite from Chester, 1 Tf the specific gravity be taken as 2.75, the molecular volume will become 293. 110 Scientific Proceedings, Royal Dublin Society. U.S., to which the formula Sp,At has been assigned ; if this be expanded to express approximately the results actually afforded by its analysis we have :—Si,,0,Al,.Mg,;Fe;H.. The molecular weight is 2970, and the specific gravity 2°71; the molecular volume is therefore 1096, or dividing by 10 (since there are 10 molecules in the group), 109-6, which is almost identical with that of serpen- tine. For the molecular weight of serpentine is 276, the specific gravity 2°5, and the molecular volume consequently 110. In view of this, and the fact that 9 out of the 10 molecules in the compound consist of serpentine, it would seem that not much error can arise if we assign to the hypothetical amesite a molecular volume of 110. There are at least two sources from which serpentine is derived, enstatite and olivine. The reaction in the case of the latter may be thus represented :— Olivine. Serpentine. 28i(0,Meg), + 20H = Si,(O:Mg),(OH), + MgO. The molecular weight of the olivine is 280, and its specific gravity 3°3 ; its molecular volume is therefore 85, while that of serpentine is 110. Thus disregarding the single molecule of magnesia on the right-hand side of the equation, the conversion of olivine into ser- pentine is accompanied by an increase of volume amounting to nearly 30 per cent. In the hydration of enstatite we have :— Enstatite. Serpentine. 8 SiOMg0, + 2 OH; = Si; (0,Mg); (OH), + Si0>. The molecular weight of the enstatite is 300, and its specific gravity 3:1; hence the molecular volume is 96°8, and the increase of volume in passing into serpentine amounts to 13-6 per cent, Had the liberated silica been taken into account, the increase would have been found to be much more considerable, and in a rock consisting of olivine and enstatite it would make itself evident, since the magnesia liberated from the olivine and the silica from the enstatite might be expected to unite to form a further quantity of serpentine. Such a case is represented thus :— Olivine. Enstatite. Serpentine. Molecules, : 12 + 6 = 9 Volume, . - 00 + 193°6 = 990 Sortas—On the Variolite and Associated Igneous Rocks. 1112 or 703°6 volumes of olivine and enstatite give rise to 990 volumes of serpentine, an increase of 40 percent. The extrusion of serpen- tine from altered olivine into cracks in the surrounding minerals and the larger fissures of the whole rock becomes thus readily intel- ligible. Turning now to the amesite molecule we perceive that its deri- vation from pyroxenic material involves great destruction of the pyroxene, as is shown in the following :— Pyroxene. Amesite. [ Si0(0,Mg) },$i,0,(0,Al),+20H, = Si(OMgO0H),[0A1(OH), |(0A10) + 4§810,. ida The molecular weight of the pyroxene in the equation is 482; and if the specific gravity be taken as 3°25, a very probable estimate, we arrive at 150 for the value of the molecular volume. Since the molecular volume of the resulting amesite is 110, we have here a loss of 40 volumes or 26°7 per cent. If, however, the volume of liberated silica be included in the account, the loss becomes a gain ; we cannot assign a less volume to this than 90, and consequently on the total transaction there will be an expansion of 150 volumes. to 200, or a gain of 33:3 per cent. Since amesite, so far as we know, is never the sole chloritic product of the hydration of pyroxene, it will be more instructive to consider examples in which both serpentine and amesite molecules are produced together; thus the volume of pennine (Sp;At,) is 6:78 per cent. less than that of the pyroxene which furnishes it, and of clinochlore (SpAt) 10 per cent. I must confess to having felt some little surprise at this result, since the general diffusion of chlorite in diabase and other hydrated basic rocks would naturally have led one to expect the chlorite to possess a larger volume than the pyroxene from which it is derived; but though this is clearly not the case, there is evidently great expansion when the total change involving the liberation of silica is considered. If the volume of clinochlore and quartz be compared with that of the pyroxene from which they result, a total expansion of 34 per cent. will be found; and since the clinochlore may be assumed to be at least as soluble as the silica, we may suppose that the surplus volume (34 per cent), which is carried away in solution, will 112 Scientific Proceedings, Royal Dublin Society. include both these products. Further, the destruction of pyroxene in weathering frequently involves the conversion of the wollastonite molecules into calcite, and this produces great increase in volume ; thus :— Wollastonite. Calcite. CaSi0; + CO, = CaCO; + S10, 116 10 Molecular volume, aa = = = = 22. The calcium carbonate is almost of the same volume as the wollas- tonite, but the total change is an expansion of about 51 per cent. It may be of interest to consider the total change of volume of a rock consisting of anorthite and augite, when completely altered by the weather. For this purpose we will assume a mixture in which the silica is equally divided between the two minerals, and we will select a pyroxene having the composition found by Teall? for this mineral, as it occurs in the Great Whin Sill, while the anorthite may be taken as ideally pure. We shall thus have :— Pyroxene, . : : . Ca,Meg., Fe ,Al Fe’ Sigs O19. Anorthite, | . ; . 11 (CasA1,8i,02.). 11 Anorthite + 11 Wollastonite? = 11 Zoisite + 11 Quartz Mol. vol., 300 x 11 41x11 268 x 11 22°5 x 11 Change in volume, ‘ : . 8195 — 3751 =— 556. 8 Wollastonite + 8 CO, = 8 Calcite + 8 Si0,. 41x 8 40x8 22°5x8 Change in volume, : : . 500 —- 328 = 172. Residual Pyroxene. Pennine. Mg,, Fe” ,Al,Fe.Siy,014 = SpAty + 16 810, 32°38 x 47 = 1518 110x138 225 x 16 = 3860. Change in volume, 3 ; 11790 dols)= 2722 The total change is thus 444 — 556 = — 112, or a contraction of 112 on a total volume of 5597, i.e. 2 per cent. It is thus evident that when‘epidotisation is a prevailing change in the weathering of basic rocks the total alteration of volume will not be large, and 1 Teall, ‘‘ British Petrography,”’ 1888, p. 157. * Calcium pyroxene molecules. Sottas—On the Variolite and Associated Igneous Rocks. 113 slight difference in the proportions of the minerals constituting the rock may determine whether, on the whole, an expansion or a contraction shall take place. The presence of a small quantity of olivine in the mixture we have assumed would, of course, tend towards expansion. If only as much olivine be added as contains 6 molecules of silica, of which already 182 molecules are present in the mixture, the contraction will become a slight expansion, thus: Pyroxene. Olivine. Pennine. Me,,Fe’sAlFel”SigO + Mg,Si60, = SpiAt, + 14 Si0, 1518 42°5 x 6 110x177 22°5x 14 Change in volume, . . . 2185-1779 = 412. In the previous case when no olivine was present the expan- sion for pyroxene was found to be 272. This deducted from 412, the expansion now found, leaves 140, by which we must increase the previous result, which we found to be a total contraction of 112, thus: 140 — 112 = 28, so that on the total change we have now a gain of 28 or 0-4 per cent. The conversion of anorthite into kaolin and calcium carbonate would bring about a very marked expansion ; thus :— Anorthite. Kaolin. CazA].S1g024 aP 38CO, ap 6H,O = 3H,A1,$1,0, + 38CaCO3. Mol. vol., 300. 300. DOs Thus while the epidotisation of anorthite is accompanied by a con- traction of about 14 per cent.; its kaolinisation, on the contrary, is accompanied by an expansion of 40 per cent.! If, in the mixture we have just considered, we suppose kaolinisation instead of epido- tisation to occur, we obtain the following :— 11 Anorthite = 383 Kaolin + 83 Calcite. - 3300 3300 1320. Change of volume, : ; - 4620 - 3300 = 1820. 19 Wollastonite = 19 Calcite + 19Si0,. 10D 760 427. Change of volume, ‘ E . 1187 — 779 = 408. 47 Pyroxene + 6 Olivine = 17 Pennine + 14 SiO). 1518 255 | 1870 315. Change of volume, ; HL 2186) 17738 = 412. 1 Possibly in this will be found an explanation of the variety of complete kaolinisa- tion of anorthite. SCIEN. PROC. R.D.S., VOL. VIII., PART I I 114 Scientific Proceedings, Royal Dublin Society. The total change is now a gain of 2140 volumes on 5852, equiva- lent to 36°4 per cent. Since anorthite will rarely be converted into epidote alone, but will usually give rise also to kaolin, it is probable that, on the whole, the bulk of the material resulting from the weathering of a basic rock will considerably exceed that which it possesses in the unaltered state. No one can have examined the slates and other rocks of the Cambrian and Ordovician systems in Leinster and elsewhere, with- out being impressed with the frequency of the association of chlo- rite with quartz in the infiltrated veins so common in these rocks. This finds an easy explanation in the simultaneous liberation of chlorite and: silica during the weathering of rocks contaiimg pyroxene; and such rocks are of the commonest occurrence in the districts traversed by the chloritic quartz veins. Before concluding the long digression which our observations on the fissured condition of the epidotised rock have suggested, it may be worth while to inquire into the volume-change accom- panying the conversion of orthoclase into muscovite and kaolin. Muscovite may be supposed to arise by the following reaction :— Orthoclase. Muscovite. 3 Al, K.81,0i, = Al, K,H,S1,004 + K,CO; ar 12 Si0,. Mol. vol., 3 x 218 274 256202225 sas The change in volume is 668 — 658 = 10. Thus, on the whole, there is practically no change in volume ; but, if the muscovite be considered alone, there is a condensation of 658 to 274 volumes. Unless, therefore, some of the free silica be deposited as quartz along with the muscovite, we should expect to find the development of the last-named mineral accompanied by marked signs of shrinkage in the orthoclase. The conversion into kaolin is as follows :— Orthoclase. Kaolin. Al, K.$1,04. = H,A1,8i,0, oP K,CO, + 4 $10,. Mol. vol., 218 100 62 90. The change in volume is 252 — 218 = 84. The expansion, on the whole, is slightly larger than in the So~Ltas—On the Variolite and Associated Igneous Rocks. 115 case of muscovite, but the condensation, when kaolin alone is com- pared with orthoclase, is scarcely less striking. 218 volumes of orthoclase are represented by 100 of kaolin. The porous character of kaolin pseudomorphs, after felspar, is, however, a familiar fact. When the transformation of minerals is effected under pres- sure, aS in dynamo-metamorphism, we should naturally expect those whose development is accompanied by contraction to be formed in preference to those in which it is accompanied by expansion; and it is possible that the excessive development of epidote in the igneous rocks of Roundwood stands connected with the earth-pressure, to which they have more than once been sub- jected. It only remains to mention the tuff, which is now a red slate with typical ‘‘ ausweichungs-clivage’’; it contains pieces of altered glass, fragments of felspar crystals, and patches and veins of chlorite. Since it occurs in company with variolitic and vesicular lava, one may fairly infer that the igneous rocks of Roundwood are situated not far from the actual site of a volcanic vent, which was in activity in Ordovician times, discharging steam and frag- mentary materials from its crater, with occasional overflows of lava. The close proximity of a somewhat coarsely crystalline diabase, once an ophitic dolerite, can scarcely be a matter of acci- dent, and one is led to suppose that in it we have a somewhat deeper-seated representative of the extruded spilite and variolite. f Tie] IX. DESCRIPTION OF SOME NEW SPECIES OF ACTINIARIA FROM TORRES STRAITS. By PROFESSOR A. C. HADDON anp ALICE M. SHACKLETON, B.A. [Read Decrmper 21; Received for publication DecrmBrr 22, 1892; Published Marcu 28, 1893.] Circumstances have delayed, and will further delay, the comple- tion of the second part of our Report on the Actiniaria of Torres Straits. This being the case, we think it advisable to put on record a description of those new species which we have already deter- mined. We hope to present our completed and illustrated memoir in about a year’s time. The following is a Table of all the species we have as yet identified in the collection made by one of us. The order in which they are here placed must be regarded as provisional, as we are by no means satisfied with any published classification of the Actiniaria. ACTINIARIA. I. Epwarpst. (No specimens collected.) Il. CertantHez. Cerianthidee. Cerianthus nobilis, n. sp. III. ZoantuHez. Zoanthidee. Macrocnemine. Parazoanthus Mowesii, H. & S.; P. Kochii, H.& 8.; BP. eeesia (?), (Dana). Brachycnemine. Gemmaria Maemurriehi, H. & 8.; G@. Mu- tuki, H.& S. Ksaurus asymmetricus, H. & 8. Zoanthus Coppingeri, H.&S.; Z. Dukesii, H.& 8.; Z. Maegillivrayi, H. & 8. ERRATUM. For last eleven lines from bottom of p. 116 read the following :— ITI. Zoantuesz. Zoanthidee. Macrocnemine. Parazoanthus dichroicus, H. & §.; P. Dougiasi, H. & S. Brachycneminez. Palythoa Howesii, H. & S.; P. Kochii, H. & 8.; BP. ceesia (?), Dana. Gemmaria Macmurrichi, H. & S.; &. Mu- tuki, H. &S. Ksaurus asymmetricus, H. & S. Zoanthus Coppingeri, H.&8.; Z. Dukesii, H. & 8.; Z. Maegillivrayi, H. & S. Happon anp SuackLeton—WWVew Species of Actiniaria. 117 TV. Hexactiniz. A. Stichodactyline. Corynactide. Corynactis hoplites, n. sp. Discosomide. Discosoma Kenti, n. sp.; D. Malu, n. sp.; BD. macrodactylum, 0. sp. Rhodactidee. Rhodactis bryoides, n. sp. Phymanthide. Phymanthus simplex, n.sp.; P. muscosus, D. sp. Cryptodendride. Cryptodendrum adhzsivum, Klunz. B. Thalassianthine. Thalassianthidee. Actineria dendrophora, n. sp. Actinodendron alcyonoideum, Q. & G.; A. arboreum, Q. & G. c. Minyadine. Minyadide. Minyas torpedo (?), Bell. p. Actinine. Actiniidee (Antheade). Condylactis Gelam, n.sp.; C. Ramsayi, n.sp.; C. aspera, n. sp. Anemonia citrima, n.sp.; Mwoiam, n. sp. Actinioides Dixoniama, n. sp.; A. Sesere, N. sp. Wiatrix cineta, n. sp. Bunodide. Alicia rhadina, n. sp. Sagartide. Phellia (?) sipuneuloides, n.sp.; P. (?) Devisi, n. sp. Paraphellia Hunti, n.sp.; P. lineata, n. sp. Whoe (?) Milmani, n. sp. Adamsia miriam, n. sp. 118 Scientific Proceedings, Royal Dublin Society. CERIANTHEA. CERIANTHIDZ. Cerianthus nobilis, n. sp. Form.—Body of great size; presence of a terminal pore not determined; marginal tentacles long, tapering, in three cycles, from about 160 to 170 in number; oral tentacles very numerous. Colour.—Upper portion of column deep brown, paler below ; marginal tentacles, deep flesh colour; oral tentacles, yellowish skin colour. Disc with radial brown lines. Dimensions.—Length of column probably about 300mm. (in alcohol 105mm.); diameter, 26 mm. (in alcohol 19 mm.) ; length of marginal tentacles, about 80 mm.; length of tube, about 800 mm. (12 inches). Habitat.—Partially imbedded in the mud on the fringing reef of Thursday Island. HEXAOTINIA. STICHODACTYLINZ. CORYNACTIDZ. Corynactis hoplites, n. sp. Form.—Column about twice as high as broad, smooth, pedal disc expanded; tentacles, capitate, of two kinds, (1) marginal and (2) centripetal, situated on the disc, the latter in at least two cycles ; mouth can be extended into a short tube, finely ridged internally. Colour.—Colour, varied ; (a) column, burnt sienna-colour, with dark paired marks at the top of the scapus; tentacles, translucent white, with a pink or white core at the swollen tip ; mouth-cone, speckled gray; throat, orange; () similar, with pinkish-brown tips to tentacles ; six pairs of marks on capitulum ; (c) transparent grass-green, with brown streaks; tentacles, transparent, green tips. Dimensions.—Diameter of column, about 8 mm.; height, about 14mm. Happon anp SHAcKLETON— Vew Species of Actiniaria. 119 © Habitat.—Between Orman’s Reef and “ The Brothers Island,” 6-7 fms., August 18, 1888; also on fringing-reef, Mabuiag, October, 1888. The various species of Corynactis are difficult to differentiate from each other, so far as the descriptions hitherto published are concerned. This species differs from the type species C. viridis, Allm., in possessing a well-marked, diffuse, endodermal sphincter muscle, as well as in other characters which we will particularize in our detailed paper. The specific name is derived from the batteries of large nematocysts in the tentacles. DISCOSOMIDZE. DiscosoMa. We place the three following species provisionally under this genus, as they appear to constitute a regular series; but we feel sure that ultimately the genus will require revision, as the type species D. nummiforme, Leuck., appears to differ considerably from other species which are commonly associated with it. Discosoma Kenti, n. sp. Form.— A very large Actinian ; column narrower below than above ; oral disc of considerably greater diameter than column, and thrown into well-marked lobes; tentacles very numerous, subulate, in continuous, rapid, irregular, waving movement ; mouth, usually with two gonidial grooves. Colowr.—Various; column, usually gray, passing into buff above, or brownish and rusty orange above, upper portion with pale or sometimes dull violet suckers; tentacles, ashy grey with a green tip, or cindery-brown, sometimes the tentacles have a pinkish lilac tip. Dimensions.—Diameter of corona, over 300 mm. (a foot or more. Habitat.—On reefs in Torres Straits. We have the pleasure of naming this fine species in honour of W. Saville Kent, Esq., who has recently done such good scien- tific and economic work in connexion with the fisheries of Torres Straits and elsewhere round the Australian coasts. 120 Scientific Proceedings, Royal Dublin Society. Discosoma Malu, n. sp. Form.—Column, soft, massive; upper portion with large suckers, to which pieces of shell often adhere; a slight but dis- tinct crenulated parapet ; oral disc of much greater diameter than column, and thrown into folds; mouth round, with two well- marked gonidial grooves; tentacles very numerous, contractile, may be reduced to mere filaments—those of the outermost row in two cycles, large, and of the same size; the centripetal tentacles appear to arise anywhere on the disc, they usually occur in short radial rows, of these the tentacle situated nearest to the mouth is the largest. Colour.— Whole body pale creamy yellow ; the tentacles shade off into pink, and have rosy-red tips. Dimensions. —Column about 100 mm. high; about 750 mm. in diameter ; diameter of corona, over 160 mm.; length of tentacles, 11mm. Habitat.—(Of single specimen) surface of reef, Mer, February 14, 1889. We name this species after the hero Malu, about whom there is a legend which evidently embodies the traditional history of the origin of a portion at least of the ancient initiation ceremonies of Mer. (Cf. “ Legends from Torres Straits,’ Folk-lore 1. 1890, p. 181.) Discosoma macrodactylum, n. sp. Form.—Salver-shaped, owing to the great expansion of the oral disc, with numerous large suckers on upper portion of column ; the long and very contractile tentacles are placed in well-marked linear series, their tips are perforated; mouth with two gonidial grooves. Colour.—Column, olive-brown, darker above, with pale spots on upper portion; disc, pinkish gray, peripherally passing into pale olive green, which shades into olive brown round the mouth; cesophagus, delicate pink; tentacles, dove-gray, with a yellowish sheen, which is most marked at the tip. Dimensions.—Diameter of disc, 250-300 mm. or more; mouth, 25mm, x 57 mm.; tentacles, 40 mm. or more in length. Happon AnD SuHackLEron—Wew Species of Actiniaria. 121 Habitat.-—(Of single specimen) surface of reef, Mer, January 18, 1889. At first sight this species has very much the appearance of an Anemonia ; the specific name refers to the long tentacles. RHODACTID. Rhodactis bryoides, n. sp. Form.—Body, salver-shaped, with a well-marked crenulated parapet; oral disc expanded, of even contour, concave with promi- nent oral cone; mouth rounded, stomatodeum with twenty-four furrows, but no gonidial grooves; one or two short, knob-like tentacles on most of the crenulations of the parapet, but the bulk of the tentacles are compound, and are grouped in numerous radial lines, twelve of which run up the oral cone; there is an annular clear space between these centripetal and the peripheral tentacles. Oolowr.—Column, buff, grayish-brown or cinder colour; dise burnt-sienna colour; tentacles various shades of bluish-green, some on the disc are brown. Dimensions.—Diameter of disc, 32 mm. Habitat.—Surtace of reefs, Murray Islands. This species can readily be distinguished from the only hitherto described species of R. rhodostoma (Khr.) and R. Sancti- Thome (Duch. et Mich). ‘The specific name is derived from its mossy appearance. PHYMANTHIDZ. Phymanthus simplex, n. sp. Form.—Column, soft, corrugated when contracted ; suckers on lower portion increasing in size from below upwards; crenulated parapet; disc flat when fully expanded, never completely retrac- tile; mouth rounded, with two cesophageal grooves; tentacles of two kinds, centripetal and peripheral ; centripetal tentacles short, conical, arranged in three cycles, the inner cycles consisting of about 48 in number; peripheral tentacles arranged in four or five cycles consist of about 192 tentacles; aboral aspect of each 122 Scientific Proceedings, Royal Dublin Society. tentacle smooth, oral aspect flattened with lateral swellings alter- nately large and small. Colowr.—Column, cream below, passing into gray above, lower portion streaked or spotted with red-lead colour; suckers and marginal crenulations white ; disc, central area cream-colour, with dark brown lines; area of the inner cycles of tentacles dark brown, a white spot in front of each tentacle ; the inner tentacles have a madder tinge with a green sheen on their oral aspect; marginal tentacles transparent brown aborally, cream colour orally, the swollen portion spotted in the middle. Dimensions.—Height, about 100-130 mm. ; diameter of corona, 250 mm. ; largest tentacles, 30 mm. x 6 mm. Habitat.—F ringing reef, Mer. Phymanthus muscosus, 0D. sp. Form.—Forty-eight rows of small tubercles on upper portion ~ of column; crenulated parapet; flat, completely retractile dise ; small round mouth; 96 tentacles, bearing alternately large and small dendritic appendages. Colour.—Column, various shades of gray, darker above than below ; disc green with dark or light spots; tentacles gray with green appendages. Dimensions. — Height, 250-500 mm. Diameter of corona, 500-750 mm. Habitat.—Surface of fringing reef, Mer. This species is allied to the type species of the genus, P. Joligo (Ehr.); but the lateral appendages to the marginal tentacles are more dendritic that in the latter species, and the rosette-like disc- tentacles are absent. It is also very close to Thelaceros rhizophore, Mitch.1. This genus cannot stand, but we believe it is to be a distinct species. Phymanthus simplex is a well-marked species. 1P. C. Mitchell, ‘‘Thelaceros rhizophore, n.g. et sp., an Actinian from Celebes,’ —Quart. Jour. Micr. Sci. xxx., (N.S.), 1890, p. 551. Happon anp SHackLETON—Wew Species of Actiniaria. 123 THALASSIANTHIN &. THALASSIANTHIDZ. Actineria dendrophora, n. sp. Form.—Column, soft, smooth ; base slightly expanded; oral dise greatly expanded, and irregularly folded or puckered, with its edge produced into lobes some 300 or 400 in number; the aboral aspect of the lobes is closely crowded with globular, pedunculated tentacles, the oral or upper surface being covered with ramified tentacles, these latter extend along the disc, in radial series, to a greater or less extent, but none reach the mouth; alternating with the lobes are comparatively large dendritic tentacles, these are more aborally situated than the lobes; disc, smooth, inclined to be crateriform in the centre, non-contractile ; mouth, rounded, on a cone with two gonidial grooves. Colour.—Column, pinkish ; dise, translucent pinkish brown, with a delicate green sheen ; mouth pale ; capitate tentacles, pink, with a cream-coloured speck on tip (they look just like pink pearls) ; dendritic tentacles of same colour as disc, but, owing to their round contour, the green sheen is more apparent, and this is especially so on the finer branches, which thus appear decidedly green. Dimensions. — Column, height about 70 mm.; diameter, 45- 50 mm.; diameter of disc, 125 mm. Habitat.—Surface of reef, Mer. This species is quite distinct from the only hitherto described species of the genus A. villosa (Quoy et Gaim.). The specific name is derived from the numerous small tree-like tentacles on the disc. ACTININ&. ACTINIIDA. Condylactis Gelam, n. sp. form.—Column, smooth, expanded at capitulum, which is fur- nished with suckers; disc feebly retractile ; mouth, circular with two or three gonidial grooves; tentacles long, in six or seven eycles, from about 192 to 240 in number. 124 Scientific Proceedings, Royal Dublin Society. Colour.—Column, red-lead colour below, passing into creamy yellow above; underside of capitulum gray, with pale suckers; (a) dise and tentacles olive brown; mouth green; tentacles with a greenish contour, and tipped mae magenta ; () dise gray ; tentacles dark gray, with a buff sheen. Dimensions—Height of column, 150 mm.; ee 44 mm. ; diameter of corona, 177 mm.; length of tentacles, 45 mm. Habitat.—On reefs at Mabuiag and Mer. We name this species after a lezendary hero of Torres Straits who migrated from Moa (a neighbouring island to Mabuiag) to Mer ; the main hill of the latter island still bears his name. Condylactis Ramsayi, n. sp. Form.—Column, soft, about as high as broad, terminating above in a well-marked parapet, but without marginal spherules or suckers ; disc, flat, considerably wider than the column, can be slowly but completely retracted; mouth, circular, with a variable number of gonidial grooves (2-7) ; tentacles, numerous, relatively short, about one-third of the diameter of the disc. Colour.—Column, usually olive-brown or green, occasionally pale magenta, pink; disc, translucent olive-brown or cinder- colour; stomatodeum, whitish; tentacles, with a grayish-brown core and a green satin-like sheen, sometimes with a pale ring near the tip, or with the tip of a paler and brighter green. Dimensions. — Height of column, about 38mm.; diameter of disc, about 46mm. Habitat.—Reef, Waier (Murray Islands). We would like to associate with this species the name of Dr. H. P. Ramsay, the energetic Curator of the Australian Museum, Sydney. Condylactis aspera, 0D. sp. Form.—-Column, cylindrical, skin delicate; the whole of the body except the disc covered with small, very adhesive suckers, so that whenever touched this Actinian adheres to the foreign body like a Synapta; fragments of shells adhere to the body; large suckers occur on the upper portion of the column; mouth, elongated; two gonidial grooves; large tentacles in three or four cycles Happon anp SHackLeton—Wew Species of Actiniaria. 125 (6 + 6+ 12 + 24 = 48), the inner cycle much the largest; usually the tentacles are considerably swollen, but they can become quite slender and flaccid. Colow’.—Body, uniform pale, translucent yellow drab or buff, finely dusted with very minute brown spots; tentacles may be faintly banded and the disc slightly variegated with dark brown. Dimensions.—Column, height 30mm., or more; diameter, about 25 mm. ; tentacles, 60-75 mm. long ; extreme diameter of corona, 175-200 mm. Habitat.--Surface of reef, Mer. Although this species presents some features which are not characteristic of the other species of genus, we do not at present see any good reason for placing it elsewhere. The specific name refers to the adhesive character noted above. Anemonia citrina, n. sp. Form.—Column, soft, with parapet of well-defined spherules ; dise feebly and imperfectly retractile; mouth round ; tentacles of moderate length, about three cycles. Colour.—Column, uniform pale lemon-yellow; disc and ten- tacles, burnt-umber brown. Dimensions.—Height of column, 30-40 mm.; diameter of corona of largest specimen, 50 mm. ; tentacles, 15 mm. in length. Habitat.—Between tides, on seaward side of a mangrove swamp, Mabuiag. This species is named from its lemon-like appearance. Anemonia Kwoiam, n. sp. Form.—Body, salver-shaped ; upper portion of column when fully expanded extends beyond the insertion of the tentacles, and forms a distinct crenulated rim; disc, with a wavy margin; mouth, round, no gonidial grooves; no suckers on upper portion of column ; tentacles in multiples of six. Colour.—Column, buff; disc, burnt sienna brown, with white spots; tentacles, brown, speckled with white proximally. Dimensions. —Corona, 155 mm., when fully expanded; ten- tacles, 22 mm. long. 126 Scientific Proceedings, Royal Dublin Society. Habitat.—Surface of reef, Mabuiag (Jervis Island). We have identified this species with the name of Kwoiam, a renowned legendary hero of Mabuiag. ACTINIOIDES,, n. g. Actiniidee (Antheadee), with more or less prominent suckers on upper portion of column ; capitular margin, with conical acrorhagi, which are provided with a well-developed battery of nematocysts. This new genus bears pretty much the same relation to the genus Actinia that Condylactis does to Anemonia (Anthea). Actinioides Dixoniana, nt. sp. Form.—Column, covered with vertical rows of sucker-like verruce ; capitular margin provided with large conical acrorhagi ; tentacles in two cycles, not in multiples of six. Colour.—Column, various shades of greenish grays and browns ; ; disc, dark greenish brown, with white markings; tentacles, olive- brown, banded with greenish white or gray on oral aspect. Dimensions. —Diameter of corona of largest specimen, 31 mm. Habitat.—F¥ ringing reef, Mabuiag. We have carefully studied the anatomy of this form, and find that the irregularities in the arrangement of its mesenteries recall those which were studied by the brothers G. Y. and A. F. Dixon in Bunodes thallia, Gosse (cf. Proc. Roy. Dubl. Soc., N. 8. VL., 1889, p. 810.) We give ourselves the pleasure of dedicating this species to these investigators. Actinioides Sesere, n, sp. Form.—Column, smooth, with about 24 vertical rows of verruce, which are small below, in the upper portion of the column these are larger, and somewhat irregular in their arrange- ment; capitulum, provided with well-defined, conical acrorhagi; disc, flat; mouth, round, raised on small cone, with no gonidial grooves. Colowr.—Column, various shades of brown and gray ; verruce, bright green; acrorhagi, light green, with dark spots; tentacles, brownish white, sometimes with green sheen. Happon anp SHackLetTon—Wew Species of Actiniaria. 127 Dimensions.—Diameter of corona, 30 mm. Habitat.—In crevices and holes in stones on the shore, Mabuiag,. October, 1888. This species is named after Sesere, the legendary hunter of the dugong, who lived on the neighbouring island of Badu (cf. “ Legends from Torres Straits,” Folk-lore, 1., 1890, p. 23. ’ Wiatrix cimeta, n. sp. Form.—Tissues, delicate ; column, short, cylindrical ; capitulum produced into a very prominent rim, from which project at least six club-shaped enlargements, which may bear secondary tubercles. on their aboral aspect; tentacles rather short, in three cycles. (12 + 12 + 24 = 48). . Colour.—Kctoderm, colourless; but the endoderm everywhere shines through, with a brown colour; processes, with white ends; secondary tubercles, bright green. Dimensions.—Height of column, 6 mm. Habitat.—Surface of reef, Mabuiag, October, 1888. This is probably an immature form; the specific name is. derived from the girdle-like appearance of the capitular rim, beset, as it were, with bosses of emeralds. It appears to us to be allied to Hoplophoria coralligens, Wils.1 Prof. Mac Murrich has, however, informed us that this species is Viatrix globulifera (Duch.), but we must confess to seeing but little resemblance between the figures given by Wilson and by Duchassaing and Michelotti.? If Dr. Wilson’s species is a Viatriv, ours must, we think, be also placed in that genus. BUNODIDAE. Alicia rhadina, n. sp. Form.—Columnar, when fully extended, conical when retracted ;. basal dise flat, adhering; scapus, delicate, with simple and com- pound tubercles mainly disposed in vertical series; capitulum, delicate, non-tuberculate ; oral disc expanded, often crateriform, 1H. V. Wilson, ‘On a New Actinia, Hoplophoria coralligens.’’ Studies Biol Lab. Johns Hopkins Univ. 1v. Pl. xlii. 2 «« Mémoire sur les Coralliaires des Antilles.” Mem. Reale Accad. Torino, (2) x1x- 1860. Pl. vi., figs. 15, 16. 128 Scientific Proceedings, Royal Dublin Society. may be flat, or at times even conical; tentacles, 48 in number in two cycles, those of the inner cycle being the longer; mouth, oval, with twelve slight ridges, but no gonidial grooves; the whole animal is extremely delicate in texture. Colowr.—Body, translucent white, almost transparent; six vertical rows of brown, and six of white tubercles, all of which have a greenish gray apex, surrounded by a narrow ring of cream colour; the inner cycle of tentacles transparent and free from colour except aslight tinge of pale pink in some lights, outer cycle similar, but with a bright orange mark at their base, and a dark violet-brown oval spot. Dimensions.—Column, when fully expanded, 30 mm. high and 17 mm. in diameter. Habitat.—Albany Pass, Cape York, 10 fms. The specific name is derived from the latinised form of padtvoc, delicate. This species is undoubtedly allied to —Journ. Geol. Soc.,. of Dublin, vol. ix. 1860-62. (5) Barry, W. H.: “Figures of Characteristic British Fossils.”—Vol. i., Paleeozoic.. 1875. (6) Surupsorz, G. W.: ‘‘A Review of the British Carboniferous Fenestellide.’’—Quart. Journ. Geol. Soc., London, vol. xxxv., p. 275. 1879. Cezar, 1 AS: ‘‘ Handbuch der Paleontologie.”—Band i. 1880. (3) Prov, Hi. A. ; ‘« Third series of descriptions of Bryozoa from the Paleozoic rocks of the Western States and Territories.”-—Trans, Acad. Science of St. Louis, vol. i., p. 448. 1860. (9) Uxricu, E. 0.: Geological Survey of Illinois.—Vol. viii., pp. 285-688. 1890. (10) Hatt, Jas. : : ‘¢ Paleontology of the State of New York.”—Vol. vi. 1887. (11) Nicworson, H. A.: ‘Descriptions of two new Genera and Species of Polyzoa from the Devonian Rocks.”—Ann. and Mag. Nat. Hist., Ser. 4, vol. xill., p. 77. 1874. 144 Scientific Proceedings, Royal Dublin Society. EXPLANATION OF PLATE VIII. [All the figures are from specimens of Hemitrypa hibernica, from Garden- field, near Tuam, Co. Galway. | Fics. 1. Transverse section, viewed by transmitted light, showing four branches or columns, each with its pair of zoccia. One of the zocecia shows the aperture, directed towards the tegmen. In three cases a pillar-like process has been traversed, the outer ex- pansion of which forms part of the tegmen. The primary ribbed reverse of the columns, with the more opaque secondary thicken- ing, can be well seen. x 20. 2. Vertical section, viewed by transmitted light, showing the reverse on the left, and the zocecia, with the pillars that support the teg- men, on the right. The tegmen itself is lost. x 30. 8. Dissection of a thin slice, viewed obliquely, showing the ribbed columns, from which the secondary deposit has been broken away ; the inner face of the tegmen is seen on the right, and a transverse section of the whole structure occurs on the surface of the slice. Three dissepiments are also seen. x 8.’ 4. Section of limestone, viewed by reflected light, showing parts .of several zoaria, crowded together, in various stages of growth. x 4. 5. External view of a zoarium, the tegminal apertures being barely visible to the naked eye. In the upper left-hand portion the teg- men has been broken away, and the fenestrules, with remnants of the columns, can be seen. Natural size. ( 145 J XI. ON THE BRIGHT COLOURS OF ALPINE FLOWERS. By J. JOLY, M.A., Sc. D., F.R.S. [Read January 18; Received for publication January 20; Published Marcu 25, 1893.] Ty is admitted by all observers that many species of flowering plants growing on the higher alps of mountainous regions display a more vivid and richer colour in their bloom than is displayed in the same species growing in the valleys. That this is actually the ease, and not merely an effect produced upon the observer by the scant foliage rendering the bloom more conspicuous, has been shown by comparative microscopic examination of the petals of species growing on the heights and in the valleys. Such exami- nation has revealed that in many cases pigment granules are more numerous in the individuals growing at the higher altitudes. The difference is specially marked in Myosotis sylvatica, Campanula rotundifolia, Ranunculus sylvaticus, Galium cruciatum, and others. It is less marked in the case of Zhymus serpyllum and Geranium sylvatica ; while in Rosa alpina and Erigeron alpinus no difference is observable.’ In the following cases a difference of intensity of colour is, according to Kerner (‘“‘ Pflanzen Leben,” 11. 504), specially noticeable :—Agrostema githago, Campanula pusilla, Dianthus inodo- rus (silvestris), Gypsophila repens, Lotus corniculatus, Saponaria ocymoides, Satureja hortensis, Taraxacum officinale, Vicia cracca, and Vicia sepium. To my own observation this beautiful phenomenon has always appeared most obvious and impressive. It appears to have struck many unprofessional observers. Helmholtz offers the explanation that the vivid colours are the result of the brighter sunlight upon the heights. It has been said, too, that they are the direct chemical effects of a more highly ozonized atmosphere. The latter expla- 1G. Bonnier, quoted by De Varigny, ‘‘ Experimental Evolutions,’’ p. 55. SCIEN. PROC. R.D.S., VOL. VII., PART I. L 146 Scientific Proceedings, Royal Dublin Society. nation I am unable to refer to its author. The following pages contain a suggestion on the matter, which occurred to me while in the Linthal district of Switzerland last summer. I have some compunction in offering the suggestion of an unprofessional. If the bloom of these higher alpine flowers is especially pleasing to my own esthetic instincts, and markedly conspicuous to me as an observer, why not also especially attractive and con- spicuous to the insect whose mission it is to wander from flower to flower over the pastures? The answer to this question involves the hypothesis I would advance as accounting for the bright colours of high-growing individuals. In short, I believe a satis- factory explanation is to be found in the conditions of insect life in the higher alps.’ In the higher pastures the summer begins late and closes early, and even in the middle of summer the day closes in with extreme cold, and the cold of night is only dispelled when the sun is well up. Again, clouds cover the heights when all is clear below, and cold winds sweep over them when there is warmth and shelter in the valleys. These rigorous conditions the fertilizers have to con- tend with in their search for food, and that when the rival attrac- tions of the valleys below are so many. I believe it is these rigorous conditions which are indirectly responsible for the bright colours of alpine flowers. For such conditions will bring about a comparative scarcity of insect activity on the heights; and a scarcity or uncertainty in the action of insect agency in effecting fertilization will intensify the competition to attract attention, and only the brightest blooms will be fertilized.’ This will be a natural selection of the brightest, or the 1 Mr. Grant Allen, I have recently learned, advances in ‘‘ Science in Arcady’’ the theory that there is a natural selective cause fostering the bright blooms of alpines. The selective cause is, however, by him referred to the greater abundance of butterfly relatively to bee fertilizers. ‘The former, he says, display more esthetic instinct than bees. In the valley the bees secure the fertilization of all. I may observe that upon the Fridolins Alp all the fertilizers I observed were bees. I have always found butterflies very scarce at altitudes of 7000 to 8000 feet. The alpine bees are very light in body, like our hive bee, and I do not think rarefaction of the atmosphere can operate to hinder its ascent to the heights, as Mr. Grant Allen suggests. The — observations on the death-rate of bees and butterflies on the glacier, to be referred to presently, seem to negative such a hypotheses, and to show that a large preponderance of bees over butterflies make their way to the heights. Joty—The Bright Oolours of Alpine Flowers. 147 brightest will be the fittest, and this condition, with the fact of heredity, will encourage a race of vivid flowers. On the other hand, the more scant and uncertain root supply, and the severe atmospheric conditions, will not encourage the grosser struggle for existence which in the valleys is carried on so eagerly between leaves and branches, and so the struggle becomes refined into the more ethical one of colour and brightness between flower and flower. Hence the scanty foliage and vivid bloom would be at once the result of a necessary economy, and a resort to the best method of securing reproduction under the circumstances of insect fertilizing agency. Or, in other words, while the luxuriant growth is forbidden by the conditions, and thus methods of offence and defence based upon vigorous development, reduced in importance, it would appear that the struggle is greatly referred to rivalry for insect preference. It is probable that this is the more economical manner of carrying on the struggle. As regards the conditions of insect life in the higher alps, it came to my notice in a very striking manner that vast numbers of such bees and butterflies as venture up perish in the cold of night time. It appears as if at the approach of dusk these are attracted by the gleam of the snow, and quitting the pastures, lose themselves upon the glaciers and firns, there to die in hundreds. Thus in an ascent of the Todi from the Fridolins hiitte I counted in the early dawn sixty-seven frozen bees, twenty- nine dead butterflies, and some half-dozen moths on the Biferten glacier and firn. These numbers, it is to be remembered, only in- cluded those lying to either side of our way over the snow, so that the number must have mounted up to thousands when integrated over the entire glacier and firn. Approaching the summit none were found. The bees resembled our hive bee in appearance, the butterflies resembled the small white variety common in our gar- dens, which has yellow and black upon its wings. One large moth, striped across the abdomen, and measuring nearly two inches in length of ‘body, was found. Upon our return, long after the sun’s rays had grown strong, I observed some of the butterflies showed signs of reanimation. We descended so quickly to avoid the inconvenience of the soft snow that I had time for no observa- tions on the frozen bees. But dead bees are common objects upon the snows of the alps. 5 L2 148 Scientific Proceedings, Royal Dublin Society. These remarks I noted down roughly while at Linthal this summer, but quite recently I read in “Natural Science” for December, 1892, vol. 1., p. 730, the following note :— “ Tate Flowering Plants.— While we write, the ivy is in flower, and bees, wasps, and flies are jostling each other and struggling to find standing-room on the sweet-smelling plant. How great must be the advantage obtained by this plant through its exceptional habit of flowering in the late autumn, and ripening its fruit in the spring. To anyone who has watched the struggle to approach the ivy-blossom at a time when nearly all other plants are bare, it is evident that as far as transport of pollen and cross-fertilization go, the plant could not flower at a more suitable time. The season is so late that most other plants are out of flower, but yet it is not too late for many insects to be brought out by each sunny day, and each insect, judging by its behaviour, must be exceptionally hungry. ‘Not only has the ivy the world to itself during its flowering season, but it delays to ripen its seed till the spring, a time when most other plants have shed their seed, and most edible fruits have been picked by the birds. Thus birds wanting fruit in tke spring can obtain little but ivy, and how they appreciate the ivy berry is evident by the purple stains everywhere visible within a short distance of the bush.” These remarks suggest that the ivy adopts the converse atti- tude towards its fertilizers to that forced upon the alpine flower. The ivy bloom is small and inconspicuous, but then it has the season to itself, and its unobservability is no disadvantage, 7. e. if one plant was more conspicuous than its neighbours, it would not have any decided advantage where the fertilizer is so abundant and otherwise unprovided for. Its dark-green berries in spring, which I would describe as very inconspicuous, have a similar advantage in relation to the necessities of bird life. The experiments of M. C. Flahault must be noticed. This naturalist grew seeds of coloured flowers which had ripened in Paris; part in Upsala, and part in Paris; and seed which had ripened in Upsala part at Paris, and part at Upsala. The flowers | opening in the more northern city were in most cases the brighter.’ 1 Quoted by De Varigny, ‘Experimental Evolution,” p. 56. Joty—The Bright Colours of Alpine Flowers. 149 Tf this observation may be considered unquestionable, as appears to be the case, the question arises, Are we to regard this as a direct effect of the more rigorous climate upon the development of colouring matter on the blooms opening at Upsala? If we sup- pose an affirmative answer, the theory of direct effect by sun bright- ness must I think be abandoned. But I venture to think that the explanation of the Upsala experiment is not to be found in direct climatic influence upon the colour, but in causes which lie deeper, and involve some factors deducible from biological theory. The organism, from the great facts of heredity of qualities and survival of the fittest, is necessarily a system which gathers ex- perience with successive generations, and the principal lesson ever being impressed upon it by external events is economy. Its suc- cess depends upon the use it makes of its opportunities for the reception of energy and the economy attained in disposing of what © is gained. With regard to using the passing opportunity, the entire seasonal development of life isa manifestation of this attitude, and the fleetness, agility, &c., of higher organisms are develop- ments in this direction. The higher vegetable organism is not locomotory, save in the transferences of pollen and seed, for its food comes to it, and the necessary relative motion between food and organism is preserved in the quick motion of radiated energy from the sun and the slower motion of the winds on the surface of the earth. But, even so, the vegetable organism must stand ever ready and waiting for itssupplies. Its molecular parts must (spider- like) be ready to spring upon the prey offered to it. Hence, the plant stands ready, and every cloud with moving shadow crossing the fields handicaps the one organism to the benefit of the unshaded plant in the adjoining field. The open bloom is a mani- festation of the generally expectant attitude of the plant, but in relation to reproduction. ) As regards economy, any principle of maximum economy, where many functions have to be fulfilled, will, we may very safely predict, involve as far as possible mutual helpfulness in the processes going on. Thus the process of the development towards meeting any particular external conditions, A, suppose, will, if possible, tend to forward the development towards meet- ing conditions B; so that, in short, where circumstances of 150 Scientific Proceedings, Royal Dublin Society. morphology and physiology are favourable, the ideally economical system will be attained when in place of two separate processes, a, (3, the one process y, cheaper than a+ (3, suffices to advance development simultaneously in both the directions A and B. The economy is as obvious as that involved in “ killing two birds with the one stone,’’ and although expressed here rather crudely, it is to be expected with certainty (I venture to think) that to foster such economy will be the tendency of evolution in all organic systems subjected to restraints as those we are acquainted with invariably are. Such economy might be simply illustrated by considering the case of a reservoir of water elevated above two hydraulic motors, so that the elevated mass of water possessed gravitational potential [the daily gains or the stored-up reserve material of the organism]. How best may the water be conveyed to the two motors [the or- ganic reactions towards conditions A and B] so that as little head as possible is lost in transit? If the motors are near together it is most economical to use the one conduit, which will distribute the requisite supply of water to both. If the motors are located far asunder it will be most economical to lay two pipes. [There is greatest economy in meeting a plurality of functions by the same train of physiological processes where this is consistent with discharging other functions necessitated by external or internal conditions. | _ A But an important and obvious consequence arises in the supply of the two motors from the one conduit. We cannot work one motor without working the other. Ii we open a valve inthe conduit both motors start into motion and begin consuming the energy stored in the tank. And although they may both under one set of con- ditions be doing useful and necessary work for us, in some other set of conditions it may be quite needless for both to be driven. - This last fact is an illustration of a consideration which must enter into the phenomenon which an eminent biologist speaks of as physiological or unconscious ‘‘ memory,” and illustrates that in the organism its development from the ovum is but the starting of a train of interdependent events of a complexity depending upon the experience of the past. 1 Professor Hering, quoted by Professor Ray Lankaster, ‘‘ The Advancement of Science,’’ p. 283. Jory—The Bright Colours of Alpine Flowers. - 151 In short, we may suppose the entire development of the plant, towards meeting certain groups of external conditions, physiologi- cally knit together according as Nature tends to associate certain groups of conditions. Thus, in the case in point, climatic rigour and scarcity of fertilizing agency will ever be associated; and in the long experience of the past the most economical physiological attitude towards both is, we may suppose, adopted. So that the presence of one condition excites the apparent unconscious memory of the other. In reality the process of meeting the one condition involves the process and development for meeting the other. And this consideration may be extended very generally to such organisms as can survive under the same associated natural conditions, for the history of evolution is so long, and the power of locomotion so essential to the organism at some period in its life history, that we cannot philosophically assume a local history for members of a species even if widely severed geographically at the present day. At some period in the past, then, it is very possible that the species to-day thriving at Paris, acquired the expe- rience called out at Upsala. The perfection of physiological memory inspires no limit to the date at which this may have occurred—possibly the result of a succession of severe seasons at Paris; possibly the result of migrations—and the seed of many flowering plants possess means of migration only inferior to that possessed by the flying and swimming animals. But, again, possibly the experience was acquired far back in the evolutionary history of the flower.! But a further consideration arises. Not only at each moment in the life of the individual must maximum income and most judi- cious expenditure be considered, but in its whole life history, and even over the history of its race, the efficiency must tend to be a maximum. ‘This principle is even carried so far that when neces- sary it leads to the death of the individual, as in the case of 1 The blooms of self-fertilising, and especially of cleistogamic plants (e.g. Viola). are examples of unconscious memory, or unconscious ‘association of ideas’’ leading to the development of organs now functionless. The Pontederia crassipes of the Amazon, which develops its floating bladders when grown in water, but aborts them rapidly when grown on land, and seems to retain this power of adaptation to the environment for an indefinite period of time, must act in each case upon an unconscious memory based upon past experience. Many other cases might be cited. 152 Scientific Proceedings, Royal Dublin Society. those organisms which, having accomplished the reproductive act, almost immediately expire. This view of nature is very repel- lent to us who reflect and are self-conscious. But it is, never- theless, evident that we are but parts of an economical system which ruthlessly sacrifices the individual on general grounds of economy. ‘Thus, if, in the life history of any individual organism, the (imaginary) curve which defines the mean rate of reception of energy at different periods of life be opposed by a second curve Energy Time drawn below the axis along which time is measured, representing the mean rate of expenditure of energy (see fig.), this curve must be of such a nature from its origin to its completion in death, when there is no further expenditure of energy except in the post- vital disintegration of the body, that the condition is realized of the most economical rate of expenditure at each period of life.* The rate of expenditure of energy at any period of life is, of course, in such a curve defined by the slope of the curve towards the axis of time at the period in question; but this particular slope must be led to by a previous part of the curve, and involves its past and future course to a very great extent. There will, there- fore be impressed upon the organism by the factors of evolution a unified course of economical expenditure completed only by its death, and which will give to the developmental progress of the individual its prophetic character. In this way we philosophically look to the unified career of each organic unit, from its commencement in the ovum to the 1 See “‘ The abundance of Life,’’ these Proceedings, ante, Vol. vu, p. 78. Joty—The Bright Colours of Alpine Flowers. 153 day when it is done with vitality, for the explanation of that preparation for momentous organic events which is in progress: throughout the entire course of development, and to the economy involved in the physiological welding of processes for the pheno- menon of physiological memory, wherein we see reflected, as it were, in the development of the organism, the association of inorganic restraints occurring in nature which at some previous period impressed itself upon the plastic organism. We may pic- ture, somewhat crudely, the seedling at Upsala swayed by organic memory and the inherited tendency to an economical prepara- tion for future events gradually developing towards the esthetic climax of its career. In some such manner only does it appear possible to account for the prophetic development of organisms, not alone to be observed in the alpine flowers, but throughout nature. And thus, finally, to the effects of natural selection and to actions defined by general principles involved in biology, I would venture to refer for explanation of the manner in which flowers om the Alps develop towards their unusual beauty. [154] XII. SUGGESTION AS TO A POSSIBLE SOURCE OF THE ENERGY REQUIRED FOR THE LIFE OF BACILLI, AND AS TO THE CAUSE OF THEIR SMALL SIZE. By G. JOHNSTONE STONEY, M.A., D.Sc., F.R.S., Vice- President, Royal Dublin Society. [Read January 18; Received for publication January 20; Published Marcu 25, 1893.] Some bacilli, e.g. some of the nitrifying bacilli of the soil, are said to be sustained by purely mineral food. If this be the case they must be supplied with a considerable amount of energy to enable them to evolve protoplasm and the other organic compounds of which they consist, from these ‘materials. Now many bacilli are so situated that this energy is certainly not obtained from sunshine, and it is suggested that it may be derived from the gases or liquids about them. The average speed with which the molecules of air dart about is known to be nearly 500 metres per second—the velocity of a rifle bullet; and the velocity of some of the molecules must be many times this, probably five, six, or seven times as swift. We do not know so much about the velocities of the molecules in liquids.as of those in gases, but the phenomenon of evaporation and some others indicate that they are at least occasionally com- parable with those of a gas. Accordingly, whether the microbe derive a part of its oxygen or other nourishment from the gases, or from the liquids about it, it is conceivable that only the swifter moving molecules can penetrate the microbe sufficiently dar, or from some other cause are either alone or predominantly fitted to be assimilated by it. Now if this be what is actually taking place, the adjoining air or liquid must become cooler through the withdrawal from it of its swiltest molecules; and in compensation, an amount of energy exactly equivalent to this loss of heat is imparted to the microbes and available for the formation within them of organic com- pounds. Sroney—Lnergy Required for the Life of Bacilli. 155 It is further evident that if this be the source of energy upon which bacilli and cocci have to draw, the minutenes of their narrowest dimension will be of advantage—probably essential— to them. Presumably it would only be limited by such other necessary conditions as may forbid the diminution of size being carried beyond a certain point. The diameter of a bacillus is frequently as small as half or a third of a micron, which brings it tolerably well into the neighbourhood of some molecular magnitudes. The transference of energy here suggested may be what occurs notwithstanding that it does not comply with the Second Law of Thermodynamics, which states that heat will not pass from a cooler to a warmer body, unless some adequate compensating event occurs, or has occurred, in connexion with the transference. This law represents what happens when vast numbers of mole- cular. events (which are the real events of nature) admit of being treated statistically, and furnish an average result. It, therefore, has its limits: and the communication of energy from air to minute organisms, which is described above, is an example of a process which is exempt from its operation; since this trans- ference is supposed to be brought about by a discriminating treatment of the molecules that impinge upon the bacillus of precisely the same kind as that which Maxwell pictured as nade by his well-known demons. It, therefore, belongs to the recognized exception’ to the Second Law of Thermodynamics, viz. that which 1 Addition received February 20, 1893.]—I# the reader has any doubt as to whether the process described in the text is one of those that contradict the Second Law of Thermodynamics, he may satisfy himself on this head by the following considerations :— Imagine a perfect heat-engine within an adiabatic envelope, with some bacilli and an abundance of their mineral food, all being at one temperature. If events take place as supposed in the text, the bacilli receive sufficient energy from the surrounding medium to enable them to assimilate their mineral food, and thereby to grow and multiply. Meanwhile the medium becomes cooler. We may then suppose that the new bacilli which have come into existence, and all the excreta, are used as fuel in the heat-engine, and that its refrigerator is as near as we please to being at the tem- perature to which the medium has been reduced. ‘The combustion of the fuel may take the form of resolving the bacilli and excreta back into the mineral substances from which they had been evolved, except that these are now at the temperature of the combustion. Let us next reduce this temperature in the heat-engine to the temperature of the re- frigerator. During this process a portion of the heat may be converted into mechanical energy, and at the end of the process everything within the enclosure is in the same state as at the beginning, with the sole exceptions that some of the bodies within the 156 Scientific Proceedings, Royal Dublin Society. occurs in the few cases in which we can have under observation the special consequences of sedected molecular events, instead of, as on all ordinary occasions, being only able to measure an average outcome from ad/ the molecular events in the portion of matter we are examining. If some bacilli—those which live on mineral food—obtain their whole stock of energy in the way here indicated, it may be pre- sumed that all bacilli get at least a part of what they require in the same way. enclosure are now at a lower temperature than at the beginning, and that the heat which they have lost has been converted into mechanical energy. It thus appears that the contents of the adiabatic envelope may be regarded as a heat-engine, all the parts of which start at a certain temperature, and which yields. mechanical energy, while the only other change is that some of its parts are cooled to a lower temperature. This contradicts the Second Law of Thermodynamics as formu- lated by Lord Kelvin, if we leave the word ‘‘inanimate’’ out of his enunciation. His statement of the axiom is:—‘‘ It is impossible, by means of inanimate material agency, to derive mechanical effect from any portion of matter by cooling it below the temperature of the coldest of surrounding objects.’’ It is legitimate here to omit the word ‘inanimate,’ as its insertion merely means that cases of exception to the law may be met with in the organic world, and if this be stated it will need to be added that cases of exception may also be found among inorganic processes; the correct statement being that the law does not apply to individual molecular events, and that therefore it need not be obeyed in the cases, whether organic or inorganic, in which any observable effect is the outcome of one-sided molecular events. It should be borne in mind that the heat of a given portion of matter is the energy of motions of and within its molecules; not necessarily of all such motions, but of those among them which are capable of restoring energy to the parts of the molecule carrying electra (see Stoney on Double Lines in Spectra, ‘‘ Scientific Transactions of the Royal Dublin Society,’ Vol. iv., Part xi.) whenever the motion of the electron has transferred energy from the molecule to the ether. As fulfilling this criterion we are probably to include all irrotational motions within the molecules, and we must also include relative motions of the molecules—all of them indeed if time enough be allowed for turmoil within a fluid to subside. It does mot include any motion which the molecules have in common, as in wind, or in the rotation of a wheel. When these circumstances are taken into account, it is obvious that the energy of the heat motions of an individual molecule undergoes rapid fluctuations, while there may be a definite average of the energy of these motions, whether estimated by what happens in an individual molecule over a’ sufficiently long period of time, or when estimated by what occurs simultaneously in all the molecules of a body. In other words, the motions of an individual molecule do not from instant to instant conform to the Second Law of Thermodynamics, although the law may apply both to the average of the motions of a single molecule taken over a long period of time, and to the average of the simultaneous motions of vast multitudes of associated molecules. As regards molecular motions (the motions within a solid, or motions within a fluid that do not produce currents in the fluid), the millionth of one second is a long period. flay vil XIII. ON THE LAW OF GLADSTONE AND DALE AS AN OPTICAL PROBE. By PROFESSOR W. J. SOLLAS, Wascen Ul. Bons. (Abstract of a Paper read January 18, 1893, and to be published in extenso in the Screntiric TRANSACTIONS OF THE Royat Dustin Society, Vol. V.) Tue law of Gladstone and Dale asserts the constancy of the ratio of the refractive index to the density for all substances, indepen- dent of the physical state in which they exist. It is expressed by the equation i= = «x, where m signifies the refractive index, d the density, and « a constant known as the specific refractive energy. If the specific refractive energy of any substance be multiplied by the molecular weight (m), a number is obtained known as the refractive equivalent, which may be indicated by the Greek letter A. If, as verified by experiment, the elements retain their refrac- tive equivalents unchanged in the state of chemical combination the refractive equivalent of a compound will be the sum of the refractive equivalents of its elements. Thus in the case of sodium oxide we have 2Na, +O, = Na,O,. Hence, given the refractive equivalents of the elements, we can find the specific refractive energy (x) of the compound: for, calling the molecular weight m, we have: mx = Na,O,, and consequently, 7 Na.O, re 2Naqa + O7% m m K Again, since —_ =k, given « and d, we can find the refrac- tive index, or given «x and the refractive index, we can find the density. 158 Scientific Proceedings, Royal Dublin Society. _ This is true for both isotropic and anisotropic crystals, the refractive index in the latter being taken as the mean of the different indices corresponding to the three chief axes of elasticity. But since the law of Gladstone and Dale holds good when » is taken as the mean of the indices in a doubly refracting crystal, we may naturally inquire what signification it can have for the maximum, mean, and minimum indices. Ny — 1 If in the case of a uniaxial crystal we put i, oe oo ae ne -1 ae indices, respectively, three suppositions are possible. «, and Km may have identical values, and then d, and d, must be different, i.e. the density of the crystal must be different in different directions; those, namely, of the optic axis and equatorial plane, or d, and d,, may be identical, in which case x, and x, must vary directly as the refractive powers, or the specific refractive energy must be different in different directions; this supposi- tion, like the last, leading to the conclusion that the constituent chemical atoms are differently arranged in different directions. = ko, 2 and n, standing for the maximum and minimum Finally, we may suppose that both « and d vary, and then both the previous conclusions will be true; the density and chemical composition will both differ, according to direction in the crystal. But if the constancy of the specific refractive energy or of the refractive equivalents of the elements be maintained in an aniso- tropic crystal, as we have seen it is, then the possibility suggests itself of using this constancy as a means of exploring the molecu- lar structure of the crystal; in other words, of using Gladstone and Dale’s law as an optical probe. As an example, we may select the two similarly constituted salts, potassium and sodium nitrates, the latter crystallizing in rhombohedra of the hexagonal system; the former likewise in rhombohedra, but also in forms belonging to the rhombic system : the refractive indices of potassium nitrate, however, are only known for the rhombic forms. The optic sign is in both cases negative, and the refractive indices are as follows :— Potassium nitrate, my, 1°5052 mn, 15046 n, 1:3338; Sodium nitrate, . N. 1:586 Nn. Ieogaae — Sottas—On the Law of Gladstone and Dale. 159: It will be observed that the maximum and median indices of potassium nitrate, which are nearly equal, differ considerably from the maximum index of sodium nitrate; on the other hand, the minimum indices of the two salts are of nearly identical value. If, as we suppose, the refractive indices stand in close connexion ‘with the chemical constituents of the salt, we shall naturally conclude that the lower indices, which are almost the same in both compounds, are connected with the radicle, which is the same in both, 7.e. the nitric oxide; while the indices, which are markedly different, will stand in direct relation to the basic radicles, sodium and potassium oxyles. In other words, between these two salts there exist two simi- larities and two differences. The two similarities are correspon- dences between the like chemical composition and the like refractive indices; the two differences are also correspondences, but in their case between the unlike chemical constituents and the unlike refractive indices. To these two may indeed be added a third, since an equally striking correspondence is to be noted between the similar disper- sion for the minimum index in both salts (the value of pq — pp. being 0-0108 for KNO;, and 0:009 for NaNO;); and again, between the very different dispersion for the maximum index in both, the value of gx — gz for KNO, being 0:041, and for NaNO,, 0:047. ‘Let us now consider what is the most probable arrangement of atoms in the sodium nitrate molecule. Evidently the pentad nitrogen is the centre of the system, and one face looks towards sodoxyl and the other towards oxygen, thus’ “oN-O-Na. But, again, the molecule must also conform to the symmetry of the rhombohedral system, and for this at least three sodium nitrate molecules must be conjoined, while to produce a rhombohedron six will be required. ‘The following arrangement then results :— In the upper half of the molecule three atoms of nitrogen are linked together by three atoms of oxygen alternating with them, and along three radii, corresponding to the three upper edges of the rhombohedron, lie three molecules of sodoxyl, linked each by its oxygen atom to an atom of nitrogen which lies on the same radius. In the lower half of the molecule the same arrangement 160 Scientific Proceedings, Royal Dublin Society. is repeated, but the triradiate group is turned round through 60°, so that the -N-O-Na rays below lie midway between those above, and thus correspond to the three lower edges of the rhombohedron. Finally, the upper and lower moieties are united by six atoms of oxygen, which are linked to the nitrogen atoms, two of oxygen to each atom of nitrogen. Thus, each crystal molecule consists of six chemical molecules, each of the composi- tion NO;Na. It may be regarded as distributed in two differently directed groups, one consisting of oxygen (and so muck of the nitrogen as belongs to it), six atoms of which are vertically linked, 7.e. parallel to the optic axis, to a nitrogen atom; and the other of six rays of -O-N-O-Na, the chemical bonds of which lie more or less parallel to the equatorial plane. It is essential to observe, that of the nitrogen atoms, only three out of five bonds of each are horizontally linked, and consequently we are led to assign only three-fifths of the molecular weight of this element to the equatorial members of the molecule, leaving the remaining two-fifths to the oxygen, which is linked vertically. Let us now suppose a ray of light to enter our molecule along the optic axis, its wave front will lie in the equatorial plane or that in which the Na-O-N-O- members are supposed to act, and since in the direction of the optic axis there is only ordinary refraction we may connect these members with the ordinary refractive index. If, on the other hand, the path of the ray be parallel to the equatorial plane it will be resolved into an ordinary ray, the transversal of which being in the equatorial plane will be related to the equatorial members of the molecule, and an extra- ordinary ray, the transversal of which, being vertical, will be related to the vertically linked components. In this direction, in an optically negative crystal, such as sodium nitrate, the refractive index of the extraordinary ray has its minimum value, and it is this value which stands in direct relation to the refractive energy or refractive equivalents of the vertically linked atoms. . We are now in a position to apply our optical probe. If the structure of the crystal be that which we have suggested, the lower refractive index should be that due to the refractive energy of the vertical components of the molecule, and the higher, that due to the refractive energy of the equatorial component. Sottas—On the Law of Gladstone and Dale. 161 Then for Na-O-N;—O- we have :— Na Ne 0. 4°89 + 3198 + 5°56 5B 4 ODT oe and ne = low OIC ys est Src eee = 2005) = ane = 2°693. Again, for N,-O- we have :— Nz O F132 = 2:18 Raa oka = 0 2274 = Ke and ne -1 0:33853 |. neha de = 1-474, The study of atomic volumes has rendered it highly probable that the sum of the atomic volumes of the constituents of a compound is equal to the total volume of the compound, and if this be so the sum of the partial volumes (7. e. of the groups Na-O-N,-O- and N,-O) should be equal to the volume of the whole salt NO;Na. Thus we have :— m 63°4 N;0.Na, om = 3-693 SOS 23 04, m, 21:6 N,0, Gh L474 = 2 = 1465, and 23°54 + 14°65 = 38:19, while the volume found by dividing the molecular weight (85) of the whole salt by the density (2°246) is 37°85, a sufficiently close approximation. The question will now arise whether or not some other distri- bution of the atoms in the molecule would not have afforded as equally an exact agreement. In order to decide this I have treated the molecule in a variety of ways, some probable, some the reverse, but in no case does such a close correspondence between the sum of the partial volumes and that of the whole salt result. If true for sodium nitrate our treatment should also hold in SCIEN. PROC. R.D.S., VOL. VIII., PART I. M 162 Scientific Proceedings, Royal Dublin Society. the case of potassium nitrate. In this case we must make use. of the rhombic form, since the refractive indices have not been determined for the rhombohedral modification: the maximum and median indices which correspond to the ordinary index of sodium nitrate are so nearly equal that we may expect to get sufficiently approximate results by taking their mean as the index for the group K-O-N;-O-. The calculations for this and succeeding salts are given in full in the extended Memoir; in this abstract it will be sufficient to state results. Thus for K-O-N,-O-, o, = 33°76; and for N,-O-, v, = 14°78, but 38°76 + 14°73 = 48-49, and the total molecular volume of the salt is 48°8. There is thus as complete a correspondence between the sum of the partial volumes and the volume of the compound as we found in the case of sodium nitrate. Another pair of isomorphous compounds, with not very dissimilar extraordinary indices, is met with in the case of dihydric potassium arseniate and dihydric ammonium arseniate. Here we have :— AsO.KH,; 1, = 1:5674, ne = 1°5179. AsO.AmH;; n, = 1:5774, mn, = 1:6117. The vertically acting groups will be -O-As,-O-K, and -O-As;-O-NH,, the horizontally acting H-O-As,-O-H in both cases. . Calculating out in the same way as for sodium nitrate we obtain the following :— As0.K; d,=8:056, 0, = 37-96. As,0,H, 5 de = 2°482, Vz, = 25°80. The volume of the salt is 63°56, the sum of the volumes of its components 37°96 + 25°80 = 63°76. As;0,NH, 5 ay = 1:933, Y= 49:15. As,0,H, 5 dp» = 2°451, V2 = 26°11.. The volume of the whole salt is 75:15, and the sum of the volumes of the component groups 49°15 + 26-11 = 75°26. A mineral isomorphous with sodium nitrate is calcite, and if our hypothesis be true this should possess a similar molecular structure, capable of affecting rays of light in the same way. A molecule of calcite should then consist of six atoms of carbon—three below at the corners of an equilateral triangle, and three above at Sortas—On the Law of Gladstone and Dale. 163 the corners of a similar triangle, but turned round 60° with respect to that below; six atoms of oxygen will link these carbon atoms vertically, and to each will be attached a molecule of calcoxyle, the atom of calcium in each calcoxyle molecule lying at the corner of the primitive rhombohedron. Thus a group ©,0 will determine the extraordinary index, and another C.0,Ca, the ordinary index. Again our construction gives partial volumes which equal in their sum the volume of the whole salt: thus the volume of C,0,Ca is 26:12; of C,O it is 10°85; their sum is 36-92; and the volume of calcite is 36:9. This result is consistent with what is known of the values of the atomic volumes of these constituents from independent evidence, as will be shown in the detailed Memoir. Magnesite, isomorphous with calcite, gives equally satisfactory results. The volume of C,0,Mg is 18°16 and of C,0,10; their sum . is 28°16, and the volume of magnesite is 28. Dolomite falls equally readily into line. The volume of CaMg0.C is 45, and of CO,, 20°4, the sum is 65°4, and the volume of dolomite is 65°01. Arragonite and cerussite differ slightly in constitution, but they equally yield to our interpretation. Calcium tungstate and lead molybdenate appear to be similarly constituted; atall events, in each, one may suppose that the arrange- ment which determines the refractive indices is similar in both; thus in calcium tungstate the horizontally acting constituent is W.0,Ca, the vertically acting W.0.; in lead molybdenate the horizontally acting component is Mo,0.Pb, the vertically acting Mo,0,. On this supposition we find :— W:0.Ca, d, a 0°388, V1 — 24:74. Mo:02, a> = 6 685, V2 = Yolo. The sum of the partial volumes is 47°87, and the volume of the ’ whole salt is 48. Mo;0,Pb, ay = 9°775, V4= 30°88. Mo,0,, dy = 3°989, V2 = 24:07. The sum of the volumes is 54°95, and the volume of the whole salt is 54. Calomel is a difficult mineral to treat, since the refractive equivalent of the mercury in it is abnormal. Taking as the 164 Scientific Proceedings, Royal Dublin Society. probable value 32, we may suppose the arrangement of atoms in the crystal to approach to Hg—H¢g acting equatorially, and Hg-Cl acting vertically, we then obtain :— Hg,, dy = 10, Y= 10. Hg,(Cl, 12 = 4°99, 02 = 26°9. The sum is 36:9, the volume of calomel is 36:3. Numerous other compounds have been examined, with inte- resting and confirmatory results; but we must content ourselves here with a single example, the most interesting, however, of them all. This is potassium copper chloride, CuCl, 2KCl, 2H,0, the refractive indices for the line B are n, = 1°6365, ne = 1:6148. It is obvious that no constitutional formula can be devised for this salt, without invoking a higher valency for some of the elements than they commonly possess. But this is a difficulty with which chemists are familiar in a large number of other cases, nor need it surprise us if in the solid state an element should exercise more numerous bonds than in the liquid or gaseous states; 1t were rather to be expected. There are more ways than one in which the components of this hydrated potas- slum copper chloride can be built together into the complete molecule: we may choose as the simplest the following :— Horizontal Plan. Vertical Elevation. H K u s H—Cl_Cu—_Cl_H B—CiCr— Cee d Hi t The atom of copper may be regarded as placed at the node of a tetragonal crystal-net, then on four rectangular ranges lying in a plane at right angles to the optic axis are the groups of —Cl-H, on two vertical ranges corresponding to the optic axis are the two groups -O-K; acting vertically we shall then have the con- stituent Cu,-O-K, which will be related to the index for the extraordinary ray, and acting horizontally Cu,-Cl-H, which will be related to the ordinary ray. Sornas—On the Law of Gladstone and Dale. 165 Taking the following equivalents, Cu, = 11:72, Cl, = 11 Ky = 8:2, H~= 1:3, O, = 2:8, we have >,:= 82°72; and for molecular weights, Cum, = 63°15, Cl, = 35°37, K,, = 39°03, On = 15°96, H,, = 1, we have 3, = 318°64 and 82:72 / 318°64 = 0°2596 = «; also 1:623 - 1 1°6311 x 2+ 1°6070 / 3 = 1:6231 and RRO aa 0:2596 = k. Then for Cu,ClH, =“ = 14:253, and &,, = 46:9, and =" = 0°3082 = ky, (n,) 1:6811 -—1 / 0°3082 =d, = 2:081, and 46:9 / 2: a4 = 9, = 22°53. Also for Cu,OK, 34 = 12-958, Sp = 65°63, and = Eile ues (n.) 16070 / 0:1974 = d, = 3:025, and 65-68 / 3:025 = » = 21.42. Finally, v, x 4 = 90°12, and », x 2 = 42°84, and 90°12 + 42°84 = 1382°9. But 318°64 / 2°4 (the density of the salt) = 132°8. There is thus between the sum of the volumes of the com- ponents and the value of the volume of the whole salt a corre- spondence almost exact. The special interest of the salt lies, however, in the fact that it is dichroic, displaying a green tint when illuminated by the ordinary ray, and a sky-blue when seen by the extraordinary ray. If our hypothesis have in it any truth, then this difference in tint should be correlated with the difference in chemical constitution which we have imagined to exist in the direction of the vertical and horizontal crystallographic axes. Let us see. Along a vertical range lies Cu,OK; this gives for the copper-oxygen compound, Cu,0,, or CuO; ;* along a horizontal range, Cu,Cl,, or CuCl; ;! evidently the copper acting vertically is more of a cupric nature than that acting horizontally, but cupric salts are charac- teristically blue, and cuprous salts are as commonly green in colour. Thus the correspondence predicated actually exists, and in stumbling on this confirmation of our hypothesis we have discovered a theory of pleochroism. ‘The commonest pleochroic 1 Of course these are impossible compounds, and are only to be regarded as shadowing forth the true relations, which are more fully discussed in the Memoir. 166 Scientific Proceedings, Royal Dublin Society. minerals are those containing iron or manganese as constituents, and it sometimes happens that a silicate which, when containing a small quantity of iron (as what is commonly called an impurity), is pleochroic, loses the pleochroism when the ferruginous impurity is absent. If then we have a ferrous constituent acting in one direction, and no ferruginous constituent in another, the mineral may be colourless in the latter, and green in the former direction. If there exist a ferrous in one direction, and a ferric constituent in another direction, the salt may be expected to be green in the former, and yellow or reddish in the latter direction. Other cases will naturally suggest themselves. Although this paper is only an abstract of the demiled Memoir, I cannot let the opportunity pass of thanking my friends who have helped me with their criticisms and advice in this inquiry. Dublin is fortunate in possessing a number of distinguished phy- sicists—I need only mention Professors Fitzgerald and Preston, and Doctors Johnstone Stoney, Joly, and Trouton, from all of whom I have received great help in discussion, but chiefly from Professor Fitzgerald, without whose encouragement the investiga- tion, which was commenced some four or five years ago, would never have been completed. 3 Bares BD S.NS.Vel. 8. Pieneue Weiohnsondel. West,Newman lith. GHCarpenter del. Plate II. West,Newman lith. Plate 1. pera ow. West, Newman hth. Trish Rotifers. = RD.S5N.S.Vol. VIL. Plate IV. 6 TTS) 3 West,Newman lth. Trish Rotifers. os 7 ‘ “ 3 = oy ET TTT - . 7 Poe SNS. VolVil api Pilgios NUTT UAL asa NN ap a 8 West, Newnan ith. D trish Rotifers . 1, Ohar Proc RDS. N.S.VolVIL | Piatev. T..8.Gdel. ; : West, Newman ith Trish Rotifers._ Plate VII. yylllllty, NT: ae Aare rN QUE Yay yey po ee 3 i ATO L.8,@.del.- West, Newman lth, Imish Rotifer 3. Proc. R.D.S.N.S Vol VIIL. Plate VIII. alt x 20 Zi x 30 GCole del . : ’ FHMichael lth. West, Newman inp . Hemuitrypa hibernica. Can o 7 ues is Bet iad L ‘ ne THE SCIENTIFIC PROCEEDINGS 3 - OF THE ROYAL DUBLIN SOCIETY. Vol. VIII.(N.8.) SEPTEMBER, 1898. Part 2. CONTENTS. PAGE XIV.—A Lecture Note on the Relation of the Theorem of Work to the Theorem of Moments. By THomas Preston, M.A., F.R.U.I., 167 XV .—Report on Polychets collected during the Royal Dublin Society’s _ Survey off the West Coast of Ireland. Part I. Deep Water _* Forms. By Fiorence Bucnanan, B.Sc., Univ. College, London. (Plates IX., X., Xi.), . : 5 : : . 169° XVI.—Notes on Depastrum cyathiforme. By G. Y. and A. Fras. Drxon, : ; : . : ‘ 5 : : . 180 -XVII.—On a Photographic Method of detecting the Existence of Vari- able Stars. By J. Jony, M.A., Sc.D., F.R.S., . : 184 XVIII.—On the Distortion of Photographic Star Images due to Refrac- tion. By Prorressorn AntHur A. Rampavt, M.A., D.Sc., . 186 XIX.—On some Pyenogonida from the Irish Coasts. By Groner H. ul CARPENTER, B.Sc., Lond., Assistant Naturalist in the Science and Art Museum, Dublin. (Plate XII.), . ; : solde XX.—On a Graphitie Schist from Co. Donegal. By Ricuazp J. Moss, EOSe i AC... . ; : ‘ : ; : . 206 The Authors alone are responsible for all Opinions expressed in their Communications, — DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY. LONDON; WILLIAMS & NORGATE, 14, HENRIETTA-STREET, COVENT GARDEN. | ig a 4 1893. : ee Ona ts Price One Shilling and Sixpence. “seman il fuse anne Roval Dublin Society, FOUNDED, A.D. 1731. — INCORPORATED, 1749, EVENING SCIENTIFIC MEETINGS. Tux Evening Scientific Meetings of the Society and of the associated — ‘ bodies (the Royal Geological Society of Ireland and the Dublin Scientific Club) are held on Wednesday Evenings, at 8 o’Clock, during the Session. Authors desiring to read Papers before any of the Sections of the Society are requested to forward their Communications to the Registrar of the Roval Dublin Society at Jeast ten days prior to each Evening Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission to the Editor. enlemayc XIV. A LECTURE NOTE ON THE RELATION OF THE THEOREM OF WORK TO THE THEOREM OF MOMENTS. By THOMAS PRESTON, M.A., F.R.U.I. [Read Frsruary 22, Received for publication Fepruary 24; Published JuNE 13, 1893.] ‘THE moment of a force with regard to any point (being the pro- duct of the force and the distance of the point from its line of action) is clearly of the same dimensions as work, and consequently the theorem of moments, which states that the moment of the resultant of two (or more) concurrent forces is equal to the sum of the moments of the forces, must be in some way related to, if not identical with, the theorem of work which states that the virtual work of the resultant in the same case is equal to the sum of the virtual works of the component forces. It is undoubtedly impor- tant that students should have the relation between these theorems pointed out to them at the beginning of their course, so that they may have a clear grasp of the principles which they afterwards employ in so many departments, and a full knowledge of the ground on which each rests, and of how far they overlap each other, or are altogether independent. I have consequently been induced by these considerations to bring under your notice the following lecture note concerning the relation of the theorem of work to the theorem of moments. This relation will appear evident at once if we remark y that the work done by any force OX, during any displacement OP, is equal to the moment with re- gard to P of an equal force OY drawn through O at right angles to OY. For the work of OX, when O is displaced to P, is OX . OM, and the moment of OY with regard to P is OY. PN, Fig. 1. and these are obviously equal since we have taken OY = OX, and PM and PW are drawn at right angles to OX and OY respec- SCIEN. PROC. R.D.S., VOL. VIII., PART II. N 168 Scientific Proceedings, Royal Dublin Society. tively. We have then the general elementary theorem that the work of a force is equal to the moment of an equal perpendicular force. Hence if we take the case of two forces OP and OQ, and their resultant R&, forming the sides and diagonal of a parallelogram, and if three others OP’, y OQ’, OR’, be drawn at right angles to . \ them, and equal to them respectively; NY ye then if O be displaced to O’ the works of - a the forces OP, OQ, OR, will be equal to the moments of OP’, OQ’, OR’, respectively, with regard to the point 0’; but since OP’Q’R’ is a parallelogram, it follows that the moment of &’ is equal to the sum of the moments of P’ and Q’; therefore the work ot R& is equal to the sum of the works of P and Q. By some such demonstration as this I think the beginner might be shown how these two theorems are related, and that when the theorem of moments is established the theorem of work follows as a corollary; or, in fact, when if has been shown that the triangle, having the diagonal OF of a parallelogram for base, and any point as vertex, is equal to the sum of the triangles having the same point for vertex, and the sides OP and OQ for bases, then we may write down as corollaries to this geometrical theorem—(1) the theorem of moments; (2) the theorem of work ; (3) the theorem (or parallelogram) of angular velocities, the latter following from the fact that, if a body rotates round any axis OP with an angular velocity measured by OP, then the velocity of any point O’ will be measured by the product of OP and the per- pendicular from 0’ on OP, that is, by the moment of OP with regard to 0’. Similarly the velocity of O’ due to a rotation round OQ will be equal to the moment of OQ, and the sum of these is equal to the moment of OF; therefore, &e. _- perme : 7 : Ee mare - ae Le} Viele a Fig. 2. [ 169 ] XV. REPORT ON POLYCHATS COLLECTED DURING THE ROYAL DUBLIN SOCIETY’S SURVEY OFF THE WEST COAST OF IRELAND. PARTI. DEEP WATER FORMS. By FLORENCE BUCHANAN, B.Sc., Univ. College, London. (Puares IX., X., XI.) [COMMUNICATED BY PROFESSOR HADDON. | [Read Frpruary 22; Received for publication Fesruary 24; Published . June 18, 1893.] Tue collection of Polychets on which I am about to report was kindly made over to me, for the purpose of identifying the species in it, by Professor Haddon after the survey of 1891. Although small it has proved to be of some interest. Only three families, namely, the Aphroditide, the Hunicide, and the Serpulide, appear to be represented in that part of the collection obtained from deep water. ‘There is also a tube of a Terebellid. There are seven different species, of which one is new, and of which one has apparently not been recorded before, except in the neighbour- hood of the far-off Island of Kerguelen. Fam.—APHRODITID. I.—Leetmatonice producta, Gr. There are four good specimens of this species dredged from a bottom of sand and gravel at a depth of 500 fathoms 54 miles off Achill Head. There is no mistaking the species, as it agrees both with Grube’s' and M‘Intosh’s’ description ; but it is curious that, as far as I am aware, it has only as yet been recorded in the South Seas near Kerguelen, though in that region it is apparently ' Grube, Monatsberichte d. k. Akad. d. Wiss. z. Berlin, 1877, p. 512. _ ® M‘Intosh, ‘‘ Challenger Report”’ xii., p. 39, Pl. viii. and iy., Af. 1-8. : N2 170 Scientific Proceedings, Royal Dublin Society. abundant. That it does occur elsewhere, although unrecorded, I can witness from a specimen of it in the British Museum (which was labelled “ Lepidonotus”) coming from Japan. At Kerguelen both it and its varieties seem not to have been found below a depth of 120 fathoms. The Japan specimen was dredged at a depth of 43 fathoms. Perhaps it is due to the fact that the Irish specimens come from aso much greater depth that, although they have well- developed eye tubercles, they have no eyes. The only other points besides the absence of eyes in which the Irish specimens differ from the Kerguelen ones are that there are not quite so many segments (43 or 44 instead of from 44-47), and that there is a great deal of individual variation with regard to the length and size of the palps on the two sides of the body, sometimes the left, sometimes the right, being the larger, but in no specimen being quite equal in size. The median tentacle was only complete in one specimen. It is very fine and delicate, and a little over half the length of the longer of the two palps in this specimen. The so- called ‘“ glochidial” sete on the elytra-bearing segments were broken off in most of the specimens, but such as there were resembled the one figured by M‘Intosh in shape. II.—Leetmatonice filicornis, Kbg. There is one specimen which I think is to be referred to this species, though it differs in one point from Kinberg’s description® ; it was dredged at a depth of 500 fathoms 45 miles off Blackrock on a bottom of sand and gravel. A good deal of confusion obtains between the species filicornis, Kbg. and Kinbergi, Baird, some authors, e.g. Malmgren* and M‘Intosh,*® regarding them as identical, others, e.g. Ehlers,® being inclined to regard them as distinct species, the difference being that, while in L. filicornis, Khbg. the median tentacle is longer than the palps, and the ventral setee have no spine below the feather-like tuft at their extremity, 8 Kinberg, K. Sv. ‘‘Freg. Eugenies Resa,’’ Zool. 11. Annulater, p. 7, pl. iii. £. 7, a—-h. 4 Malmgren, Ann. Polych., p. 3. 5 M‘Intosh, Trans. Roy. Soc., Edin., vol. xxv. Pt. 11., 1868-9, p. 407. 6 Ehlers, ‘‘ Results of Dredging off the U. S. Coast Survey Steamer ‘ Blake.’ ”’ <“ Report on the Annelids,’’ p. 44, pl. vii., f. 6, and vui., f. 1-5. & Bucuanan—Report on Polychets. 171 in L. Kinbergi, Baird, on the other hand, the tentacle is shorter than the palps, and there ¢s a spine to the ventral sete. In the specimen in the Irish collection the median tentacle is long and very slender, but it is still only about half the length of the palps. The ventral setz, such as are complete (a great many were broken at the tips when I received the specimen), show mostly no trace of a spine. One or two, however, did show a sort of rudimentary or (?) broken spine. I have figured both kinds of setze on Pl. rx., fig. 1 (4. and B.). The specimen seemed to me, therefore, to be intermediate between the two so-called species in question, and I was inclined to agree with Malmgren and M‘Intosh that they were one. But then another difficulty arose. Ehlers is, I believe, the only writer who mentions on which segments the elytra occur. In his L. Kinbergi they are on segments 2, 4, 9, 7, . .. . 23, 26, 29. In the specimen I had before me they are on segments 2,4,57,.... 238, 25, 28, 31. Hoping to throw some light on the question I went to the British Museum to examine Baird’s original specimens of Z. [inbergi, and what speci- mens there are of L. filicornis with regard to the three points at issue: the length of the tentacles, the spine of the ventral seta, and the position of the elytra. In all the specimens, both of Baird’s L. Kinberyi (of which there are a large number, all from the North Sea off the Shetlands’) and of those labelled Z. filicornis, where the median tentacle is still present, it is shorter than the palps, being trom + to 3 their length. Taking several of Baird’s L. Kinberge at random, and examining their ventral sete, I was surprised to find that the greater number of these on most specimens had no spines (fig. 1a.); sometimes there were some with rudimentary spines (fig. 1 B.) beside those with none, but only on a few speci- mens did I find well-developed spines on the ventral setee (fig. 1 c.), 7 T may as well mention here that in the bottle labelled Z. Kinbergi, by Baird, there are present besides the Laetmatonices a good number of specimens, looking at first sight not unlike them, which are not Letmatonices at all, but which are really the Aphro- dite obtecta of Vhlers (Joc. cit. p. 42, pl. vi.), so that the specimen which I obtained at Plymouth, and mentioned in my Report to the British Association last year as being found for the first time on British Coasts, was not really new to Britain, though it had not been recorded before. It is owing to the kindness of the authorities of the British Museum that am able to comment on the specimens there; and I should like here to express my thanks for the facilities that have been given me. 172 Scientific Proceedings, Royal. Dublin Society. but when present at all they seemed to form the larger number of the sete, there being only a few with no spines or only rudi- mentary ones besides them. In all the other different specimens labelled LZ. filicornis that I examined the spines were well developed. Only in the “ Challenger”’ specimen, where very few ventral sete remained, these had rudimentary spines only. All this tends to confirm M‘Intosh’s view that there is but one species varying individually with regard to the spines on the ventral setee and prob- ably also. with regard to the relative lengths of palps and tentacle, although, as far as I know, it is only Kinberg’s original specimens which have the tentacle longer than the palps. When, however, I proceeded to count the elytra I found that on all the specimens I examined, and I examined a good many of both L. Kinbergi and L. jfilicornis, they were placed, as in the Irish specimen, on segments 2,4,5,7, . . . . 23, 25, 28,31. I am therefore led to conclude that only one species has as yet been found in British Seas. This we may call Letmatonice filicornis, Kbg. The relative length of the tentacles and palps may vary, though the tentacle is usually shorter than the palps*; there may or may not be a spine to the ventral setee (or possibly the presence of a large number of spined setee may be a sexual character acquired at certain times of year) ; the elytra are always on segments 2, 4, 5, 7,. . ; 23, 25, 28, 31. To this species I should be inclined to refer the L. violascens of Grube,’ as there are in the British Museum (in the same bottle as Baird’s Z. Hinbergi) several specimens with a distinct violet tinge to their elytra, which I believe to be the same as the one specimen from which Grube described his species. Many of these, like Grube’s specimen, have no felty covering” ; the. palps vary in length, but the tentacle is usually a good deal shorter. The ventral setae mostly, but not entirely, have well- developed spines. The elytra are as in the other specimens with regard to their arrangement, and I should consider their colour 8 The palps do occasionally vary in length on different sides of the body here as in L. producta, though not to so great an extent. This variation shows howlittle one can rely in this instance on the relative lengths of the head appendages in fixing the species. ° Jahresbericht d. Schlesischen Gesellschaft, for 1874, p. 65. 10 The Ivish specimen also had no felty covering over its back, though it had what appeared to be the remains of it at the sides of the body. Grube himself calls atten- ‘ion to the fact that the felty covering is not always present in L. filicornis. Bucuanan—Report on Polychets. 173 either as an individual variation (sexual or otherwise), or possibly as allowing them to rank as distinct variety, though not as a distinct species. From this species L. filicornis (including the L. Kinbergi of Baird and the L. violascens of Grube) we must distinguish another species for the Z. Kinbergi of Khlers, the chief specific difference being that the elytra are on segments 2, 4, 5, 7, . . . 23, 26, 29. Whether the Z. armata of Verrill™ belongs to this species, as Khlers suggests, orto L. filicornis must remain undecided, as it is not stated to which segments the elytra are attached. Fam.—EHunNIcIDz. IJI.—Eunice philocorallia, n. sp. A Eunice, presenting a good many individual variations, but which I have not been able to refer to any known species, occurred abundantly in parchment-lke tubes, inhabiting colonies of Lophohelia prolifera. I give as its specific diagnosis the fol- lowing :— Body light in colour, and iridescent, arched on the dorsal surface, tapering posteriorly. Prostomium bearing five tentacles, varying greatly in length in different individuals and with regard to one another in the same individual, but generally long, the median one being usually the longest, and reaching back over about eight segments. Palps divided by a groove each into a small median and a larger lateral lobe. One eye on each side at the base of the external tentacle. First (peristomial) segment nearly as broad as the four following ones. Second segment sharply marked off from it, except at the sides, bearing two long, smooth tentacular cirri, generally reaching beyond the palps even, though frequently varying in length on the different sides of the body. Third segment with well-developed dorsal and ventral cirri, but parapodial lobe minute and with very few sete. Para- podia on all the other segments consisting of one well-developed lobe bearing a dorsal and ventral cirrus; dorsal cirrus long, un- jointed, filamentous; ventral cirrus filamentous, and about one- third the length of the dorsal in the first four segments, after that short and blunt, swollen at the base; dorsal setee both capillary 11 Verrill, Proc. U. 8. Nat. Mus. 11, 1879, p. 168. 174 Scientific Proceedings, Royal Dublin Society. and chisel-shaped; ventral setee compound, the appendage with two hooks; acicles two anteriorly, but posteriorly sometimes as many as five (three dorsal and two ventral). Branchiz beginning on the ninth segment (seventh parapodia), with one, two, or three filaments, present on all the following segments, until very near the posterior extremity of the body, but with never more than four filaments, which are from a quarter to half the length of the dorsal cirri, and arranged in a small comb. Two anal cirri. Maxillee with six teeth each side, or with only five on the left; unpaired Sageplatte with six teeth, paired with four on the left side, eight on the right. No. of segments, 110-152; length, 120-190 mm.; breadth, 65-8 mm.; length of each of first three segments, 0-3-1 mm. ;: length of following segments, 1:3-1:8 mm. ; Tubes of a parchment-like consistency, with jagged lateral openings. Found inhabiting colonies of Lophohelia prolifera,, dredged at a depth of 200 fathoms, fifty miles off Bolus Head, Kerry. The various points are illustrated, and some of the individual differences shown in the figures, Pls. 1x. & x., figs. 2-8. The figure on Pl. x1. shows the relation between the worm and the coral. Appa- rently the worm is commensal on the coral, and to some extent modifies its growth, the coral growing round the worm-tube which thus becomes embedded in the coonenchyme. I have often seen parts of colonies of Lophohelia prolifera with hollow tubular cavities. similar to those we have here, and it seems very probable that they are likewise due to the presence of worms, although, as far as I know, no worm has as yet been described as taking up its abode in this particular coral. It would be interesting to know the nature of the worm, if present, inhabiting colonies from other localities. With regard to the one before us, I may call special attention to one specimen (Pl. 1x., fig. 4), in which there are two. tentacular cirri on the right side in the second segment, instead of one (the left tentacular cirrus happens to be broken rather near its base in this specimen). Instances of such duplication, or even 12 Other worms have been described on other corals; and different crustaceans, as is: well known, frequently cause modifications in the growth of coral. The subject is dealt with by Semper in his ‘‘ Natural Conditions of Existence as they affect Animal Life.’’ Bucnanan—Report on Polychets. 175 triplication, of organs on one side are not uncommon in Poly- cheets. Both Ehlers and Quatrefages, for instance, mention the occurrence of the same thing in Eunice gigantea. M*‘Intosh* mentions it in a Nothria. I have also occasionally noticed the duplication of an ordinary dorsal cirrus on one side in Eunice gigantea and other polychets. Perhaps the most striking ex- ample I have seen of the duplication of an organ on one side is in a Chiceia in the Royal College of Surgeons Museum, where there is a second perfect branchia smaller and nearer the dorsal median line than the ordinary one, on one side (the left), near the posterior extremity of the body (twenty-eighth segment). The branchiz of Chleia, being somewhat complex structures, this duplication is more remarkable than that of simple structures like cirri. The species would seem to be most nearly allied to the E. floridana of Ehlers,* but differs from it in the greater length of the dorsal cirri and in the possession of a smaller number of branchial filaments, also somewhat in the shape of the maxille. There were three small Hunices, one of only 20 mm. in length in the coral itself, another of about 30 mm. in the same bottle with the coral, and the third, of 86 mm., in a red serpulid tube, dredged with the coral. These I take to be the young of Eunice philocorallia. The jaws have the same six teeth each side, and are in other ways much alike. In the smallest specimen there is only a single filament to each branchia (except on a few segments here and there, where there are two), and this is almost as long as the dorsal cirrus in some segments. The same variation in the length of the tentacles occurs as in the adults, the right inner lateral tentacle being a good deal—longer than the median or than any of the other tentacles. In the same way, the right tentacular cirrus of the second segments is longer than the left. In the other two specimens the branchie, except in the first few segments after their appearance at all, have two filaments, and occasionally even three. I have figured the head and one parapodium of the largest of these three specimens (PI. x., figs. 8 and 9). 13 Ehlers, ‘“‘ Borstenwtirmer,” p. 311. 14 «¢ Quatrefages,’’ Annélés, vol. 1., p. 312. 15 M‘Intosh, ‘‘ Challenger Report,’ x11., p. 328. 16 Ehlers ‘‘ Report on Dredging, &c.,”’ doc. cit. p. 88, pl. xxii. 176 Scientific Proceedings, Royal Dublin Society. In a species in which so many individual variations occur, it is curious that the branchiz should begin so regularly on the 9th segment on each side, as this is one of the points most liable to variation in the Hunicide. Only in two specimens (one young and one adult) did I find the branchize beginning on the 10th instead of on the 9th segment on one side of the body. With regard to the tentacles, although not annulate as a rule, apparent anuulation occasionally occurs in one or other of the ten- tacles of the adult (cf Pl. m., fig. 2); and in two of the young specimens there are faint traces of annulation. It seems to me doubtful whether so much importance should be attached to the an- nulation of the tentacles, as Grube does for instance in his Revision of the Eunicide in the Jahresb. Schles. Gesellsch. for 1877. Ehlers draws attention to the variation in individuals with regard to this point for EL. rubrocincta." The same may be said for the dorsal eri (cf. fig. 7a.) Fam.—SERPULID&. (a. Serpulidee proper.) IV.—Serpula Philippii, Morch. (Serpula vermicularis, Phil.). Two specimens of this fairly-common species** occurred with the Lophohelia prolifera above mentioned. In both of them the well developed operculum is on the left side, the rudimentary on the right. A third specimen, which I think is referable to this species, was dredged 45 miles off Blackrock, at a depth of 275 fathoms. It only differs from S. vermicularis as usually described, in having eight instead of seven thoracic bundles of sete. Variations with regard to the segments between which the change of sete takes place do, however, occur in other members of the family (e. g. Sabella viola, Grube, A. f. N. Jahrg. 29. 1863, p. 58). In this specimen the well-developed operculum is on the right side, the rudimentary one on the left. 7 Ehlers. ‘‘ Borstenwtirmer,”’ p. 345. 18 Perhaps the best figure of the species extant is the one given in Cuvier’s ‘* Régne Animal.”” Annelides (Edition acc. de Planches), pl. iii. fig. 1, under the name of 8. contortuplicata. Bucnanan— Report of Polychets. 177 V.—Hydroides pectinata (Kuppf.) v. Mrallr. (= H. norvegica, Gunn. and Hupomatus trypanon, Clp.) Several specimens of this species occurred, all attached to the spines of Cidaris papillata, dredged both 40 miles off Achill Head, at a depth of 220 fathoms, from a bottom of fine sand, and 45 miles off Blackrock, at a depth of 275 fathoms, from a rocky bottom. Ciaparéde” also mentions it as occurring on the spines of Cidaris. The number of pairs of teeth to each spine of the oper- culum is not necessarily limited to two, as Claparéde seems to imply, and there may be as many as sixteen spines to the operculum. (b. Sabellides.) V1.—Dasychone Savignii, Johnst. There is one specimen which I venture to refer to this species, because as far as Johnston’s description” goes it agrees with it, and because the Dasychone argus, Sars (the D. Dalyelli, Koll.), to which Malmgren” refers it with a query, differs from it in having eyes on the branchiz. My specimen, like Johnston’s, has no eyes on the branchiz, and also, like Johnston’s, the branchie are longer in proportion to the body than they are in the Dasychone argus or the D. lucullana of Sars, to one of which species the Sabella (D.) bomby« of Johnston, from which he distinguishes his S. (D.) Savigni, probably belongs. (Malmgren unites all three species; Carus ” distinguishes two species—the D. lucullana of Delle Chiaje and Sars, and the D. polyzonos, Pane., including D. Da/yelii, Koll., and D. argus, Sars, but does not say to which he would refer Johnston’s D. bombyx). For the sake of clearness I have figured my specimen (figs. 10-12), and subjoin a specific diagnosis. Dasychone,* with branchize more than half the length of the 19 Claparéde, Ann. Chet. d. G. d. Naples Suppl. p. 527, pl. xiv., f. 4. 20 Johnston, ‘‘ Catalogue of Worms in the Brit. Mus.,” p. 261. 21 Malmgren, Nordiska Hats. Annulater Ofvers, af. K. Vet. Ak. Férh. 1865, p- 403, and Annul. Polych., Jbid. 1867, p. 241. 22 «Carus. Faune Mediterranex,’’ p. 272. 23 It may be convenient to have the generic diagnosis at hand. I therefore quote the substance of that given by Carus :—Collar thin, divided into two halves; setigerous tubercles beginning on the collar segment, with winged capillary sete, long and slightly curved at the apex; uncinigerous tori beginning in the second segment, each bearing a 178 Scientific Proceedinys, Royal Dublin Society. body ; filaments varying individually in length and not necessarily equal in number on both sides of the body (16-19), richly barbed on the ventral side, but with very few, only two, or sometimes three, very short barbs on the dorsal side, and with no ocular spots. Prostomial tentacles lanceolate, one-third length of branchie. Change of sete 8/9. Capillary sete of thorax of two kinds. Dark spots between the sete and tori extending nearly to the posterior end of the body through about the first thirty segments. On each ventral shield on either side of the middle line through the same segments there is also a dark spot.” Number of segments, about 45. Length (without branchie) about 10 mm.; branchiz, 6 mm.; breadth, 1:5 mm. Tubes of closely adhering mud and fine sand. Locality, 50 miles off Bolus Head, 200 fathoms, ‘‘ coral’ bottom. The specimen is not very complete, and I have had to ‘‘ restore” it somewhat in figuring it. A peculiarity in my specimen is that the posterior end is bifid (Pl. x., fig. 10), but the anus apparently is between the two prongs, not as in Claparéde’s specimen of Salma- cina incrustans,”> also double. Tam not sure in how far I am justified in associating this with Johnston’s species,”* but think it will be less confusing than making a new species for a single and not quite complete specimen. Fam.—TEREBELLIDA. The tube of a Terebella, which is probably the 7. flabellum of Baird” and M‘Intosh** was dredged 40 miles off Achill Head at a depth of 220 fathoms. single row of avicular uncini, everywhere of the same form. Branchie forming a semi- circle somewhat convoluted at the base on each side, apex of each filament naked, short and subulate, bases connected to form a membrane, dorsal appendages to branchial filaments present, but short, arranged in pairs; ocular spots on the branchie in some species, not in others. A black spot on each side of the body between each torus and bundle of capillary set. 24 The same thing occurs, judging from some Naples specimens, in D. ducuilan, Sars and D. Ch. ees Claparede,”” Ann. (Ohoet. Bt-pi1,) pal 71, plex centro ee 26 Johnston’s type specimen, as Malmgren has already observed, has now got no branchiz, and would be very difficult to diagnose. *7 Baird, Journ. Linn. Soc., vii., p. 157, pl. v., figs. 1 and 2. *8 M‘Intosh, ‘‘ Challenger Report,”’ p. 447, pl. 1., fig. 1. Fig. Bucuanan—Report on Polychets. 179 EXPLANATION OF PLATES. PLATE IX. . Neuropodial sete of Letmatonice filicornis, Kbe. A and B, from the specimen in the Irish collection. c, from a specimen in the British Museum. 2. Anterior extremity of Hunice philocoraliia, n. sp. Dorsal view. Fig. 3. Same (of another specimen), ventral view. The white part of the mandibles is seen projecting from the mouth. Fig. 4. Dorsal view of the first three segments of another specimen, show- ing the double tentacular cirrus on the right side. Fig. 5. Maxille. Fig. 6. Mandibles. PLATE X. Fig. 7, Parapodia— a, of the third segment. b, of one of the middle segments.” c, of one of the posterior segments. Fig. 8. Dorsal view of anterior region of a young Hunice philocorallia. Fig. 9. Parapodium from about the middle region of the same. Fig. 10. Dasychone Savignit, Johnst. Ventral view. Fig. 11. Left side of anterior part of the body of the same to show the shape of the collar. . Sete of same. a and 8, capillary sete of thorax. ec, uncinus. bool By Bo. Eunice philocorallia in Lophoheha prolifera, the coral broken so as to show the posterior extremity of the worm as well as the anterior. The parchment-like tube of the worm is also seen. This figure was kindly drawn for me by Mr. E. T. Brown of the Zoological Laboratory of University College. 29 The branchie are not usually as long as they are in the parapodium here figured. iy isons XVI. NOTES ON DEPASTRUM CYATHIFORME. By G. Y. ann A. FRAS. DIXON. [Read May 21, 1890; Received for publication Marcu 24, 1893; Published June 18, 1893.] Depastrum cyathiforme, Gosse.—We have found this rare Lucernarian on both sides of Dalkey Sound. It adheres to the under-sides of granite boulders. It is troublesome to keep in captivity, as it must be lifted daily out of the water for a couple of hours to supply the place of the fall of the tide. It is necessary to chip off the piece of stone to which the base adheres, for if removed from its attachment it seems to have no power of adhering to any new locality. We have never observed a specimen which had been detached from its foothold re-attach itself, though it might live for some time at the bottom of the tank. As this animal has been rarely met with, and never fully described, we append a full account of its external form. Form.—Urn-shaped when expanded; quarter of an inch in diameter, rather more in height; globular and furrowed when contracted. In the extended state the animal has a conspicuous flexible sta/k, with an irregularly expanded, flat, adhesive foot : the stalk forms about half the entire height, and when the animal is. contracted assumes an anularappearance. The wmbrella is broadly campanulate, its distal end being reflexed or turned out, and furnished with numerous over-arching tentacles. The sub-umbrella is deeply concave ; half-way between its tentacular edge and the mouth (measuring along an imaginary line drawn from the tentacles to the lip of the mouth) four buttress-like processes issue from the sub-umbrella and stretch across to the mouth, each joining the latter at one of its four corners. Between these buttresses the sub-umbrella forms deep pouches, each pouch being bounded externally, and to a certain extent inferiorly, by the Dixon—WNotes on Depastrum Cyathiforme. 181 sub-umbrella, internally by one of the sides of the quadri- lateral columnar mouth-tube, and laterally on each side by one of the buttresses. The mouth is very variable: it is at one moment a plain four-sided funnel; at another it is closed and folds its thick lips so that the oral aperture becomes a mere slit, or perhaps four slits, arranged like a St. Andrew’s Cross. In large specimens the limbs of this cross may be still further modified by zig-zag foldings. The tentacles are knobbed and numerous : in normal specimens we have never found less than thirty-six, and never more than ninety-six. In small specimens they are set in a single row; in large specimens they are set in two or more rows, and are divided into eight groups. We believe the following is the arrangement that obtains in adult forms :—eight small tentacles are more remote from the mouth than the rest; four of these correspond accurately with the buttresses and mouth-angles, and divide the tentacular margin into quarters, the other four mark the centre of these quarters. Hach of these eight principal tentacles has a small tentacle on either side and a little in front of it. Sometimes these small tentacles are not knobbed, but rather pointed ; in large specimens, however, they are knobbed like the rest. Between each pair of these groups, consisting of the principal and adjacent and small tentacles, are nine large knobbed tentacles, in each alternate eighth of the margin four of these being in front and five behind, five being in front and four behind in the remaining eighths. There is a slight rim or parapet outside the tentacles; the tenta- eles do not appear to be retractile, but when the animal closes, they are turned inwards and downwards, and covered by the rim being drawn closely over them. Colouwr.—Dirty chocolate-brown throughout, the stalk being © paler than the rest, the darkest portion being the masses of generative organs which appear through the transparent body- wall. The tentacles have a core of dark colouring both in the tube and in the knobs. The stalk also has a dark core, while the expanded foot is transparent. Some individuals obtained at Dalkey exhibited a bright brick-red colour shining through their tissues. These individuals were growing among colonies of Amerecium proliferum the colour of which they resembled. 182 Scientific Proceedings, Royal Dublin Society. In the allied forms, Depastrella, Tessera, and Tesserantha, Haeckel figures ridges running along the umbrella, and dividing it and the stalk or crest into four regions. No such ridges are to be seen in Depastrum cyathiforme. In his description of this animal, Allman states that the stalk is ringed regularly. We have seen rings on the stalk when it is not stretched to its full length, but they are not constant, are sometimes incomplete, and invariably disappear when the animal is erected to its full height. In adult forms the umbrella usually exhibits a somewhat quadrilocular form, being bulged out by the the large bundles of generative organs which are arranged in four V-shaped dark masses, and may be distinctly seen through the more pellucid body-wall. In a few specimens we found existing a hexagonal, not an octagonal, arrangement of the parts; one such specimen had 108 tentacles in twelve groups of nine each, approximately equal. The tentacles, when the animal was not quite expanded, appeared not to be arranged in groups, but to form three continous rows. Sections of this specimen showed that it possessed six mesenteries, six gastro-genital pockets, and six radial chambers. We found that the arrangement of mesenteries and chambers in normal specimens, as revealed by sections, agreed with that described by H. James-Clark. Sections cut across a very young specimen demonstrated the absence of the radial chambers in the earlier stages of growth. Longitudinal sections show that the animal possesses a circular muscle, ectodermal in origin. The mesogloea is thrown into a number of folds which project out into the ectoderm, and on which the muscles cells are arranged. The muscle is well defined and by no means diffuse. It is situated outside the tentacles, and its presence will account for the appearance of the contracted animal. As the result of the careful examination of numerous specimens, continued over an extended period of time, we are of opinion that the animals described by Sars, Allman, and Gosse, must all be rele- gated to one and the same species as that which we have found. We believe that the different points of distinction attributed by Sars to Lucernaria cyathiformis (Fauna Litt. Norveg. [1846] p. 26, Drxon—Wotes on Depastrum Cyathiforme. ~183 pl. 3, figs. 8-11), by Allman to Carduella cyathiformis (Quarterly Journal of Microscopical Science [1860], vol. vili., p. 125, pl. 5, fis. 1-6), by Gosse to Depastrum cyathiforme (Ann. & Mag. Nat. Hist. [1860] vol. v., p. 481), are due to the variations to be met with in specimens of different ages and sizes, and to the variability of habit exhibited by the animal. This view has already been suggested by H. James-Clark (Journ. Boston Soc. Nat. Hist. [1863] vol. vi., p. 550, n. SCIEN. PROC. R.D.S., VOL. VIII., PART ii. 0 ) Eee] XVII. ON A PHOTOGRAPHIC METHOD OF DETECTING THE EXISTENCE OF VARIABLE STARS. By J. JOLY, M.A.,. SoD, | 1s lain Se [Read Aprit 19; Received for publication Aprit 21; Published Junz 13, 1893.] Ir is very probable that the number of variable stars known to us. is but a small fraction of the actual number of such stars. Many of such stars doubtless possess so small a degree or so slow a. rate of variation of brightness as to render observation by us of the changes impossible, at least by any existing method of observa- tion. But there is probably a large number of stars, whose varia- tions might be observed if a continuous photometric record of their brightness could be kept. This method should be such as would keep under observation, not one, but groups of many stars simul- taneously, for there is, of course, a large degree of chance that an observer, systematically observing some few stars at random might not be so fortunate as to include a variable star among the number. Another quality which should be possessed by any photometric method applied to this study is that of being automatic, meaning by this that its record should be independent of the physiological state of the observer’s eyesight, and independently of him, con- tinuously record the intensity of illumination, for the variations sought for may be very slow. I venture to suggest the following method of meeting these requirements by the aid of photography. Ti the photographic plate, instead of being fixed within the telescope in the ordinary way, were driven with a slow eccentric circular motion, so that the image of each star describes a small circle on the surface of the plate, the intensity of the light from the star might be observed upon successive favourable nights, over long periods of time; the strength of the circular curve traced upon the plate depending upon the brightness of the star und the rate at which its image travels upon the sensitive film. Jotyv—On Variable Stars. 185 The plate, when developed, would thus reveal a number of circles, or part-circles, of stars down to the magnitude at which they failed to impress their paths on the film. The examination of these traces would reveal, on comparing successive plates, in the case of any appreciable variation in bright- ness of a particular star, either a strengthening or weakening of the linear image, or possibly a complete fading out of the trace. Irregularities in the driving gear or atmospheric influences would, in affecting all stars upon the plate in a similar fashion, be probably in this way differentiated from real variations in bright- ness. A full exposure of six minutes has been recommended by the Paris congress as suitable for securing good measurable images of eleventh magnitude stars. A linear velocity of one millimetre in from ten to thirty minutes would probably secure sufficient linear definition of stars down to the eleventh magnitude. But of course the most suitable rate to meet any particular requirement would be matter of trial. The radius of the circular motion is also of impor- tance, as the number of complete linear images obtained at any particular exposure would be the more reduced the larger the radius employed, the images moving off or entering upon the plate in its extreme positions. In connexion with this latter consideration, a circular movement commends itself in preference to any other. It would also probably cause a minimum of confu- sion in the overlapping or crossing of images. 02 iimiser yt XVI ON THE DISTORTION OF PHOTOGRAPHIC STAR IMAGES DUE TO REFRACTION. By PROFESSOR ARTHUR A. RAMBAUT, M.A., D.Sc. [Read Aprit 19; Received for Publication Aprit 21; Published Juty 25, 1893.] Amonesr the principal advantages of the photographic method of making astronomical measures is the fact that, by its aid, much larger distances can be measured than is possible in the case of direct observations with any other instrument than the heliometer ; but when the distances over which the measures extend reach such large proportions as 2000” or 3000’—distances which are by no means uncommon in the study of astronomical photographs—the various disturbing causes, which affect the relative positions of the stars, become very much more effective than in the case of the shorter distances with which, up till recently, we have been accus- tomed to deal. The most important of these disturbing causes is the refrac- tion. In the “ Astronomische Nachrichten,’’ No. 3125, I have recently published formule, by which the correction for refraction to the relative position of any two stars on the plate may be computed in a manner which I have found in practice to be exceedingly convenient. Since, however, the stars are constantly changing their distance from the zenith all the time that the exposure of the plate continues, the correction for refraction is also constantly chang- ing, and a certain distortion in the shape of the images must take place, the amount of which will vary according to the altitude of the star and the length of time during which the exposure lasts. This distortion will, no doubt, be a small quantity; but in the more delicate researches of astronomy, such as the determination of the parallax of a fixed star, where we aspire to measure a quantity RamBaut—Photographic Star Images due to Refraction. 187 of less than one-tenth of a second, every possible disturbing cause must be examined into and allowed for with all available rigour. | In order to investigate how far the image of a star on a photo- graphic plate can be distorted by the refraction, I take the formule which I have given in the “‘ Astronomische Nachrichten ” for the correction for refraction in R. A. and declination respec- tively. If we denote by a and 6 the R. A. and declination of any star, and by ¢ the latitude of the observatory, and by @ the sidereal time of the observation; if, further, da and dé denote the differ- ences in R. A. and declination between this star and another, and if Ada and Adé denote the corrections for refraction to da and dé re- spectively, and (3 be the coefficient of refraction at the zenith dis- tance of the star, we find, cos @ Sin v sin (u +6) cot cos (m + 26) Ada cos 6 = 3 ee Sein ino) da cos 6 ee Gann) > and cos d COs v 1 Adés = B | N sin? n sin?(u + 0) da ee 6 Es sin?(m + 8) \? in which m, 7, p, v are determined by the equations, tan m = cot ¢ cos (@-a), cot u = tan ¢ cos (0—a), cot m=sinmtan(@-a), and cot v=cos m tan (0-a). Hence we may write— Ada cos 8 = AX + BY, and Add = CX + DY, in which X and Y are the rectangular co-ordinates on the plate of the second star referred to the first as origin, the axis of X being | in the direction of the parallel at the first star, and A, B, C, and D are constants computed for the position of the first star at the moment of observation. This is a form of the expression which is exceedingly con- venient where a number of stars on one plate have to be measured. 188 Scientific Proceedings, Royal Dublin Society. But it will be seen’ that 0, the sidereal time, occurs in the quanti- ties A, B, C, D, which consequently are not absolutely constant when the exposure lasts for an appreciable time. In the neighbour- hood of the horizon, too, the value of ( changes so rapidly that another source of variation is introduced. In taking astronomical photographs of a group of stars it is usual to select one star as guider, and setting this on the intersee- tion of a pair of cross lines in the focus of the guiding telescope before the plate is exposed, to keep it exactly on this intersection all the time the exposure continues. The driving clock of the telescope, of course, if correctly rated will keep the instrument continually pointing at the star, but it is necessary, in order to correct the minute irregularities which are inseparable from even the best of clocks, and to eliminate the effect of the changes of refraction on the motion of the guiding star, to control the move- ment with the hand by means of the fine-motion-apparatus pro- vided for that purpose. But even with these precautions, it is still only possible to keep one star fixed in position on the plate. Hence the amount by which the image of another star is disturbed on the plate is measured by the change which takes place in the differential refraction relatively to the first star between the beginning and the end of the exposure. Hence, if A., Bo, Co, Do are the values corresponding to the beginning of an exposure, and Aj, Bi, C,, D, those calculated for the end of it, we shall find the amount of distortion— in RA = (4,- A,) X + (Bi-B) Y=aX + bY, and in declination = (C, - C)) X + (D,- Dy) VY = cX + dV. From these equations I have computed the following tables which give the values of the quantities a, 0, c, d, for 0°, 20°, 40°, and 60° of declination, and for every fifteenth degree of hour angle, the quantities Ao, B,, C,, Do being taken as referring to the time of the meridian passage of the star, and » being taken as the latitude of Dunsink Observatory, viz. 53° 28’ 13”. RamBaut—Photographic Star Images due to Refraction. 189 Taste [.—Dercuination 0°. Hour Angle. a | 6 | c | a | Zen. Dist. 1h 0:00002 0-00011 000011 0-00003 54°48’ 2 "00009 -00025 “00025 “00016 58 54 3 00027 "00052 "00052 “00049 65 13 4 "00079 *00125 *00125 -00143 12 39 5 00322 -00468 *00468 00596 81 7 Taste JI.—Dercuination 20°. Hour Angle. a | é | c a Zen. Dist. jh 0:00001 0:00007 0:00006 0:00001 35°21’ 2 “00008 “00014 “00012 “00003 40 32 3 “00009 "00023 00022 “00011 47 55 4 -00019 00037 "00040 *00026 56 18 5 “00041 "00061 00077 -00064 65 12 6 °00104 °00115 "00180 00187 74 +4 a "004038 "00684 "00672 00872 82.34 Taste I1].—Derctination 40°. Hour Angle. a | 6 | c ad Zen. Dist. | 1h + 0°00001 0-°00005 0:00005 0-00001 16°52’ 2 *00002 “00012 “00011 “00002 24 21 3 "000038 "00019 “00017 00004 32 57 4 00006 “00029 "00027 “00008 41 54 tt) “00010 "00042 00042 -00017 50 39 6 00015 “00064 "00065 “00038 58 56 7 “00020 “00099 "00104 “00086 66 34 8 00028 -00161 00175 -00206 73 18 9 + 0:00027 00269 “00301 "00531 78 58 10 — 0:00010 "00419 “00479 "01369 83 3 190 Scientific Proceedings, Royal Dublin Society. Taste TV.—Dectuination 60°. | ‘ Hour Angie. a | b c d | ‘Zon. Dish 1h —0:00001 0-00004 0-00007 0:00000 10°33’ 2 -00001 -00008 -00015 -00000 17 34 3 “00002 -00014 “00023 “00000 Oa aS 4 “00004 “00022 “00032 “0000 32 24 by) 00007 00033 "00043 -00002 39 27 6 "00014 00048 00055 -00009 45 58 7 “00024 -00065 -00067 “00021 51 51 8 “00039 -00081 -00077 “00040 56 54 9 -00061 “00090 -00079 “00069 61 2 10 -00086 “00082 -00069 -001038 64 6 11 -00107 -00050 “00041 “00133 65 59 12 -00116 -00000 -00000 -00145 66 39 The accompanying curves (figs. 1, 2, 3, 4) are traced with these quantities as ordinates, the hour angles being taken as. abscissee, and the ‘‘ Zenith Distance Curve” is added in each case- for convenience of reference. In the case of the B and D curves. the ordinates have been measured below the line of abscissee to. avoid confusion. From these curves, or from the tables them-- selves, it is easy to find the amount of the distortion which a star image undergoes when the exposure lasts from any given hour angle to any other. For instance, if a star at the equator is photo- graphed from the time when its hour angle is 4" to the time when its hour angle is 5", we find, in Table L., ; | (2) (4) (¢) (d) Corresponding to 44, 0:00079 0-:00125 0-:00125 0-00148 9 » OF, 003822 00468 -00468 -00596 Difference, 0:00243 0:00343 0:00843 0:00453 Now if we consider another star on the plate which differs in k. A. and declination from the guiding star by 1000”, or, which Sey ai ml een oe pseraction in i (IES a Res raction in TL 4 a me a Gia enith Distance “aaa eel A Refraction in —- Deolination JGR aes |_| Lt ee Retaction in 70° Zenith Di. rey pa cel JCal a JZ 1s ales ae eae hal ZD-90 G:000 = /aaaaee mol ESS Jee ae Soe oa ee ea ee action ~~ D TK epetnatin sig ET 22 TS es | 7422 FO ETT Zo AES ea Pt oe | Irepraction in i i Peetenne 4-H Ee} --FP 4 cee 192 Scientific Proceedings, Royal Dublin Society. is the same thing, a star at a distance of 1414” and position angle 45°, we find the distortion— in RA = 0°00243 x 1000” + 0:00343 x 1000” = 2743 + 37-43 = 57:86, and in declination = 0:00348 x 1000” + 0:004538 x 1000” = 3°48 +4:538 =7 -96. Hence we see that the centre of the image of the second star will be drawn out through a length of nearly 10”, and will make an angle of about 386° with the direction of the parallel in which the diurnal motion takes place. This is, of course, rather an extreme case, as it will be seen from the ‘‘ Zenith Distance Curve”’ that, while the hour angle changes from 4" to 5%, the star passes from a zenith distance of 73° to about 81°, a position in which no very great precision could be expected. If, however, we refer to the curve corresponding to 40° decli- nation (fig. 3), and investigate the distortion which the star under- goes in passing from 60° to 75° zenith distance, we shall find the following quantities. Corresponding to a zenith distance of 60° we find the hour angle 6°12, and to 75° an hour angle 8-25, and for these hour angles we find, (a) (2) (c) (@) at 612 0:00014 000067 0-00070 0-00040 at 8-25 -00028 + 00183 + -00204 += -00270 0:00014 0:00116 0:00184 0:00230 If therefore as before we take da and dé each equal to 1000” we shall find, aX = 014, cX = 1°34, bY =1°16, dY = 2°30, “OX + OY =f 30," eX Ad Yo — one: Hence the distortion amounts to 3”°87 in a direction inclined to the parallel by an angle of about 17°. It should, however, be remarked that in this case the exposure would last for more than two hours which is a much longer RamBaut—Photographic Star Images due to Refraction. 198 exposure than would in any case be given to a plate intended for accurate measuremeut, in which case the exposure will generally be limited to fifteen minutes at most. Of course if the change in the refraction were uniform and the intensity of the light of the star constant, then in all positions, although the star image would no longer be a circle but a line of some sensible length, still by taking the middle of this short line as the point to measure from, and computing our formule for the middle of the exposure, we should eliminate the effect of refraction. But in the neighbourhood of the horizon the rate at which the refraction changes is very rapidly accelerated, and the intensity of the light of the star rapidly diminished by atmospheric absorption as the zenith distance increases. From both of these causes, there- fore, the denser part of the star image will lie nearer the position which the star occupied at the beginning of the exposure if the star is approaching the western horizon and the measures made from it will be in consequence affected with error. Ii the star is near its rising, the end of the exposure will have the greatest effect in determining the position of the image. It is therefore of importance to investigate how far we may assume the variation of the refraction to be uniform for a quarter of an hour. It will be obvious at once, without calculation, from an examination of the curves in figs. 1, 2, 3, and 4, that down to a zenith distance of 60° we introduce no sensible error by assuming the increase of the differential refraction to be uniform for this limit ; and if we compute the amount of distortion in a quarter of an hour from this cause, we shall find that in this time a star - for which da and dé are each 1000” changes its position on the plate, at a declination of 0° by 07-15 i * sg Oi se OF 20 5 wap’ gai. LO rssh, Cielo, 3 35 BGO Or09 In a quarter of an hour, too, the star’s zenith distance will not vary by more than 3°, by which it will not lose one-hundredth part of its light, so that we need not consider the minute change in its photographic activity. 194 Scientific Proceedings, Royal Dublin Society. We thus conclude that, within the limits we have taken, so long as the zenith distance does not exceed 60°, no sensible error can arise through the distortion of a star by refraction if the measures are in all cases made from the centre of the image, and the coefficients in the formule of reduction are computed for the time corresponding to the middle of the exposure; but that if photo- graphs obtained with longer exposures are utilized for the determi- nation of the relative position of stars, it will be necessary to know what star on the plate was used as guider, and the distortion by refraction must be investigated for all stars at any considerable distance from it. ON SOME PYCNOGONIDA FROM THE IRISH COASTS. By GEORGE H. CARPENTER, B.Sc., lLonp., Assistant Naturalist in the Science and Art Museum, Dublin, (Prate XII.) [Read June 21; Received for publication Junz 28; Published July 25, 1893.] Turoucu the kindness of my friend Professor Haddon I have recently had the opportunity of examining the Pyecnogonida, dredged in 1890-91 by the “ Fingal” and “ Harlequin,” when engaged in surveying the West Coast fisheries under the auspices of the Royal Dublin Society. At his suggestion I now sub- mit a report on this material; and, through the courtesy of my chiefs, Drs. Ball and Scharff, I am enabled to add what may be learned from the specimens preserved in the Dublin Museum of Science and Art. Altogether I have examined eight species of these animals from our coasts, five of which are not in the list given by Thompson (1), which is, so far as I know, the only memoir on Irish Pyenogonida ever published. That list contains nine species,’ and I regret that I can only confirm three or four of them. Inquiry from Mr. 8. B. Stewart, Curator of the Belfast - Museum (to whom my best acknowledgments are due), has elicited the reply that Thompson’s specimens are not in that institution, and it is to be feared that they have not been preserved at all. Their discovery, if possible, is specially desirable, as half the species are referred to forms described by Goodsir, as to the identity of whose species the greatest doubt exists among recent workers at the group. Also, the great majority of these specimens were obtained from the north of Ireland, while the specimens which I have examined are all from Dublin Bay or from the west. The present list must therefore be regarded as representing but a small part of what we may hope to learn of the Irish Pyenogonida, when all our coasts have been adequately searched. ' Munna Kroyert, Goods., which is not a pycnogon at all, but an isopod, appears in Thompson’s list by some strange error. 196 Scientific Proceedings of the Royal Dublin Society. Family.—_NYMPHONIDZ. Genus.—Nympnon, Fab. Nymphon gracile, Leach (Johnst.). This species has been found in Dublin Bay by Mr. W. F. de V. Kane, and in Queenstown Harbour by Professor Haddon. It is also recorded from the shores of Antrim and Down by Thompson. As it is described and figured very clearly by Johnston (3), there can be little doubt that Thompson’s determi- nation may be accepted, and that this form may be presumed to have a wide range around our coasts. Beyond the British Isles it is known from the south coast of Norway and the shores of Denmark and Holland; and Schimkéwitsch (2) has recently recorded it from the coast of South America, off Cape Vergini, where a single specimen was found by the “ Vettor Pisani.” It frequents shallow water. Nymphon rubrum, Hodge. At present, this species is known in Irish waters, only from Dublin Bay and Dalkey Sound, where Professor Haddon dredged several individuals of both sexes in 1882. A single female was also secured off Dalkey Isiand, in September, 1892, by the Dublin Naturalists’ Field Club. Except in the British seas, it has only been found on the southern coast of Norway (7). Nymphon gallicum, Hoek. This fine species, which was described by Hoek (4), from the zoast of Brittany, is not recorded for any other locality than the west coast of Ireland. An adult male taken by Miss A. Warren, in April, 1892, on the shores of Killala Bay, was noted by me in the Irish Naturalist (vol. 1. p. 168). The species has also been found at Broadstone by Mr. A. G. More, and at Broadhaven by Professor Haddon. It was dredged by the “ Fingal” in Brandon Bay (St. 18), at a depth of from 9-16 fms. on a sandy bottom, and by the “‘ Harlequin” (St. 160) in Boftin Harbour, at a depth of 1 or 2 fms., among sand and weeds. Quite recently I have received specimens from Mr. A. R. C. Newburgh, from the shores of Bantry Bay, taken at low-water mark. This, like WV. gracile, appears to be a shallow-water species. CaRrPENTER—On some Pycnogonida from the Irish Coasts. 197 Thompson’s list contains four other species of Mymphon. “‘ NV. grossipes, Linn.” is inserted on the authority of Templeton’s old list (5) as occurring in the north of Ireland, but what species is meant by this it is quite impossible to say. N. Johnston, Goods. (6) is recorded from Belfast Bay. This is one of the old species which modern writers have failed to recognise. From an examination of Goodsir’s figures, I am inclined to regard it as identical with NV. grossipes, Fab. (Kr.), which, together with the allied species is clearly defined and excellently figured in Sars’ recent work (7). It is to be hoped that future investigations of our northern coasts may reveal which of the larger Nymphons are really to be found there. Another species from Donaghadee (10 fms.) is called WV. femoratum, Leach, by Thompson, but the identity of this will probably always remain uncertain, as swollen thighs (Leach’s specific character) are characteristic of nearly all female pyenogons. The fourth species has been recognised by Sars, and I therefore insert it in the present list; it is placed, together with some other northern Nymphonide, in a special genus. Genus.—CH#TONYMPHON, Sars. Chetonymphon spinosum (Goods.). Nymphon spinosum, Goods. Thompson records this species from Belfast Bay. Goodsir (6) save no locality for his type, but probably took it in the North Sea. Sars has found it off the west coast of Norway (7). It ranges farther south than any other species of its genus, which is characteristic of Arctic seas. Family.--PALLENIDZ, Genus.—AnorpLopactryLus, Wils. Anoplodactylus petiolatus (Kr.). This minute but very distinct species 1s represented by a single female example dredged by the ‘‘ Harlequin ” (St. 223) in Loughrosmore Bay, Co. Donegal, from a sandy bottom, at a depth of 4-9 fms. It was first described from the Danish seas. Under the name of Pallene pygmea, Hodge (8), it is described from Plymouth Sound and the coast of Durham, while 198 Scientific Proceedings, Royal Dublin Society. as Phoxichilidium pygmeum, Hoek (4) records it as occurring off the coasts of Brittany and Holland at a depth of 1-7 metres. Dohrn (9) found it also in the Mediterranean, and described it as Pallene longicolle; and Sars records it from the south and west coasts of Norway. Lastly, Schimkéwitsch (2) obtained a single example from the “ Pisani” collections, taken at Port Lagunas, in South America. The species has therefore an extremely wide range. Genus.— Puoxicuitipium, M.-Edw. Phoxichilidium femoratum (Rathke). This species occurs both on the east and west coasts. Miss A. Warren has found it in Killala Bay; Mr. Kane has obtained it in Dublin Bay, and Prof. Haddon in Dalkey Sound. Thompson records it (as Orythia coccinea, Johnst.) from Strangford Lough. This is a widely-distributed northern species, recorded from the coasts of Greenland, Lapland, Norway, Denmark, and Scotland. The species from the eastern coast of North America, P. mavillare, Stimps., is in all probability identical; but I would follow Sars in regarding Hoek’s P. femoratum (4), from the coasts of Brittany and Holland, as,distinct from the present form. Thompson records also Phowichilidium globosum, Goods. (6), from Portmarnock. This is a species which it is hardly possible to recognise} without types. It can scarcely be identical with P. femoratum (as Sars thinks possible), for Goodsir was apparently acquainted with that. species, and gives points of distinction between them. Possibly it is identical with Hoek’s P. femor- atum. Family.—PHOXICHILIIDZ. Genus.—-—-Puoxicuitus, Latr. This genus is sometimes classed in the same family as Pye- nogonum. The two genera agree in having both lost their three foremost pairs of appendages, except the false legs of the males. But they differ so considerably in other points, as to suggest that they have reached their present degraded state through quite independent lines of descent. Schimkéwitsch (10) suggests that Phoxichilus has come down from the Nymphonide through the Pallenide, while Pycnogonwn has been derived from a form resembling Rhynchothoraz, as Dohrn (9) also believed. CaRPENTER—On some Pycnogonida from the Irish Coasts. 199 Two distinguishable forms of Phovichilus occur in our seas, yet so nearly related that it is doubtful whether they should be regarded as distinct species. ‘They have, however, been differen- tiated and named by former observers ; so I venture to keep them separate, at least until intermediate forms are found connecting them. Phoxichilus spinosus, Mont. (REIS sane toss Teiotoe7 | P. spinosus, Hoek (in part). A single male of what I believe to be the typical form (11) of Montagu’s species, was dredged by the “ Fingal” off Aran Island in July, 1890. In his remarks on the Phowichili from the coast of Brittany, Hoek (4) mentions that two males, out of ten referred by him to P. spinosus, were much larger and more spiny than the others. He found no corresponding females, and was hence led to infer ‘“‘un dimorphisme dans le sexe masculin.” Through the kindness of my friend, Prof. D’Arcy Thompson, of Dundee (who has in many ways helped me in the study of this group), I have been able to examine a male and female from Plymouth (where Mon- tagu’s type was taken), and females from Jersey, which correspond closely with the Aran specimen; the females are, however, less _ spiny than their mates. hey differ from the next form (P. /evis) in being nearly twice as large,' having the proboscis much thicker proportionally at the end, bearing conspicuous spines on their lateral processes, and showing more numerous and larger spines on the legs. The openings of the cement-glands on the femora of the male number twenty-five or twenty-six (fig.5): nearly the same number (twenty-four) as Dohrn (9) gives for his large Mediterranean species, P. charybdeus. Our form agrees with P. charybdeus in its swollen proboscis; but the latter species has the spines on its lateral processes less conspicuous or absent. It has, moreover, relatively longer legs than P. spinosus. Two conspicuous blunt spines are present (fig. 1) at the front of the cephalic segment in the male; in the female they are hardly to be recognized. 16mm. long and 40 mm. in extent. Montagu gave one-fourth of an inch as the length of his type. SCIEN. PROC. R.D.S., Vol. VIIl., PART II, P 200 Scientific Proceedings, Royal Dublin Society. Phoxichilus levis, Grube. [ Pl. x11., figs. 2, 4, 6, 8. ] P. spinosus, Sars (7), Schimk. (10); P. spinosus, Hoek (4) (in part). This form is, as has been said, much smaller! and less spiny than the true P. spinosus. The structural differences, pointed out above, are, however, so relative that many naturalists would hesitate to rank the two forms as “‘species.”” There are only nine- teen or twenty cement-gland openings on each femur of the male in this form (fig. 6). The spines on the lateral processes are small or absent. There is no doubt from Sars’ figures and descriptions (7) that this is the Phowichilus which occurs on the west coast of Nor- way. Grube’s types (12) were from the Breton shore, where Hoek also found the animal, and referred it, as mentioned above, to P. spinosus.? Jarzynsky is said to have taken it also on the coast of Lapland. On our coasts, Dr. Scharff found specimens cast up on the North Bull, Dublin Bay, after a strong S.E. gale in October, 1892. Miss A. Warren sent it to me last summer from TGlala Bay,’ and Mr. A. R. C. Newburgh has found numerous examples in .Dunbeacon harbour at the head of Dunmanus Bay. Many of the males in this consignment bore egg-masses. I have figured parts of these two Phoxichili for comparison (Pl. xi1.), the corresponding organs in each being drawn to the same scale. The proboscis of this form is not swollen at the end (fig. 2) as much as that of P. spinosus (fig. 1); but both forms have the proboscis thicker in the male than in the female. In the shape of the proboscis, P. /evis closely resembles P. vulgaris, Dohrn, from the Mediterranean; the latter is, however, a smaller and more slender animal, and the male has but fifteen or sixteen cement- glands on each femur. Schimkéwitsch (10) has recently given detailed descriptions of the species of Phovichilus, and notes various points of difference between the present animal and P. vulgaris. He seems, however, to have had but very few specimens of each 1 3-4 mm. long and 25 mm. in span. 2 In his Report on the ‘‘Challenger’? Pycnogonida, however, Hoek says that P. levis may be readily distinguished from P. spinosus. ° T recorded these in the Irish Naturalist, vol. i., pp. 42, 165, as P. spinosus. CARPENTER—On some Pycnogonida from the Irish Coasts. 201 for comparison, a serious drawback in such a variable genus, in examples of which too much stress must not be laid upon the presence or absence of individual spines. For example, as a rule, we find but three spines at the end of the dorsal aspect of the femur in P. levis (fig. 6), while P. spinosus has five (fig. 5) ; but in some examples which I would refer to P. devis, the two supplementary spines are present, though very small. Grube’s distinction by the absence of the two frontal spines is not reliable. They are generally absent, but not always, and are figured as present by Sars. The shape of the proboscis, and the number of cement-gland openings on the male femora seem the only constant distinctions, not only between P. spinosus and P. levis, but also between these and Dohrn’s two Mediterranean species. It seems to me that P. /evis has as much right to distinction from P. spinosus, as from P. vulgaris, or as P. charybdeus has from P. spinosus. The four forms are, however, so very similar in most structural points, that whether they are to rank as ““species”’ or “ varieties” must remain a matter of opinion. It seems not unprofitable to note their minuter details, for it is at least possible that the naturalists of the future may be able to observe the further divergence of these forms until they become undoubtedly distinct species. The genus appears, as has been said, to have arisen from Nymphon-like ancestors, and to be one of the most recently differentiated genera of the group. With this suggestion its distribution agrees, for while its head-quarters are the North Atlantic and the Mediterranean, we know that it is represented at scattered points in the southern hemisphere. Bohm (138) described a species /. meridionalis from Singapore; Haswell (14) records P. charybdeus from the coast of Australia, and Schimkéwitsch found a female of the same species in the “ Pisani”’ collections from the Abrochos Islands off the coast of Brazil (2). This dis- tribution contrasts with that of an older genus, such as Vymphon, which ranges uniformly over the temperate and cold seas of both hemispheres; it also contrasts with the truly discontinuous distribu- tion which would characterise a still more ancient genus which was on the way to extinction. We may infer, therefore, both from the difficulty of marking off the species of Phowichilus and from its 202 Scientific Proceedings, Royal Dublin Society. range in space, that it is a genus of comparatively recent origin which will, in course of time, develop into several well-marked species. Family.—AMMOTHEIDZ. Genus.—PasirHox, Goods. Pasithoe vesiculosa, Goods. Thompson records a single specimen from off Dalkey Island, which he referred to this species. The genus is one which can hardly be recognised by modern authors; yet, as the form can- not be proved identical with any previously described pycnogon, I think it best to insert it, and trust that the types may be recovered, or fresh specimens secured, which will place its identity beyond doubt. From a consideration of Goodsir’s figures (15, 16), I would regard Pasithoe as nearly allied to Ammothea, and not to Collosendeis with which Sars (7) associates it. Family.—PYCNOGONIDZ. Genus.—Pycnoconum, Brinn. Pycnogonum littorale, Str. This is our commonest species of pycnogon, and there can be little doubt that it occurs all round the coast. It is recorded by Thompson from Bangor, Co. Down, and from Dublin Bay, under the name of P. balenarum, this name having been erroneously given to the animal through its confusion with the amphipod Cyamus, which is parasitic on whales. P. Zittorale has been taken at the North Bull, Dublin, and also in Dalkey Sound, by Prof. Haddon. It was dredged at several stations off the west coast, in great numbers, by the “ Fingal” :—Clew Bay, 15 fms.; Galway Bay (St. 21), 16 fms., sand; off Achill Head (St. 64 and 72), 144 fms., and 127 fms. fine sand; off the Skelligs (St. 114), 80 fms. sand and mud. Beyond the British seas, this species is known from off the coasts of Lapland, the White Sea, Iceland, Green- land, Denmark, Germany, Holland, Belgium, France, North America, Japan, Chili, and Kerguelen. Its bathymetric range is as remarkable as its geographical extension. On our own coasts it has now been traced from the shore to a depth of nearly 150 fms. ; CaRPENTER—On some Pycnogonida fromthe Irish Coasts. 208 and Wilson (17, 18) notes specimens from the east coast of North America from more than three times that depth. The specimens which I have examined, obtained in March and April, are all immature, while those taken in June, July, and August, are nearly all adult. The egg-mass carried by the male is circular, like a cushion, and nearly as large as the animal itself. My best thanks are due to Prof. Haddon and to the collectors mentioned above, who have kindly supplied me with the spe- cimens; and I am specially indebted for the generous help afforded me by Prof. D’Arcy Thompson in giving and lending me specimens for comparison. This paper must be regarded as but a preliminary record on the subject; and it is to be hoped that systematic work, specially around our northern coasts, may largely increase the knowledge of Irish Pycnogonida. REFERENCES. (1) THompson, W.: “The Natural History of Ireland,” vol. iv. London, 1856, (p. 412). (2) Scuimxiwirscu, W.: ‘“« Sur les Pantopodes recueillis par M. le lieutenant G. Chierchia pendant le Voyage de la corvette ‘ Vettor Pisani’ en 1882- 1885.” — Atte della R. Accad. det Lincei (4) Memorie vi., 1890, p. 329. (3) Jonnston, G. : ‘‘An Attempt to ascertain the British Pycnogonide.”’—Wag. Zool. Bot. i., 1837, p. 368. @)eHoux, PP. C. : “ Nouvelles Etudes sur les Pycnogonides.”—Arch. Zool. Exp. et Gén., 1x., 1881, p. 445. (5) Tempzeron, R.: “‘ Catalogue of Irish Crustacea, Myriapoda, and Arachnoida.””— Mag. Nat. Hist., ix., 1836, p. 9. (6) Goonstr, H. D. S.: ‘‘ Descriptions of some new species of Pycnogonide.”— Hdind. New Phil. Journal, xxxii., 1842, p. 186, 204 Scientific Proceedings, Royal Dublin Society. (7) Sars, G. O.: ‘«The Norwegian North Atlantic Expedition, 1876-78.” Vol. xx., ‘« Zoology—Pycnogonidea,’’ Christiania, 1891. (8) Hopes, G.: ‘List of the British Pycnogonoidea, with Descriptions of several new Species.”— Ann. Mag. Nat. Hist., (8) xili., 1864, pa kis: (9) Domry, A. : ‘* Fauna und Flora des Golfes von Neapel, m1. Pantopoda.”— Leipzig, 1881. (10) Scuimxnwitsce, W.: ‘Notes sur les Genres des Pantopodes.”—Arch. Zool. Exp. et Gen. (2) ix., 1891, p. 508. (11) Monraev, G. : ‘Description of several Marine Animals found on the south coast of Devonshire.”—TZrans. Linn. Soc., ix., 1818, p. 81. (12) Grosz, E. : ‘‘Mittheilungen tber St. Malo und Roscoff, . . . .”— in which certain organisms are grown. Those observers isolated from sewage two aerobic organisms, which they named Bacterium denitrificans a and 3. By quanti- tative experiments, they showed that, when these organisms are grown in almost any infusion containing organic matter and also nitre, the whole of the nitrogen of the nitre is evolved as gas, and that the whole of its available oxygen is combined with carbon to form carbon dioxide. Some ammonia is formed, but it is derived, they state, from the nitrogenous constituents of the nutrient medium employed. The authors show that the organisms will not develop in liquids free from nitrate and kept out of contact with air. They therefore regard the decomposition of the nitrate as a fermentation consisting of the direct oxidation of organic carbon at the expense of its available oxygen. The decomposition of the nitrate may therefore be expressed thus :— qi): 4 KNO, = 2N, + 2K,0 + 5 O,. Qh “sce 0) = sicor (3). 2 K,0 + 2 CO, = 2 K.COs. If the decomposition of the peroxide above described be regarded as analogous in character, then the whole of its available oxygen should combine with organic carbon, and manganous carbonate be finally formed, thus :—- (1). 2 MnO, = 2 MnO + O,. (2). C40, = CO, (3). MnO+CO, = MnCO,. That these reactions would be attended with the evolution of a 1 Ann. de la Science Agronomique, 1885, I., 226; also abstract Chem. Soc. Journ., XLIX., p. 820. Aprnry—On the Reduction of Manganese Peroxide in Sewage. 249 considerable quantity of heat, and would therefore constitute a source of considerable energy to the organisms, is evident from a consideration of the following thermal data taken from Thomsen’s ‘¢Thermochemische Untersuchungen ”’ :— 2[Mn,0,H?0] = 189,440 2) (Mn Oe eEeOi = 232,660 Loss = — 48,220 COA] B 96,960 [MnH?0?, CO?Aq] = 13,230 110,190 ~ 43,220 + 66,970 Freshly precipitated peroxide also suffers reduction to manga- nous carbonate when it is mixed with solid fermentable organic matters. I have recently been able to put this to test on a some- what large scale at some sewage purification work where manga- nate of soda is employed for treating the sewage. At the works referred to, the greater portion of the solid matters in suspension in the sewage are first separated by mechanical subsidence; the sewage is then mixed with a water solution of manganate of soda; the peroxide, which afterwards separates, is allowed to subside, together with matters remaining in suspension in sewage, to the bottom of the tank in which the operation is conducted. It is finally drawn off from the tank in the form of a mud. I obtained several hundredweight of this mud, and first drained it on a gravel-bed, and, when of sufficient consistence, I made it up into a large heap, and allowed it to slowly air-dry in a covered shed. After being left in this condition for about three months, I found the interior portions of the heap had assumed a grey colour, only these portions immediately exposed to the air had retained the original brown colour of the peroxide. I detached some small lumps from the heap, allowed them to 250 Scientific Proceedings, Royal Dublin Society. completely air-dry, and then submitted a portion to analysis, with the following results :— Insoluble mineral matter, . : : : 12°16 Moisture, . . 15°68 Organic matter reslable 3 in dilate HCl, . 4:00 Organic matter soluble in dilute HCl, . . 4°85 MnO, . : : : : : . 24:60 Cad; & : : 3 : : : ae) VAST) Fe,0, / 41,0) oe MeO: ! : : : : é 2 4560 pAal 110 K,0, GND OR ee: ; : Y : : . 0:005 NiO, CoO, | traces Zn0, COMTI ie wa Mame OE fs 1 QoN5 SOs; : : ‘ : : ! 2 (Ora, Oa: : ' i : : ; . 0°59 Cl, ; i : : : ‘ : . trace 100°695 It is evident from the above results that the manganese was present mainly as manganous carbonate. not only float in water sub- merged to a certain point (pre- ferably near the upper end), but will be in a state of equili- brium when placed at any or in every position down to a certain angle, which angle depends on the exact outside form of the . tube. For instance, if A B (fig. 1) be a tube closed at B Fre. 1. and perfectly symmetrical round the axis A B, and the total weight of the tube be equal to the weight of water which is displaced when the tube is sunk to C, the weight of the different sections along the axis AB, can he so distributed that the tube will equally well remain in any other position, except it be so far turned over that the cylindrical part of the tube is lifted out of the water at one end and dipped at the other. By making the spherical part of about the proportions of the figure, the tube can be depressed to within 25° of the horizon, and | still remain in perfect equilibrium. Now, suppose the tube to have a pair of trunnions attached at the water-line, and these carried on a polar axis of, say, the English type (see fig. 2), we have an equatorially-mounted telescope of any size, without any weight whatever on the bearings of the Dec axis, or, the tube may be lightened by an amount nearly equal to the weight of the polar axis, and there will then be practically no weight whatever on the bearings of that axis. So here we have a case of, say, an 80-ton telescope mounted and carried by an equatorial, but without throwing any weight whatever on that equatorial; and the force necessary to drive the instrument is independent of the weight of the telescope, and dependent only on the friction necessary to be overcome in carrying the tube at an exceedingly slow rate through the water. AY So eco —\-—-]--... Gruss—Lquatorial Mounting for large Reflecting Telescopes. 255 Fia. 2. SCIEN. PROC., R.D.S., VOL. VIII., PART III. 256 Scientific Proceedings, Royal Dublin Society. Let us inquire into any possible disadvantages that may be urged against this form of mounting:— Ist. That the temperature of the water will often be different from that of the air; and consequently that there will be a detri- mental mixture, at the mouth of the tube, of air from inside the tube, which will partake of the temperature of the water, with the outside air. This I would propose to avoid by making the tube double, with a space of some 3 inches between inside and outside tubes, hermeti- cally closed except at the lower end, where there would be apertures in the inside envelope. The space between the two tubes would be connected through the trunnions with an air-pump, worked by a gas or other motor, which would continually exhaust the air from between the two tubes, and thus cause a current of the outside air to pass continually down the tube and back to the pump by the space between the two tubes. This would keep the temperature of the inside tube and the air in the tube constant with that of the outside air. 2nd. The limited range of the equatorial. i have stated that the instrument would be in perfect balance down to 25° from the horizon. If desired, though no longer perfectly balanced, it can be used lower by employing a chain or wire rope connected between the lower end of the tube and the upper end of the polar axis, and the amount which the instrument would be out of balance, between 25° and 20°, would be very trifling. Again, it will not be convenient to use the instrument within some 15° of the Pole. It could be planned to go somewhat closer, but when it is considered that nine-tenths of the work required to be done can be commanded by this instrument, it is clearly better to design it to do that nine-tenths well than to strain it into doing another 5° that would only be useful on very rare occasions. drd. It may be urged that the friction of the water will prevent the rapid setting of the instrument. In a telescope of this size all the motions would be effected by motors of some description, guided by the observer from a commutator-board at the eye-end, and there would be no diffi- culty in setting the telescope quite as quickly as could be expected, considering its great size. Grusp—Lquatorial Mounting for large Reflecting Telescopes. 257 4th. It may be objected that currents will be set up in the water by the moving of the telescope, which currents will affect the steadiness. No doubt this will be the case to some extent, but these will soon subside, and the motion necessary for following the stars will be so slow that no perceptible effect of this kind will be felt from it. _ As to convenience in getting at the eye-end, there need be no difficulty whatever in this form. As the eye-piece is only about | 15 feet from the centre of motion, the movement of the observer is never more than 3 feet per hour. By means of a platform such as that shown in fig. 2, running on rails, and quite independent of the instrument, the eye end is readily accessible at all times. To overcome tbe rotation of the tube as the instrument moves in right ascension, I would pierce the tube for eye-pieces every 30° round its circumference, and mount the flat mirror and cell in a collar so as to enable it to be readily rotated through intervals of 30°. By these means the image of the celestial object to be observed could be sent through either or any of the perforations of the tube, and the observer always observe in the direction most convenient to himself. passe | XXIX. ON THE GREAT METEOR OF FEBRUARY 8ru, 1894. By PROFESSOR ARTHUR A. RAMBAUT, D.S8c., F.R.A.S. [Read Marcu 21; Received for publication Marcu 30; Published Apri 25, 1894.] I ruinx it will be of interest to the Society to lay before it the facts relating to a great meteor which appeared on February 8th of this year, as far as I have been able to ascertain them. This remarkable object attracted the attention of thousands of people at various places over a region containing nearly 100,000 square miles, from Whitby in Yorkshire to London, and from Ballinasloe to Chelmsford in Essex. Even at night it does not often occur that a meteor is seen over such an extended tract of country; but to have been so widely conspicuous within a few minutes of noon, on a day when bright sunshine almost universally prevailed, the meteor must have been one of very unusual dimensions. At three minutes after noon, mean Dublin time, on the day in question, I happened to be standing in the grounds of the Obser- vatory at Dunsink, when suddenly my attention was drawn to a brilliant object, which first appeared at an altitude of 25° (as nearly as I could estimate it) above the horizon. It fell in a vertical direction, and disappeared behind some trees at a height. of, as nearly as possible, 5° above the horizon. To me it appeared of a distinctly greenish tint. The motion was not very rapid, but the phenomenon was so sudden and unexpected that I made no attempt to estimate the duration of its flight. On account of the exceptional brilliance of the phenomenon, I put a notice of it in some of the daily papers, and in reply have had accounts from a very large number of people who happened to see it in other parts of this country and in England. Most of these accounts are, however, of such an indefinite character as to be of little or no use in determining the path of the body. RamBaut—On the Great Meteor of February 8th, 1894. 259 I may, perhaps, take this opportunity to point out that obser- vations of meteors should be principally directed to obtaining estimates, with as high a degree of accuracy as possible, of the altitude and bearing of the object at epochs during its flight, which can afterwards be identified. At night it is best to note its position at first appearance and at disappearance, or at the moments when explosions take place, with reference to the stars which lie along its track. In the daytime its position must be referred to terrestrial objects, such as trees or houses. The observer should also note the exact spot on which he stands, so that he can subsequently determine the direction of the meteor accurately with the proper instruments. To determine with precision the length of time for which the meteor remains visible is more difficult. Of course it is impossible to get out a watch and to compare it with sufficient rapidity, and the usual course is to repeat some familiar piece of poetry all the time the object is in view, noting the exact syllable at which it disappears. If then the same passage is afterwards repeated before a clock, the duration of the meteor’s flight can be very approximately obtained. The observer ought to devote his principal attention to the bearing of the object at the beginning and end of its flight. From this datum alone, as observed at two different stations, it is possible to determine the region over- which the meteor passed. In order to determine its height in miles above the EHarth’s surface it is, of course, also necessary to know the altitude, but a single reliable observation of this sort is sufficient for our purpose, whereas it is absolutely necessary that we should have the bearing determined at two stations, at least, before we can decide as to the track of the body. Accounts of this meteor have reacied me from the following places :— IRELAND. Dublin. Templeogue. Dundrum. Rathgar. Clondalkin. Kilcock. Monkstown. Malahide. Ballinasloe. Cloniarf. Raheny. EKdenderry. Blackrock. Drumecondra. Glaslough. Kingstown. Terenure. Belturbet. Sandycove. Glenageary. Drumree. 260 Scientific Proceedings, Royal Dublin Society. ENGLAND. Holyhead. Bicester. Dudley. Berkhampstead. Woburn Sands. Camberley. Shrewsbury. Droitwich. Doncaster. Buntingford. Great Malvern. Wellingborough. Bedford. Bardney. Aylsham. Rugby. Mildenhall. Llandilo. Coventry. Kine’s Lynn. Stoke Newington. Ampthill. Hertford Heath. Worcester. South Woodford. Canes, near Harlow. Brentwood. Oakham. Gamlingay. Manchester. Downham Market. Loughton. Beverley. Stevenage. Wylde Green, Bir- Chester. Saffron Waldron. mingham. Oxford. Gloucester. Buckden. Berriew. Hull. St Ives (Hunts). Leeds. Gosberton, near Hertford. Chelmsford. Spalding. Northampton. Fulbourn. Chipping Norton. Martley. Warmington. Canningtown, Sheffield. Derby. London E. Loddington. Hereford. Leicester. Hempstead. Maldon. Hly. Pershore. Wimbledon. Loughborough. Great Thurlow. Cheadle. Swindon. Cheltenham. Maidenhead. London. Banbury. Devizes. Swavesey. Pondsbridge. Birmingham. Biggleswade. From the accounts which have reached me of the altitude and azimuth of the meteor at its first appearance, I have computed that it was first noticed when over a spot situated in longitude 2° 54’ W. and latitude 53° 40’, and at a height of 59-4441 miles. For computing the position of the meteor at disappearance I have only three observations of azimuth and two of altitude available. These agree, however, fairly well in indicating a posi- tion in longitude 1° 35’ W. and latitude 53° 35’. The two obser- vations of altitude at the time of the meteor’s disappearance place it at a height of 13°4 and 14:4 miles respectively. With regard to the velocity I have no very reliable data- RamBaut—On the Great Meteor of February 8th, 1894. 261 The time of flight has being variously estimated at from 1 to 5 seconds. One observer states that it remained visible from 15 to 17 seconds, but he is quite unsupported by others in giving it such a long life. Taking 3 seconds as a mean of the estimates— which will agree well with my recollection of the appearance— we find, since the length of the track was 57 miles, that the object was moving with a mean velocity of 19 miles per second, or very approximately that of the Earth in its orbit. We may say, therefore, that the object was first seen at a height of very nearly 60 miles, almost vertically over the estuary of the Ribble, at a point between Southport and Preston, and about one-quarter of the distance from the former town. That it travelled across Lancashire and part of Yorkshire at an average rate of 19 miles per second, and finally disappeared from view at a height of 14 miles, over a spot between Wakefield and Sheffield, at about three-fifths of the distance from the latter. It is usual in an inquiry of this sort to seek ‘the direction in space from which the meteor came—the radiant, as it is called— and this is obtained by producing backwards the track in which it was seen to move. In this case, however, such an investigation is out of the question, since there is evidence to show that the path was of a curvilinear form, while there are not sufficient observations available for determining the shape of the curve. In most cases the path of a meteor deviates but little from being a straight line, the velocity imparted to it by the Harth’s attraction being but small as compared with the velocity with which itis moving through space. In the case before us, however, since the portion of the Harth’s surface over which the meteor passed was moving towards the west with a velocity of nearly 19 miles per second, or nearly the whole relative velocity observed, we see that this was probably a very slowly-moving body in space before it came under the influence of the Harth’s gravitation. Under these circumstances it is not to be wondered at that the path in which it moved was found to be considerably curved. Thus, Mr. John Pycock, of Gamlingay, Cambridgeshire, describes it as “making a long curving sweep through the sky.” Mrs. A. W. Wills, Wilde Green, Birmingham, saw it “ descending rapidly in a curve, not vertically.” Miss Laura Wood, Berk- hampstead, says that it “fell in a graceful arch”; while Mr. 262 Scientifie Proceedings, Royal Dublin Society. Edward Coleman, of Ampthill, Bedfordshire, describes it as twisting towards the east before disappearing. The mode of the meteor’s disappearance is somewhat doubtful. To most observers it seemed to vanish while still at a considerable height, without sparks or noise. To Mr. J. R. Hird, of Bardney, Lincoln, however, it “‘ appeared to break up in four or five pieces, which also vanished instantly.” Mr. Paul de O. Potter, King’s Lynn, describes it as having “ dispersed just as it was about to fall,” and Mr. Thomas Cole, of St. Ives, Huntingdonshire, saw it ‘“‘ explode amidst a magnificent shower of sparks.” Although I sent a notice to the English Papers, directing attention to the fact that the meteor was last seen over South Yorkshire, and suggesting that inquiries should be made as to whether anything unusual had been observed there in the way of a fall of stones or iron, I have not heard of any such occurrence having been noted, and it is probable that the body was wholly dissipated at a height of about 14 miles, where it is last reported to have been seen. fee XXX. ON A METHOD FOR COLOURING LANTERN SLIDES FOR SCIENTIFIC DIAGRAMS AND OTHER PURPOSES. By PROFESSOR J. A. SCOTT, M.D. [Read Marcu 21; Received for publication Marcu 30; Published Aprin 25, 1894. ] THe method of colouring the gelatine film with the anilin and other dyes is not new; butin the form in which it has been prac- tised hitherto, the dyes have been thickened and used on the sur- face after the manner of ordinary pigments. In the method which I have adopted, the gelatine is stained simply without the addition of any medium. In orderto make the colour run evenly, the gelatine film should be moist, but not wet with drops of water— the most favourable condition being immediately after the final washing of the slide is completed, and the film allowed to drain ; but if this should not be convenient, the slide may be placed in water for a quarter of an hour, and then drained. If the slide has been dry for some days or weeks, a greasy film appears on the surface, which should be removed with a little methylated spirit before soaking in water. In this damp condition the colour will be absorbed slowly and evenly, when a dilute solution of the dye is applied with a brush. The colours show no tendency torun. The intensity of colour depends primarily on the strength of the original solution, and secondly on the length of time it is allowed to act on the gelatine, so that local shading can be produced by keeping the brush in one spot fora longer time. Should the trial be unsatisfactory from any cause, the colour can be completely removed by soaking in clean water for some time, and the slide can be re-painted. If the colours are placed simply on the gelatine, almost any of the dyes can be used ; but some are more likely to fade than others, and a few are more easy to lay on evenly. If, however, the colours have to be mixed, either before painting or by overlapping on the gelatine, it is important to remember that some of the dyes act 264 Scientific Proceedings, Royal Dublin Society. chemically on each other, and produce new bodies, which may be granular or of a newcolour. Ordinarily, yellow and blue make green: thus, indigo carmine, when mixed with either picric acid, napthal yellow, or tartrazene yellow will produce various shades of green; but if methylene blue be mixed with the same yellows, a purple colour is produced with picric acid, an orange with napthal yellow, and a green with tartrazene yellow. The colours which I have found satisfactory both as to mix- tures and ease of laying on evenly are—eosin, tartrazene yellow, vesuvin, indigo carmine—with soluble blue as a useful alternative for the last for bright green, when mixed with tartrazene yellow. Methylene blue, methyl violet, and iodine green did not appear to be satisfactory colours. As some of the anilin dyes are liable to fade on exposure to light, I painted a test slide with parallel lines of the colours just mentioned and others, and having covered one half of the plate with black paper, placed it in a lantern illuminated with a Brockie- Pell are lamp. The light was maintained at intervals, as was found convenient, until a total of five hours had been reached, when it was found that eosin, methyl violet, and iodine green faded most; others slightly, and tartrazene yellow and indigo carmine very little, if at all. Subsequently, a similar plate of eosin, atlas scarlet, and two varieties of erythrosin was illuminated for five hours before the arc-light, in the hope that one of them would prove more permanent than eosin. They were, however, very similar in their permanence. One sample of erythrosin, obtained from Schuchardt of Gorlitz, seemed a trifle better than the other make of erythrosin and the other colours. ; Itis difficult to find a dye so brilliant as eosin, even erythrosin being much more purple ; so I have recommended eosin as one of my selected colours, notwithstanding its defects ; it must, there- fore, be applied a little more intensely, if the slide is intended for much use. Very faint pinks will fade completely ina few minutes in the lantern, while, on the other hand, I have slides in use for years which have been rather strongly coloured, and show no appreciable amount of fading yet. Coloured outline diagrams may be made on clear glass by using, with an ordinary pen, solutions of the dyes which have been Scort—On a Method for Colouring Lantern Slides. 265 thickened with dextrine to give a body to the colour: about 10 per cent. dextrine is sufficient; the glasses should be well cleaned before writing. In a compound diagram, if the first colour be allowed to dry, other colours may be rapidly written over the former ones without risk of removing them. For these inks any colour may be used. Iodine green and eosin inks make a parti- cularly brilliant contrast. A very good dark ink, not absolutely black, may be made from Antoine’s “ encre noire,’”’ made slightly alkaline with ammonia, and thickened with 10 per cent of dextrine. [ 266 ] XXXI. ON A MOUNTING FOR THE SPECULA OF REFLECTING TELESCOPES, DESIGNED TO REMOVE THE IMPEDI- MENT TO THEIR BEING USED FOR CELESTIAL PHO- TOGRAPHY AND SPECTROSCOPY. By G. JOHNSTONE STONEY, M.A., D.8c., F.R.S., Vice-President, Royal Dublin Society. [Received Aprit 17; Read Aprit 18; Published Junz 2, 1894.] I.—Intropvuction. Rer.ectine telescopes have conspicuous advantages over refractors, accompanied, however, by one defect which has greatly interfered with their usefulness. One of the advantages they have is that they are less costly. The glass of which specula are constructed need not be of good quality, and is therefore cheap : moreover the figuring of the one surface of the speculum of a reflector, although it requires to be effected with about six times the accuracy that is needed for any one of the four surfaces of the object-lens of a refractor, is easier and therefore less expensive than the very difficult task of combining the conditions which must be fulfilled by the four surfaces of a good object-glass. A speculum is therefore cheaper, perhaps about one-fourth of the cost of an equally good object-lens. But their great excellence lies in their optical per- formance; from their being absolutely free from the chromatic nuisance, and, moreover, from their spherical aberration, if corrected at all, being corrected for rays of all refrangibilities. This would give the reflector an overwhelming advantage over the refractor, and especially in photographing the heavens, or in using the spec- troscope, were it not for their one defect—that their line of colli- mation is apt to shift. Owing to this serious defect they can only be used for celestial photography and spectroscopy by persons whose powers of manipulation are altogether exceptional. The object-lens of a refracting telescope may be supported entirely by its edge, and is always so supported. This is suffi- cient, although, when the telescope is pointed towards the zenith Sroney—Compressed Air Support for Specula. 267 the lens sags down, owing to its own weight, and assumes a very sensibly different shape from what it has when the telescope is pointed horizontally. In fact this distortion of form, although considerable, does not sensibly affect the image. That this can be the case may be easily seen by remembering that the waves of light m which constitute the rays a, b, ¢, d, €o must reach the point o in exactly the same phase, or very nearly the same Haat phase, in order that they may be able to unite and form an image there. Now this condition will be fulfilled if these rays all take the same time to travel from a wave-front mn outside the lens, to o. Hach of the rays passes first through air, then through the lens, and then through air. Light travels slower in glass than in air; and accord- ingly the requisite condition will be fulfilled if the form of the lens obliges those rays whose course is less bent to pass through a duly regulated greater thickness of glass. The waves of the central ray have the shortest distance to travel, but find the thickest part of the lens in their path. They are therefore most retarded. The rays } and d have farther to travel, but meet with a thinner part of the lens and are less retarded, while a and e which have the longest journey are still less retarded; and if the lens has been properly figured they all reach o at the same instant of time. Now let the telescope be pointed upwards. The lens, as it is supported only by its rim, sags down in the middle by its own weight. Hach ray, except those at the margin, has now a little farther to travel in air from mn to the lens, but it has.a little less to travel from the lens on to 0; and on the whole the time spent upon the part of its journey which is in air, is almost exactly the same as before. Again, the glass, though it sags down a little, has not become anywhere sensibly thicker or thinner. Hach ray traverses almost exactly the same thickness of glass as before, and occupies the same time in doingso. Accordingly, the air part and the glass part of the journey of each ray occupying almost exactly the same time as before, the whole time spent by each ray in travelling from mn to o is almost exactly the same, whether the telescope is pointed horizontally or vertically. The case of the speculum is very different. Here the journeys 268 Scientific Proceedings, Royal Dublin Society. are altogether in air; and if the mirror were supported only by its edge, it would sag down when pointed towards the sky, the central ray would then have farther to travel to reach the mirror than the marginal m rays, and again farther to get from the mirror to 0. The wave front of the central ray will accordingly reach o Be) ig. too late to unite with the waves travelling along a ore. These will already have passed o. Hence a speculum must be kept from sagging: and to this end must be supported continuously over its whole back, and with such extreme delicacy that all parts of the back of the mirror shall be equally pressed. If the mirror could be kept horizontal, it might be floated on mercury; but as during the use of the telescope it has to be sloped into different positions, a layer of the delicate springs of which flannel consists has been used for the support of smaller specula up to a 15” or 18” aperture, and the mechanical contrivance called a bed of levers for the larger ones, the edge of the mirror being supported in some way which allows its back to lean freely against the bed of levers, or layers of flannel, as the case may be. Whether it be the levers or the layers of flannel that are used, they inevitably yield when the pressure upon them varies, and it becomes difficult to prevent the line of collimation—that is, the optical axis of the mirror—from shifting a little relatively to the tube of the telescope, when the telescope is carried from one posi- tion to another—so difficult that it is only in the hands of very skilful manipulators, like Dr. Isaac Roberts, that celestial photo- graphs can be satisfactorily taken with reflecting telescopes. Never- theless, when they are so taken, they surpass those which ean be produced by refractors. 2.—THE Proposep Mountine. The following seems to be a way in which this difficulty can be entirely gotten rid of, and specula made available both for celestial photography and spectroscopy, and in astronomical in- struments of precision :— Let the mirror If be made the front of an airtight cell, such as that represented in the diagram, which consists of three chambers Stonzy—-Oompressed Air Support for Specula. 269 A, B, OC, of which A and C communicate with one another, and contain compressed air, while B is open to the atmosphere and contains a regulator which causes the pressure within A and C to vary by the right law when the telescope is moved from one alti- tude to another. This regulator consists of m, a corrugated disk like the cover of the vacuum-cham- « ber of an aneroid barometer, and na weight which leans against m, and is kept from slipping sideways by wires p, g, 7, of which p and q are shown in the figure. If the pressure within the cells C and A (which communicate with one another) becomes too great for the proper support of the mirror, n will move forwards and cause the index / to make electric contact with one of two studs, in consequence of which a valve is opened that lets some of the imprisoned airescape. If, on the other hand, the pressure is too small, » moves backwards, contact is made with the other stud, and a passage is opened between a gasometer holding compressed air and one of the chambers A and C. This regulator will vary the pressure within the chambers A and C when the telescope is moved about, and will cause it, in each posi- tion of the telescope, to settle down to that which is precisely the right amount to support the mirror without flexure, at that elevation. The mirror may be brought into a pre-determined position by being placed just in contact with studs x, y, s, and then cemented round the edge by some cement, like Archangel pitch, which will adapt itself to the mirror and hold it firmly without straining it. If necessary, the front of the cell may be strengthened by flanges to prevent distortion when the cell is placed on its side. Mounted in such a cell, which can be rigidly fixed within the tube of the telescope, it is anticipated that the line of collimation of the instrument will be as fixed, and may be as much depended upon as that of a refractor; and if this be so, reflecting telescopes may be made available for photographing the heavens and photo- graphing the spectra of stars, in the hands of any astronomer engaged in this class of work. 970 Scientific Proceedings, Royal Dublin Society. Another advantage which this arrangement has is, that it will | | enable reflecting telescopes to be sloped downwards, and used in ~ such a siderostatic instrument as that which Sir Howard Grubb made for Queen’s College, Cork. To slope the telescope down- wards it is only necessary to place the airtight compartments A and Cin communication with a partially exhausted gasometer and the open air, through the passages which before connected it with the open air and a gasometer of compressed air. If an instrument of this kind is to be used for photography, the telescope is to be directed towards the South pole and fixed immovable; while the only parts to be carried round by the polar axis are the siderostatic flat mirror, mounted on a cell of a new pattern, and the photo- graphic plate-holder, or these with an eye- piece to enlarge the image. The weight to be carried round may be still further reduced, and at the same time some light saved, since the siderostatic mirror, M, and its supporting cell, ©’, may be perforated in the middle,” and the photographic apparatus, placed below them, on the polar axis. The mounting of such an instrument would be so much less expensive than that of an equivalent equatorial that the whole cost, including that of the siderostatic mirror, would probably be less, while the instrument itself would be very much more easily manipulated than the equatorial. Such an instrument should produce good photographic work, now that large flat mirrors of great excellence can be produced. For accurate spectroscopic work the arrangement seems to offer even greater advantages, for the spectroscope, as well as the telescope, may be absolutely fixed, and the only thing that needs to be moved is the siderostatic mirror. There remains a point to beconsidered. A large mirror cannot be removed and replaced upon its bed of levers. It must be ground and polished upon it, and allowed to continue afterwards upon it in the telescope. Can the corresponding arrangement be made with the new cell while manufacturing the mirror? I think so. What is required will be to place the mirror in a cell (not necessarily the same cell) filled with compressed air or with Fic. 4. Stonry— Compressed Air Support for Specula. 271 water under pressure, and suitably to counterpoise the grinder or polisher. Perhaps the usual mode of counterpoising will be found sufficient, or if necessary a light cell of the new kind may be adapted to the grinder or polisher, and the whole counterpoised, so as to secure a perfectly clean cut over the surface of the mirror, without pressure upon one part more than another. One other point seems worth noticing: that if the figure of the mirror, when finished, be slightly too hyperbolic or elliptic, it may perhaps be brought nearer to the true form by a slight increase or decrease of the pressure of the air upon its back, which could be easily secured by dividing the front chamber of the cell into two compartments with a regulator acted on by a spring between them. It may perhaps be well to mention that the pressure of the air to be stored in the gasometer needs only to be of moderate amount, and can be easily provided by an automatic water-dropping arrangement. ‘Thus to support a glass mirror five inches thick, a maximum pressure of only one inch of mercury is requisite—‘.e. one-thirtieth of an atmosphere. On the whole there seems reason to hope that reflectors may, with advantage, be substituted for refractors in photographing the heavens, for spectroscopic work, and in some instruments of preci- sion; that the instruments will be cheaper, and the work produced by them distinctly better. SCIEN. PROC. B.D.S., VOL. VIII., PART III. U een XXXIT. ON THE SELECTION OF SUITABLE INSTRUMENTS FOR PHOTOGRAPHING THE SOLAR CORONA DURING TOTAL SOLAR ECLIPSES. By ALBERT TAYLOR, A.R.C.Sc. (Lonp.), A.R.S.M., F.R.A.S. [Read May 16; Received for Publication May 18; Published Juzy 25, 1894.] Tue great success obtained by the various parties which observed the Total Solar Heclipse of 1893, April 15-16, is extremely valuable, not only as giving us a very complete record of the form and structure of the Solar Corona at the time of the eclipse, but also as indicating the best methods, both photographic and instru- mental, for future work in the study of the phenomena of eclipses. Although full descriptions and discussions of the results have not yet been published, sufficient is known to enable us to form definite conclusions on certain hitherto disputed points; and as the next observable total solar eclipse is on August 8, 1896, and the organi- zation of expeditions to observe it should be commenced at once, I have thought it might be useful to briefly indicate, in this paper, what I think should be the main considerations guiding the organisers and observers of future eclipses. There is such a great variety in actinic brightness of the various phenomena of an eclipse that it is practically impossible to get all of them by one exposure on a photographic plate. As I have previously pointed out (“ Observatory,” vol. 16, p. 95), we may roughly divide the phenomena into four main divisions—the chromosphere and prominences, the inner corona with polar rays, the middle corona extending from 10’ to 30’ from the limb, and the faint extensions which have been traced, visually, some 5° from the limb, and which are only very slightly more actinic than the surrounding sky. There are very few difficulties in photographing the first three of these portions, but there has been considerable discussion as to the best method of photographing the faint external extensions of the corona. The eclipse of 18938, April 15-16, has added materially to our knowledge on the latter point, and has also assisted us in indicating the direction of future work for the brighter parts of the corona. & Taytor—On the Photographing of the Solar Corona. 273 The instruments previously used had been of comparatively small aperture and of moderate focal length, the limits of six inches aperture, and six or seven feet focus being very rarely exceeded. Professor Pickering, at the eclipse in California, 1889, January 1, used a photographic object-glass of 13 inches aperture and 16 feet focus (the longest focal length up to that time), and Father Perry, at the eclipse at Salut Isles, French Cayenne, 1889, December 21-22, used a mirror of 20 inches aperture and 40 in. focus; but these were exceptional instruments. In 1893, April 16, four stations were occupied, and the eclipse was successfully photographed at all of these. Professor W. H. Pickering was at Minasaras, in Chili, and used a 5-inch object- glass of about 48 inches focus, stopped down to 3 inches aperture, and a 20-inch mirror of 45 inches focus. Professor Schoeberle, of the Lick Observatory, was at Mina Bronces, in Chili, and he and his assistant, Mr. W. F. Gale, of New South Wales, used two instruments, one of 4:96 inches aperture, and 46 feet focus, and the other of 64 inches aperture and 6 feet focus. At Para Curu, in Brazil, I used two optical combinations, one a 4-inch photographic lens of 60 inches focus, and the other a 4-inch lens of about the same focus, but fitted with a triple cemented negative enlarger of 8 inches negative focus, which enlarged the image 3 diameters, thus corresponding to 4 inches aperture and 15 feet focus. At Fundium, in West Africa, Serjeant J. Kearney, R.E., used a double camera exactly similar to mine in Brazil. Comte de la Baume Pluvinel, of Paris, who was also at Fundium, West Africa, used nine different objectives (mounted on one stand), all of sensibly the same focus, 13 metres (4 feet 10 inches), and with apertures varying from 155 mm. to 5 mm. Other instru- ments were used at the various stations, but these are the chief ones, and those from which valuable scientific results were obtained. The principal departures from ordinary practice were the long focal-length instruments, 46 feet in Chili, and 15 feet in Brazil and Africa, and the exceptionally small apertures, 5 mm., of Comte de la Baume Pluvinel, in Africa. One of the most disputed points in eclipse photography has been as to the proper exposure to obtain the faint extensions of the corona without fogging the plate by the skylight. Captain Abney has shown that we may look upon a photograph as repre- senting 200 different shades; or, in other words, that on a 274 Scientific Proceedings, Royal Dublin Society. correctly exposed and developed negative a difference of 3 per cent. in the intensity of light can be detected. It should there- fore be possible, by correct exposure, to detect the corona on the sky when the skylight forms 993 per cent. of the light, and the corona $ per cent. The problem is to obtain nega- tives showing this difference, and two diametrically opposite opinions were held as to the best method of securing this. The American observers and Comte de la Baume Pluvinel held that short exposures and slight photographic action were necessary, whereas most English authorities held that it was only by long exposure and great photographic action that we could hope to secure the faint extensions. The photographic action on a plate is the product of three factors—the effectiveness of the lens, the duration of the exposure, and the sensitiveness of the plate. The effectiveness of a lens or mirror was defined by the International Photographic Congress at 2 Paris as 100 , where @ is the aperture, and fthe focal length of the optical instrument; so that in comparing the photographic action on plates taken with various instruments, the formula becomes 100 ea t. s.. Where ¢ equals the time of exposure, and s is the sensi- tiveness of the plate. Assuming plates of normal sensitiveness 2 used throughout, we get 100 5% as the formula for comparing the photographic actions on the various plates used for the corona ; and the application of this formula to the eclipse plates of 1898, April 15-16, gives very interesting results. With the English instruments exposures of 2, 5, 15, 20, 50, 120, and 150 seconds were given; and applying the formula we get :— 4-inch lens, with enlarger :— 4-inch lens, 60 inches focus :— 1 second = 044. 1 second = ‘444. 2 seconds= 088 2seconds= 888 TR ve 8) Bi loge) ) it | 27228 SS hyp yess de) = ee Oe Oy B51 f=) LOGGG A) IS 88 20 = EER eR BOG pop pe 25222 50 ,, = 22-292 120) = 5838 190.) = 5esae 150 ,, = 6°666 ° 150 ,, = 66°666 TayLtor—On the Photographing of the Solar Corona. 275 An examination of my photographs taken in Brazil shows that there is a steady increase in the extension of the corona on the plates of the first series, in which the photographic actions increased from ‘088 to 6°666, although the latter suffered slightly from sky fog; but in the second series there is a steady increase up to 20 seconds, and practically no gain is shown by the 50, 120, and 150 seconds, while the two latter plates have suffered very much from sky fog, and the inner portions of the corona are hopelessly burnt out. The best all round result for the inner and middle is obtained by a photographic action of less than 1, and there is a loss in external corona when the photographic action reaches 22. With Professor Schoeberle’s instruments a similar result is obtained. The 4:96-inch object-glass, of 46 feet focus, gives a photographic action of ‘0086 for 1 second exposure, and the photo- graphs taken with this instrument, in which the photographic action never reaches 1, are magnificent for the inner and middle corona, while they also show some portions of the external corona- With the 64-inch lens of 6 feet focus, the photographie actions were :— (1 second corresponds to a photographic action of *766.) Instantaneous, say = second, = ‘005 lsecond = ‘766 2 seconds = 1:°582 A Mes B G4 Se E18 10 Ue ii 660 16)" 29-256 cy ron” 507; He finds the best picture of the external corona is given by 16 seconds, corresponding to a photographic action of 12-256, a greater photographic action than this resulting in sky-fog and loss of detail in the external corona. The best photographie action found by Professor Schceberle falls between the English best (8-888) and the first English result in which loss by sky-fog is found, and indicates that an exposure of 29 or 380 seconds with the 4-inch lens of 60 inches focus is about the limit of good results. To go beyond this is to lose detail. 276 Scientific Proceedings, Royal Dublin Society. Comte de la Baume Pluvinel had his various photographic cameras arranged to have photographic actions varying in such a manner that the greatest was 1000 times that of the least.. He finds, as a general result, that the best all-round negative is given by a photographic action equal to 4: but this does not agree with the results obtained in Chili and Brazil. A probable explanation is, that whereas in Chili and Brazil the sky round the corona was perfectly clear during totality, at Fundium there was light haze in the sky. M. Deslandres says there were ‘*faint clouds,” and these would necessarily be illuminated by the corona, and would give a far brighter sky than was found in Chili and Brazil. Comte de la Baume Pluvinel, at Salut Isles, in 1889, Dec. 21-22, found, using photographic actions varying from 185 to 18, that the best result was given with an action over 13 and under 82, this agreeing very nearly with the results found by Professor Schoeberle and myself in 1893. I have at present no precise details of Professor Pickering’s exposures, and so cannot get his photographic actions, but the comparison of his results with those of Professor Schosberle and myself will be extremely interesting in settling this important point. There can be little doubt that the idea that long exposures and great photographic action are necessary for the external por- tions of the corona must be abandoned; and in devising instru- ments for future eclipses, there is nothing to be gained in this direction by the use of photographic actions exceeding 15 or 16. This will enable instruments of much greater focal length to be used for future work. An instrument working at a yo will secure all the external corona in about 15 or 16 seconds, and one at a zs will secure everything in about 100 seconds. In addition to a lens working at this ratio I would recommend the use of a 12-inch object-glass of 40, 50, or 60 feet focus, which would enable pictures of the corona to be obtained on such a scale that the image of the moon would be over 4, 5, or 6 inchesin diameter. Short exposures with this would give the inner and middle corona with all the beauty and delicacy obtained by Professor Schceberle in Chili; and 100 seconds’ exposure would give nearly all the corona that is within reach of the photographic method of attack Taytor—On the Photographing of the Solar Corona. 277 in the present state of photography. That such lenses can be easily and efficiently mounted and used was clearly shown by Professor Schceberle ; and it seems to me, after the results of 1893, that it is only by such object-glasses as I have indicated that such an important occurrence as a total solar eclipse should be attacked in future, if we wish to add to our knowledge of the corona. There does not seem to be any great difficulty in mounting these long-focus instruments. Professors Todd and Bigelow at Cape Ledo, 8. W. Africa (1889, Dec. 21-22), adopted a tripod stand, with a sand piston for one leg, which was so arranged that the shortening of the leg as the sand ran from under this piston caused the telescope to be moved to follow the sun during the eclipse. As this necessitated the use of a long tube, supported on what looked to me an unstable mounting which would certainly shake in a wind, I do not think any great success can be anticipated from this form; certainly the risks of failure would be greater than if some form of fixed tube were adopted. We can use a fixed tube in any of three ways :— (a) With a heliostat, in which a mirror is carried on a polar and declination axis, and is driven by clock-work, so as to throw the sunlight always in the same direction, ¢.e., into the horizontal telescope tube. (6) With a mirror mounted on a polar axis driven by clock- work, the tube of the telescope being placed in the meridian, and inclined at an angle equal to the latitude of the place of obser- vation. (c) On the plan adopted by Professor Schoeberle, with the tube adjusted in altitude and azimuth so as to point to the sun at mid-eclipse, the photographic plate being moved so as to follow the sun during totality. The first two of these plans are open to the objection that the sun’s image, as reflected from a mirror, rotates as the polar axis carrying the mirror is moved in right ascension. This rotation would amount to over 20 minutes of arc in 100 seconds’ exposure, and would probably be sufficient to blur the finest details of the inner corona. The first is open to the additional objection that with a heliostat-mounting the motion of the polar axis is commu- nicated to the mirror by means of a jointed rod, and the motion through this is a series of slips, and not the perfectly even motion 278 Scientific Proceedings, Royal Dublin Society. that is absolutely essential for the best work. These two objections practically dispose of the first method ; and the rotation of the corona introduced by the second method is a serious objection. The chief objection to Professor Scheeberle’s plan is that the image of the sun travels across the field of the object-glass during the eclipse, and that it is only at mid-eclipse that the plate is exactly in the optic axis of the object-glass. As the movement of the sun in 3 minutes of time is about 45 minutes of are, and the field of a good object-glass is practically perfect over at least 2°, and very good for 1° on each side of this, this objection is not a serious one, for we could rely on getting good definition during a 6 minutes eclipse, and we rarely get such duration for these phenomena. ‘The only moving parts in this arrangement are the plate-carrier and plate, and these are extremely light, so that very perfect motion can be given by a very simple clock, or by some simple water-motor similar to that adopted by Professor Hale, of Chicago, in his spectroheliograph. With the apparatus used in Chili Professor Schceberle gave exposures of 32 seconds, and obtained perfect pictures. The instrument of the future for obtaining the inner and middle corona at eclipses will probably be some simple apparatus founded on this principle, in which a long-focus object-glass will be used, and small photographic action obtained on the plate. [ 279 ] XXXIIT. ON DERIVED CRYSTALS IN THE BASALTIC ANDESITE OF GLASDRUMMAN PORT, CO. DOWN. By GREN- VILLE A. G. COLE, M.R.LA., F.G.8., Professor of Geology in the Royal College of Science for Ireland. [Abstract of a Paper published in eatenso in the Scrmntir1c TRANSACTIONS OF THE Royat Dvusurin Society, Vol. V.] Tue author described a large composite dyke showing at this point a band of andesite on each of it, from 4 to 17 feet wide, and a more recent dyke of eurite in the centre, 36 feet across. The eurite includes numerous blocks of andesite, and sends off veins into it; but the pyroxene and glass of the latter rock have pecome remelted at the contact, a delicate interpenetration of the two magmas has occurred, and the porphyritic crystals of quartz and pink felspar from the eurite are found completely surrounded by the dark andesite. Thus a pre-existing rock comes to include erystals derived from one that has subsequently invaded it, and hand specimens, without study in the field, would be of a most misleading character. XXXIV. ON THE FOSSIL-FISH REMAINS OF THE COAL MEASURES OF THE BRITISH ISLANDS. PART I].—Acanruopwwa. By tae tate JAMES W. DAVIS, F.G.S., F.L.S., F.S.A., &e. [This Paper is published in the Screntiric TRANsAcTions oF THE Royat DuBLin Socrery, Vol. V.] SCIEN. PROC. R.D.S., VOL. VIII., PART IIT. x F280 XXXV. ON HOZOONAL STRUCTURE OF THE EJECTED BLOCKS OF MONTE SOMMA. By PROFESSOR H. J. JOHNSTON- LAVIS AND DR. J. W. GREGORY, F.G.S. [Abstract of a Paper published in extenso in the ScteNTIFIC TRANSACTIONS OF THE Royat Dusuin Society, Vol. V.] Tue authors show that the limestone blocks, of Mesozoic age, in Monte Somma have frequently become metamorphosed into crystalline masses consisting of alternating bands of calcite and various silicates. The authors regard the silica, magnesia, &c., as derived from the igneous rock by chemical interpenetration and interaction. Where the silicate, as often happens, is olivine (montecellite), or a pyroxene, a complete simulation of the struc- ture of Hozoon Canadense is produced. The layers of silicates occur parallel to the surfaces of any igneous vein that may have intruded into the limestone, and they become closer to one another in the areas farther removed from contact. ‘he “proper wall,” the “stolons,” and in places the “canal system” of Hozoon are recognizable under the microscope; and the authors adduce evidence to show that the typical eozoonal limestone of Canada may have arisen similarly as a product of contact metamorphism. 4 —L) —?) ee THE SCIENTIFIC PROCEEDINGS | ROYAL DUBLIN SOCIETY. Vol. VIII. (N.S.) SHPTEMBER, 1895. Part 4. CONTENTS. PAGE XXXVI.—The Automatic (i cone By. the Rey. RicHarp C. Bopxiy, . 281 XXXVII.—The Occurrence of lebohes in irae Demavenah Co. Westmeath, 1893, 1894. By J. R. H. Mac Fartans, Staff-Commander R.N. (Retired), F 288 XXXVIII.—On Pucksia Mac Henry, a New Fossil from ihe Caanean Rocks of Howth. By ProFessor Soxuas, D.Sc., LL.D., F.R.S., 297 XXXIX.—A Chllestion of Tepiieneera or Toeere West iefeten: By Grorcr H. Carprentrer, B.Sc., Assistant Naturalist, Science and Art Museum, Dublin, . : 304 XL.—On the Gold Nuggets hitherto found in the Gute Wicklow By V. Bat, C.B., LL.D., F.R.S. (Plate XIII.), . . 381i XLI.—Survey of Fishing Gummi West Coast of Ireland, 1890-91. Notes on the Hydroida and Polyzoa. By J. E. Dunrpen, A.R.C.Sc. (London) ; Curator of the Museum of the Institute of Jamaica. (Plate XIV.), . 325 XLII.—On the Chemical Examination of Organic Matters i in River Waters. By W. E. Apeney, F.I.C., Associate of the Royal Calléze of Science, Ireland ; Curator in the eye University of Ireland, . 337 XLIII.—Branched Worm-tubes and Aesorotaithne. By Eee A. C. Happon, M.A., F.Z.S., Boxe cee of ee Dublin, ; 344 XLIV.—A Method of Thereaaing the Beton of Contiduans Lise house Lights. By Jouw R. WieHam, M.R.I.A., Member of the Council of the Royal Dublin Society, 7 3 347 XLV.—Of the Kinetic Theory of Gas, regarded as Tllnetearire§ Nature. By Guoren Jonwnstone Stoney, M.A., D.Sc., F.R.S., Vice-President, Royal Dublin Society, : . 3851 The Authors alone are responsible for all Opinions expressed in their Communications. DEO BETA PUBLISHED BY THE ROYAL DUBLIN SOCIETY. WILLIAMS AND NORGATE, 14, HENRIETTA-STREET, COVENT GARDEN, LONDON; 20, SOUTH FREDERICK-STREET, EDINBURGH; AND 7, BROAD-STREET, OXFORD. 1895. ; Bs gon Price Three Shillings. \ 4; tom Ing fy, an We al Muean Roval Dublin Society, FOUNDED, A.D. 1731. INCORPORATED, 1749. EVENING SCIENTIFIC MEETINGS. THE Evening Scientific Meetings of the Society and of the associated bodies (the Royal Geological Society of Ireland and the Dublin Scientific Club) are held on Wednesday Evenings, at 8 o’Clock, during the Session. Authors desiring to read Papers before any of the Sections of the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at Jeast ten days prior to each Evening Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission to the Editor. Pee", | XXXVI. THE AUTOMATIC IMAGE-FINDER. By THE REV. RICHARD C. BODKIN. [Read NovemBer 21, 1894; Received for Publication Novemprr 23, 1894; Published January 21, 1895. ] 1°.— Construction of the Instrument, and the Principles upon which it is based. THe instrument which I have the honour of bringing under the notice of the Royal Dublin Society is called the Automatic Image-Finder. This name but very inadequately expresses the end and scope of the instrument ; still I could find no better. The real object I had in designing and constructing the instrument is threefold :— 1. To show where the image of any object placed before any lens must be formed ; 2. To prove that the image is found there; and 3. To help to explain the construction of the various optical instruments in use, such as the microscope, telescope, camera, and projection lamp. Thus the Automatic Image-Finder is essentially a teaching instrument. The construction of this instrument is very simple, and depends on a few elementary principles. 1. It is well known that the image of an object is invariably seen where the rays proceeding from that object meet, or seem to meet, ¢.g. if the rays meet at A (fig. 1), we see the image at A; if they meet at a we see the image at a; and if they do not meet at all, but merely seem to meet at a’, then we see the image at a’. 2. The rays proceeding from any point in an object always meet (or, if not, at least seem to meet) at some point or other alony SCIEN. PROC. R.D.S., VOL. VIII., PART IV. Y 282 Scientific Proceedinys, Royal Dublin Society. the secondary axis drawn from that point. Thus, if A is the point in the object, the image of that point will be found some- where or other along the line AA (fig. 1). If a is the point, its image will be found somewhere along aa (fig. 1). & Jee, Ie Keeping these two principles in view we may proceed. Since we always see an object where the rays proceeding from that object meet, or seem to meet, and since they always meet (approximately), or seem to meet, at some point on the secondary axis, evidently the all-important point is to find where they meet the secondary axis. Now this is found very simply, for if we can show where any one ray cuts the secondary axis, all others must cut itat the same place. Nowit so happens that it is a matter of extreme simplicity to show where a ray drawn from the object parallel to the principal axis must cut the secondary axis from that point. And this is the great fundamental principle to be attended to in the construction of the instrument. The secondary axis from any point passes as a straight line through the centre of the lens. Consequently we have one point (viz. the centre of the lens) in this line always fixed, and so this point acts like the centre ofa circle round which the line revolves. It may therefore be aptly represented by a pivot and a line revolving round it. This may indicate all the positions that the secondary axis can occupy, no matter where the object may be. We can therefore easily find the various positions of one of the lines. | Now for the position of the other line, viz. the line proceeding from the same point in the object, and drawn parallel to the Bopxin—The Automatic Image-Finder. 283 principal axis. The position of this line presents no difficulty whatsoever ; in fact it is absolutely fired and constant, no matter what the position of the object may be. This of course is at once quite clear when stated, for a ray parallel to the principal axis must of necessity pass through the principal focus, and so we have two points fixed in this straight line (viz. the point where it cuts the lens and the principal focus), and therefore the position of the line is determined. In fact, to indicate its position, we have only to draw a straight line from the point where the parallel ray cuts the lens to the principal focus, and produce this line indefinitely. In a word, one of the lines (viz. the parallel line) is constant in position, and the other moves up and down along it. It therefore only remains to determine the position of one of the lines at any moment, and that is easily done, since one of the points is fixed, and acts as the centre of a circle, and the other is immediately determined by the position of the extremity of the object as it moves along in its course. In order to apply these principles with greater ease, attention is here directed to figure l. Let AB represent the object; then the rays drawn from the extremities of the object and passing through the centre of the lens, will proceed as straight lines, as seen in the figure (lines AA and BB). Now another straight line drawn parallel to the principal axis, and meeting the lens at H, must pass through /, and so we have its position determined. From a consideration of these principles we arrive at a very simple rule for drawing the images of any object placed anywhere before a lens (or mirror). It is this :— 1. From the extremities of the object, draw secondary axes (or straight lines ‘passing through the centre of the lens). ww . From the extremity of the object, draw a straight line parallel to the principal axis and cutting the lens. 3. From the point where this line cuts the lens, draw a straight line through the principal focus, and produce it indefinitely. 4. Where this line cuts the secondary axis there is the image Y 2 284 Scientific Proceedings, Royal Dublin Society. Now the Image-Finder is merely an embodiment of this rule in simple mechanism, and so it furnishes an easy and rapid means of drawing images, no matter how the position of the object may vary. To see this more clearly we have only to look at the figure of the instrument (fig. 2). Here we have the object, viz. the arrow AB. 1. From the extremities of this arrow (viz. A and B), we draw secondary axes represented by the wires AA and BB, and these revolve on a pivot which represents the centre of the lens. 2. From the extremity of this object or arrow we draw a straight line parallel to the principal axis. This is represented by the parallel wire AF. 3. From the point # where this wire cuts the lens, we pass a straight wire 4# through the principal focus. 4. Where this wire cuts the secondary axis AA there is the image, v.g. at A. To be brief, the Image-Finder consists of an arrow or object capable of moving backwards and forwards along two parallel wires, which represent the parallel rays proceding from the object. From the point at which one of these parallel rays meets the lens, proceeds a ray passing through the principal focus; this indicates the course pursued by the parallel ray after refraction. Lastly, from the extremities of the object pass two straight lines through Bopx1n— The Automatic Image- Finder. 285 the centre of the lens; these represent the secondary axes, and by their motion round the pivot (caused by the mere approach and recession of the object) they indicate the various positions that must be assumed by the secondary axes, corresponding with the various positions of the object. Now according to the principles above laid down, where the lines (in their motion) intersect the refracted parallel ray, there is the image. 2°.—How to work the Image-Finder. In order to work the Image-Finder, and see how it enables us to know the position of the image at any moment, and to discover the laws of lenses, we have only to slide the arrow or object backwards and forwards, and then note where the rays intersect : there then isthe image. The mere motion of the arrow causes the secondary axes to travel in and out, and to assume their proper positions according to circumstances, thus intersecting the refracted parallel ray (which is constant in position) at various points, showing thereby where the image is, whether it is real or virtual, larger or smaller than the object, erect or inverted. To discover the laws of lenses by means of the Image-Finder we have only to observe that— 1. If the object or arrow is at infinity (or as far away as possible), the rays meet at f, and so the image is there: it is real and smaller than the object. 2. If the object is at 27, we find that the rays meet at 2f, and so the image is there. Further we see that as the rays really meet, the image is real, of the same size as the object, and inverted. 3. If the object is at f the rays go out parallel, and so never meet. In this case the image is said to be at infinity. 4. If we place the object anywhere between infinity and 2/f, we observe that the rays really meet somewhere between f and 2f. Consequently the image is there ; it is real, smaller than the object, and inverted. 5. If we place the object anywhere between 2f and f, we note that the rays really meet only between 2/ and infinity. Therefore the image is there ; it is real, larger than the object, and inverted. 286 Scientific Proceedings, Royal Dublin Society. Lastly, if we place the object between f and the lens, we find that the rays diverge on the far side, and can only be made to appear to meet on the opposite side of the lens. Where they appear to meet, there is the image; it is virtual, larger than the object, and erect. Should we now desire to use the instrument for another lens of different focal length, we have only to move the nut representing the principal focus to the required position in its slot, and then clamp it there, and move the object as before. If we wish to employ the instrument for the demonstration of the properties of concave lenses, we have only to change the position of the principal focus, and bring it to the front of the lens, as seen in the figure (fig. 2). Now withdraw the wire passing through the former principal focus, and insert it in the moveable nut at the far side, and also in the extremity of the section of the lens. This gives us the new position of the parallel ray after refraction through a concave lens. Move the object backwards and forwards as before, and you can discover for yourself all the laws and properties of concave lenses. In this case you will find from the instrument that the image is always virtual, smaller than the object, and erect, no matter what the position of the object. Norr.—In the case of virtual images with convex lenses, in order to find their positions, the rod passing through the extremity of the lens and the principal focus must be slid through the holes in which it fits, and so brought to the front of the lens. Still, as before, where this line intersects the principal axis, there we have the image. This instrument, with very slight alterations, and worked on the same principles, illustrates and proves all the properties of concave and convex mirrors. 3°.—LHxperimental Proof of the Laws of Lenses. The second end to be secured by the use of this instrument is to prove experimentally that the images really are formed at the points indicated. This is done in the simplest possible manner. Over the arrow, a source of light, such as a candle, is fitted ; over the section of the lens, a glass lens of the given focal Bovxin—The Automatic Image- Finder. 287 length is fixed; and at the intersection of the rays a screen is placed to catch the image of the candle. Now, by moving the arrow in order to catch the image, the screen must be placed at the intersection of the rays, and nowhere else, thus proving experi- mentally the truth of the above principles, and the correctness of the working of the instrument. 4°,.— Explanation of the Construction of Optical Instruments by means | of the Image-Finder. Lastly, the Automatic Image-Finder enables us to explain with ease the construction of the various optical instruments. All we have to do is to state precisely what we desire to get, and then apply our principles and our instrument to secure it. For example, suppose it is required to construct a projection apparatus, what is wanted is an enlarged real image. Now, to secure this, the object must be placed outside the principal focus, else a virtual image would result; and since the image is to be larger than the object, it is found by moving the arrow that it must be placed between f and 2/7. In a word, we see that a projection apparatus consists of a double convex lens of moderate focal length, the object being placed between f and 27. Again, if it is required to find out what the construction of the microscope is, there must be a virtual image, and it must be larger than the object. This granted, it follows at once that it must consist of a convex lens, for no other lens. gives an image larger than the object (in a double concave lens the image is always smaller than the object). Now since the image is to be virtual and the lens convex, the object must be placed inside the principal focus and only a little inside, else the image is not as large as possible. Al this is clearly seen by moving the arrow in the instrument into various positions. The telescope, camera, &c., admit of a similar easy explanation by means of this instrument. f 268 a XXXVI. THE OCCURRENCE OF SEICHES IN LAKE DERRA-- VARAGH, CO. WESTMEATH, 1893, 1894. By J. R. H. MAC FARLANH, Staff-Commander R.N. (Retired). [COMMUNICATED BY PROFESSOR D. J. CUNNINGHAM, M.D., F.R.S., HON. SEC., B.D.S. | [Read NovemBrr 21; Received for Publication NovemBeER 23, 1894 ; Published Marcu 30, 1896. | Towarps the close of the last century, attention seems to have been first drawn to, and observations made of, phenomenal changes of the level of the water in many of the Swiss lakes; these alterations consisting of a series of rising and falling water occurring at in- definite periods, the whole movement occupying different spaces of time, varying from ten minutes to nearly an hour; the time so occupied being apparently dependent on the positions where the observations were taken on the several lakes. This complete movement of rise above, and fall below, mean level has been termed a seiche. The amplitude of a seiche is the extreme difference of level so produced. The duration of a seiche is the time in seconds from the moment when the water is at mean level, until it is again at mean level, after passing through one maximum and one minimum.* There would appear to be no records of observations made of seiches in any of the lakes of Great Britain or Ireland, but the non-existence of these alterations of level must not therefore be assumed, as they may be of such rare occurrence, or the rise and fall of so slight a character, that they have hitherto escaped notice. The observations made at Lake Derravaragh, although un- avoidably incomplete, leave no doubt as to the existence of seiches 1See ‘‘ Lake,’”? by J. Y. Buchanan, Esq., F.R.S., m Encyclopedia Britannica, 9th ed., vol. xiv., p. 220. Mac Fartane—Seiches in Lake Derravaragh, Co. Westmeath. 289 on that lake; later on I shall endeavour to show the difficulties in obtaining satisfactory results. Until the alterations of the level of the water in Lake Derra- varagh first came under my notice, seiches were quite unknown to me. I must therefore approach the subject with diffidence, giving, as fully as possible, the results of the observations made in the order in which the seiches occurred, and afterwards stating any ideas deduced from them. I may premise that the house occupied by me, during the time these observations were being taken, was situated about twenty yards from the edge of the lake, and therefore in a most favourable position for observing; also that, with a view to noting the rise and fall of the lake for fishing purposes, I had placed a batten, marked in feet and inches, on one of the piles of an old pier; this batten, and the gauge which afterwards replaced it, being situated on the weather side of the lake with respect to, and in perfect shelter from, the prevailing winds. 1st Observation.— When going out in a boat on the lake, on the afternoon of the 38rd October, 1893, I noted that the level of the lake, then only slightly above its lowest during summer, was standing at half-an-inch above the lowest mark on the batten ; returning about two hours later the level was half-an-inch below the same mark. Puzzled by this change of level of 1 inch, in such a short period, I carefully watched the batten until dark, from 5” 10™, to 6" 25", during which space of seventy-five minutes there occurred three complete movements; two falling and one rising, or about twenty-five minutes to each movement, the amplitude being two and a half inches.? The batten giving very rough results, I constructed a gauge which would rise and fall with the water, and a pencil attachment registering the amplitude; this enabled me, on the next day, to take a number of observations, but the change of level was then subsiding, the amplitude being only 1 inch, and the duration of the seiche thirty-six minutes. Gradually the movement became less, until about 4 p.m., when it entirely ceased. 1 Although, in the definition of a seiche, already given, the time is said to be expressed in seconds, for want of delicate appliances I can give nothing less than half a minute, except when as a result of the mean of several observations. 290 Scientific Proceedings, Royal Dublin Society. It may here be remarked that during the time these observa- tions were being taken, on the 3rd and 4th October, there was no wind. In attributing, as I did, these changes of level to seismal influences, it would appear that the same impression was also first entertained by previous observers; the theories now held in con- nection with them are briefly as follows :— I. That they are caused by downward rushes of wind on the surface of the lake, accompanied by changes of barometric pres- sure. II. Dr. Forel attributes seiches to local variations of atmo- spherie pressure giving impulse, the effect of which would be apparent for a long time as a series of oscillations. He adds, how- ever, that he attributes seiches having a greater amplitude than 1:5 metres to earthquake shocks. * III. In 1881, Mr. Plantamour, an authority on this subject of seiches, assured the writer of the article in “Encyclopedia Britan- nica” that he was utterly at a loss for a satisfactory explanation of their causes. IV. From the observations of Jallabert, Bertrand, Saussure, and Vaucher the following law, connecting seiches with movements of the barometer, has been deduced. ‘The amplitude of seiches is small when the atmosphere is at rest; the seiches are greater the more variable is the atmospheric pressure; they are the greatest when the barometer is falling. 2nd Observation.—The level of the lake having been carefully watched subsequent to the changes observed on the 4th October, it is improbable that any variation took place until the second obser- vations, which are as follows :— During the night of the 7th and morning of the 8th December, a heavy gale was blowing from the N.W., the barometer standing at 29:20” in themorning. Between 11 a.m. and noon the lake was rising and falling steadily, the amplitude of the seiche being 0°8 inches; this amplitude was reduced to 4 inches at 4 p.m. 1 Le Léman ; Monographie limnologique par F. A. Forel, Lausanne ; F. Rouge,1892. Note:—The Bibliography is at p. 455, and the chapter on Limnologie gives all that is known about seiches. 2 Barometer readings reduced to sea level. Mac Fartane—Seiches in Lake Derravaragh, Co. Westmeath. 291 From the mean of a number of observations the duration of the seiche was 39 minutes; and it was observed that the time occupied by the rising was less than that of the falling in the proportion of about 8 toll; ze. the time of rising occupied about 16 minutes and falling 22 minutes; this was also noticed in subsequent observations. 9th December.—Calm weather ; amplitude of seiche 4°26 inches. Duration of seiche (mean of fifteen observations), 37°2 minutes. Barometer in the afternoon 29°65 rising. 10th December.— Barometer 29°20 amplitude of. seiche in the forenoon 1-5 inches, increasing to 31 inches in the afternoon. Duration 39 minutes. 11th December.—Barometer 29.45 ; greatest amplitude during the night 3:1 inches, decreased to 1 inch in the morning. 12th December.—Barometer 29°60 ; amplitude about 0°5 inch. From the 9th to 12th December, calms and light breezes with fine weather generally prevailed; but from the 138th to 17th, the lake was rising steadily from heavy rains; and in this condition the character of the seiches was entirely altered, and no satisfactory observations could be taken. 8rd Observation.—On the morning of January 27th, it was blowing in heavy squalls from the S.W., and the lake was rising and falling too quickly for observation ; but towards the afternoon, the wind having shifted to N.W., and somewhat subsided before dusk, the rise and fall had become steady and a few observations were taken :-—Amplitude 5-1 inches ; duration about forty minutes ; barometer 29°50 inches. I should feel inclined to divide the seiches occurring on Lake Derravaragh into two classes. J. Gradual rise and fall, when observations of amplitude and duration of seiche may be recorded. This class appears to occur only when the lake is otherwise at rest, or rather when it is not receiving any accession of water from rainfall, and during the year that I remained at Lake Derravaragh was only noticed on three occasions. It has been previously stated that on the 8rd and 4th October the weather was calm ; during the 8th December blowing a gale ; on the 9th of December again a calm; and on the 27th January, 292 Scientific Proceedings, Royal Dublin Society. 1894, a gale subsiding; so that there is some difficulty in under- standing in what manner the seiches occurring on those several days could have been influenced by wind. The barometer was not observed during the October seiches, but on all other occasions of their occurrence a low barometer was registered. II. What I would term the other class of seiches occurred frequently during the many heavy westerly gales of winter, at which time the level of the lake was being continually altered by rains, and the seiches then assumed a totally different character, the rise and fall being no longer slow and steady, the water rushing upon, and receding from, the shore in the form of waves. The gauge, situated on the weather shore, and in perfect shelter, showed these variations as a quick pumping, making observations of duration impossible, although nearly 6 inches of amplitude was frequently registered. Characteristics of the shores in the immediate neighbourhood of the spots where observations are taken, most probably govern both amplitude and duration of a seiche, but the duration so affected may be fairly constant at each station where observa- tions are taken, although the amplitude may differ considerably on different days.’ On referring to the accompanying plan of Lake Derravaragh, it will be seer that the observation spot is somewhat peculiarly situated as regards its surroundings: to the west and north-west the hills about Knockbody rise directly behind the house, and on the opposite side of the arm of the lake, at less than 400 yards distance, Knockross springs abruptly from the lake. To the south-westward of the house, the land becomes somewhat lower (about 100 feet above the lake) ; and in gales from that quarter, the wind, blowing across the lake, impinges on the steep side ot Knockross, and is deflected back on Knockbody (see dotted line) with such violence that it becomes, under those circumstances, a bad lee-shore fora boat. It will thus be seen that the observation spot is apparently contained in an approximate right angle, formed by the advancing and deflected wind. I have already alluded to the difficulties in obtaining complete 1“ Take,” Eneyclopedia Britannica, 9th ed., vol xiv., p. 220. Mac Fartane—Seiches in Lake Derravaragh, Co. Westmeath. 293 observations of seiches; if they came in due course, as in the case of an eclipse of a heavenly body, there would be no difficulty in obtaining observers for a number of stations on a lake, in which case some result, as to the effect of the surroundings of the dif- nockross \249 @ Streamstown Ho. SS \ 55 i Laké Ho.atyes 65\ 4253 62 58 64 ton 8 \A 61 70 77 & Faughalstown 49 56 5! A187 Mornin: A 233 donore Ho. [o} Scale of Irish miles. 4 4, ML OOM —— LT oO Ww & ro) > mo Hy 2 aise ves eceqgn —-.2 0 19 “ao. Pe) Oo o8 us oo s uo <6 w _ i oO oO Ag Scale of English Statute miles. LAKE DERRAVARAGH. o > — ss} o ” o > fo) 2 Ls} ~ o 2 iS) N ~ = BO o < 1 ough Ree, rz) > & i ® £ £ 5 ” c & 3 E 3 2 = ® e = Y) a0 = as) = 5 ° i) R,Inny t ferent stations might be arrived at; but when a seiche may occur at any time it renders it almost impossible to obtain synchronous observations except at considerable expense. Lake-dwellers might be roused to take an interest in the subject, but, even then, 294 Scientific Proceedings, Royal Dublin Society. simultaneous observations could never be satisfactorily carried out, unless, perhaps, the dwellings were connected by telephone or telegraph, as an observer at a station on a part of the lake, sub- ject to large amplitudes, would observe a seiche that might be totally missed at another station where the amplitude was slight Self-registering gauges might be used, but a number would be required for simultaneous observations on a lake; the clockwork movement would need attention, and specially fitted protection from the weather, this all becoming a costly experiment. At Lake Derravaragh, at first, the theory that seiches might be due to seismal influence, appeared to be not altogether devoid of foundation. The abrupt manner in which the hills rise from the southern part of the lake seemed to point to a great depth of water; and local rumour currently reported that at the foot of Knock Hyon the lake was 500 feet in depth, or as deep as that hill is high above it. From the soundings taken it will be seen that the deepest water 89 feet, at low water of summer, is actually at the foot of Knock Hyon ; but this depth is really very little in excess of the depths generally surrounding it, and the bottom is singularly flat, and consists of, or is thickly covered by tenacious mud. I believe that, in the cases of some other lakes where seiches have been found to occur, attempts have been made to connect a periodical rise of an alge to the surface, with the changes of level. From my experience, it appears that Lake Derravaragh “ purges,” as it is locally termed, at all seasons of the year, 7. e. large quan- tities of algze rise to the surface, rendering the water turbid to the depth of a foot or more, and should a strong breeze be blowing at the time, large collections of the bright green sub-aquatic plant may be found in all the indentations of the lee shore. Although I have noted it as being on the surface prior to the occurrence of a seiche, it was so frequently to be seen, that it is impossible to form any connection between them. On examination! this alga was found to be Celospherium Riitsingianum (Nag) a plant which had been found in some parts of Ireland by Dr. John Barker, and shown by him at the Dublin Microscopical Club on 19th November, 1868. It differs from the 1 Professor Fred. O. Bower, pD.sc., F.u.s., Glasgow University, kindly examined and identified this plant. Mac Fartane—Seiches in Lake Derravaragh, Co. Westmeath. 295 common form of Volvox, the clusters or groups of cells, which form the families, being more or less lobated or constricted, and showing a decided but very gentle independent motion of an oscillatory character, giving the idea of the existence of cilia, although none could be discovered." Another somewhat phenomenal occurrence on the shore of Lake Derravaragh is seen in a small portion of a covert of Knock- body. During summer rains, or when the atmosphere is heavy with warm moisture, large volumes of steam, resembling smoke, issue from about the tree tops, but only in a circumscribed area of about an acre in extent. When seen under favourable circum- stances, this presents a very curious spectacle, as if large fires had been kindled under the trees; the dense steam, rising in volumes at times, again dying down, having every appearance of smoke. Local opinion is divided on this matter; the shaft of an old mine; fairies lighting fires; or a small mouth of Hades being the most favourite explanations. The cause, without doubt, is warm air condensing over a spring of very cold water situated in that particular part of the covert. A traveller in North America assures me that on many an occasion a similar spectacle was there hailed with great delight, manifesting, as it did, the presence of a cold spring. It is highly probable that seiches occur on many, perhaps on all, lakes; but that in the majority of cases the amplitudes are so slight that the occurrence escapes notice; this is greatly borne out by the fact that it was only dueto the careful watching of a batten, specially put up, that the seiches on Lake Derravaragh were ever noticed, although having, as far as at present known, an amplitude reaching 6 inches. Before concluding this Paper I should wish to mention a phenomenal rise and fall of the river Shannon which I observed subsequent to writing the preceding notes. I was fishing on the river about eight miles above Lough Derg, and happened to notice a stake, standing up from the bottom of the river, with its head showing about 3 inches above the water. A very short time afterwards my boatman drew my attention to ‘See Quarterly Journal Microscopic Society, 1869, p. 197. 296 Scientific Proceedings, Royal Dublin Society. the fact that the stake was covered, remarking that the river appeared to be rising very rapidly ; not long after about 3 inches of the stake was again visible, and later on I again saw it covered. I had left home the night before in pouring rain, with a low and falling barometer ; but had no instrument of the kind with me. In a river, controlled as the Shannon is, by gates or sluices, it may be possible that the rise and fall was due to their influence ; but it is to be doubted if two successive rises, such as I observed, could be caused by them. At that time I was leaving for another part of the river, otherwise might have made more observations ; but it now appears to me to be a matter for consideration as to what effect a seiche occurring, say, on Lough Ree, above where I observed this rise and fall, would have on the river, 7. e. would each rise on the lough send down more water ? Again, suppose a seiche to occur on Lough Derg, in the other direction, what would be the effect, if any, on the river P Mention has already been made of the influence of the sur- roundings of a station on amplitude and duration of a seiche; if, however, it could be shown that the total effect could be observed in a river, flowing in or out of the lake, the element of surround- ings might be eliminated, as the river should give the mean of both amplitude and duration of the seiche for the whole lake. While the cause of seiches remains practically unknown, except that they appear to be usually accompanied by low barometric readings, there is much room for various conjectures, but I venture to hope that a more general knowledge of their existence may induce many, having opportunities, to keep a watchful eye for their occurrence. To give satisfactory results, synchronous observations are indispensable, with characteristics of the land surrounding the stations, and, in addition to amplitude and duration of the seiche, the barometer should be carefully noted ; also wind ; and if deflected by land, as in the case of the observation spot on Lake Derra- varagh. Soundings of the lake should be obtained ; perhaps, tem- perature of the water; also if a rise of alge to the surface accompanies a seiche. It would also be an interesting matter to know whether the rise and fall is simultaneous on the whole lake, or if the water is rising at one station and falling at another at the same time. [ 297 j XXX VIII. ON PUCKSIA MAC HENRYI, A NEW FOSSIL FROM THE CAMBRIAN ROCKS OF HOWTH. By PROFESSOR SOLLAS, D.8Se., LL.D., F.R.S. (COMMUNICATED BY PERMISSION OF THE DIRECTOR-GENERAL OF THE GEOLOGICAL SURVEY.) [Read Decemper 19, 1894; Received for publication January 15; Published Frepruary 15, 1895.] Tue barrenness of the rocks of Howth and Bray in organic remains is rendered rather more than less surprising by the un- doubted fact that living organisms were not entirely absent from the seas in which these rocks were deposited. This is proved by the occurrence in rare localities of such problematical forms as Oldhamia, and still more conclusively by the innumerable worm- borings, which traverse the brilliantly coloured sandstones of the cliffs, near the Needles. Worms naturally suggest the contemporary existence, in some place or other, of a great variety of lower forms of life both animal and vegetable; but of the remains of these scarcely any direct indications have as yet been discovered in our district. The nature of the rocks is generally not ill-fitted for their preservation. Fine grained slates which have retained such deli- eate markings as those of Oldhamia, might fairly be expected to present us with some remains of the skeletons of graptolites, brachiopods, or trilobites, if any of these had lived in association with Oldhamia. That no trace of these or any other organisms, except worms, has hitherto been discovered, in spite of the most careful searching, seems open to only one explanation: and one is led to suppose that the Cambrian sea around Dublin, was for some reason or other, during the greater part of its existence, an almost lifeless area. The fewer the fossils, the more strenuous must be our search for them; and I have now to describe a curious structure, which I SCIEN. PROC. R.D.8., VOL. VITI., PART IV. Z 298 Scientific Proceedings, Royal Dublin Society. found while in the company of my colleague, Mr. MacHenry, at Puck’s Rocks, Howth, close to the spot where the late Dr. Kinahan discovered specimens of Oldhamia, and in the same slates that furnished me with certain spherical bodies, suggestively similar to Radiolaria. The new fossil presents itself as long, narrow, thread-like markings (fig. 1), which stand out in slight relief on the weathered cleavage faces of the rock, from which they are further distinguished by a difference in appear- ance due to difference in material, since the threads consist chiefly of quartz, with which is associated a small quantity of iron pyrites. The slate is of exceed- ingly fine texture, and greenish grey in colour: its cleavage planes are coinci- dent, or nearly coincident, with the original planes of lamination. The threads are confined to one particular band of slate not more than eight inches in thickness, and in this are only found through a narrow tract some two or three feet in width, where, however, they are very abundant, so that on breaking the. slate open, numbers will be seen on every fresh cleavage plane. mre. Gl The threads are of uniform breadth, Surface of a slab of slate bearing from 0°5 to 1:25 mm. across, and of 7 “#4 Henye Nat, size. indefinite length up to 5 or 6 cm.: for a centimetre or two they may preserve an almost straight course, but usually they run in a gently undulating fashion, making now and then a sudden turn, and sometimes apparently plunging abruptly inwards across the cleavage planes. Down the middle line of each thread, runs a longitudinal depression, bordered on each side by swollen margins, and the whole is crossed from side to side by numerous fine and close transverse ridges and furrows. Slices showing longitudinal sections may be readily prepared for microscopical examination by splitting off a thin lamina along the cleavage, and grinding it down to the requisite thinness: trans- verse sections must be cut in the usual way with a lapidary’s wheel. Sottas— On Pucksia Mac H. enryi. 299 Sections in both directions present a median and two lateral regions corresponding to the longitudinal depression and lateral Transverse sections (X 60). ridges already mentioned. The transverse sections (fig. 2) have usually a lemniscate form, two broad lateral lobes being united by Z2 300 Scientific Proceedings, Royal Dublin Society. a narrow central bridge: this and the proximal part of the lobes consists of an irregular mosaic of quartz grains, while the remaining distal part of the lobes is composed of fibrous quartz, the fibres of which proceed from the granular mosaic outwards to the margins of the lobes, lying in close parallelism to the cleavage planes of the slate. The distinction of the fibrous from the granular quartz is clearly marked, and is sometimes emphasised by the presence of minute black granules, apparently of iron pyrites, which are dotted along the line of junction. Similar granules not infrequently occur arranged in circles within the fibrous quartz, as though surround- ing spherical growths of chalcedony. Pyrites in larger or smaller crystals, sometimes partially converted into limonite, may take the place of silica, over any part of the section, without as a rule dis- turbing its form (fig. 2, ¢, e, f). A want of symmetry is not uncommon in the sections. The upper and lower margins of the lobes may be unequally curved, and then it usually happens that the are of greater curvature lies on the upper side of one lobe and on the lower side of the other. When the inequality is very marked the granular quartz extends into each lobe along opposite margins (fig. 2, c). A bifurcation of the lobes is sometimes to be observed as shown in fig. 2, e. A still more extreme case is represented in fig. 3. Fie. 3. Transverse section, showing bifurcation of the lateral lobes (x 60). The form presented by the transverse sections is probably not original. ‘The threads have been squeezed flat in the planes of cleavage ; and to discover the primitive form we should seek for the transverse section of a thread running across the cleavage planes. I have not, however, found completely satisfactory evidence of such sections. Those which seemed to be transverse were oval in outline, with a granular centre and fibrous margins, the fibres running parallel to the long axis, and being most abundant about its extremity. ‘There is just a possibility that these are disjointed fragments of longitudinal sections ; if they re not but are actually Sortas—On Pucksia Mac Henryi. 301 tranverse, then the original form of the threads may have been cylindrical. It is remarkable in this connection that transverse sections of the slate rarely present any other than truly transverse sections of the threads. In no single instance, though many slices were cut, has a thread been observed running directly transverse to the cleavage, a fact which rather tends to diminish the probability that the oval forms, seen in tangential sections of the slate, are truly transverse sections of the threads. | The longitudinal sections (figs. 4, 5, 6) present a median band of granular quartz, bounded on each side by a band of fibrous quartz, and though the boundary between the lateral and median regions is well defined, it is often possible to trace several marginal fibres into a common origin in one of the central Fic. 4. Fie. 5. Longitudinal section (x 6). The Longitudinal section (X 60). black spots represent iron pyrites. granules (fig. 5). The outer boundary is sharply marked—fairly even or faintly crenate, swelling out into rounded protuberances 302 Scientific Proceedings, Royal Dublin Society. suggestive of mammillary chalcedonic growth. In some instances the whole section is transversely constricted at irregular intervals as though segmented. The length of the segment shown in the figure (fig. 6) is 5 mm. Combining the information we have obtained, it is clear that the form of our fossil is at present that of a flattened band with much thickened margins, but whether this is original or not is by no means certain. Quite possibly the pristine shape was cylin- drical, and in that case the fossil may merely repre- sent a cylindrical cavity which has been filled up with silica and deformed by pressure or perhaps a corroded and subsequently silicified sponge spicule like those of the glass rope sponge Hyalonema. The shape of the tranverse sections, however, is difficult to account for on such supposition. A cylin- drical tube under the pressure which gave rise to cleavage in the slate would be converted into a flat band of elliptical section, and would not be lemnis- cate as in our examples. On the other hand it may be the silicified remains of some organism such as an Annelid or perhaps of a plant. Its appearance, however, is more worm than plant-like, and I would hazard the conjecture that it may be another trace Fic. 6. of the same organism that produced the markings ,,honsitcinal sec. known as Oldhamia. The dimensions are consistent **tictions ( 7°)- with such a view; both are probably worm-markings ; both occur in the same rocks in the same locality. ‘The new fossil requires an independent name, and I propose to call it Pucksia Mac Henryi. ‘“‘Pucksia ” is a mere collocation of letters recalling the place of occurrence. The specific name is a tribute to my colleague, Mr. MacHenry, of the Geological Survey. The slate in which Pucksia occurs is found on microscopic examination to consist almost entirely of scales of white mica, lying of course with their flat faces parallel to the planes oi cleavage. A chemical analysis of the slate yielded the results given in column I. Its composition approaches very closely that of a phyllite analysed for Gumbel by Schwager (Roth. Chemische Sottas—On Pucksia Mac Henryi. 303 Geologie, Bd. 11., p. 443). His results are shown in column II. As might naturally be expected in the case of a rock so largely made up of mica, the composition of the slate does not differ greatly from that of the constituent mica, as will be seen by reference to the column III., which gives the composition of a muscovite mica also analysed by Schwager (Hintze, Handbuch der Mineralogie, p. 6381). 1 II. III. Oey) Wo BO54 ee. 852504 45 cy Sorel POE BE. Os, 2) S8:897 ¢o 40 8Oe 002 oe a, 80,04 SOMME Fores GRE ait, CWS ao ay Re MeO sy IOS 1 et ae Oca ees 8s POMP MTs 17) SOOM hk LN ASED ui Sp 4d OMe shi .S6149 Bier tole uf 14-00 ECM in fis vari BhT SO kay oa Coro lwnues, Face HOP eit or nC TAO: (raud asf MaKe af tts ies 100-950 100-02 99:62 1 [Including 1°51 per cent. of TiOz. 2 Including a small quantity of FeO. 3 Determined by loss on ignition. [ 3804 | XXXIX. A COLLECTION OF LEPIDOPTERA FROM LOKOJA, WEST AFRICA. By GEORGE H. CARPENTER, B.Sc., Assistant Naturalist, Science and Art Museum, Dublin. [Read January 23; Received for Publication January 25; Published March 4, 1895.] Wuite stationed on duty at Lokoja, at the junction of the River Benue with the Niger, Captain C. W. Soden gathered a small collection of Lepidoptera, a set of which were secured by the Dublin Museum. As this district is less known zoologically than many other parts of West Africa, it seems worth while to publish a list of the species, especially as the collection includes an un- described variety of Huphedra cyparissa, Cram., and new species of Xanthopsilopteryx, and of Antheua. I would acknowledge kind help from Messrs. Buen Kirby, . Hampson, and Heron, when comparing some of these insects with the British Museum Collection. - The figure after each species indicates the number of specimens. RHOPALOCERA. NYMPHALIDA. KurLe@inz. Tirumala petiverana, Dbl. and Hew. (1).—An African species. Limnas alcippus, Cram. (9).—A wide-ranging species, Australia to West Africa. Amauris niavius, L. (3).—A West African butterfly. ACRAINA. Acrea neobule, Dbl. and Hew. (4).—An interesting species, recorded from Abyssinia and the Congo, with its nearest relations in Madagascar. CarPEnTER— Collection of Lepidoptera from Lokoja, W. Africa. 805: A. lycia, Fb. (1). A. cecilia, Fb. (2).| All these species have a wide range over the A. zetes, L. (9). African continent. A. serena, Fb. (4). A. camena, Dru. (1).—West African species. A. lycoa, God. (1). is i NYMPHALIN#. Atella eurytis, Dbl. and Hew. (10) Junonia clelia, Cram. (8). J. crebrene, Trim. (8) J. orithya, L. (2).—A species occurring in India as well as in Africa. Precis terea, Dru. (1).—West African species. P. chorimene, Guer. (4). “ “ P. Galami, Bav. (6). Hypanus ilithyia, Dru. a Ln aian aa African. Hypolimnas misippus, L. (6).—Australia toyWest Africa. @ var. inaria, Cram. (2).—Australia to West Africa. Neptis agatha, Cram. (4).—African species. Euryphene phranza, Hew. (1).—West African species. Euphedra ceres, Fab. (1). Be 5 E. Crockeri, Butl. (1). 5 3 E. cyparissa, var. durata, nov. (8). This beautiful variety agrees in form and pattern with the type of cyparissa, but has the sub-apical spot of the fore- wings bright golden instead of dark green; the dark green of the under-side of the fore-wings is also largely replaced by the golden colour. This variety resembles Z. sarcoptera, Butl., but has no red beneath the base of the fore-wing. Hamanumida dedalus, Fab. (5).—African species. Charaxes epijasius, Reiche (6).—Recorded from Senegal and Abyssinia. C. achemenes, Feld. (2). ecan species. Palla varanes, Cram. (2. ,, ‘ ‘| Species with a wide range in Africa. 306 Scientific Proceedings, Royal Dublin Society. LIBYTH AIDA. Libythea labdaca, Westw. (1).—Recorded from Sierra Leone. LYCASNIDAL. Tarucus plinius, Fab. (1).—This is an Indian species, and I am not aware that it has been yet recorded as occurring in Africa. T. pulcher, Murr. (1).—A West African species. Virachola anta, Trim. (1).—This species is recorded only from South Africa. Its presence on the Niger shows it to have a wide range over the continent. Sithon nomenia, Hew. (1).—A West African species. Myrina hymen, Fab. (1). 39 Pr) PAPILIONIDA. PIERIN#. Eurema senegalensis, Bdv. (2).—A West African species. E. regularis, Btl. (2). Ef. soe, Hopff. (1). These species are described from East Africa. They must therefore have a wide range over the Continent. There are specimens of the latter from Natal in the British Museum Collection. Pieris creona, Cram. (2). P. calypso, Dru. (6). ; ‘ : ee Tachyris saba, Eb. (4). All species with a wide range in Africa. T. sylvia, Eb. (4). Eronia poppea, Don. (1).—A. West African species. Catopsilia pyrene, Swains. (2).—African species. Callosune evippe, L. (2).—A West African species. C. arethusa, Dru. C. ocale, Bdv. CARPENTER— Collection of Lepidoptera from Lokoja, W. Africa. 307 PAPILIONINA. Papilio ridleyanus, White (1).—Recorded from the Congo. P. leonidas, Fb. (10). P. demoleus, L. (18). P. policenes, Cram. (3).|All these species have a wide range in P. pylades, Fb. (14). Africa. P. nireus, L. (1). P. erinus, Gray (2). HESPERIID Zi. Celenorrhinus galenus, Kb. (1).— A West African species. HETEROCERA. SATURNIIDA. Gonimbrasia nictitans, Eb. (2).—A West African species. _ SPHINGID Ai. Cherocampa gracilis, Butl. (2).— A. West African species. Pergesa irregularis, W1k. (1). 5 A Diodosida fumosa, Wk. (1). A Nephele variegata, Butl. (2).—Recorded from the Congo. NV. funebris, Fb. (1). Fe = NOTODONTID Ai. Antheua nigrolineata, sp. nov. (1).—Male (fig. 1). Expanse of wings, 37 mm. Head and thorax grey. Antenne yellow. Abdomen yellow above, basal segment ~ white; white beneath; spotted with black along the sides. Wings white; fore-wing with pale yellow costa, a strong black streak along the median vein for three- fourths the length of the wing, and a few Fic. 1. scattered black scales. Antheua nigrolineata. This is a very distinct species. Its nearest ally appears to be A. spurcata, Wlk., from Sierra Leone, which is larger, has a yellow streak on the fore-wing, and a differently-marked abdomen. 308 Scientific Proceedings, Royal Dublin Society. AGARISTID A. Egocera Boisduvalii, Lat. (1).—A West African species. Ah. rectilinea, Bdv. (8). a Xanthopsilopteryx Kirbyi, sp. nov. (1).—Male (fig. 2). Expanse of wings, 65 mm. Head and thorax black. Head with two white spots before, and two behind antenne; thorax with a row of four white spots in front, and three across centre. Abdo- men yellow, banded with black, and a large black anal tuft. Fore- wings black; near the base a row of four small white spots below the costa, and three yellow spots. Beyond these, two yellow spots ; Ab one near the costa, semicircular, ge I RN. convex towards the base, one aU AapSIIpIe ELT touching the inner margin, triangular. Beyond these, a row of three yellow spots; one near the costa, semicircular, convex towards the apex, the central larger and quadrate, the third near (but not touching) the anal angle, small and triangular. Beyond these, a large subapical transverse yellow spot of flattened elliptical shape. Tip of wings white. Hind-wings brilliant orange, with black border, narrowest at anal angle, broadening and then narrowing again along hind margin, broadest at apex, which is tipped with white. The species of this brilliant genus are very similar in general aspect, but the markings appear to be very constant, and thanks to the British Museum Collection, and Mr. W. F. Kirby’s Monograph of the group (Trans. Ent. Soc., 1891), the present species (which I have much pleasure in dedicating to that naturalist) could be separated from its allies. It is nearly related to X. superba, Butl., but the size is smaller, the fore-wings proportionally much narrower, and the sub- apical spot smaller and narrower. From X. eva, Mab., X. indecisa, Wlk., and X. africana, Butl., it may be separated by its inner yellow band broken into two spots, those species having the band entire. In X. wanthopyga, Mab., the second CarPENTER— Collection of Lepidoptera from Lokgja, W. Africa. 309 band (in our species broken into three spots) is entire. Its nearest relation is, perhaps, X. fatima, Kirb., an East African species, but in that the second yellow spot of the first row does not extend along the inner margin, while the sub-apical spot is irregular in form. NOCTUIDAE. Cyligramma latona, Cram. (5).—South and West African species. C. fluctuosa, Dru. (2).— West African species. Hypocala Moore, Butl. (2).—This species was first found in India and Ceylon, but is known to occur as well in West Africa. Ophiusa algira, Li. (1).—A. very wide-ranging species, from South Europe to the Cape and to Burmah. Achea catocaloides, Guen. (1).—A West African species. A. esea, Cram. (2). i F A. chameleon, Guen. (1).—A variable species with a wide range in Africa. This specimen has the wings almost unico- lorous. Entomogramma nigriceps, W1k. (1).—A West African species. Othreis fullonica, L. (1). O. materna, L. (1). These two species have both a very wide range, the former ranging from West Africa through India and Malaya to Australia, the latter as far as Java. I am not aware that O. materna has been previously recorded from Africa. ARCTIIDA. Teeniopyga evidens, Guér. (1).—Recorded from Senegal. LITHOSIIDA. Argina cingulifera, Wik. (1).—Recorded from the Congo. Deiopeia pulchella, Li. (1).—This species ranges over the whole of the warm and temperate parts of the Hastern Hemisphere. 310 Scientific Proceedings, Royal Dublin Society. PYRALID:. Margaronia sericea, Dru. (1).—A West African species. ZY GARNID Ab. Euchromia fulvida, Butl. (2.)—A West African species. Of the eighty forms comprised in the above list, sixty-nine are, so far as is known, peculiar to the Ethiopian region, and thirty- nine of these have hitherto been found only in West Africa. Five of the remaining eleven are common to the Ethiopian and Oriental regions, one to those two regions and also to the Pale- arctic, four to the Ethiopian, Oriental, and Australian regions, and one to all the regions of the Old World. It will be noticed, therefore, that about fifteen per cent. of the species are not peculiar to the region in which they were found. This is an indication of the fact that there is less speciality in the lepidopterous than in the vertebrate fauna of each great zoological division of the earth’s surface. The relationship between the Ethiopian and Oriental faunas, shown in this small collection by the specific identity of such a fair number of insects with Indian forms, would, in a collection of vertebrates, be indicated hardly at all by identical species, but only by common genera or families. ewe lit) XL. ON THE GOLD NUGGETS HITHERTO FOUND IN THE COUNTY WICKLOW. By V. BALL, C.B., LL.D., F.RB.S. (Prate XIII.) [Read Frepruary 20; Received for publication Frpruary 22; Published Juty 15, 1895.] In the Science and Art Museum there are two lead models, belong- ing respectively to the original Royal Irish Academy and the Royal Dublin Society Collections, of a large gold nugget which was found in Wicklow in 1795, and weighed, as we shall see, about 220z. Being anxious to provide a proper descriptive label for these models, | commenced, some time ago, an investiga- tion of the various historical facts and of the supplemental tra- ditions and myths (for such they have proved to be) regarding the discovery and the disposal of the original nugget, and I now propose to record the results of these researches. The actual discovery of the nugget took place, it is believed, in or before September, 1795; and tradition asserts that on the occasion of the visit of George IV. to Ireland, in 1821, it was either presented to his Majesty at the instigation of an “ officious mem- ber” of the Dublin Society, or, when merely intended to be shown, was claimed by the king as a droit, placed in his pocket, and never seen or heard of again by the Society, having been given, so it is said, to a lady, who caused it to be melted down. This,in . brief, is the story which has been tacitly accepted by all who have written about the nugget for the last thirty or forty years. So far as is known it was first actually published so recently as the year 1865,' but according to a letter received last September from the late Mr. Gilbert Sanders, it seems to have been current at an earlier date. And, as we shall see, there is said to have been a claimant for the authorship of the fable in the year 1833. 1 Journ. Geol. Soc., Ireland, vol. xi., 1865, p. 100. 312 Scientific Proceedings, Royal Dublin Society. Like all such stories, and I have had to deal with many in my researches regarding Indian myths, the number of variants of the details is in the inverse ratio to the number of authentic facts. The majority! of these variants concur in the statement that the incident above referred to took place when his Majesty visited ‘Leinster House on Friday, the 21st August, 1821. But of that visit there is a printed account’; and although it is a record of the transactions which took place on the occasion, there is not the least reference in it to a gold nugget, and the Registrar of the Royal Dublin Society informs me that he has not been able to trace any allusion to it in the MS. records of the Society, and it is certainly not mentioned in the printed ‘“ Proceedings.” If the story be true, the nugget must have been the property of the Dublin Society, or have been deposited in its care at the time. It is not, however, included in any of the early Cata- logues of the Society’s Minerals and other possessions, which still exist. On the contrary, that of 1832 affords internal, if indirect, evidence that Sir Charles Giesecke, who was in charge of the minerals from 1818 to 1832, had himself never seen the nugget, for, in his supplementary remarks on Irish minerals, Catalogue, p. 241, he merely says that the largest mass of gold ever found in Wicklow weighed about 25 oz., and that a model of it was in the Museum. Here there is no mention of the history of the nugget, while the ascription to it of the weight 25 oz. is apparently incorrect. Besides the two models above referred to, there are at least two others, one in the Geological Museum of Trinity College, which is the only one with an original(?) label, as follows :— “‘Moddel of a piece of gold found at Croughan.” ‘This is in an old-looking handwriting, and, as will be noticed, in an obsolete orthography. The fourth belongs to Dr. Fraser, who obtained it from Mr. Glennon. In a letter from Mrs. Baker, daughter of the latter, which Dr. Fraser has placed in my hands, it is stated that the model was cast by her father for a gentleman who 1 One version of the story, however, is that the nugget was presented to George TY. on the occasion of his visit to Powerscourt, but Lord Powerscourt informs me there is no foundation for it. Another version connects the donation with the Earl of Meath, as we shall see. 2««The Royal Visit,’? &e. Dublin: Crookes, 8vo, 1821. Batu—Gold Nuggets found in Co. Wicklow. 313 presented the original to the Dublin Society. This I cannot, under the above-mentioned circumstances, accept as authentic. I think it more probable that Dr. Fraser’s model came into Mr. Glennon’s hands from some predecessor of his, or was perhaps purchased by him at a sale, or it may have been merely a copy of the Dublin Society’s model. Having ascertained that there were no copies of this model in the museums of London or Edinburgh, I have supplied the deficiency from some plaster casts which have recently been prepared. If the history about to be presented is, as I believe it to be, the true one, then the original mould from which the models were cast was probably prepared about the end of the year 1795 or the beginning of 1796, and the best chance of finding any record of the-fact would probably be in the press or magazines of that period, which have as yet only been partially examined for that purpose. The Dublin Society’s model is the best and sharpest of the four, and was probably the first taken from the mould, which became injured by successive lead castings, as is commonly the case. Before completing the history which follows, I made inquiries through Mr. Richard Holmes, Librarian at Windsor Castle, as to the possibility of the nugget being still in existence, and as to there being anything on record regarding it, but I have been in- formed by him that so far he has been unable to trace it. With reference to the origin of the story connecting this nugget with George IV., it may be suggested that a gold nugget received, as we shall see, from the Government in 1800, which at the time of his visit was in the collection of the Royal Dublin Society, and is now in the Science and Art Museum, may have been shown to his Majesty as being an object of special interest. It weighs 1502°5 grs., vide post, p. 321, and Pl. xut., fig. 3); but, if so, as it is here still, the statement made in some of the stories that the king thereupon put the nugget into his pocket is thereby dis- proved. As regards the large nugget which weighed nearly 2 lbs. it is ridiculous to suggest that his Majesty could have so far for- gotten his dignity as to have done so, and it is in itself sufficient to discredit the whole myth. There is no evidence, it may be added, of any other nugget having been in the possession of the SCIEN. PROC. R.D.S., VOL. VIII., PART IV. 2A 314 Scientific Proceedings, Royal Dublin Society. Dublin Society at the time, which might have been given to the king instead of either of the above. One informant assures me that Mr. Patrick Brophy, State Dentist, claimed to have been the inventor and retailer of the story about George IV., and professed to have amused the Marquis of Wellesley with it at a dinner party during his second Viceroyalty in 1833. Dr. Fraser has suggested that a Mossop medal, made of Irish silver, which was certainly presented to the king, was possibly the origin of the story. This may have been the foundation. Or there may be some truth in the story that a nugget was given to the king by the Harl of Meath, as I am informed by the pre- sent Harl that there is a tradition to that effect in his family. Discovery of the 22 oz. Nugget (see Pl. xut., fig. 4).—In letters written by John Lloyd, F.R.S.* and Abraham Mills’ to Sir Joseph Banks, President of the Royal Society, they describe respectively the results of their visit, in company with Mr. Weaver, to the scene of the Wicklow gold washings. Mr. Weaver’s own account was not published till many years later. I do not propose to deal here with all the traditional stories as to the discovery of nuggets, and the annual search for gold which appears to have been carried on by certain families who shared the secret for at least ten or twelve years before the year 1795. The discovery of the washings at Croghan Kinshela was first made public in September of that year. The rush took place soon afterwards, and the working by the peasantry continued till the 15th October, when, under orders of the Government, a detach- ment of the Kildare Militia took possession of the washings for the Crown, and the peasantry retired quietly. According to Mills the latter had, during the six weeks, disposed of £5000 worth of gold at about £3 15s. per oz. = 800 ozs. It is not clear from the above authors alone whether the 22 oz. nugget which was first referred to by Lloyd was found 1 Dated Cronbane, 4th November, 1795. Read 19th November, 1795. Phil. Trans., vol. Ixxxvi., 1796, pp. 34-87. 2 Dated Cronbane, 21st November, 1795. Read 17th December, 1795. Phil. Trans., vol. Ixxxvi., 1796, pp. 38, 44. See also Trans. Roy. Dub. Society for 1800, vol. i., Pt. i., p. 454. Batt— Gold Nuggets found in Co. Wicklow. old by the peasantry before the 15th October, or by the Government between that date and the 8rd—4th November when his letter was written. As affording some clue to the discovery and original owner- ship, an account of it in the Grentleman’s Magazine,’ however, states that it was found in September, 1795, and was the joint pro- perty of eight labourers. It can scarcely therefore be identified with a nugget which was said to have long been used as a weight in a shop, in the belief that it was copper ore, till it was bought by a tinker and sold to a jeweller in Capel-street for a large sum. Of this tale there are several variants.” The following account by Mr. W. H. Jones, has been received through Mr. G. H. Kinahan :— . “T know_of no record of the quantity of gold found unless that given in ‘Lewis’ Topographical Dictionary.’ I always heard of a large nugget being found by a tenant of Mr. Wm. - Graham, of Ballycooge. It was used by the finder as a weight to weigh wool, until a pedlar called and offered a high price for it. The man began to think it valuable, and declined to part with it, but brought it to Mr. W. Graham, his landlord, and gave it to him. Mr. Graham presented it to Lord Meath, and Lord Meath presented it to the Dublin Society Museum, where there is a model of it, I understand, at present. Inever heard of a nugget being found at Coolballintegart. The Graham family have all died out, and I am quite certain that they left no written record; they were not people likely to keep a diary; indeed, according to report, poor Shemus McGlinnon, who found the nugget, got little by it.” At a meeting of the Royal Geological Society of Ireland held on the 11th January, 1865, Mr. J. Knight Boswell stated that he was told by a family named Byrne, farmers at Croghan Kinshela, some thirty years previously, that in the upper part of one of the rivers they found a mass of metal, about a pound and a-half in weight, which they supposed to be copper. It remained for several years in their possession, and was used by them as a weight; but at length it was disposed of to a travelling tinker who carried it to 1 Vol. 66, pt. i., 1796, p. 8. » Journ. Roy. Geol. Soc., Ireland, vol. xi. (New Ser., vol. i., Pt.i.), 1865, p. 99. 2A 2 316 Scientific Proceedinys, Royal Dublin Society. Dublin, where he sold it for a large price to a jeweller in Capel- street. That was what led to the Government investigations there in 1796. ! This appears to be due to a blending by the family of the story of the discovery, about 1784 or 1785, by John Byrne, of a nugget of a quarter of an ounce,” with that of the 22 oz. nugget which was certainly not sold to a tinker as we shall presently see. Lloyd says (p. 36) that it was intended to present the 22 oz. nugget to his Majesty George III., for which purpose it may be supposed that the Government acquired it. Gerrard Kinahan* includes it and two others, mentioned by Mills, of 5 oz. and 2 oz. 17 dwt., and one of 20 oz. 2 dwt. 21 grs. mentioned by Molesworth in his table as having been found by the peasants. I am quite satisfied that the nugget weighed by Molesworth,‘ though his language is obscure, was the same 22 oz. one, and that the weight he gives was either its weight in water, or the weight of pure gold in the nugget, and that it should not be regarded as re- ferring to a separate nugget as Kinahan suggests. Molesworth found its specific gravity to be to that of pure gold as 12 to 18; and Kirwan found that of another specimen to be as 13 to 18. The Hibernian Magazine’ gives a somewhat exaggerated account of the value of the mine. it refers to a nugget that was in the possession of Mr. Atkinson, agent to Lord Carysfort, for which eighty guineas was offered, but was refused. The story also is related of a yarn-dealer who, for ten years, had used a piece of “cold ore” as a two-pound weight, believing it to be copper ore, and had broken several pieces from it to adjust the weight. It had then recently been sold for a considerable sum. Most of the early writers whom we have quoted from in this Paper simply attribute a weight of 22 oz. to the nugget, namely, Lloyd, Mills, and Kirwan,° in 1795-6; and, among later writers, Mallet in 1849, and Gilbert Sanders and R. Scott in 1865. 1 Journal of the Royal Geol. Soc., vol. xi., 1865, p. 99. 2 See Phil. Trans., vol. Ixxxvi., 1796, pp. 34-37. 3 <¢ On the occurrence and winning of gold in Ireland,”’ Journ. Roy. Geol. Soc., Ireland, vol. vi. (New Ser., Pt. ii.), 1882, p. 147. 4 Phil. Trans. 1796, vol. Ixxxvi., pp. 44, 45. 5 Part ii., 1795, p. 382. 6 Mineralogy, vol. ii., p. 93 n. Batt—Gold Nuggets found in Co. Wicklow. 317 Apjohn,' upon what authority is not stated, gives the weight at 227 oz., and “B. D.” says 22 oz. avoirdupois! which seems a curious measure for gold. It would be equal to 26 oz. 18 dwt. troy, but then it is inconsistent with the further statement that the nugget was sold for £80 12s., or at the rate of £4 per oz.; for in that case the weight would only have been 20 oz. 6 dwt. troy. Finally, Sir Charles Giesecke said it weighed 25 oz., which, combined with the absence of further information, convinces me that he never saw the nugget, that it had in fact left Ireland before he arrived in 1813. Subsequent History.—From the letter signed “ B. D.” to the editor of the Gentleman’s Magazine,* which has already been quoted, the purchase of the nugget appears to have been made by Turner Camac who paid for it, itis said, £801 2s. Turner Camac, as one of the partners of the Hibernian Mining Company, was a well- known personage. This Company issued tokens which were popularly known as Camacs; several varieties were issued during the years 1792, 1796. The record just referred to goes on to say that the nugget was then, January, 1796, already believed to be “in the possession of his Majesty ” (George III.), but we are left in doubt as to the person or persons by whom the project of presenting it to him, originally mentioned in November, 1795, by Lloyd,* had actually been carried out. A clue has been found, however, in rather a curious way. I am informed by Dr. W. J. Fitzpatrick, to whom I referred the question, with reference to the George IV. story, that he had casually become aware of the fact that a gold nugget had been presented to George III. by a gentleman named Abraham Coates, and that the discovery was made as follows:—In the papers of Mr. Kemmis, Crown and Treasury Solicitor, a payment of £300 was ordered in the year 1803 to be made to Abraham Coates of _ Arklow. Noticing this, Dr. Fitzpatrick instituted inquiries in 1883 as to what was known regarding Abraham Coates, by his 1 Catalogue of Minerals in Museum of Trinity College, Dublin. 2 Vol. 66, Pt. i., 1796, p. 8. 3 See also Penny Magazine, vol. xiii., 1844, pp. 426-7. + See his letter in Phil. Trans., vol. lxxxvi., 1796, p. 36. 318 Scientific Proceedings, Royal Dublin Society. descendants, with the result that he then made the following memo- randum which he has now placed at my disposal :— “J learn from the Coates family that Abraham found, in one of the Wicklow mines, a nugget of gold which he sent to George IIT. The King, much interested, got the ore made into a snuffbox, and signified to Lord Brabazon, as M. P. for Wicklow, that it would gratify him to hear of Mr. Coates being appointed to some lucrative post in the county. Soon afterwards Mr. Coates received the office of Coast Surveyor. It was his business to keep a sharp eye on all ships touching the Wicklow coast. Coates was a J.P., and there is a street in Wicklow called after his name.” My attention being thus called to Abraham Coates, I at once remembered that he was one of those who accompanied the troops to take possession of the mines, as is mentioned in the following rather sarcastic remarks from the Gentleman’s Magazine dated Dublin, October 20:—‘ The mines at little Peru (otherwise Croghan Mountain) were taken possession of on behalf of his Majesty. Major Brown of the Royal Hngineers, attended by Mr. Coates, Port Surveyor of Wicklow, marched two companies of the Kildare Militia from the Barracks of Arklow towards the place where the gold is got; but, with great judgment and propriety, on consulting with that active and spirited magistrate, Thomas King, Esq., it was judged proper to send a constable before them to read a proclamation, and advise the crowd to disperse and leave the ground. In an hour afterwards, the Major, accompanied by Mr. King, Mr. Hayes, Sub-Sheriff (who readily attended), and Mr. Coates, marched the army (about sixty-eight men rank and file) to the place, when the crowd immediately, without riot or resistance, dispersed. “When men who conduct themselves with such coolness, judg- ment, and spirit, as these gentlemen did, support the Laws, there is no danger of opposition. It is much to the credit of the pea- santry of the county of Wicklow that not the slightest opposition had been given to the execution of the Law; that county is not eursed with disloyal defenders.’”! Whatever promotion Abraham Coates may have received, as stated by his family, at the instance of the King and on account 1 Gentleman’s Magazine, October, 1795, vol. 65, Pt. ii., p. 870. Batit—Gold Nuggets found in Co. Wicklow. 319 of his presentation of a nugget to his Majesty, he is by the above brought into touch, so to speak, with the 22 oz. nugget, and as he was styled Port Surveyor then, the change may have been to that of Coast Surveyor, as he is called in Dr. Fitzpatrick’s Memoran- dum. I am not prepared at present to follow up this identification of the donor and recipient of the 22 oz. nugget any further, but I think we are justified in the conclusion that Abraham Coates and Turner Camac were probably the donors, or, at least, were con- nected with the donation, and that George III. was the recipient. Although I have not been able to obtain information from Windsor Castle as to the existence of any trace of this transaction, I by no means despair of such being ultimately found. That a snuff-box was made of a 22 oz. nugget may seem incredible, but possibly in some other form, and with an inscription, the metal may have been preserved, and this record of fact and dissipation of myth will, I trust, aid in its ultimate identification. It may not be generally known that the discovery of the mines led to a dramatic performance being enacted at Covent Garden, under the title: —‘‘ The Lad o’ the Hills; or, the Wick- low Gold Mines:” a Comic Opera, by Mr. O’ Keeffe. Having thus placed the history of one of the largest Wicklow nuggets in a clearer position than it has hitherto occupied, and brushed away some of the myths and traditions which have for . so many years obscured it, let us proceed to discuss the histories of the principal remaining Wicklow nuggets known to fame. I studiously avoid discussing the question of the character and production generally of the Wicklow Mines themselves; that has already been well done by the late Mr. Gerrard Kinahan. Pro- bably he had neither the means nor the opportunities for conduct- ing a critical investigation into the histories of the individual nuggets; this has rendered it desirable that they should be discussed fully and at length; and it must be added that his table giving the weights and other particulars of the nuggets found, requires considerable amendment in the light of the facts here collected and placed in order. Nugget of 5 ownces.—John Lloyd in his letter to Sir Joseph 1 See Hibernian Magazine, Pt. i., 1795, p. 461. 320 Scientific Proceedings, Royal Dublin Society. Banks, dated 4th November, 1795,' besides mentioning the nugget of 22 oz., which it was intended to present to his Majesty, refers to one of 5 oz. which was destined “for the cabinet of a nobleman adored in this country.”” Whether Earl Camden, the then Lord Lieutenant, was indicated by this reference I cannot say. Possibly it may have been the Harl of Meath. If the weight of this nugget was really 5 oz., then it cannot be identified with any of those of lesser weight which are de- scribed in the following pages. It may have been the one said to have been given to George IV. by the Harl of Meath as we have - seen. According to Mills it and the 22 oz. were the only two of superior weight which had then been found. Weaver,” at a later period (1819) speaks of nuggets of 18 oz., 9 oz., and 7 oz., in addition to that of 22 0z., but of these we have no other record. And here we may conveniently refer, too, to one of 24 oz. (valued at £100), and another of 6 oz. (valued at £30), which are said to have been found by the peasants in 1856. The authority quoted by Gerrard Kinahan’ is Mr. Hugh M‘Dermott of Arklow, but nothing further seems to be recorded regarding them. Nugget of 2112 gis. =4 oz. 8 dwt.—In the year 1844 the Mining Company of Ireland exhibited at their stall in the Royal Dublin Society’s Exhibition,‘ together with a cake of silver of 8933 oz., obtained from lead, a nugget of gold of about 40z. I have not been able to refer to the original catalogue of this Exhibition as yet; two of the daily papers* of the time, however, attest the fact, but the “ Evening Mail’’® by a misprint gave the weight as 40 oz.! and this probably was the source from whence the ‘“‘ Mining Journal”’” quoted the latter weight. Hence originated the supposed champion nugget of the United Kingdom, which 1 Phil. Trans., vol. lxxxvi., 1796, p. 362, Joc. cit., p. 44. 2 Trans. Geol. Soc., vol. v., 1819, pp. 115-304; and Phil. Mag. vii., 1835, p. 3. 3 Journ. Roy. Geol. Soc., Ireland, vol. xvi., Pt. ii., 1882, pp. 146 n., 147. 4 See Proceedings Royal Dublin Society, vol. Ixxx., p. 214. 5 Saunders and Evening Post of June, 1844. & Dublin Evening Mail, 7th June, 1844. 7 Mining Journal, 1844, vol. xiv., p. 199. Batt—Gold Nuggets found in Co. Wicklow. 321 Calvert! points out exceeded in weight the Crawford nugget of 30 oz., said to have been found in the 16th century. Thus our champion proves to be a myth. This nugget of 2112 grs. was subsequently obtained by Sir Robert Kane from Mr. R. Purdon, Secretary to the Mining Company of Ireland; and I am informed by Dr. Fraser that in the year 1862 he saw it on exhibition in the Museum of Irish Industry. In the year 1865, together with some other specimens, including ancient Irish ornaments of gold, it was stolen from the Museum, and was, in all probability, promptly consigned to the melting pot ; so that we are not likely to see it again. Nugget of 1502-5 yi's.=3 og. 2 dwt. 14-5 grs. (see Pl. x11. fig. 3).— Formerly the weight of this nugget was stated to be 1507 grs.,” and the specimen is still so marked on the label. The difference is probably due to the removal of a sample, say 4°5 grs. for assay. Appended to a reprint of the paper by Mills in the Phil. Trans., which has been referred to above, p. 314, the Transac- tions of the Royal Dublin Society for 1800° contain some notes, including the following :—“ By command of our Noble President, Earl Hardwicke, Lord Lieutenant, the Museum of the Society has been furnished with a lump of gold weighing 3 ounces, and 1 ounce of small scales from these mines; the lump is of a pris- matical form; on two sides are several grains of white quartz, sunk in the metal; on several of the small scales the quartz is also discoverable.”’—G. Vallancy. Although this description hardly conveys a proper conception of the amount of quartz present in the nugget, which really per- meates the mass, it cannot but refer to the very specimen under description, and of which the figure conveys a good idea. The scales, so called, are still in the Collection. The very true remark has before now been made with regard to the Wicklow gold, that although as yet it has not been found in quartz (i.e. in sitw), quartz is often found in the gold. 1 «Gold Rocks of Great Britain and Ireland,’’ London, 1853, p. 174. Mr. G. Kinahan seems to have been misled by this authority when referring to the 40 oz. nugget. See Journ. Roy. Geol. Society, vol. vi., Pt. ii., 1882, p. 140, note. 2 In Giesecke’s Catalogue, 1832, p. 241. It is referred to however as weighing oz. and as 1500 grs. in Journ. Roy. Geol. Soc., vol. xi., 1864, p. 99. 3 Dublin, vol. i. 1801, p. 465. O22 Scientific Proceedings, Royal Dublin Society. Nugget of 1332 grs.=2 02. 15 dwt. 12 grs. (see Pl. xut. fig. 2).— Recently I have been shown by Mr. E. Johnson a Wicklow nugget which belonged to his father. Its weight is as above, and the form is somewhat peculiar, having a flattened wedge-like shape, somewhat resembling that of a razor, and reproducing no doubt the outlines of the cleft in the quartz wherein it was formed. This nugget has long been in the possession of Mr. Johnson’s family, and it may perhaps be identical with the one of 2 oz. 17 dwt.’ mentioned by Mills ;? but, so far as I am aware, there is nothing known more than an approximate correspondence in weight to connect them. Its value at present is said to be £11 5s. [Since the above was written, it has been purchased for the Museum. | Nugget of 815°2 grs. (formerly in Trinity College Museum).— This specimen is described in Apjohn’s Catalogue of Minerals, No. 1973, as being penetrated by several cavities and vega as above. It was found at Croghan Kinshela. Nugget of 326 grs. (see Pl. xut., fig. 1).—This nugget belongs to Mr. T. H. Longfield, by whom it was purchased, being at the time labelled as being from Wicklow. From its general aspect and similarity to other specimens that was probably its place of origin. Its form will be seen from the figure. Itmight be com- pared both in shape and size to a quarter of the kernel of a good-sized walnut. Nugget of 820 grs.—Mr. Gilbert Sanders,? in some interesting remarks on the Wicklow gold fields, with the working of which, by the Carysfort Mining Company, he was associated, states that the largest nugget which had come under his personal notice only weighed 320 grs. Nugget of 180°8 grs.—This specimen is described in Apjohn’s Catalogue of Minerals (Trinity College Museum), No. 1974, as being an irregular wrinkled mass of the above weight. It was 1 This weight was misquoted in the Gentleman’s Magazine, vol. 66, Pt. i., 1796, p. 1020, as though it were 21 oz. 17 dwt., so causing some confusion. 2 Phil. Trans., vol. Ixxxvi., p. 44. 3 Journ. Roy. Geol. Society of Ireland, vol. xi., 1865, p. 101; and vol. xvi., 1882, p. 146. Batt—Gold Nuggets found in Co. Wicklow. 023. found at Croghan Kinshela, and appears to be identical with the one mentioned in the 1818 Catalogue under No. 816. In the Edinburgh Museum, there are five nuggets of Wicklow gold which there is reason to believe were formerly in the well- known collection of the late Chancellor Brady. I am informed by Dr. Traquair that they weigh as follows :— 1.—6°48 grams = 100°01 grains. Teoria, os SDS: %, m.—s'50 , = 35402 «,, Ivo fo. 3 = Arad V.— 1°84 ©,, = 2°28°396. |,, Models of these have recently been presented to, and are now exhibited in the Science and Art Museum, Dublin. In the Museum of Practical Geology in Jermyn-street, there are in all seven nuggets of Wicklow gold, as follows; for the descriptions I am indebted to the Curator, Mr. F. W. Rudler :— I.—Gold associated with cavernous quartz, not much rolled, 30°749 grams (= 47453 grains). IL.—Gold associated with pure white quartz and much rolled, 26°377 grams = 407-99 grains. III.—Gold associated with iron-stained vein quartz, much worn, 15:963 grams = 246°34 grains. IV. anp V.—Two small irregularly shaped masses. VI. anv VII.—Two small flattened nuggets. Models of the first three of these have also been recently pre- sented to the Science and Art Museum, Dublin. 324 Scientific Proceedings, Royal Dublin Society. EXPLANATION OF PLATE XIII. Wicxtow Gorn. 1. Nugget weighing 336 grains, the property of Mr. T. H. Longfield, see p. 322. 2. Nugget weighing 1382 grains (2 oz. 15 dwt. 12 grains), now in the Science and Art Museum, see p. 322. 3. Nugget weighing 1502-5 grains (3 oz. 2 dwt. 14°5 grains), now in the Science and Art Musenm, see p. 321. 4. Model of nugget weighing 22 oz., believed to have been presented to George III. in the year 1796, see p. 314. ee [ 325 J XLI. SURVEY OF FISHING GROUNDS, WEST COAST OF IRELAND, 1890-91. NOTES ON THE HYDROIDA AND POLYZOA. By J. EH. DUERDEN, A.R.C. Se. (London); Curator of the Museum of the Institute of Jamaica. (Puarz XIV.) [Read January 23; Received for publication January 25; Published Juty 15, 1895.] Tue following communication consists of notes on only the more important species of Hydroida and Polyzoa, collected by the Survey. A fuller and complete list of the Irish representatives of these two groups of the Zoophytes is in preparation, and it is intended there to record the abundance of more common forms obtained. In the present Paper, the following Hydroids are recorded as new to Ireland :— Tubiclava cornucopie, Norman. EHudendriuwm insigne, Hincks. Perigonimus gelatinosus, n. sp. P. inflatus, n. sp. Campanulina panicula, G. O. Sars. Bimeria vestita, T. S. Wright. The following Polyzoa are also recorded as being collected by the Survey, and new to Ireland :— Bicellaria Alderi, Busk. Flustra Barleei, Busk. Triticella pedi- cellata, Alder. Campanulina panicula, G. O. Sars, is new to the British seas, being previously known only from Christiania Sound. Perigonimus gelatinosus and P. inflatus are new to science. HYDROIDA. Tubiclava cornucopie, Norman. In the collections obtained from Blacksod Bay I found four shells of Astarte sulcata, each with the animal inside, and each bearing at its posterior end a colony of numerous individuals of this interesting species. The zoophyte takes up this posterior 326 Scientific Proceedings, Royal Dublin Society. position on the shell, so that it may receive the full benefit of the food-particles which may be in the current set up by the living mollusc, as has been shown by Canon Norman. it is a very rare species, and new to Ireland. It has previously been obtained by Canon Norman from about twenty miles north of Unst, in Scot- land, parasitic on the shells of Astarte sulcata and Dentalium entalis; and by Mr. Alder, from the coast of Northumberland, also on Dentalium entalis. The Irish specimens from Blacksod Bay were obtained at a depth of from six to eight fathoms. Eudendrium insigne, Hincks. In this minute species the stem is ringed throughout and not much branched. It is now recorded for the first time from Ireland, having been collected by the Survey from Lough Swilly at a depth of from eight to twelve fathoms. It is only known from a few English localities. Perigonimus repens, T'. 8. Wright. A rich supply of different forms of the genus Perigonimus has been collected by the Survey. It is a somewhat difficult group to study, especially from spirit material; and it is only by com- parison with an abundance of forms that reliable identifications can be obtained. ‘The limitations of the species are not well defined in the size, amount of branching, and the characters of the polypary. Some of the species have certainly been described from too limited a supply of material. A much branched condition of P. repens is represented on Plate xiv., figure 1. There are five distinct branches or bifur- cations, one of them bearing a characteristic gonophore. Others, arising from the same colony, were also elongated, but with- out any branching, exactly as represented in Alder’s drawing of the species reproduced by Hincks on pl. 16, “ Brit. Hyd. Zooph.” The polypary is thin and delicate, but less so proxi- mally. It is covered with a rather thick layer of a gelatinous substance, in which is embedded foreign matter, consisting mostly of fine mud. ‘The stems at their origin have two or three distinct DurErpen—Wotes on the Hydroida and Polyzoa. 327 annulations, and a less amount of the gelatinous and foreign encrusting matter. ‘The gonophores show a distinct delicate con- tinuation of the polypary over them. In the great amount of branching, and also in the ringed origin of the stems, this form varies from the description given of P. repens ; but these characters I regard as insufficient to establish a specific distinction. A colony of this form was obtained growing luxuriantly on a Scaphander from Galway Bay, from a depth of 15 fathoms, and another colony from off the Skelligs, at a depth of from 40 to 80 fathoms. Collections from Dingle Bay also yielded this more branching form with the stems annulated at their origin. From Bantry Bay I received a colony of the form resembling the one which Mr. Alder regards as the young stage of P. repens (“Brit. Hyd. Zooph.,” fol. 17). It was growing upon a crab. The stems are quite short compared with the examples described above. One interesting feature in these is, that within the gastric cavity of many of the polypites a nematode is present. I have found this relationship in quite a number of cases, both in specimens of Perigonimus and of Bougainvillia. It appears as if the nematode were capable of making its exit, as I have found them projecting some distance beyond the mouth of the polyp- ite, and in other cases quite free amongst the branches. It is evidently a condition of partial parasitism. Perigonimus gelatinosus, 0. sp. (Pl. XIV., figs. 2 and 3.) Stems short and simple, or longer, and with a few branches; polypary yellowish, gradually thinning above, and greatly ex- panded to form a thin covering for the polypites; nine or ten dis- tinct annulations at the origin of the stems; somewhat wrinkled; covered on the outside with a gelatinous envelope, developed to a greater or less extent with foreign particles embedded in it, and extending so as to completely enclose the contracted polypites. Polypites, with a conical proboscis, in contraction strongly fusiform or nearly spherical; tentacles about eight. Gonophores numerous, produced on the stems, borne on long peduncles, often slightly ringed at irregular intervals, and with a 328 Scientific Proceedings, Royal Dublin Society. delicate continuation of the polypary all over, and also a thin transparent layer of the gelatinous substance. Gonozooid not known. This species appears to be a very well defined one, possessing, as it does, a combination of characters which separates it from any other described form. Its closest allies are P. vestitus, All., and P. pailiatus, T. 8. Wright. The former, however, has the polyp- ary yellowish brown, with adherent particles of sand; there are no annulations at the base, and no gelatinous covering to the polypary: the gonophores, also, are only invested for about half their length by the polypary. P. gelatinosus agrees with P. pal- liatus in having the body of the polypite clothed up to the level of the mouth with a gelatinous envelope; but differs in the well- developed, ringed, occasionally much branched stems, and in the gonophores being borne on the stems, and not on the stolon. It is possible that when P. vestitus and P. palliatus have been redis- covered in any number in their original locality—the Firth of Forth—that then, as Mr. Hincks believes (‘‘ Brit. Hyd. Zooph.,” p. 95), they may be shown to belong to the same form, and then this present species may go along with them. It certainly pre- sents somewhat of a combination of the characters of the two. Until this is done, however, it seems best that it should remain separate, and rank as a distinct species. In one colony, obtained from the south-west of Ireland, the creeping stolon was so closely reticulated as to form an almost continuous chitinous crust on the shell on which it was growing. The species well illustrates the variability to which the different representatives of the genus Perigonimus are liable, and the danger of founding specific characters upon an individual colony. In the form represented in fig. 2 the stems are short, unbranched, and have the gelatinous envelope very thick. In the other form (fig. 3), from a different colony, the stems are much longer, more branched, and the gelatinous envelope only feebly developed. From careful comparison, however, and experience of a number of forms, I have no doubt but that they all belong to the same species. Habitat.—F rom rather deep water, growing on shells inhabited by Pagurus. Station 183, Dingle Bay; depth, 40 fathoms.— (R. D.8.): Log 738, south-west of Ireland; depth, 50 fathoms. DurrpEn—Wotes on the Hydroida and Polyzoa. 329 Log 42, 94 miles south-west of Castletown. Berehaven; depth, 37% fathoms.—(R. I. A.).’ Perigonimus (?) inflatus, n. sp. (Pl. XIV., fig. 4.)! Stem erect, simple ; polypary horn-coloured, smooth, firm, form- ing above a thin, delicate, cup-like enlargement, within which the polypite is largely retractile. Polypite large, much swollen in contraction, borne on a neck~- like extension of the ccenosarec; body generally pendent; ten- tacles 8; gonophores unknown. In the absence of the gonophores, this form can only he referred provisionally to the genus Perigonimus; but there can be little doubt, from a comparison of it with other species, that it belongs to the genus. I have found numbers of specimens rising from stolons creeping over other zoophytes, such as Sertularia abietina. The stem appears to be always simple, and the polypary over the greater part is rather thick and firm; but a little below the base of the polypite it thins more or less suddenly, and extends to form a delicate covering to the neck-like prolongation of the coenosare and the body of the polypite. This thin portion is somewhat coated with fine earthy matter. Little of this occurs on the thicker portion of the polypary. Towards the base the stem is a little wrinkled. The natural position of the polypite appears to be that of drooping from the neck-like portion. This species is most closely allied to the Perigonimus nutans of Hincks,” especially in the “large elevated polypites and pendent habit,” which Mr. Hincks regards as the striking feature in his species. It differs from it, however, in that the polypary extends to form a cup-shaped enlargement, within which the polypite is retractile, in the greater firmness of the polypary, and in the slight wrinkling towards the base. It does not appear to be such a 1 In the present communication I have also recorded some of the examples which were collected by the Royal Irish Academy Survey of the South-west Coast of Ireland, 1885, 86, ’88. For the Report on the Hydroida of these collections, see Proc. Roy. Irish Acad., 3rd Ser., vol. iii., No. 1. * Ann. and Mag. N. H., Ser. 4, vol. xix., p. 149, pl. xii., fig. 1. SCIEN. PROC. R.D.S., VOL. VIII., PART IV 2B 330 Scientific Proceedings, Royal Dublin Society. delicate form as P. nutans. The differences amongst the nume- rous described species of this genus are often very slight; and it seems not at all improbable that these two may ultimately be united, if it can be shown that the nature of the polypary is variable as to the formation or otherwise of an enlargement for protection to the polypite. It may possibly be that the polypary changes with age, and that the enlargement and firmness not distinguishable in Hincks’s examples may appear later. Only by a study of numerous examples in the living state can this be deter- mined; but until the point is settled, it seems best that P. nutans and P. inflatus should remain separated, if only to stimulate further inquiry. This new species we owe to the labours of the Royal Irish Academy Survey of the South-west Coast of Ireland, but it seems best to insert it on the present occasion. Habitat.—Growing on Sertularia abietina, and other zoophytes from deep water off the south-west coast of Ireland. Obtained on material trawled from two distinct localities:—Log 72, 11 miles south of Glandore Harbour, from a depth of 54 fathoms ; Log 37, 13 miles south-west of Galley Head, from a depth of 43 fathoms.—(R. I. A.). Bimeria vestita, T. S. Wright. A single specimen of this peculiar form was collected from St. 240, Lough Swilly; depth 6 to 83 fathoms. It does not appear to be at all common around the Irish coasts, as this is the first time it has been recorded for the country. It is known from several British localities. Bougainvillia fruticosa, Allman. Tn correspondence with Mr. Hincks, I submitted to him a form of Bougainvillia loaded with gonophores, which appeared to agree with his description of an intermediate form, mentioned on p. 112 «Brit. Hyd. Zooph.,” and figured on pl. xix., fig. 3. He agreed with me in my determination of this form. However, com- paring it carefully with the description and figures of Allman’s B. fruticosa, I fail to find any character of importance in which my specimens differ from that species. The stem is sub-alternately branched; the polypites are incapable of retracting themselves Durrpen—Wotes on the Hydroida and Polyzoa. bol within the expansion of the polypary to the same extent as in B. ramosa, and the gonophores are distributed over the ramules, as in Allman’s well-known figure in the Gymnoblastic Hydroids. It differs from Allman’s description in having the outer surface of the polypary covered with very fine foreign particles, giving it the appearance of being sanded over. Considering that the locality agrees approximately with that from which Professor Allman obtained his specimens, I have less hesitation in regarding these forms as the same. /P. fruticosa was first collected from Kenmare River, Co. Kerry, while the specimens I have under consideration came from Bantry Bay. They consist of numerous small por- tions obtained growing on the limbs of a Stenorhynchus, which must have torn them from the parent colony to decorate itself with. On some of the specimens was one of the long fusiform parasite capsules, which serve as nests for larval Pycnogonida. I have also found these capsules, of somewhat similar shape, on B. ramosa, so that they cannot be regarded as characteristic of one species. Campanulina turrita, Hincks. (Pl. XIV., figs. 5 and 6.) Stem distinctly ringed throughout, either short and simple, or crowdedly branched, and somewhat zigzag in shape; at each bend a branch given off, which generally branches immediately. Hydro- thece with almost parallel sides in the middle, but narrowing slowly towards the base, and with an operculum composed of short, con- vergent segments. Polypites with about 18 tentacles. Gronothece broad, and sub-truncate above, tapering downwards, shortly stalked, and borne on the stem. Gonozooid closely resembling that of C. acununata. This species was first described by Mr. Hincks (“ Brit. Hyd. Zooph.,” page 190; pl. xxxvi., fig. 2) from drawings supplied him by Professor Wyville Thomson. Having since supplied Mr. Hincks with specimens collected from different parts of the Trish coast, he draws attention in a letter to me to the fact that Thomson’s figure, and consequently the description based upon it, is erroneous in the method of branching. It is represented as if the ramules were given off in groups of two or three at each bend 2B2 3o2 Scientific Proceedings, Royal Dublin Society. in the stem. Examination of actual specimens shows, however, that only one is given off from the main stem at each bend; but this generally gives off another quite close to its origin. The abundance and approximation of the branching gives a very crowded appearance to the colony. The hydrothece in Thomson’s figure are also a little too elongated. The species appears capable of existing under two very diffe- rent habits. In one case the creeping stolon gives rise only to short-ringed pedicels, each bearing a single polypite. When first I obtained this form I was under the impression that it was an entirely new species. Subsequently, however, I found examples creeping, over Crisia in which, besides this simple habit, there were springing from the same stolon some in which the pedicels became more elongated, and others in which the stems were abundantly branched, as in the more common form. The gonothece do not seem to be abundant. I have obtained them on colonies from Blacksod Bay and from Dursey Island. Although the species has been found from localities all round the Trish coast, it apparently has not been recorded from other parts of the British Isles. Habitat.—Very abundant on Zostera, Holywood, Belfast Lough (Professor Wyville Thomson): Blacksod Bay (R. D.58.): Bantry Bay, on Crista. Dalkey, on other zoophytes. Bundoran, Donegal Bay, on Alge. Dursey Island, on Laminaria and Coryne. Roundstone, Connemara, on Zostera, (J. H. D.). Campanulina panicula, G. O. Sars. (Pl. XIV., figs. 7 and 8.) Stem erect, branched, straight; slightly annulated at the origin, springing from a thread-like stolon forming a complex network over other foreign bodies, terminating in a hydrotheca ; branches arising alternately, three or four annulations at their origin, smaller than the stem, either no further branching, each supporting only a single polypite, or divided dichotomously once or twice. Hydro- thece very thin, obconic; not sharply marked off from the pedi- cels, closed by an operculum formed of numerous long convergent segments. Polypites capable of great extension. Gronothece and Gonozooid not known. Height, 1 cm. DvuErpDEN—Wotes on the Hydroida and Polyzoa. 330 This species was first found and described by Professor G. O. Sars from Drobak, in Christiania Bay,’ where it is a rare form. It has apparently not been obtained before from British waters. It was found growing profusely on two Fusus shells inhabited by hermit-crabs, trawled by the Survey from a depth of 220 fathoms off Achill Head. It is a delicate species, and the polypary is quite colourless in spirit specimens. ‘The polypites are very fragile, and capable of great extension. The stem is perfectly straight and upright, and the branches are given off mostly alternately. The examples obtained from the west coast of Ireland agree with Sars’s descrip- tion and figures of the Scandinavian specimens, except that the branching is not so prolific. This character, however, seems liable to considerable variation. On some stems most of the branches will be simple, only two or three presenting a bifurcation, and then these are near the apex. Other stems have the majority of the branches divided. In Sars’s specimens a second bifurcation occurs, produc- ing an appearance quite suggestive of the specific name. Owing to the fact that the reproductive bodies are not known, the exact generic position cannot be determined, but there seems little doubt from the form of the hydrothece and the polypites that it is a species of Campanulina. Many of the pedicels, and often the upper part of the stem, have occasional annulations, suggestive of frequent renewal of the polypites and extension of the polypary. Habitat.—On Fusus shells, from deep water off the west coast of Ireland. ‘T'wo shells, each with a large number of stems, were trawled by the Royal Dublin Society’s Survey, at a distance of 40 miles off Achill Head, from the great depth of 220 fathoms. POLYZOA. The Polyzoa collected by the Survey, although numerous, are not of such great interest as the Hydroids. Some of them have already been noticed.» The important additional Irish localities 1 Forhand. Videnskabs-Selskabet. Christiania, 1873, p. 121, pl. v., figs. 9-13. 2 On Some New and Rare Irish Polyzoa,’’ Proc. Roy. Irish Acad., 3rd Ser., vol. iii., pp. 121-136. 334 Scientific Proceedings, Royal Dublin Society. for the rarer species will be found in the List of Irish Polyzoa which is in preparation. The following species call for somewhat more special notice :— Bicellaria Alderi, Busk. This rare form was found growing on Flustra Barleei, Busk, from Station 114, off the Skelligs, at a depth of 80 fathoms. Only a small portion was obtained, but it exhibits all the distinctive features of the species. As usual in British examples, contrasted with Scandinavian, the avicularia were absent. Like the Flustra on which it was growing, this is the first time it has been recorded for Ireland, and it has only previously been found in British waters from the Shetlands by Mr. Barlee and Canon Norman. Flustra Barleei, Busk. A large colony, nearly 2 inches in height, was trawled from off the Skelligs, along with the previous species. In the large unarmed rectangular cells and oblique position of the avicularia it is easily distinguished from the other more common F lustras. The immersed. ovicells are well shown in this Irish specimen. The species has only previously been obtained from British waters by Mr. Barlee, from Shetland, and “between Whalsey and Balta, and off Unst,” by Canon Norman. The present occurrence con- siderably extends its southern range. Triticella Boeckii, G. O. Sars. This species, previously only known from Christiania Sound, was first recorded by me (/. c., p. 131) for British seas, as having been obtained by the Royal Irish Academy Survey from Bere- haven, growing on Portunus depurator. On two or three different occasions the Royal Dublin Society’s Survey trawled it in Kenmare - River, in each case growing on Gronoplax angulata. Only a few individuals were present on one specimen, as the crustacean ap- peared to have lately shed its shell. Another Gonoplax was almost covered with large scattered clusters, they being especially abun- dant on the antennz. Both the peduncles and zocecia are very variable in size according to their position in a dense cluster. ‘The more central ones are much longer, and quite overtop the others. A third Gonoplax had its shell also partially coated with the Polyzoan. Dusrpen—WNotes on the Hydroida and Polyzoa. 309 Triticella pedicellata, Alder. In the communication above mentioned, I also recorded (p. 133) this rare British species as having been trawled by the Royal Dublin Society’s Survey from two localities—off the Skelligs, depth 80 fathoms, growing on Buccinum undatum and Natica catenularia ; and also off Slyne Head, depth 55 fathoms, on Trochus magus. Barentsia nodosa, Lomas. Also previously mentioned (/. c., p. 186) as being collected by the Royal Dublin Society’s Survey from Killybegs and Smerwick Harbour, growing on Alge. A block of limestone, perforated by boring molluscs, was trawled from the great depth of 500 fathoms, at a distance of 45 miles off Blackrock, west of Ireland. It is interesting to note that the following species of Polyzoa were found encrusting it :— Schizoporella linearis, Hass., very abundant. Mucronella vario- losa, Johnust. Smittia reticulata, Macgl., and Diastopora patina, Lamk., in abundance. This is probably the greatest depth from which some of these forms are known. etepora Beaniana, King, was also trawled from the same depth at the same time. [ EXPLANATION OF Pure. 336 Fic Fie Fic Scientific Proceedings, Royal Dublin Society. EXPLANATION OF PLATE XIV. . 1.—Perigonimus repens, T. S. Wright. Magnified. . 2.—Perigonimus gelatinosus, n. sp. Polypites retracted within the gelatinous envelope. Magnified. . 3.—Perigonimus gelatinosus, nu. sp. More branched form, with polypites extended. Magnified. . 4.—Perigonimus inflatus, n. sp. Magnified. . 5.—Campanulina turrita, Hincks. Showing arrangement of branch- ing. Magnified. . 6.—Campanulina turrita, Hincks. Reticulated stolon, with only single polypites on short pedicels. Magnified. . 7.—Campanulina panicula, G. O. Sars. Stem, slightly enlarged . 8.—Campanulina panicula, G. O. Sars. branch. More enlarged. Portion of stem with pesaa 8 GGT. ON THE CHEMICAL EXAMINATION OF ORGANIC MATTERS IN RIVER WATERS. By W. E. ADENEY, F.1.C., Associate of the Royal College of Science, Ireland; Curator in the Royal University of Ireland. [Read May 22; Received for publication May 24; Published Jury 15, 1895.] In the paper which I brought before the notice of the Society last month’ I gave the results of an extended experimental inquiry, which showed that the fermentation of organic substances, contain- ing nitrogen, or mixtures of them with ammonium compounds, takes place progressively in two distinct stages in the presence of mixed organisms natural to surface waters—aerobic conditions being continuously maintained throughout the mass of the fermenting liquid. It was demonstrated by those results that during the first stage the organic matters—nitrogenous or non-nitrogenous— are completely broken down, the carbon and nitrogen (if pre- sent) being almost entirely converted into carbon dioxide and ammonia, a small quantity of organic matter remaining as such, but in an altered form; and that, during the second stage, the ammonia is oxidized to nitrous or nitric acids, or both, and that at the same time the organic matters, formed during the first stage of fermentation, may be partially or completely oxidized, carbon dioxide and possibly nitric acid being formed; and that further the second stage does not commence until the conclusion of the first. 1 Scientific Trans. Royal Dublin Society, vol. v. 338 Scientific Proceedings, Royal Dublin Society. The results of this inquiry further showed that careful deter- minations of the more obvious products of each stage of fer- mentation, viz. carbon dioxide and of ammonia during the one, and of carbon dioxide (if formed), and nitrous and nitric acids during the other stage, together with accurate determinations of the dissolved atmospheric oxygen consumed during both stages, afford data by which both the character and actual quan- tity of fermentable matters, present in a polluted water, could be estimated with sufficient accuracy for the purpose of water analysis. In this short paper I propose to give an example of the applica- tion of this method of inquiry to the examination of the water of a small stream for unfermented, or, in other words, polluting, © organic matters. At the time when the samples, with which I experimented, were collected, the volume of water flowing through the stream was very small, probably not equivalent to as much as 100,000 gallons per day. The stream consisted almost, if not entirely, of drainage waters from cultivated land, and received, some little distance above the points at which my samples were taken, considerable volumes of drainage matters from neighbouring houses, a portion of which, however, had been subjected to a process of purification before being allowed to flow into the stream. . Two samples were collected on the 28th April, 1894, at 1 p.m. One sample was taken from a point about 200 or 300 yards below the lowest discharge of house drainage, above referred to; the second sample was gathered from the lower end, and near the outlet, of a small pond-like enlargement of the stream at a point about 100 or 200 yards below the first. In this second case the sample collected was taken at a depth of about one foot below the surface of the water. The bottles in which the two samples were collected were com- pletely filled and carefully stoppered, and conveyed without delay to my laboratory. Both examples were examined by the ordinary method of analysis as well as by the method of examination above referred to, on the afternoon of the same day as that on which they were collected. ApEnEY— Organic Matters in River Waters. 309 The ordinary method of analysis gave the following results :— Constituents expressed as parts per 100,000. No. tr. No. 2 Nitrogen as freeammonia,. . 3 0°440 | 0°130 Ni itrogen as albuminoid ammonia, c 0:006 0-010 Nitrogen as nitrates, . ... .- 0:992 1:084 Nitrogen GIS UNFORS 6 5 og eo 0-024 0-018 GT ORIN N ee elisi Woon) ht Garret Ve 6°5 6°8 Sample No. 1 was slightly turbid but practically colourless ; it contained a small quantity of matter in suspension. ‘Temperature at the time of collection was 54°5 Fahr. Sample No. 2 was very slightly turbid, but colourless, and practically free from suspended matter. The temperature when collected was 52°°5 Fahr. Both samples were neutral to test-papers. The above results led to the conclusion that the stream water, at both points represented by the samples, contained very little organic matter in solution, and that nitrification of ammonia was possibly rapidly proceeding in it. When, however, the history of the stream was taken into consideration, it seemed extremely likely that these organic matters were largely, if not entirely, unfermented, and that it was quite possible that denitrification, rather than nitrification, was going on in the water, more especially as nitrous acid was found in distinct quantities in both samples.’ These doubts could, as I have shown in my former communi- cation, be definitely settled by allowing the waters to ferment out of contact with air, and determining the changes in composition of the dissolved gases and inorganic nitrogenous bodies which would result. As I anticipated these doubts, I first analysed the dissolved gases in a portion of each sample immediately on uncorking the bottlesin which they were collected, and, at the same 1§ee R. Warrington, F.R.S., on “ The Chemical Action of some Micro-organisms,”’ —C.58. J. 53, 742. Also J. H. M. Munro, D.8c., on ‘‘The Formation and Destruc- tion of Nitrates and Nitrites in Artificial Solutions, and in River and Well Waters.’’ —C.S8. J. 49, 667. 340 Scientific Proceedings, Royal Dubhin Society. time, I put up other portions for fermentation, both operations being carried out as described in my former Paper. I was, however, unable to examine these latter portions for the results of fermenta- tive changes until nearly seven months afterwards, viz. the following November, owing to pressure upon my time by other duties. In the following Table the results of analysis, before and after keeping, are given :— Gases expressed in c.cs. at O° and 760 mm., bar., and other consti- tuents as grammes, per 1000 c.cs. of water. Date of commencement N as N as N and of conclusion CO; O, Ne NH, N,O; N,O; of Experiment. Sample No. 1 | April 28, 1894, | 116-05 0°99 15:08 0044 00024 “00992 55 Noy. 21, 1894,| 123-68 0 lleiiealwd -0050 | 0 “00900 Differences, | + 7°63 | — 5°99 | + 2:09 |+-0006 |—-00024 | — -00092 No. 2 | April 28, 1894, | 116-39 7°38 | 15:58 | -0013 | -00018 | -01084 »» | Dec. 12, 1894,| 119-71 0 15°63 | -0006| -00016 | -01174 Differences, | + 3°32 | — 7:38 ah —:0007 |—-00002 | + -0009 The fermentative changes recorded in the preceding Table show at a glance the character of the organic matters in the two samples of water. It is evident, for example, that the organic matter in sample No. 1, or a portion of them, bad not undergone fermentation at the time the sample was collected. This is shown by the fact that not only was the free ammonia increased in quantity by fermenta- tion, but that all the nitrous acid and a portion of the nitric acid were reduced. Hvidence of the reduction of the then two bodies is afforded not only by decreased quantities of nitrogen as nitrous and nitric acid shown after fermentation, but also in the increase in volume of the dissolved nitrogen. It may indeed be stated in the light of the experimental evidence given in my former Paper, that the fermentative changes recorded for the sample No. 1 was entirely confined to those ADENEY—Organic Matters in River Waters. 341 which characterize a first stage fermentation, viz. a breaking down of unfermented organic matter, and a conversion of its carbon and nitrogen into carbon dioxide and ammonia. The results given for the second sample show that, notwith- standing the fact that it yielded a decidedly larger quantity of albuminoid ammonia than the first, it contained much less unfer- mented organic matter, and that in consequence, we have less carbon dioxide formed; and instead of ammonia being formed, more than half of that originally present was oxidized to nitric acid. Judging from the quantity of dissolved oxygen consumed, and the quantities of carbon dioxide and nitric acid formed, we may safely regard the former product as aresult of a first-stage fermen- tation; the latter product resulted, of course, from a second-stage fermentation or true nitrification. Ii these experiments had been carried farther, as they could have been in the manner described in my first Paper, it would have been possible to have determined the exact volume of oxygen necessary for the complete oxidation of both the unfermented organic matters and ammonia present in each sample. They go sufficiently far, however, to render it possible to draw definite conclusions as to the extent of pollution of the stream water by organic matters at the two points examined. In the first place, both samples were highly oxygenated at the time they were collected, sample No. 2, more especially, notwithstanding the fact that it was collected afoot below the surface of the stream. It may therefore be concluded that, since both samples were neutral to test-paper, and were therefore in a condition favourable to bac- terial fermentation, the organic matters were present in too small quantities to encourage a bacterial growth sufficient to cause a rapid consumption of the atmospheric oxygen dissolved in the water, and thereby to endanger fish or the higher forms of vegetable life. In support of this conclusion, that fermentation was proceeding very slowly in the stream at the points examined, I may quote an experiment which I made with a sample of the stream water gathered a few days previous to that on which the two samples under discussion were collected. 342 Scientific Proceedings, Royal Dublin Society. The sample was taken from much the same part of the stream as sample No. 2, and also one foot below its surface. The dissolved gases and other significant constituents were determined on the day of collection, and a portion of the sample was preserved out of contact with air for a period of four days, and again examined. The results obtained were as follows :— N as N as N Date. CO, | O, | Nz NH, N.O. N,0, | April 20,1894, . . .| 119-26 5:98 16°44 0009 | :00018 | -00952 April 24, 1894, . . .| 120°56 5°32 16°38 001 00012 | -009388 Differences, | + 1°30 | — -66 The sample was slightly turbid, practically colourless, and contained no suspended matters. It was neutral. When first collected it yielded :005 grms. N as albuminoid ammonia per 100,000 c.es. of water. These results show that even during the comparatively long period of four days, only -66 c.cs. of oxygen out of a total of 5:98 c.cs. per litre were consumed. Had considerable quantities of fermentable organic matters been present in the water, there can be no doubt, from the experiments recorded in my first Paper, that the oxygen would have been absorbed in a few hours after fermentation had set in. It will be noted that the time given for fermentation, in the case of samples Nos. 1 and 2, was seven and eight months, respectively. This length of time was not necessary, but was unavoidably allowed for the reason I have already stated. In a neutral water containing so small a quantity of fer- mentable organic matter as each of these two samples, the time necessary for the first stage fermentation, judging from experiments recorded in my first Paper, would not exceed one month ; and that required for the completion of the two stages, the final result of which would be the complete oxidation of all ammonia present, would not exceed two months. Ineed scarcely dwell upon the great power which this new ApENEY— Organic Matters in River Waters. 343, method of examination, compared with those hitherto in use for the examination of river waters, places in the hands of chemists for gaining a knowledge of the true character of the fermentable matters to be found inriver water. I would, however, again draw attention to the important fact which I dwelt upon in my first communication, viz. that it is possible to determine by means of this new method not only the total volume of oxygen required for the complete oxidation of the fermentable matters, including ammonia, in water, but also to distinguish the portion consumed during the first stage of fermentation from that consumed dur- ing the record stage—a distinction, for reasons I have already given, of the utmost importance in connection with the technical . consideration of the pollution of river water. (seer XLII. BRANCHED WORM-TUBES AND ACROZOANTHUS. By PROFESSOR A. C. HADDON, M.A., F.Z.5., Royal College of Science, Dublin. [Read January 23; Received for publication May 20; Published Juny 27, 1895.] Numerous specimens of Lophohelia prolifera were dredged at a depth of 220 fathoms, fifty miles off Bolus Head, county Kerry, during the Society’s Fishery Survey.!. Most of these are infested by the tubes of Hunice philocorallia, Buch. Miss Buchanan? refers (p. 174) to the commensalism of the worm with the coral, and 1K. W. L. Holt: ‘‘ Survey of Fishing Grounds,”’ etc., Proc. R.D.S., VII. (N.S8.) 1892, p. 261. 2 “Report on Polychets, collected during the Royal Dublin Society’s Survey off the West Coast of Ireland. Part I.—Deep-Water Forms.’’ By Florence Buchanan. Proc. R.D.8. VIII. (N.S.) 1893, p. 169. Hapvpon—Branched Worm-tubes and Acrozoanthus. 345 states that the worm to some extent modifies the growth of the coral, the coral growing round the worm-tube which thus becomes embodied in the ceenenchyme. Although Miss Buchanan describes the tubes as having a “ parchment-like consistency, with jagged lateral openings,’’ she does not allude to the branched character of the tube, nor does this appear in her plate x1. I have therefore thought it advisable to draw attention to this character, and to figure a specimen (p. 334) which exhibits it in a fairly satisfactory manner. I have indicated by numbers all the orifices in the tube, and there were probably several others, as the specimen figured is only a fragment. Immediately after the side branch at 2,the tube divides into two main branches, the one has two orifices, the other has four, three of which are close together, and diverge something like the crown tines of a deer’s antler. In the Zoological Department of the Royal College of Science, there is a somewhat similar worm-tube associated with Oculina virginea ; but the commensal worm is unknown, and the locality of the specimen is unrecorded. In this specimen there are six lateral openings, most of which are at the extremities of short branches, and there are indications of two other orifices which have been covered by the coenenchyme of the coral. Professor E. Ehlers,1in his Report on the Annelida collected on the “‘ Blake”? Expeditions, describes the branched tubes of the following Polychetes :—Hunice floridiana, E. tibiana, and LE. con- glomerans. ‘The first species has lamellose papyraceous tubes, often variously contorted with lateral ragged openings irregularly placed, though, in general, alternate. In Z. tibiana the sub-pellucid horny tube is either cylindrical and straight, or regularly serpen- tine; at every bend there is a tubulated aperture directed back- wards, with an expanded fimbriated border.” Lastly, the whitish paper-like tube of H. conglomerans has only a single orifice, one end is closed, and there are several spots and prominences which also appear to have been once open, and subsequently closed over. 1

b>e. 382 Scientific Proceedings, Royal Dublin Society. conic is a double line on the surface. The latter case is impossible, for the well-known trace of the surface on the plane y=0 shows no double points where the plane ,=0 meets y=0; hence the plane 7,=0 touches the surface. Again, the etieord P=0 and the ellipsoid of elasticity have manifestly the same planes of circular section, and therefore ; i= 0: ip => a) 1,=0 are four planes of circular section of the ellipsoid P=0. This proves one of Hamilton’s theorems; but it appears that these four circles all lie on one ellipsoid, and assuming for a moment that the reciprocal of the wave surface is the wave surface of BpeuSais! (the sphere of reciprocation being «2 +y?+s°-1=0); then, by reciprocation, it appears that the wave surface has four conical points, the tangent cones at which all envelop one ellipsoid whose equation is ee 2 y i 3 1 O(a 20?) § 2a8es a Oieic) ea: I shail show later on. The reader will have no difficulty in remembering the value of P if he recollects that P is the quadric factor of - Similarly the equation may be written Q’ + mm msm, = 0, where Q stands for CE +DY +2 +E(e+y +3) -e(a +0’), a /o—e + yf eb + Cf Fa0?. It is not necessary to write down the values of 2, m3, m. It may be noted that all the imaginary sections in this case lie on the real ellipsoid Q=0. and 7, is Bootru—On Fresnel’s Wave Surface. 383 Similarly, the equation may be written RK? + mnngns = 0, where £& stands for Ce +t ee? +e (ery +2?) -7 (+e), B/C-e+y/@—b'+ a/ &=8, with corresponding values for 2, %, %- In short, Q is the quadric factor of Ce and R& of a, dz dat Once more the equation may be written and 7, for S?+ pip2psyu = 0, where S stands for OP +0)? +0 (C +0) +O (G+ 0 )e — 206%, and p, for £0. /B—C+ybS C-— 0 +20/ a’ — b’, with corresponding values for p2, ps, ps. If we omit the terms in W of the fourth degree in 2, y, s, then the remainder is nearly the value of S with the sign changed. In short, if we had four vari- ables, x, y, , win Wso as to make it homogeneous in these variables, then S is a factor of a dw It is considered important by some writers on Physical Optics* to determine the equation of the cone whose vertex is the centre of the ellipsoid of elasticity, and whose base is one of the circles in the case jee + Uppal = 0. Its equation is, by the foregoing principles, written down thus: [ee + Py + ese +b (e+ y’ +2) | P(e -e) Gy PEG Pe / Pe) ee aa). on simplification, this becomes C(P-C)?+0(ae-e)y+e(a—-v)# —a#3(¢ £a\/ Gao) (a? = 6°) (8 — c*) ¢)= 1 See Bassett, Physical Optics, Art. 116, p. 123. 384 Scientific Proceedings, Royal Dublin Society. I may remark that these four circles treated in this way only produce two cones, as /4,=0 and /,=0 produce the same cone, so likewise do 7, and i. I shall now make a few remarks on a specially restricted system of tangential coordinates. Considering A, m, v as the parameters of the variable plane Av + py t+ve-1=0, it is required to find the relation between X, pu, v, which subsists when the plane passes through the pole of Az+ By + Cz+D=0 with respect to the sphere et+yt+2—-1=0. Now, if this point be w’y’s’, we must have Av’ + py’ + vs’ -1=0; also, we must have yet ei ae ae ee Ti D’ Ys D ae. De therefore AX + Bu+ Cv+ D=0 is the required condition, and it is called, in tangential coordinates, the equation of the pole of Azv+ By + Cz+D=0 with respect to the sphere e+yt+2?-1=0. Similarly, an? + MhAp + bu? + 2gdv + Quv + ev? +20 + 2m + 2nv+d=0 is the tangential equation of the reciprocal of aa + 2hay + by? + 2gua+ 28fyz + ce + 2le + 2my + 2nze+d=0. Now, since the wave surface is known to be the envelope of the plane AL + Wy + VB =2, NG 74 vy 2 ace = at yo va vi Ye and V+ w+’ =1, where ie Boorn—On Fresnel’s Wave Surface. 385 it follows at once that the locus of the foot of the perpendicular from the origin on a tangent plane to the wave surface is x 3 y : z ee a ey so ee a ee 2 2 w2 and as the inverse of this latter surface with respect to the sphere e+y+s2?—-1=0 is the reciprocal of the wave surface, its equation is therefore e oP 3 =e Se ee O(e?+yt+s)-1l Petty +2)-1 - C(Pe+yt+es)-l ’ but this is the wave surface of the reciprocal of the ellipsoid of elasticity. In other words, “the reciprocal of the wave surface is the wave surface of the reciprocal of the ellipsoid of elasticity.’’? Now, the equation of the wave surface for the ellipsoid eo yf # 5 e a B ae e —1=0 must be, by the foregoing, T? + vi vev3v,= 9, where 7' stands for eC (a + 0) + 2a°ey*? + va (0? +0) -(v? +e), and v, for co / &—0+2a/P—C+f/a—e, with corresponding values for v2v3»,; hence the equation in tan- gential coordinates of the wave surface of aa? + by? + cs’ -1=0 is w+ AAAs, = 0,7 where a stands for Ne? (a? + 0) + 2Ware + va’ (0? +) — (+e), and X, for er Ne. /@—-B+ va /P—e+ fa —e, with corresponding values for 2, As, As. This mode of writing its equation shows that M9, opel. A 0s A= 0 1 See Salmon’s Swifaces, page 426. 386 Scientific Proceedings, Royal Dublin Society. are four points on the surface, tangent cones from which all envelop the surface whose equation in tangential coordinates is a =0 (the existence of an infinite number of double tangent planes all passing through a point outside the surface is excluded, as we saw that its reciprocal has not an infinite number of double points all lying on a plane), and the equation in Cartesian coordinates of the surface represented by a= 0 is xe y 3 1 (a? +b") Y Bee @ (PP) C+ Ht as stated above. It now appears that the equation of the surface may be written in tangential coordinates in three other ways, showing the exis- tence of the twelve imaginary conical points. I shall notice one case only, namely, o + pip2psps= 9, where o stands for (0? +0) N+ (P+ a") p+ (a+ 8) Vv? - 2. This is obtained from the value of S of the reciprocal surface just as @ was obtained from the value of P of the reciprocal; similarly the values of Q and & for the reciprocal would furnish the values of the enveloped ellipsoid in the two cases which I have omitted. Also, p, stands for N/A PO ern, She tan PO This is the case where the four conical (imaginary) points are, at infinity, and the tangential equations of these points are pi=9, p2=9, ps=9, ps=9; hence the Cartesian coordinates of these points are subject to the relations! a y” g2 P-@ ¢-a@ &-b” that is, to et+yt+2=0, and @a’+By?+c3*=0. It may, however, be remarked that a double point is not always a 1 See Salmon’s Surfaces, lust paragraph on page 423. Bootu— On Fresnel’s Wave Surface. 387 conical point ; the cone would be two planes for some double points. Since w+ Ard2Ashs = 0, then AG = 0, re = 0, A3 = 0, Na = 0 are the tangential equations of the four real conical points, and therefore, from what we have already said, the Cartesian coordi-_ nates of these points are written down from, say he /@-B + va /P—-C- fae; | opm that is, eee” a — as is well known. The equation of the tangent cone at a conical point may be calculated in various ways, and referred to its vertex as origin, has for its equation e (7-0) 7 Z (a+ 0) az b-—e ee 40°¢ a—b ac J (@- b?) (0? ifr *) a 0, the axes are parallel to the axes of the ellipsoid of elasticity. Now, since this cone has for its vertex 7,3, and envelopes the ellipsoid, ee + y + i aes 0 PE@LB) 288 VIO) Ciro its equation is? Bln ey — OF and the reader can verify that the equation is equivalent to the form just given when the values of ay,2, are substituted. 1 See Dublin Moderatorship Examination, 1845; Griffin’s Tract on Double Refrac- tion ; or Bassett’s Physical Optics, page 123. 2 P= 0 is the polar plane of x1y121 with respect to = = 0. 3 Tn connexion with what has been written, the reader might consult the footnote on page 438, Art. 405, of Salmon’s Surfaces ; and for an interesting proof that the plane 7; = 0 touches the wave surface in a circle, see page 184 of the Solutions of the Cambridge Problems aud Riders for 1878, edited by Dr. Glaisher; he ought also to look up the footnote on page 273, Art. 192, of Preston’s Theory of Light (first edition). 388 Scientific Proceedings, Royal Dublin Society. The four polar planes of the conical points with respect to == 0 consist of two pairs of parallel planes, and any two not parallel are equally inclined to the circular sections of the ellip- soid of elasticity. I have calculated the volume of a singular tangent cone cut off by the polar plane of its vertex with reference — to S=0; its value appears to be xr we (@ oe b’)? (0? = ce)? which I leave to the reader to verify. [ 389 ] XLIX. ON THE ROTATION-PERIOD OF THE “GARNET” SPOT ON JUPITER. By ARTHUR A. RAMBAUT, M.A., D.Sc., F.R.A.S. [Read Marcu 18; Received for Publication Marcn 20; Published June 30, 1896.] Osservations of Jupiter’s telescopic appearance have been especially interesting during the present opposition of the planet, on account of the conspicuous markings which have been deve- loped on its surface since it was lost to sight in the Sun’s rays. When Jupiter reappeared last autumn from conjunction, it was found that two new, well-defined, dark spots had broken out in what is known as the north tropical zone. These seem to have been first observed by M. Antoniadi of the Observatory of Juvisy, who, writing tothe Bulletin de la Société Astronomique de France, describes the second—the following—of these as “ rouge grenat trés foncé,” and says that on October 15th it was so dark that it might have been taken at first for the shadow of a satellite. In respect of shade, this spot is quite remarkable, standing out more distinctly than any of the other markings on the disc, and has, as a matter of fact, been mistaken by more than one observer (who on looking at the planet was unaware of its existence) for the shadow of a moon, until a reference to the Ephemeris showed that none of the moons were in a position to cast such a shadow at the time. This spot covers about 5°°5 in zenographical longitude, and about half that in latitude, and is of a very well-defined oval form. Its actual linear dimensions are about 4200 miles long by about 2000 miles broad. 390 Scientific Proceedings, Royal Dublin Society. Apart from any theory as to the nature and mode of genesis of these spots, whether they be due to upheavals of the matter forming the visible surface of Jupiter in a manner somewhat analogous to the origin of sunspots, or to the formation of dark clouds in his atmosphere, or to the temporary withdrawal of a heavy pall of vapours, thus forming a rift through which we get a glimpse of the interior parts of the planet, it will be obvious that observations of the movements of such spots must be of great value, as enabling us to determine the elements of the rotation ~ of the planet—the position of its polar axis, and the time in which it completes a rotation. Since the time of Schroeter the movements of many such spots have been observed, and the curious result is arrived at, that different parts of the surface rotate at different rates. Tt will of course be understood that this anomalous behaviour is quite independent of the fact, that the equatorial parts move with a higher linear velocity than those nearer the poles, a law which must hold for any rotating solid sphere such as the Harth or Mars. But in the case of Jupiter it is found that the different spots complete a rotation in different periods, a state of affairs which is quite incompatible with their being each rigidly attached to a solid rotating body. In this respect Jupiter resembles the Sun itself, where the rate of movement of spots on the whole diminishes as the spot is more and more removed from the equator. In the case of Jupiter this variation is scarcely so regular as in that of the Sun, but there are distinct differences in the periods of rotation of different zones which conspire with other facts in regard to its physical character, such as its low density (less than one quarter that of the Harth and only 1:29 compared with that of water), and the marked polar compression of its globe, in leading us to the conclusion, that we are here dealing with a body, to a great extent at least, in a state of vapour. As was pointed out recently by Mr. A. Stanley Williams in the Monthly Notices of the Royal Astronomical Society, there are nine distinctly marked zones, whose periods of rotation have been well determined. RamBaut—Rotation-Period of “ Garnet” Spot on Jupiter. 391 These are :— Zenographical Zones. Zone. Latitude. Period. if + 85° to + 28° Qe bo e120". LT. +28 ,, +24 9 542 — ‘to 9" 56e™. ei. +24 ,, + 20 9 48 — to 9 492. IV. +20 ,, +10 QP ioom ood. V. +10 ,, -—12 9°50 20: VI. —-12 , -18 9 55 40. VIL. -14 ,, —28 9 55 40. (The Red Spot.) VEIL. -—18 ,, -37 9] ob iekssls IX. —87 ,, -— 585 9 55 5. The “Garnet” spot to which our observations relate is situated in Zenographical latitude + 13°, and is therefore included in Zone IV. of Mr. Williams’ paper. The observations were made with the “South” equatorial refractor, and the Pistor and Martin’s filar micrometer, which contains two movable parallel wires at right angles to a single fixed one. The micrometer was set, so that the movable threads were parallel to the direction of the system of belts, and the single wire set, so as to bisect the equatorial diameter of the planet, as Fig. 1. represented in figure 1. ‘The wires being kept in this position, the time was noted; at which the preceding end of the spot first touched the wire, that at which the spot was bisected by the SCIEN. PROC. R.D.S., VOL. VIII., PART V. 2F on 392 Scientific Proceedings, Royal Dublin Society. wire, and the moment of last contact with the wire: the mean of all three being taken as the time of apparent central transit of the spot. This time of apparent central transit is affected by three distinct sources of error, which cannot be ignored when accurate results are sought. These may be described as (1) the correction for parallax, (2) the correction for the velocity of light, and (8) the correction for phase. Taking these in order we have :— (1). The correction for parallax. This is due to the change in the relative positions of Jupiter and the Harth in the interval between two apparent central transits. By the period of rotation is of course meant a “sidereal”’ rotation, ¢.e. the interval which elapses between two transits of the spot, as it would appear S Fig. 2. from a fixed point at an infinite distance. This is very different from the interval between two transits, as seen from a moving body like the Karth, comparatively speaking, in the vicinity of the planet. RamBaut—Rotation- Period of “ Garnet” Spot on Jupiter. 398 We must, therefore, in the first instance reduce the time of transit to what it would have been if seen from some particular direction. For this purpose it is convenient to select the longi- tude of the Sun at opposition, represented in fig. 2 by the line J,L,S, or the line JH’ which is parallel to it. We thus see that previous to opposition the spot will transit with regard to this line before the apparent transit takes place, and after opposi- tion the apparent will take place before the real central transit. - That is to say, that before opposition we must diminish the time of observation by the interval which the spot takes to move through the angle H’ JH in the figure, whereas after opposition the correction will be a positive one. To calculate its amount, we remark that the angle ESE = SJE - J Sd. But if Z and L, denote the longitude of Jupiter at J and Ji, and if / represent the longitude of the earth at H, and if R and D denote the distances of the Sun and Jupiter expressed in units of the mean distance of the Earth from the Sun (all of which may be obtained from the Nautical Almanac), we see that sin SJE = sin JSEH. = or ; ae SJE = sin? (5 sin J} sz) =a, say. Also, JSJ=L,-L, and JSE=L-1, so that the correction which is to be added is the time of describing the angle SPE = sin 5 sin (¢— Di) ' (Zn z L) Knowing approximately the time of rotation (P), we have, finally, the correction for parallax iP z [sin Ip sin( 2 2) +(Z.-2)| x gee (A) (2). The correction for the velocity of light.—In consequence of the finite velocity of light, any phenomenon taking place on Jupiter will not be seen by us, even at opposition, for thirty-five 2F 2 394 Scientific Proceedings, Royal Dublin Society. minutes afterits occurrence. Of course, if this delay or retardation were constant, it would not affect our observations, but on account of our constantly changing distance from the planet this retarda- tion will vary between wide limits. Comparing again our obser- vations with those made at the moment of opposition, we see that the correction to be applied is the difference in the times which light requires to travel the distances JH and J, (fig. 2). If 7 is the time which light occupies in traversing the mean radius of the Harth’s orbit (viz. 8"™°317), this correction is there- fore evidently — D \ (D, - D\P-- (5-1). DE. Ee We have, lastly, (3). The correction for phase.—Although the great distance of Jupiter from the Harth prevents its ever assuming a very marked gibbosity, as is seen at each synodical revolution in the case of Mars, yet there is a certain amount of phase which will sensibly affect observations, such as those with which we are at, present concerned. For, the phase is so small—the defect of the diameter Fig. 3. never exceeding 0’:35—that to the eye the form of the dise is always perfectly symmetrical, and consequently the method above described of setting the micrometer will have the effect of placing the single wire so as to pass through C’, the middle point of BD (in fig. 3), instead of through O, the middle point of AB, RamBaut—Rotation-Period of “ Garnet”? Spot on Jupiter. 395 and it is clear that the amount of displacement CC’ is half the defect AD. To calculate the amount of this correction, we remark that in fig. 4 (in which the circle 4D’B represents the equator of Jupiter, and JS and JE the directions in which the Sun and Earth respectively lie—cf. fig. 2), the arc BD’ measures the proportion of the illuminated hemisphere visible at the time, and since the Fig. 4. apparent disc is an orthogonal projection of the visible portion of the illuminated hemisphere of the planet, we see that JC” is the amount of the displacement of the centre due to phase, and this is equal to 34D. But AD=4AB (1-cos AJD’) = 4AB x (1-cos SJE). Also, the angle CJC’ being very small, we may take its arc CC’ as equal to its chord, i.e. CC’ = JC” =i AB x (1 -—cos SJH). Now the time of moving from C’ to C is the same fraction of the whole period that the are CC’ is of the whole circumference of the equator, or P the correction for phase = ;AB (1 — cos SJE) x 7tAB Also, SJE is the angle we have already denoted by a, so that we have, finally, 3 P the correction for phase =sin’ 3a x a (C.) It is obvious, too, that before opposition this correction will be positive, and after opposition, negative. 396 Scientific Proceedings, Royal Dublin Society. I now come to the actual observations, which were made at Dunsink, on every available opportunity, between February 9th (when my attention was first directed to the spot) and March 16th. The first four observations were made by my assistant, Mr. Charles — | Martin ; the others by myself. In the following table (p. 397) I give the actually observed times of transit expressed in Greenwich mean time, the three corrections referred to above, and the corrected times of central transit. In the last column is given the number of revolutions which had taken place since the first observation. We have next to consider the treatment of the observations for the deduction of the period of rotation. We must assume that each of these observations, the first included, is affected with a certain amount of error. If then we assume that the first transit took place at some epoch (Z,) nearly, but not exactly, coincident with the time of the first observation (71), and if we denote the number of revolutions which have elapsed between JT, and any subsequent transit by 7, each observation will give us an equation of the form— OA Weep ached Lh Now, if we take 7, = 7, +, where wv is a small correction to be determined, and P = P, + y where P, = 9° 55™ 348, and y is a small correction, we have T,+e+7(Po+y)=T, or erry= T,— 7, —7rPo =n. In this way we find the following equations of condition, taking 7, = Feb. 9th, 8° 12™ 565 (G. M. 'T.) :— No. Equations of Condition. Residuals. Weight. Observer. 1. c+ O.y= 0 — 1™ 248 1 C.M. 2. e+ 3 y=- 311 +3 40 1 6 3. t+ d.y=+ 186 —-4 33 = 5 4, e+10.y=— 92 fo eal 1 ie 5. 2+27.y=—-1038 + 1 1 A.A.R 6. 2+ 29. ¥=-— 186 + 38 1 55 the E484. y= 28 = 118 1 f 8. e+41l.y=- 36 -1 15 1 of Sh 2+651.y=—107 - 10 1 Py LO: 2+70.y=-118 el 1 as De “2+ 87. y =— 204 +1 4 1 5 Zee Ramraut—Rotation Period of “ Garnet”? Spot on Jupiter. 397 L8 o¢ 8h L oF G¢e I- 003 - 0- 68% + g-98 68 4 gee a ()°) Perna OL Gin aos ane e 9. 63 — Pb: PST — 8- Z9F + 8-8¢ GG 9 = 06 < T¢ eke (HIP KY eta = 8- 801 - 8: GIb + 0-81 0% OT 4st: yore I? Gor Ole eenoG Gel Or) 8 aia Bessel: p19 ¢ 2 Sy UO Cee ee Zs th IF 6 8&3 e2cles Nieto) les 6. sce + Ooc1 wee G © Dae Caeeanes 6% Ones Gar OG ()s TIE = ¢. 79 - €- 6ge + 9-cF 1G 2b : Cyl KG Ig IL @1 02 Sas = 0-19 — Gamegear (pei Je ai unde O01 2 EtG [lke tS Usd Sap ome G- Le + 6n8¢ ec TL ; Cla Me ae G fA AS (UE (Silt oe ¥- 8S = 9. $86 + 9-€8 0¢ 6 eee » g 13 #9 §1 OT 92 9= LoGe= 6. 836 + L-P1 1G 81 io Seas 0 s9G w6I 48 Pp6 O-sG — 9.336 — %-260% + L-shG w6 48 : ‘q36 Arenaqoiy ran ‘OUILT, pe}I9LI0D 10) gq ‘Vv ‘OulL], 9yeq ‘AMLIdNP NO LOdg ,,LaNUVO,, HHL dO LISNVUT, TVALNAD AO SAI, 398 Scientific Proceedings, Royal Dublin Society. These lead to the normal equations — 10:°257+ 3858:25y=—- 1087-5, 309°204 + 19592°25y = — 42197°5, from which we obtain the following solution :— Weight. e#=— 172452 + 36°4 3°9 y=- 064+ 0°53 | 7420-0; while the probable error of a single observation is + 72°. We thus get for the period of rotation of the spot— 95 55™ 33-36 + 05-53, and the epoch from which to reckon the rotations— February 9th, 8" 11™ 3158. It will thus be seen that this spot is moving at about the average velocity of the zone in which it lies; and it is interesting to note that this period agrees within one-fifth of a second with the value deduced by Schroeter 109 years ago from 242 revolu- tions of a spot, a fact which goes to show that there has been no permanent change in the period of rotation of this region in the interval which has elapsed since then. fromeonl ie: NOTE ON IRISH ANNELIDS IN THE MUSEUM OF SCIENCE. AND ART, DUBLIN.—No. I. By W. C. M‘INTOSH, Professor of Natural History in St. Andrew’s University. [Received for Publication Juty 14; Published OcronEr 10, 1896.] Prorsssor Happon lately forwarded a collection of Irish Anne- lids made during various dredging expeditions. The specimens. were preserved with considerable care, and duly labelled. At the same time an extensive series of Annelids from the Science and Art Museum was sent, at the instigation of Dr. Scharff, by the lamented Dr. Valentine Ball. I am much indebted to these gentlemen for their courtesy in handing these over for examina- | tion, in order that the forthcoming monograph of the British ' Annelids might be as complete as possible in regard to distribu- tion. For convenience, each collection may be placed separately under each species, and in this instance the list goes as far as the Sigalionide. It was hoped that, in these collections, examples of the rare Spinther oniscoides of Dr. George Johnston would have been present, for his example was dredged by Mr. W. _ Thompson, in Belfast Bay, in 6-10 fathoms, but no trace of such was found. The occurrence of two new species, and a few varieties, show that still more is to be done in our country in this group of Invertebrates. List or IrisH ANNELIDS. Aphrodita aculeata, L. Bantry Bay, No. 92, 1892, of moderate size; off Howth (Lambay excursion, 1886), the specimen (8 inches) having Lowo- soma and a Campanularian parasitic on the feet and the ventral surface; Station 114, 80 fathoms, young example; Station 122, young; Station 126, small; Stations 127 and 128, two of moderate size; Station 147, small. 400 Scientific Proceedings, Royal Dublin Society. [In Science and Art Museum. | Berehaven, 14 inches; off Howth (Lambay excursion, 1886) ; S.-W. Ireland, log. 55, 23-35 fathoms; R.I. A. Exped., 1886, small; log. 53, 70-80 fathoms, R. I. A. Exped., 1886, R. Scharff, small; off Baltimore, 8.-W. Ireland, 34 fathoms, 1855; Bantry Bay (82), 1892. Lepidonotus squamatus, L. Blacksod Bay (6), July, 1890; Salthill, Co. Dublin; S.-W. Treland, A. G. More; Dalkey, Co. Dublin, A. C. Haddon, 1855; mouth of Bantry Bay, 37-35 fathoms, 1885; R. I. A. Exped., Station xxx, No. 171, June, 1890. [In Science and Art Museum. | Berehaven, 1886, one bearing ova; Glandore, S.-W. Ireland, 4 fathoms; R. I. A. Exped., 1883, young; Malahide, 1886, A. C. Haddon ; North of Ireland Ord. Surv. Coll., Bantry Bay, 1892. Lepidonotus clava, Mont. Variety, with the tips of the ventral bristles longer; Bantry Bay (107 and 103), 1892. Nychia cirrosa, Pall. Prof. Haddon, mouth of Bantry Bay, 37-35 fathoms, 1885, small; ibid., 1892; Blacksod Bay (5), June, 1890, along with tube of Lanice conchilega. . [In Science and Art Museum. | Berehaven, S.-W. Ireland Exped., 1886; Broadhaven Bay, A. G. More, very large; Dalkey Sound, 1892, medium. Lagisca propinqua, Malmgren. S.-W. Ireland Exped. (53), 1886. [In Science and Art Museum]. Glandore, S.-W. Ireland Exped. (85), 4 fathoms; R.I.A. Exped., 1886; Berehaven, R.J.A. Exped., 1885; Bantry Bay (33), 89-35 fathoms, 1885; and (103 and 177), 1892; Malahide, 1886, A. ©. Haddon; Great Arran Island, Co. Galway; Berehaven, R. I. A. Exped., 1886; Nymph Bank, 8. Ireland. M‘Inrosp—WNote on Irish Annelids. 401 Harmothoe imbricata, L. [In Science and Art Museum. | Station xxx (171), June, 1890, variety; Baltimore Bay, December, 1889, Father Davies; Bantry Bay (42), 33 fathoms; R. I. A. Exped., 1886; Bundoran, Donegal, August, 1889, Dr. Scharff ; specimen, locality not marked; Salthill, Co. Dublin, A. C. Haddon; Blacksod Bay (5), July, 1890; Long Island Sound (40), 83-5 fathoms; R.I. A. Exped., 1886; Berehaven, R.I. A. Exped., 1885; Bantry Bay (177), 1892; Malahide, Co. Dublin, A. C. Haddon; Broadhaven Bay, A. G. More; Dingle Bay (152), 1889; Portmarnock, October, 1889, R. Scharff. Harmothoé Fraser-Thomsoni, n. sp.’ S.-W. Ireland Exped. (46) ; 93 fathoms, R. I. A. Exped., 1886, along with MWalmgrenia castanea on Spatangus Raschi. 'This species, which had been procured by the “Knight Errant,” in the Atlantic in 1880, is characterized as follows :— Head somewhat near that of Lagisca, having a pair of widely separated eyes posteriorly, and a larger pair on the lateral eminence. Palpi of moderate length, with rows of minute papillae. Body of considerable length and breadth; bristled segments 39-40. Dorsum has touches of brown pigment, pos- teriorly, as in Lagisca. The lateral nephridial eminences are prominent, but there are no papilla. Scales, 15 pairs, mottled- brown, covering the dorsum; first, small and rounded; rest, more or less ovoid ; border smooth, anterior and inner half studded ‘with small horny papille, outer and posterior areas have sparsely distributed large tubercles, with an ‘interrupted row along the posterior border. Dorsal bristles stout, moderately long, and slightly curved, with closely arranged spinous rows, and a short smooth tip. Ventral bristles bifid, the secondary process coming off at an angle. Dorsal cirri appear as if fusiform from the gradual nature of the dilatation and the long filiform tip, and have clavate cilia. Ventral cirri slender, with a few clavate cilia. 1 Figures will be found in the forthcoming Part 1I. of the British Annelids, Ray Society. 402 Scientific Proceedings, Royal Dublin Society. Harmothoé lunulata, D. Chiaje. [In Science and Art Museum. | S.-W. Ireland Exped. (44), 108 fathoms; R.J. A. Exped., 1886, — Evarne impar, Johnston. [In Professor Haddon’s Collection. | Long Island Sound (40), 33-5 fathoms; R.I. A. Exped., 1886; Salthill, Co. Dublin, A. C. Haddon; Blacksod Bay (6), July, 1890. [In Science and Art Museum. | Berehaven, R. I. A. Exped., 1885; S.-W. Ireland Exped. (31), 893 fathoms; R.JI. A. Exped., 1886; Glandore (85), 4 fathoms; R. I. A. Exped., 1886, with remarkably mottled scales; Bantry Bay (103), 1892. Evarne Johnstoni, M‘Intosh. [In Royal Dublin Society’s Collection. | Station 115, 62-52 fathoms, Aug. 20th, 1890. Antinoe finmarchica, Malmgren. This rare form was dredged at No. 56, in 93 fathoms, during the R.J.A. Exped., 1896. It is an inhabitant of deep water, and had previously been got on the West Coast of Ireland, and during the “Porcupine” Expedition of 1869, at considerable depths. Malmegrenia castanea, M‘Intosh. [In Professor Haddon’s Collection. | S.-W. Ireland Exped. (No. 46), 93 fathoms, on Spatangus Raschi (28, 56), 15th July; R.I. A. Exped., 1886. [In Science and Ait Museum. | S.-W. Ireland Exped. (48), 480 fathoms; R.I.A. Exped., 1886. Alentia gelatinosa, Sars. [In Royal Dublin Society’s Collection. | Killeany Bay (in ditt.), 8rd June, 1890, large; Blacksod Bay, trawl, 5th July, 1890, ¢ carrying ova; Birturbuy Bay, 10th June, 1890. | M‘Inrosp—WNote on Irish Annelids. 4038 [In Science and Art Museum. | Berehaven, R. I. A. Exped., 1885, small. Polynoé scolopendrina, Sav. [In-Royal Dublin Society’s Collection. | Blacksod Bay, 6th July, 1890; Bantry Bay (28), 387-35 fathoms, R. I. A. Exped., 1885; Dalkey, Co. Dublin, A. C. Haddon ; in tube of Zerebella? [In Science and Art Museum. | Berehaven, R. I. A. Exped., 1886, good specimens; Ibid., 1885; Dingle Harbour, A. G. More. Sthenelais boa, Johnston (= S. Idune, H. Rathke). [In Professor Haddon’s Collection. | Off Bray Head, Co. Wicklow, A. C. Haddon, 28 fathoms - (116), 1892. [In Science and Art Museum. | Malahide, Co. Dublin, A. C. Haddon, 1886; small (young). Berehaven, R.I. A. Exped., 1885, good; Broadhaven Bay, A. G. More. Sthenelais limicola, Ehlers. [In Royal Dublin Society’s Collection. | Mouth of Kenmare River (21), 41 fathoms, R.I. A. Exped., 1885. [In Science and Art Museum. | S.-W. Ireland Exped. (48), 480 fathoms; R.I. A. Exped., 1886 ; Ibid. (55), 23-38 fathoms; R.I. A. Exped., 1886, mouth of Kenmare River, ué supra; S.-W. Ireland, Station v., 1885; R.1I. A. Exped. Sthenelais,' n. sp. Dredged off the South-west of Ivreland, log. 45, at 328 fathoms: R. I. A. Exped., 1886. Head absent ; body seemed to be long and narrow, with pro- minent feet; only the posterior region remained. Scales, on every foot on the posterior fragment, large, covering the entire * It is unsafe to name imperfect specimens, but this form should bear the title, S. Haddoni. 404 Scientific Proceedings, Royal Dublin Society. dorsum of the narrow body, and uniform in outline. They are perfectly smooth on surface and border, and thus differ from those of the other British species. A shallow notch occurs at the exter- nal margin, and a more acute one at the hilum. The distribution of the nerves is well seen. The feet have an unusually long, straight branchial process dorsally, and three ciliated pads beneath it on the dorsal curve. The dorsal lobe is clavate (narrower at the base), much bevelled dorsally at the tip, and with a long, slender papilla stretching from the apex. The dorsal bristles form a long tuft of rather boldly serrated bristles superiorly, and they diminish towards the ventral edge; the ventral lobe forms an irregular spear-head, the longer slope being inferior, and the apex from which the spine projects is prominent, and bears a papilla. Inferiorly is another pro- minence behind the lower group of bristles. The upper ventral bristles are slender, the distal ends of the shafts having eight or nine whorls of spikes, the terminal process apparently being simple—in the form of a tapering acicular process with a needle- like tip, a condition probably due to repair, since some show a many-jointed needle-like tip. Others, with stronger shafts, next follow, with shorter, simple tips numerously jointed. Some of the more slender shafts at the ventral border of the stout series present many-jointed tips, with a minute claw. ‘Then follows a large, fan-shaped group of most slender bristles, with a few spines at the tips of the slightly-curved shafts, and long (6-8) jointed, hair- like tips. The ventral cirrus is long and subulate, and its tapering tip reaches as far as the apex of the ventral lobe. So far as can be observed, this is the nearest approach to Leanira, only the more slender forms of the stouter series of bristles in the ventral division presenting a very finely bifid ex- tremity. Pholoé minuta, Fabricius. [In Royal Dublin Society’s Collection. | Kilronan Bay, Aran Isles, 3rd June, 1890. [ 405 ] ile THE HYDROIDS OF THE IRISH COAST. By J. E. DUERDEN, A.R.C. Sc. (Lond.) ; Curator of the Museum, Kingston, Jamaica. [Read May 20; Received for Publication, May 22; Published Ocroser 10, 1896.] Havine left Ireland, I have considered it advisable to summarize my results, however incomplete, of the known species of Irish Hydroids, upon numerous collections of which I have been employed for two or three years. The list also contains the records. of those whose occurrence has been noted by other workers in the group. The following are the principal publications referring to Trish forms :— . Dr. A. Hill Hassall, in a ‘Catalogue of Irish Zoophytes,’’ and in a “Supplement ’”’ to the Catalogue, made the first attempt at a list of the Irish Hydroids (1841a, 18410). Mr. William Thompson, in his “ Natural History of Ireland,’ gives a number of localities for different species (1856). Prof. G. J. Allman has described and referred to, in various publications, a number of representatives obtained from Ireland. In the “‘ British Hydroid Zoophytes”’ (1868) the Rev.T. Hincks summarizes, under each species, the Ivish localities where rarer forms are known to occur, being indebted mainly to the lists and collections of Prof. Allman, Dr. Hassall, Mr. W. Thompson, Prof. Wyville Thomson, and Mr. G. S. Brady. “The British Association Guide to the County of Dublin” (1878) records about fifty species for this part of the coast, from the collections of Mr. M‘Calla, Dr. Hassall, Prof. J. R. Greene, Hon. Miss Lawless, Mr. D. St. J. Grant, and Prof. H. W. Mackintosh. Prof. Haddon, in a “ Preliminary Report on the Fauna of Dublin Bay” (1886), adds several species. Mr. Kirkpatrick (1889) records the specimens obtained on a deep-sea trawling expedition off the south-west of Ireland. 406 Scientific Proceedings, Royal Dublin Society. Prof. Herdman, during the cruise of S. Y. “ Argo” round the west coast of Ireland (1889), obtained fourteen species of Hydroids. My own results are founded upon the material collected by the different Fishery Surveys of the West Coast, undertaken by the Royal Irish Academy (1893) and the Royal Dublin Society (1895) ; also upon collections made on expeditions in connection with the “‘ Royal Irish Academy Fauna and Flora Committee” to the Bantry Bay district and to Donegal Bay, and upon various collecting trips on the east coast (1894 a, 1894). Some of these results have already been embodied elsewhere. In all, my exami- nations make an addition of about twenty-three to the Irish Hydroids, including two new species and one new to Britain. The present list contains 101 species—35 Athecata and 66 Thecata. The west coast is much richer in the former group than is the east coast, yielding many of the minuter species.’ Order.—HYDROIDA. Sub-Order.—I. Aruxcara. I. CLAVIDZ. Clava multicornis, Forskal. Obtained growing profusely on the limbs and carapace of Inachus, from Lough Swilly ; on Stenorhynchus, from Killybegs ; Ballinskelligs Bay, at a depth of 55 fathoms (R. D.S.) ; Dursey Sound; Kenmare River; Berehaven; abundant on Fucus, from Roundstone ; Donegal Bay rock-pools (J. H. D.). Clava squamata, Miller. Recorded in the British Association List for county Dublin (1878). Tubiclava lucerna, Allman. Obtained by Prof. Allman on stones between tide-marks in Dublin Bay (1863). It does not appear to have since been found on the Irish coasts. — 1 Since this Paper was written, Mr. F. W. Gamble has published (Lrish Naturalist, May, 1896) “‘ Notes on a Zoological Expedition to Valentia, Co. Kerry,’’ in which he records several Hydroids obtained. , Durrpen— The Hydroids of the Irish Coast. 407 Tubiclava cornucopie, Norman. A rare species collected by the Royal Dublin Society’s Survey from Blacksod Bay. Colonies were found living on four different shells of Astarte suleata, with the living animal inside (1895). Il. HYDRACTINIIDZA, Hydractinia echinata, Fleming. A common species, living on shells inhabited by hermit-crabs ; obtained in abundance from all localities where dredging has been carried on. III. PODOCORYNIDZ. Podocoryne carnea, Nars. First recorded for Ireland from collections made by the Royal Irish Academy from Long Island Bay (1898); Galway Bay, on Nassa; Blacksod Bay, on Aporrhais (R. D.8.). Podocoryne areolata, Alder. Obtained among the collections from the deep-sea trawling expedition off the south-west coast of Ireland (1889); Dursey Head and Berehaven (1893). IV. CORYNIDZ. Coryne pusilla, Geertner. A fairly common form in the rock-pools. On Fucus, Bere- haven (R. I. A.) ; on Zanthea, Kilkeiran Bay (R. D.S8.) ; rock- pools of Donegal Bay; Dursey Island; Rush (J. E. D.). Coryne vaginata, Hincks. Tide-pools of Clew Bay (Hincks) ; common on the southern shores and in Dublin Bay (Allman); north-east coast (W. Thomp- son). Coryne van Benedenii, Hincks. Placed in the county Dublin list as rare at Killiney Bay (Hon. Miss Lawless). SCIEN. PROC. R.D.S., VOL. VIII., PART YV. 2G 408 Scientific Proceedings, Royal Dublin Society. Syncoryne frutescens, Allman. Found at Kingstown, county Dublin, attached to floating logs in a reservoir exposed to the tide, and constantly supplied by sea- water from Dublin Bay (1872). Syncoryne eximia, Allman. On sea- weed from Scotch Bay, Kingstown (1886). Owing to the absence of gonophores, Professor Haddon considers this identification not absolutely certain. V. CLAVATELLIDZ. Clavatella prolifera, Hincks. Coasts of Cork (1872). VI. EUDENDRIIDZ. Eudendrium rameum, Pallas. A colony of this species, perfect as a miniature tree with the gonophores as fruit, was dredged from St. 125, 40 miles off Bolus Head, at a depth of 115 fathoms (R.D.8.). A large Hyas araneus from Lough Swilly, collected by the same Survey, had covered itself almost entirely with branches of the Hydroid. Also obtained from many other parts of the coast. Eudendrium ramosum, Linn. Collected by the different Surveys from various points of the coast. It is especially abundant on the east coast, being washed ashore in company with various other zoophytes torn up by the trawl. Eudendrium capillare, Alder. This more delicate form was obtained growing abundantly on the inside of an old Pecten shell from Casheen Bay. The gono- phores were (April) undeveloped on any of the individuals. On a sponge from Kilkeiran Bay, rather common, with gonophores on the lower part of the stem ; amongst the shore collections from Blacksod Bay, from off Malin Head, growing on Fusus (R. D.8.) ; Berehaven (1893) ; Dublin Bay (1886). Eudendrium insigne, Hincks. Lough Swilly (1895). Durrpen— The Hydroids of the Irish Coast. 409 VI. ATRACTYLIDZ. Atractylis arenosa, Alder. On the west coast at a depth of 50 fathoms (1893); shore collections at Rush, county Dublin (18940). Perigonimus repens, T. S. Wright. Berehaven, growing on Sertularia abietina; on Scaphander, Galway Bay ; off the Skelligs, depth 40 to 80 fathoms; Dingle Bay (1893). Perigonimus gelatinosus, Duerden. On shells inhabited by Pagurus from rather deep water, Dingle Bay, depth 40 fathoms (R. D.S8.); south-west of Ireland, depth 50 fathoms; 94 miles south-west of Castletown, depth 37% fathoms (1895). Perigonimus (?) inflatus, Duerden. On Sertularia abietina and other zoophytes from fairly deep water, 11 miles south of Glandore Harbour, depth 54 fathoms ; 13 miles south-west of Galley Head, depth 43 fathoms (1895). Perigonimus (?) linearis, Alder. South of Glandore Harbour, depth 54 fathoms (1893). Garveia nutans, I’. 8. Wright. South-west corner of Dalkey Island, associated with Tubularia humilis and T. indivisa (1886). Bimeria vestita, T. S. Wright. Lough Swilly (1895). Dicoryne conferta, Alder. This zoophyte, growing on shells inhabited by hermit crabs, is not uncommon on the west coast ; found growing luxuriantly, with the gonophores on the branches well developed, around the mouth of a Buccinum shell, and also on that of a Fusus, from off the Skelligs, depth 50 fathoms; from Kenmare River (R. D. S.); Bantry Bay; Berehaven; at a depth of 50 fathoms off the south- west of Ireland (1898). 2 G2 410 Scientific Proceedings, Royal Dublin Society. Heterocordyle Conybearei, Allman. This species was founded on specimens growing in consider- able abundance on old univalve shells, tenanted by hermit crabs, found at the Harbour of Glengariff, county Cork (1864). Bougainvillia ramosa, Van Beneden. Colonies of this hydroid are known from various Irish locali- ties. Several of the specimens bear the club-shaped capsules previously observed on Hydractinia and Syncoryne, which function as the nests of pyenogon larve (Hodge, Ann. Mag. Nat. Hist.). Glandore Harbour, with parasite capsules; Dingle Bay; Bere- haven (R.JI.A.); off the Skelligs, 80 fathoms; Lough Swilly, from off the shell of a Buccinum, and bearing parasite capsules (R. D.8.); Donegal Bay rock-pools (J. E. D.). Bougainvillia fruticosa, Allman. Professor Allman founded this species on specimens obtained from a large piece of floating timber in the estuary of the Kenmare River (1864). On limbs of Stenorhynchus, with nest of larval Pycnogonida, Bantry Bay (1895). VII. TUBULARIIDZ. Tubularia indivisa, Linn. Generally distributed on our coasts. Dredging in Dalkey Sound yields fine specimens. Tubularia larynx, Hl. and Sol. Belfast Lough (W. Thompson); obtained in considerable abundance in the luxuriant rock-pools of Bundoran, and at several other points around the coasts (J. H. D.). Tubularia simplex, Alder. From Berehaven, growing on an old Pecten shell (1898). Tubularia bellis, Allman. Dursey Island, on the sides of the rocks at extreme low-water with the gonophores well developed (J. Hi. D.). | j 4 Durrpen— Zhe Hydroids of the Irish Coast. 411 Tubularia humilis, Allman. On rocks above the level of low-water spring tides, near the mouth of Kinsale Harbour (1864) ; Dalkey Island (1886). Ectopleura Dumortierii, Van Beneden. Of this species Mr. Hincks says :—‘‘ Professor Wvyville Thomson has recorded the occurrence of this Belgian zoophyte in Belfast Bay ; but specimens of the dried polypary from this locality, which he has kindly sent me, are much stouter and of coarser texture than any examples I have seen of H. Dumortierii, and, I believe, must be referred to some other species ”’ (1868). Corymorpha nutans, Allman. Professor Haddon, dredging in Scotch Bay, Kingstown, had the good fortune to obtain two specimens of this species (1886). Sub-order.—I1. T'HEcAPHORA. I. CAMPANULARIIDZ. Clytia Johnstoni, Alder. One of our commonest zoophytes. Some much-branched forms, with gonothece, were obtained from Queenstown, growing on Aporrhais; and another, with very large calycles and stems branched, was found growing in small tufts on a Lernea parasitic on a whiting (R.D.S.). Obelia geniculata, Linn. Plentiful from all parts, growing especially on Laminaria. Obelia gelatinosa, Pallas. This species does not seem to be common around the Irish coasts, as it has apparently not been before recorded. I have, however, found fine colonies in the rock-pools of Howth. Obelia longissima, Pallas. A single colony, about nine inches long, with gonothecz, was obtained by the Royal Dublin Society Survey from Galway Bay ; Howth (M‘Calla) ; Donegal Bay (J. E. D.). 412 Scientific Proceedings, Royal Dublin Society. Obelia dichotoma, Linn. Common from most localities. Obelia flabellata, Hincks. Abundant in the rock-pools of Bundoran; Donegal Bay Roundstone (J. H. D.) ; “ Argo” Cruise (1891). Campanularia volubilis, Linn. A somewhat common species growing mostly on other zoophytes. Blacksod Bay ; Port Stewart; off Malin Head (R. D.8.); Dursey Island; Dublin Bay (J. E.D.). © Campanularia Hincksii, Alder. Common in deep water in the north of Ireland (Wyville Thomson); abundant in Dublin Bay (J. E. D.). Campanularia integra, Macgillivray. Recorded for Ireland only from Belfast Bay (1868). Campanularia verticillata, Linn. Occasionally trawled in Dublin Bay, and also found washed ashore after storms. Campanularia caliculata, Hincks. Obtained by Professor Allman from Courtmasherry Harbour, County Cork; by R. Allman from Old Head of Kinsale, county Cork ; Dublin Bay Campanularia flexuosa, Hincks. Collected from most localities. Very abundant in the rock- pools around Bundoran. On specimens from Berehaven many of the gonothece contained small Nematodes. Campanularia angulata, Hincks. Recorded from several localities growing on Zostera marina, its favourite habitat. Campanularia neglecta, Alder. Dalkey Sound, growing on other zoophytes (J. E. D.); Blacksod Bay (R. D.8.); “ Argo” Cruise (1891). DurrpEen— The Hydroids of the Irish Coast. 413 Campanularia raridentata, Alder. Glandore Harbour, growing on Bougainvillia ramosa (1898) ; Ballyeotton, on worm-tubes; Blacksod Bay, on Sertularella polyzonias (R. D.S8.). Gonothyreea Loveni, Allman. Although not recorded in the Dublin List, I have found this interesting species in great abundance, practically covering all the Fucus for a considerable area, under the wooden bridge leading to the North Bull, Dublin Bay. All stages in the development of the sporosacs could be followed. At this spot I have likewise obtained the variety mentioned by Professor Allman as forming “ long, lax tufts, in some cases three or four inches long.’”’ Abundant on Fucus trom Lough Atalia (R. D.8.); Dublin Bay (1886); Carrick- fergus; Monkstown, near Cork (Wyville Thomson). Gonothyrea gracilis, Sars. Dredged by Mr. G. 8. Brady in Birterbuy Bay, Connemara, growing on the tests of Ascidians and other objects (1864). Gonothyreea hyalina, Hincks. On Hydralimania falcata, from Port Stewart, showing the gonothecea (R. D.S.); on the shore between Laytown and the mouth of the Boyne (1894 a). IT. CAMPANULINIDZ. Campanulina turrita, Hincks. On Zostera, Holywood, Belfast Lough (Wyville Thomson) ; Blacksod Bay (R. D. 8.); Bantry Bay; Dalkey ; Bundoran; Dursey Island; Roundstone, Connemara (1895). Campanulina panicula, G. O. Sars. On two Fusus shells trawled 40 miles off Achill Head ; depth 220 fathoms (1895). Opercularella lacerata, Johnston. North of Ireland (Wyville Thomson). 414 Scientific Proceedings, Royal Dublin Society. Ill. LAFQ@IDZA. Lafcea dumosa, Fleming. Known from various localities all round the coast. Lafoea parvula, Hincks. On Nitophyllum, from the north of Ireland, collected by Prof. Hincks, Toronto (1868). Lafoea pocillum, Hincks. On Eudendrium, at Monkstown (D. St. J. Grant) ; on Diphasia attenuata, Dublin Bay (1886) ; on Vesicularia spinosa, thine (2 ED.): Calycella syringa, Linn. Very abundant, growing on other zoophytes, in dredzinee from all parts of the coast. Calycella fastigiata, Alder. Apparently a rare British form, but rather plentiful on the west coast of Ireland. On Sertularia abietina, Ballinskelligs Bay (R. D. 8.): south-west of Galley Head, 48 fathoms; Dursey Island, south of Glandore Harbour; south-west of Ireland, 50 fathoms (1898). Calycella pygmea (Alder), Thornley. This is the Lafwa pygmea of Alder (MS.). It has lately been transferred to the genus Calycella (1894) after confirmation of Alder’s manuscript figure of it as an operculated form, and the discovery of the gonotheca and gonophore, which, except in size, closely resemble those of C. syringa. Previously to seeing Miss Thornley’s Paper, I had observed the same character on material gathered at Roundstone, Connemara, and am able to confirm both the presence of the operculum and the extra-capsular gonophore. The hydrotheca in the Irish specimens is not so sharply marked off from the pedicel as in the figures given by Hincks, Pl. xl, and the number of rings may be as many as six or seven, Some specimens also show that, as in C. syringa, the upper part may be divided into segments by lines of growth, but I have never seen more than one, while there are occasionally two or three in the latter. j Lo Durrpen—The Hydroids of the Irish Coast. 415 It was found to be rather abundant creeping over Fucus collected along the shore at Roundstone. Prof. Haddon obtained the species from Dalkey. Cuspidella grandis, Hincks. A rare species, found growing on worm-tubes from Bally- cotton, at a depth of 30 fathoms (R. D. S8.); Birterbuy Bay, Connemara (G. 8S. Brady). Cuspidella costata, Hincks. On tubes of Tabularia indivisa, Berehaven, 1893. Filellum serpens, Hassall. Common all around the coast, growing on other zoophytes. V. COPPINIIDZ. Coppinia arcta, Dalyell. Dredged from most localities, growing principally on Sertu- laria abvetina. VI. HALECIIDZ. Halecium halecinum, Linn. Common. Halecium muricatum, Eil. and Sol. Giants’ Causeway (Hassall). Halecium Beanii, Johnston. Common from all parts. Halecium tenellum, Hincks. A small colony, growing on Tubularia from the Fairy Bridge, Donegal Bay (J. E. D.). Halecium plumosum, Hincks. Described by Mr. Hincks from an Irish specimen in the collec- tions of Trinity College, Dublin. It has apparently not been noticed since. 416 Scientific Proceedings, Royal Dublin Society. VII. SERTULARIIDZ. Sertularella polyzonias, Linn. Found in abundance all round the coasts. Sertularella Gayi, Lamouroux. Birterbuy Bay, Connemara (G. 8. Brady) ; Dublin Bay. Sertularia rugosa, Linn. South-west of Galley Head (1893); Bundoran, Donegal Bay {J. EK. D.). Diphasia rosacea, Linn. Plentiful at most stations. Diphasia attenuata, Hincks. Dublin Bay (1886) ; south-west of Galley Head (1898). Diphasia fallax, Johnston. South-west of Galley Head, from a depth of 48 fathoms (1893). Diphasia pinaster, Ell. and Sol. Belfast Bay (Hyndman) ; Dublin Bay (W. Thompson) ; Giants’ Causeway (Hassall). Diphasia tamarisca, Linn. South-west of Galley Head (1893) ; rare in Dublin Bay (Hassall). Diphasia alata, Hincks. South-west of Galley Head (18938). Sertularia pumila, Linn. Abundant everywhere. Sertularia gracilis, Hassall. Birterbuy Bay; Blacksod Bay; Casheen Bay, growing on Fucus (R.D.8.) ; Cork Harbour (Haddon); Laytown (1894 a). Sertularia operculata, Linn. Very plentiful, especially on Laminaria washed ashore. Duerpen—TZhe Hydroids of the Irish Coast. 417 Sertularia filicula, Ell. and Sol. Trish coasts (W. Thompson). Sertularia abietina, Linn. Obtained from most dredgings, with numerous other zoophytes growing parasitically. Sertularia cupressina, and var. argentea, Linn. Dredged from most localities. Colonies of this species, suffi- cient to fill several large jars, were obtained from Lough Swilly by the Royal Dublin Society’s Survey, with numerous other zoophytes upon them. Hydrallmania faleata, Linn. Trawled and washed ashore in great abundance. Thuiaria thuja, Linn. A rare Irish form. Recorded in the Dublin Bay list. Thuiaria articulata, Pallas. Dublin Bay (Ellis) ; north of Ireland (W. Thompson). VIII. PLUMULARIIDZE. Antennularia antennina, Linn. Dredged from numerous localities. Antennularia ramosa, Lamarck. Generally distributed. Aglaophenia pluma, Linn. Known from different spots all round the coast. Aglaophenia tubulifera, Hincks. Small portions attached to the body and limbs of Stenorhynchus, Blacksod Bay (R. D.8.). 418 Scientific Proceedings, Royal Dublin Society. Aglaophenia pinnatula, Ell. and Sol. One of the numerous collections made by M‘Caila from Round- stone, Galway; also collected by Miss M. Ball from Youghal, profusely investing about six inches of the stem of Laminaria digitata. Mr. Hincks says that Miss Ball’s remarkable specimens have supplied the principal cabinets in the country. Plumularia pinnata, Linn. Collected from many parts of the coast. Plumularia setacea, Ellis. A common species Plumularia Catharina, Johnston. On worm-tubes from Ballycotton, depth 30 fathoms (R.D.S.) : Arran Island (Barlee) ; Dublin Bay (J. H. D.); south-west of Galley Head (1898).) Plumularia echinulata, Lamarck. An abundant species in the shallow waters of the west coast. Bantry Bay (R.D.S.); plentiful on Chorda filum, Roundstone ; Dublin Bay (J. E. D.}. Plumularia similis, Hincks. Donaghadee (Hyndman) ; on Fucus, Berehaven ; Dublin Bay (Gin 135 10). Plumularia halecioides, Alder. On the appendages of Stenorhynchus, Berehaven (1898) ; “ Argo” Cruise (1891). Plumularia frutescens, Ell. and Sol. Dublin Bay (Hassall) ; south of Ireland. Durrpen—The Hydroids of the Irish Coast. 419 REFERENCES. 1841a. Hassatt, A. Hitz, ‘‘ Catalogue of Irish Zoophytes.” Ann. Mag. Nat. Hist., vol. vi. 18415. Hassatt, A. Hitz, ‘‘ Supplement to a Catalogue of Irish Zoo- 1856. 1859. 1863. 1864. 1868. 1872. ee. 1886. 1889. 1891. 1893. phytes.”’ Ann. Mag. Nat. Hist., vol. vii. Tompson, W., ‘‘ Natural History of Ireland.” Attman, G. J. Ann. Mag. Nat. Hist. Attman, G. J., ‘‘ Notes on the Hydroida.” Ann. Mag. Nat. Hist. Atrman, G. J., ‘‘ Notes on the Hydroida.” Ann. Mag. Nat. Hist., May, July. Hincxs, T., ‘‘ British Hydroid Zoophytes.” Atrman, G. J., ‘‘Gymnoblastic or Tubularian Hydroids,”’ vol. ii. Macxrintosa, H. W., ‘‘Hydroida.” Brit. Assoc. Guide to the City and County of Dublin. Happon, A. C., ‘‘ Preliminary Report on the Fauna of Dublin Bay.” Proc. Roy. Irish Acad., 2nd ser., vol. iv., Science. Kirxrparricr, R., ‘‘ Deep-Sea Trawling Expedition off the 8. W. Coast of Ireland.” Ann. Mag. Nat. Hist. Herpuan, W. A., “ Biological Results of the Cruise of the S. Y. ‘Argo’ round the West Coast of Ireland, 1890.” ‘Trans. Biol. Soc., Liverpool, vol. vy. Durrven, J. E., ‘‘ Report on the Hydroida collected by the Royal Irish Academy Survey off the 8. W. Coast of Ireland, 1885, 1886, 1888.” Proc. Roy. Irish Acad., 3rd ser., vol. iii. 1894. Tuorntey, L. R., “Supplementary Report upon the Hydroid Zoophytes of the L. M. B. C. District.” Trans. Biol. Soe., Liverpool, vol. viii. 420 Scientific Proceedings, Royal Dublin Society. 1894a. Durrpen, J. E., ‘‘ Hydroids and Polyzoa collected between Lay- town and the Mouth of the Boyne.” Irish Naturalist, vol. ii1., No. 8. 18946. Durrpen, J. E., ‘‘ Notes on the Marine Invertebrates of Rush, Co. Dublin.” Irish Naturalist, vol. iii., No. 2. 1895. Dvrrpen, J. E., ‘“‘Survey of Fishing Grounds West Coast of Treland, 1890-91. Notes on the Hydroids and Polyzoa.” Proc. Roy. Dub. Soe., vol. viii. (N.S.). [ 421 ] LII. THE DISTRIBUTION OF DRIFT IN IRELAND IN ITS RELATION TO AGRICULTURE. By J. R. KILROE, (formerly) F.C.S., H. M. Geological Survey. (PuatEe XV.) [Read Aprit 22; Received for publication Aueust 10; Published January 11, 1897.} Tux interest which your Society has for a long time taken, and is taking, in the advancement of agriculture, has earned wide- spread and just recognition. One of your commendable objects is the encouragement of Science as applied to industrial purposes ; and in consonance with this aim, I have the honour of laying before you some remarks upon the distribution of Drift deposits in Ireland in their relation to agriculture. The subject of these deposits is one which has frequently been dealt with since 1824 when Weaver first called attention to the limestone gravels of Carlow, Wicklow, and Wexford. Amongst the investigators who have laboured in this field of inquiry may be especially mentioned the Rev. Maxwell Close, whose exhaustive paper on the general glaciation of Ireland appeared in 1866. Since that time many additional observations have been noted by the staff of the Geological Survey, and appear in the official publications as well as in Professor Hull’s “ Physical Geology,” in Mr. Kinahan’s“ Geology of Ireland,” and in papers by these and other authors, amongst whom may be mentioned Professors Sollas and Cole, Mr. Praeger, and Members of the Belfast Naturalists’ Field Club. Hitherto, however, the Drift has been treated of, in detail, from a purely geological, rather than from an economic, standpoint ; and the attention which agriculture imperatively demands and is receiving at the present time, may warrant the application to that industry of the information available in the above sources, parti- cularly the maps and memoirs of the Geological Survey. It has generally been assumed that the structure of the Harth’s crust under a country, and the consequent geographical disposition of the strata, determine the nature of the superincumbent soils, and 422 Scientific Proceedings, Royal Dublin Society. enable one to forecast the degrees of natural fertility which should be expected in different localities. ‘To a certain extent this hypo- thesis holds, but, in our latitudes at least, it is subject to consider- able modification, which it is one purpose of this paper to define. Few in this day will dispute that soils are derived from the solid rocks which form the crust. When, however, one examines the detritus (mingled clay, sand, stony particles, etc.) resulting from rock decay throughout the country, and finds materials obviously derived from limestone strata, overlying granite, as in parts of the county of Dublin, and covering Silurian grits, as in parts of Wicklow and Wexford; débris of metamorphic rocks over limestone in Sligo, and over granite in Donegal, etc., it is not unnatural that some would question whether the disposition of geological strata has any direct bearing upon the local character of their earthy covering. Nor are such questions confined to the uninstructed. The lucid and well- informed author of a work on the “ Principles of Land Valua- tion,’ signing himself “Aleph,” apropos of this, says: ‘“ The relation between the soils and the underlying rocks is such, that any classification of the rocks, as, for instance, the division of the limestone into four descriptions, can be of no agricultural importance whatever.” The circumstances alluded to are, I believe, to be accounted for by transplacement of rock detritus, which have obtained on a grand scale through the agency of land ice, and possibly of icebergs ; and such departure from what may be regarded as the natural order of things, has been attended with marked advantages to the agricultural interest, such as— (1). A greater extension than would otherwise obtain of fertilizing materials. (2). A mixing of materials drawn from different sources, which generally conduces to fertility. The transplacements mentioned above have resulted in the present distribution of soils and subsoils, which we may speak of combinedly as Drift; and in this aggregate view of it we may conceive of an extensive covering made up of a confused mixture of stones and earth, robing two-thirds of the country or more; 1 E. Ponsonby, Dublin, p. 68. 7 b ; . 4 Kitror— The Distribution of Drift in Ireland. 423 lying chiefly in the low grounds, where, however, the naked rock frequently presents itself over small areas; and in places rising to heights of 1350 or 1400 feet} on hill sides, softening the asperities of contour, and otherwise modifying the landscape. Above the 1500 feet contour line extends an area of some 800 square miles, which may be regarded as waste mountain land. About 836 square miles between the 1500 feet and 1000 feet con- tours, contain very little Drift, well-nigh all the Drift falling below the latter contour, where it covers a large portion of the 30,836 square miles,’ between this contour and the sea, probably over 20,000 square miles, including portions concealed by bog. This is shown by stippled dots on the published one-inch map of the country, which is accompanied by LJxplanations, containing general descriptions of the Boulder-clays. Detailed descriptions, however, are not published, though notes are given on the unpublished six-inch maps (which may be seen by the public at the Geological Survey Office), describing the superficial drift in many places: and such notes are of great value from an agricultural point of view; for fertility in Drift-covered areas is more dependent upon the character of the transported materials than on the nature of the rock which they conceal, and for the representation of which alone colouring is used on the published map. Mr. Albert Pell says, in the Journal of the Royal Agricul- tural Society of England (Part I. 1890) with reference to this subject: “It is with the surface that the farmer has to do. A geological Hl Dorado of fertility may be below him at a depth of 4 feet; but if the space between that and the sole of his plough, or the hoof of his live-stock, be taken up by a layer of Boulder- clay, it might as well be on the other side of the world, for all the good that it will do him.” A map which would be likely to meet the requirements should indicate the superficial drift which forms the soil, and in most cases the subsoil, by light tints of colour, decided by the materials of which the Drift is chiefly composed, heavier tints being appropriated to areas of uncovered rock. The light tints might be lined diagonally to represent a different 1 Rey. M. Close records the occurrence of transported blocks on the Dublin moun- tains, at a height of 1760 feet. See Paper Jour. Roy. Geological Society, Ireland, vol. for 1866, p. 10. * Ascertained by the Ordnance Survey Staff for Sir R. Kane. SCIEN. PROC. B.D S.,-VOL, VIII., PART VY. 2H 424 Scientific Proceedings, Royal Dublin Society. Boulder-clay beneath, when such is known to exist. The addition of letters, descriptive of the nature of the soil in each locality, and numbers attached to the letters to indicate the depth at which a marked change takes place in the subsoil, would supply all the information reasonably demanded on a good agricultural map. The small map accompanying this paper is on too minute a scale to show the different kinds of drift: its object is to represent the drift-covered areas, and those in which the rock of different formations is seen. To illustrate the nature of such information, and the great variety assumed by the detritus met with throughout the country, I have been enabled to make a collection of soils and boulder-clays from different places, and examinations of the same. The method adopted in the examinations is described in detail at the end of © the paper, where also the results appear in tabulated form. It will, I think, be admitted that detailed information of this character is a necessity, if the cultivator is to be placed fully and intelligently in touch with the geology of the country, and if the resources of the soil are to be turned to the best account. In any endeavour to stimulate and foster local effort, by technical instruction or otherwise, attention scientifically directed to the nature and properties of soils could not fail to prove advan- tageous. Agriculturists would become more intelligently aware of the deficiencies of the soil, and how best to meet them; of the resources naturally available therein, and how best to profit by them. Indeed any system of agriculture planned upon economic lines, and assuming to be in any sense perfect, must give Geology a prominent place—a fact which claims recognition in the opera- tions of an Agricultural Board. Referring to a geological map of Ireland, it will be observed that Carboniferous limestone occupies a large tract forming the central plain. Grits, shales or slate of the Carboniferous, Old Red Sandstone, and Silurian formations also cover large districts; mica-schists and quartzite, which are metamorphosed shales and grits, occur extensively in Londonderry, Mayo, and Galway. We also find igneous rocks of different ages, which penetrate and overlie the sedimentary rocks mentioned. These are divisible into acid, basic, and intermediate groups, according as they contain a greater or smaller quantity of silica. The chief consideration ; y Kitroe—The Distribution of Drift in Ireland. 425 regarding rocks, in the agricultural point of view, is their chemical composition, seeing it is from this that the elements of natural fertility must be drawn. Soil, earth, or “clay,” as known to the agriculturist, consists of a mixture of pure clay (hydrated silicate of alumina), usually with finely-divided felspar, or felspathic mud, undecayed rock particles, small stones, and more or less organic matter or humus (i.e. decayed vegetable and animal substances). If the stony particles were entirely withdrawn, and the impalpable mud or clay only were used for plant growth, it would soon become exhausted of whatever mineral nutrients it contained. The stony particles and fragments contain the stock supplies of fertilizing minerals. ‘hey are constantly undergoing decomposition in the field by oxidation and solution, owing to which their enrich- ing elements are transferred to the clayey matrix.1. An observant person, noting the stony contents of a soil, may form a fair judgment of the chemical constituents he may count upon in it —a course which will direct him, in the absence of chemical analyses, towards the most advantageous selection of manures. Here, also, we find the reason of the well-known advantages attaching to rotation cropping. Crop after crop of the same kind, which would draw most largely upon one or two minerals in the soil, would exhaust the storehouse of these minerals; while a rotation of crops gives time, before the same crop is repeated, for the replenishment of the storehouse at the expense of the stony particles. Soils derived severally from the rocks upon which they rest would rarely possess all the constituents essential to fertility. Those formed by the disintegration of acid igneous rocks, granites, felsites, &c., felspathic grits, sandstones, quartzite, shale, slate, and mica-schist would lack or be deficient in several important ingredients such as lime; while those derived from basic igneous rocks, basalt, dolerites, diorites, serpentines, &c., limestone, and calcareous grits will be deficient in potash. The celebrated fattening lands of Meath and North Kildare— 1The matrix possesses the notable property of absorbing the leading manurial _ substances—phosphoric acid, potash, lime, magnesia, and soda, as well as ammonia. It therefore serves as a convenient storehouse wherein nutriment is temporarily laid up in available form for crops. 2H2 426 Scientific Proceedings, Royal Dublin Society. “ the richest soil ” which Wakefield “ever saw turned up with plough ”—are over limestone, but being drift soil it is usually deep, and contains an admixture of other rock débris.!_ The bene- ficial effects accompanying the intermingling of various kinds of rock detritus is dwelt upon by Dr. Fream,’ who points out that the most fertile veins ofland in England follow the junction of different geological formations. In our own country the proverbial fertility of the Golden Vein in Tipperary and Limerick is doubtless due to the mingling of materials derived from the Silurian and Old Red Sandstone hills, the Galtees and Slieve Phelim on either side, with those derived from the limestone of the valley, as well as from the acid and basic igneous rocks which there penetrate the limestone. The Glacial deposits of Ireland are distinguishable as Upper and Lower Boulder-clays, both of which are frequently to be met with in the same section, and inter-glacial beds, which are strati- fied sands and gravels occasionally to be seen between the two Boulder-clays. These beds, known as “ Middle Sands and Gravels,”’ though frequently covered with Upper Boulder-clay, are not often to be observed resting upon the Lower ; and in many cases they may be regarded as washed or rearranged representa- tives of the latter Boulder-clay. Throughout wide tracts over the central plain, and on the flanks of the Dublin and Wicklow mountains, they form the surface; in which case the soil is gravelly and porous. The Upper Boulder-clay also frequently yields a porous soil, being often rudely stratified, and con- taining layers of sand. The Lower clay not only is now of great thickness in many places, as may be seen in each of the four provinces, but seems at one time to have had a very wide extension over the country. In very many places it is seen to consist chiefly of limestone débris, drawn probably from the great central plain; and to this fact must be attributed the fertility of the country on each side of the Leinster granite range, where the limestone drift covers some 900,000 acres of Dublin, Wicklow, Wexford, Waterford, Carlow, and Kilkenny. The solid crust is there formed of Silurian and other rocks equally incapable of yielding so fruitful a soil. The same may be said of 1 See Nos. 1-9 in the Table at the end. 2 « Soils and their Properties,’ pages 104, 105. Kitroe— Zhe Distribution of Drift in Ireland. 427 the fertile district skirting Bantry Bay, where a thick deposit of Limestone Boulder-clay is to be found, and of the country stretching _ north-eastward by Newbliss in the county of Monaghan, where a good soil rests upon unpropitious Silurian rock. An advantage, which should not be lost sight of, attaches to the transportation of limestone débris to areas where it does not form part of the solid crust, namely the abundant supply of limestone boulders, for burning for agricultural and other purposes, which is readily procurable from the deeper portions of the drift in such places. Nutriment may be drawn from considerable depths by such plants as lucern and sainfoin; and, through capillarity, fertilizing constituents in solution may be placed within reach of ordinary plants; yet it is manifest that ordinary herbage and rotation crops are mostly dependent upon the uppermost two or three feet of the soil and subsoil. A layer of clay, therefore, which might be over- looked in deep sections of drift, may, to the agriculturist, be a matter of prosperity or the reverse. As a general rule the uppermost layer of clay, even when it rests upon another Boulder-clay, is derived chiefly from the rocks of the immediate locality, which appear here and there through the drift—mingled with material derived from the Lower clay, and those carried from higher grounds adjoining. This will be seen by reference to soils and subsoils at Rathdrum, Glenealy, Baltin- _ glass; and at other localities, also mentioned in the table, in the eounties of ‘l'yrone and Fermanagh. In many places, especially in the higher grounds, the soils and subsoils have doubtless been formed by the disintegration of rock | in situ; and it becomes difficult to say where this runs into true drift. The latter is easily recognizable, however, when it rests (1) upon a glaciated surface; or (2) upon a Lower Boulder deposit ; or when it is (3) intermingled with foreign rock detritus, or (4) contains glaciated boulders. I add a few remarks upon the appended Table. In estimating the proportion of stones in a soil, with a view to the preparation of such a'l'able, to reckon only the boulders does not give a true idea of the soil contents; for numerous small fragments affect its character, it is needless to say, more than a few large ones; and the frequent occurrence of boulders of a certain kind does not 428 Scientific Proceedings, Royal Dublin Society. necessarily indicate an abundance of small fragments of the same kind of rock. A general estimate therefore could alone be given; and comparative abundance, which partly depends upon the sizes of the fragments selected for reckoning, is indicated by the numbers 1, 2, 3, 4, 5, according as the species of rock heading a column, is occasionally, commonly, abundantly, very abundantly, or, almost solely, represented. In giving the results as to car- bonate of lime, also, the same numbers are used with similar intent, without aiming at strict statement of quantitative results. Samples of clays, about 2 lbs. in weight, including pebbles, as they naturally occurred therein, were procured from the different places named in the Table. Soils and sub-soils, or Upper and Lower clays, from each locality, were taken at the same point, geographically. All were perfectly dried in the air, and at a ~ low oven-heat, and weighed. They were then sifted through wire netting of about =3;th-inch mesh, so as to separate all frag- ments of such a size as to admit of safe determination. These were well rubbed with the fingers over the sieve, so as to remove all clay adhering to them, and examined with the aid of a lens, after being washed, dried, and cracked with a hammer, so as to expose fresh surfaces. Little difficulty was experienced in classi- fying and arranging them in the various lithological groups set forth in the Table. The materials which went through the sieve were again sifted through wire netting of ~th-inch gauge. The gravel which lay on the sieve was rubbed between the fingers, and lightly triturated in a mortar, until no small lumps of clay remained. This was re- sifted, and all the clay and fine sand which passed through weighed, to ascertain the percentage of their aggregate in the samples. The relative quantities of carbonate of lime in the samples was ascertained by treating the finer gravel and coarse sand with cold hydrochloric acid, diluted with about an equal quantity of water. The comparative amount present in each case was judged by the degree of effervescence caused by the escaping carbonic acid gas. It will be noticed, on examining the Table, that soils in lime- stone districts are not very calcareous, though they might be expected to be so. Chert (appearing in the columns under the head of quartz) is to be frequently met with in soils over limestone, Kitroze— The Distribution of Drift in Ireland. 429 limestone boulder-clays, and gravels; and this substance is known to have been embedded in limestone. The latter material there- fore seems to have been dissolved away, possibly to a great extent since the porous Upper clays were deposited, leaving the but slightly soluble chert. Blocks and pebbles of “rottenstone,” after calcareous grits and shale, also occur abundantly in the Upper clays, with scarcely any calcareous matter remaining. ‘This dis- solving out of calcareous matter from the soil of Ireland has been hastened probably by cultivation, but is doubtless due chiefly to the humidity of the climate. [TABLE OF SOILS, SUB-SOILS, ETC. TABLE SHOWING NATURE OF ABBREVIATIONS.—L. =loam; 8. = subsoil ; r. = red; b. = brown; 1. = light; dance,—5 being maximum. OBIAHAroWr Da cdritt = Ueme, L. C. = Lower Boulder-clay ; G. = gravel; s. = sandy; g. = d. = dark ; SOILS, SUBSO Upper Boulder- cla gray; y-. = yello Prod ad Ped eo head Pt ofa edo pR eM oad te a bd 2 Sample Subjacent rock. Locality. County P Weg — Dunboyne, Meath of) ” C ” Was a: os S. of Dunboyne, 25 j (oxy Ing Cry 6 Limestone, 35 Fe 4 U. C., — Lucan, Dublin, g. L.G.,. Limestone, ota nde 30 Soules — Skerries, . a S.(10ft. below), | Limestone, oe We Gee, AA Sallins, i Kildare, b. s. L., — Cabra, Kells, . : Meath, oe We O Grit and slate, . ay “3 f, 5 U. C., — Greystones, Wicklow, - fo dle, (Qin Grit and slate, . on : 9 : lo Wing — Grange Con, . if ’ - 2 Ga ” ” is ” .G.(20ft. below), | Grit and slate, . op ts 30 1 Wo Gap ae » + | Glenealy, 5 its : A i Rathdrum, 3 es Ws Gay < — Kilsallagh, Mayo, ree Dan Oe Mica-schist, bp i i S5 Wa Ge — Near Westport, 5 (5 Ie Ohy e Limestone, 99 PP 96 b. 8s. L., _— », Newport, - s. U. C., as ” ” ” g. L.C., Limestone, He A 9 UtCr ae == S. of Castlebar, — WesCo — W. of Kilboyne, Mayo, 1s dhe Gor, Limestone, re 5 A b. D. (surface), a At Kilboyne, 55 5 x 6 Manulla, 99 Dis) O. Rk. §&., W. of Castlebar, ss U. C., Limestone, Aghagad, Roscommon, Vie Ce ” ” ” Ga Fs Limestone, Ap 20 bs Ue Cy— iss — Castlecoote, 55 ibs Cgc Limestone, .. E be sy las — Bantry, Cork, U. C. => s., ae 9 9 ap Wis Coy Grits and slate, 90 ” : USCre ee — Derryvree, Fermanagh, bees iz Limestone, 99 : b. D., : Me 1 “alte of Lishellaw, int We Gage — Omagh, Tyrone, g. L. C., Limestone, ” IDs, O.R.S., 2 mule S. of Omagh, As : b. U.C., — Newbliss, . | Monaghan, gL. C., Grits and slates, 5 5 ; D., Granite, Baltinglass, Wicklow, . D., Grits and slates, Ballinhassig, Cork, 1, 2, 3, 4, 5 comparative abi — i is] ‘a “9]8US pus 7 eee ee ee Ee a elie eae el es | 3 = o Be -9u0]SoUT Shah [Losier] Pesissh cost SPP coaifiesy| lisse Iialpee ional espa sha shs Heri cped | | cues cn a/ee a |S a po 5 a *SyOOL : aes faiaeae ome APS eh eS) ASST We See ie ESET SE STS See ars So | 4 el |p Pai, Mes sar OTR abet Se aa eal UF sige nea) gical ele leaielee aches ecole iS = & | pue oes e[vqg a Of | es ie eae ™M 3 8 “410Y9 3 zeny Gov (on ees eatiS Mirela Poe Laelia | | | [eeueeRSNKSN |S Gel te | \(ireet teeta | [eos [teins ater ae oa 2 3 ‘ey1zj1enb pue Ba casS oer ors feo Cayes ca apad, cna Cr metal FeSUES Raha) ia) SNES pet nee eee eee ae = ae} a ‘118 ‘auo}spurg . 5 Zz a "qs orpyeds[o jy 1 ASS emote Se ES TI eS IT ish Sens ks a [SLANE 2 a “SIPOL om oO 4 a =i Joceeees a 4 = oO a snoouSt poy (Byles ie ae Vee (ia eee i eee Tesslcsis ester BS Neal cal 25 i sess es eft ea -] — ane Oo . 9ULIT FO oyeuoqIBd Fo CUCL CIID OD HODEDEAY | AIG 1 D1 | Peo | [) IGDICRS NN ies ISAS REN re Sit HOS Hn alae | far Ajyuenb oaryeredu0y 4 pach ee EL PO eo el See Seg ee a a = | 2 Je) ~ ros a Ne eARIs P5 Py : ° 5 a) I tat ia i p3eseee [PR OSeaearose ates ak [18 5 pu pues osiz0) re 1D OID | HiDODrMHAAHAAMANMOANAHTHOMHA A easel : Sn ne ent ete ne emanate meer ner SNR Se ce pees" NIL mena er ON err rea Ao TABLE SHOWING NATURE 0 4 rs OILg, SUBSoryp BOULDER CLAYS IN VARIOUS PLACES ABBREVIATIONS.—L. = loam; S. =subsoil; D. = drift; U. @ L. C. = Lower Boulder-clay ; G. = gravel; s. = oe era roe Boulder- clay . \) Copa Rock Fracmenrs ann Bourpers 4 7 j 8. = sandy; g. = pray. ’ yr. = red; b. = brown; 1. = light; d. = dark; 1, 2, 3. 4 BEY 5 Y- = yellow, Conn ee Potash-Alumina-Silica Group, || 'me-Phosphate-Magnesia x D> A Deg ae p aq dance,—5 being maximum. Comparative abun. {- te) AG “8 let a 6 | Sueur: uP, a ‘co qa. a eles il2 | ®/8s] 3 [eal 3 * | A i) ue] oO. 3 on © g: ; ¥ | SP 38 ay ‘3 a3 3° a : D a No. Sample. | Subjacent rock. | Localit ] a4 | of, Pe 23 S $2 if els bg FI ee | i: C 1G me Se) ets Bs oH & |od >| oo § 3 o | Ounty, | Geologingd? & 8 ge t= na Be lel Ss 28 2 Eis | ——$__— Peoloriog@é | 8 | 8a |S | & |a*| os BBM 3% 1 ae = a 2 | sae see ac a Be & 3 = oyne, mee STAG, i : Tamectone S. of Dunboyne, " 2 = 3 sell pee == 1 3 ; a eS: = | Sateiy oe ikea 2 beer 3 a = 1 3 BareG) | Times Tho 5 gl BOASE ee | Reese, | eer = = 3 7) Cece aes eee Timestones a Palin, eee pee ear eg ae 5 2 $ | b.S.(10ft. below), | Limestone aekerries, x 4 — 1 | — el 2s 2 3 10 au oS 7 ak Siti ge g Srinll ees 3 1 2 = 5 3 pea ligace We eat > || Setting, | Saladin 3 9 || a | 8) a = 3 5 : —— Cale alls ildare, 1 2 5 : g- u. (Obra . | Grit and slate, . eure nicellss: - | Meath, Z ep 3 3 FL ad = 2 z Zz bs izes ; * we Gr ” ” A - is : => — 3 = Be - - one Cas . | Grit and slate, . mary - «| Wicklow, . 3 3 ; : a 3 — = 5 5 ol ae at a Grange Con, . Hae 5 tale Rea oe 4 2 16 L.G.(20ft.below), | Gri Oo Hace, ea eee ed — | | — aE 4 — (iy i) SE LIUve dy Gutand:clate, Oh ae ee igo |e sien mere gellis==e Seep = — 2 1g | Drift ” » + | Glenealy, ; ’ : H) = = 3 = = 3 2 Tom elee UGE po 8 || RS ee : tah eile ell 4 1 - = ilsallael =e oe — ae 20 | Ce Teen a Sewanee ee eee —. h S e ae = 2) | aL ate Gu 2 aE ee a Near Westport, .| |, 3 S| as 2 a | ow 3 — = 93 | Lb.s.L. | | oy tae = 1 9 3 5 z 3 3 5 a4 | y-s.U.C., = = » Newport, «| 5, 8 Seal |e 3] — 1 : ra ES 25 | d.g.L.C., © | tim a2 ” a = 1} — | 6 ive peo = — 96 | y. GC, estoue, Ala, i ; - ee 1 4 1 5, = — z= 37 Poe. a oe 5-0 astlebats , — 4 1 — 5) mn tes — = as 28 | 1.b.L.C., . | | Limestone Ca ae } || 8 alles = z e 9 | ’ : ” , 5 on = = = b | ae an 2a) a: b. D. (surface), . . | At Kilboyne, aes 5 seal ie ayaa es ae z ey || ean 2a ” . | Manulla, : -* 5 235 1 ; 1 = 5 wis 32 = rc - | re R.S.,. . | W. of Castlebar, 5) ! 5 a= cS 1 | = _ 5 = ae y- i Ba imestone, . | Aghagad, Roscommon, i 3 4 1 = = 5 = 24 | LG. - erimetonens || ss z ey loses eC otal i ll 5 | y-b. U.C.=S., . a Castlec a 5 =| = = 3 36 | y-L.G, . ” | Limestone, piece: 2 ke sa 1 2a |) } om — = 2 = BE ten ee i panty, Cork, Pa ere alle I 2 7 ees I = 1 = 39 | dg. L.C:, . * «| Grits and slate, as ie : 1 = l 3 = 2 = 5} 40 |}y-U.C, . — Derryvree Fermanagh, 4 = B= 2 tas u | 1 oe d. b. g. L. C:, Limestone, 5 ies i ; 1 lines A 1 3 = yi 1 ] mB I. ee : - _ | Lmile 8. of Lisbellaw. a ; 1 =o 3 : = a i | 2 | 4 y- U.C., _ Omagh, é . | Tyr = = ; = 44 | dg. PC: Limestone, mee : vey l = 2 5 A = A = ao r. a ; 0) R.S5 2 mile S. of Omagh, oie 8 1 | ae i 9 = 3 = y- b. U.C.,. — Newbliss . | Monaghan A || al tar 1 or = 47 d. g. L. om | Grits and slates, 6) : : ” : : = _— ; 1 1 oe é 2 48 | ¢-D., Granite, - _ | Baltinglass, - . | Wicklow, - — 9 ‘5 1 = = = — 49 | s.D., Grits and slates, | Ballinhassig, . | Cork, 38 Beles 2 d 1 +i A = ala eo ee 3 2 2 = [ 432 ] LULL. NOTE ON THE WORM ASSOCIATED WITH LOPHOHELIA PROLIFERA. By FLORENCE BUCHANAN. SwHorty after the publication of the Report on the Deep-Sea Polycheeta obtained during the Royal Dublin Society’s Survey off the West Coast of Ireland,’ wherein I described, as a new species, Eunice philocorallia, a worm inhabiting colonies of Lophohelia pro- lifera, the late Mr. George Brook kindly drew my attention to the mention of a similar worm, inhabiting this coral, by Bishop Gunnerus, in 1768,’ who refers to it as the Nereis madrepore pertuse. Seeing that later writers, Malmgren‘ and others, had identified the Nereis madrepore pertuse of Gunnerus with Leodice norvegica, Li, and having ascertained, by comparison with type specimens of the latter species kindly sent me for the purpose by Dr. Armauer Hansen, that the Irish specimens were not Leodice (or rather Hunice®) norvegica, L., I concluded that I was still justified in having given a new specific name, although I should, probably, have referred the NV. madrepore pertuse of Gunnerus to it. I have, however, recently come across a Paper® in the K. Norske Selsk. Skr. for 1880, in which the author, V. Storm, makes a new species, which he calls Leodice gunneri, for the Nereis madrepore pertuse of Gunnerus and the L. norvegica, auct. I have no doubt, from his description, and from the examination of the inhabitants of some Lophohelia colonies dredged off the Norwegian _ 1 This Journal, vol. vi., Part 1., No. 15. Cf. also ‘‘ Branched Worm-tubes and Acrozoanthus,”’ by Prof. A. C. Haddon, vol. viit., Part 1v., p. 344. * K. Norske Vid. Selsk. Skr. Throndhjem, 1768, pp. 50-51, PI. ii. 3 Madrepeora pertusa is the old name for Lophoheha prolifera. 4 Malmgren. Annulata Polychaeta. Ofvers. K. Vet-Ak. Forh., 1867, p. 190. ° There is no distinction between the genera Leodice and Eunice. 6 Storm V. Bidrag til Kundskab om Throndhjemsfjordens Fauna. K. Norske Vid. Selsk. Skr., 1880, pp. 92-95. . Bucuanan—On the Worm associated with Lophohelia Prolifera. 433 coast by Professor Lankester and kindly lent me by him, that Storm had before him the same worm as I have named Eunice philocorallia, and I would therefore withdraw my name of Eunice philocorallia in favour of his Hunice gunneri. Dr. E. von Marenzeller’ described in the same year as myself a Eunice inhabiting the Lophohelia prolifera colonies of the Medi- terranean ; and he refers his specimens to the Eunice floridana of Ehlers which I had mentioned as being the species most nearly allied to my Lunice philocorallia. He had only two imperfect specimens before him; and it seems to me that what differences there are between his specimens and mine are such as might occur between individuals of the same species. I hope that he will agree with me in referring his Hunice floridana to the Eunice gumeri, Storm. If he is right in identifying the species with the E. floridana of Ehlers,’ then this must be regarded as a second synonym of F. gunneri, and we have the following synonymical table :—— Eunicr GUNNERI, Storm. Nereis madrepore pertusee (JV. norvegica) Gunnerus, 1768. Leodice norvegica, auct. ex parte. (non L. norvegica, L.) Leodice guinert, Storm. 1880. (?) Hunice floridana, Ehlers, 1887. Eunice philocorallia, Buchanan, 1893. EHunice floridana, v. Marenzeller, 1893. It only remains for me to apologize to Science for having con- tributed to the long list of unnecessary specific names. 1 Denkschr. Ak. Wien. tx. Ber. Comm. Erforsch. éstl. Mittelm., pp. 31-33, Pl. i1., f. 6. 2 For my own part I would leave the Lunice floridana, Ehl., for the present, as a distinct species. I do not feel certain of its identity with the inhabitant of the Lophohelia colonies. fy coal LIV. ON SOME DRAGONFLIES IN THE DUBLIN MUSEUM OF SCIENCE AND ART. By GHEORGHE H. CARPENTER, B.Sc., Lond., Assistant Naturalist in the Science and Art Museum, Dublin. (Prare XYI.) [Read NovemBer 18; Received for Publication, Novemper 20, 1896 ; Published, Fepruary 22, 1897.1 Havine recently, with the kind assistance of Mr. W. F. Kirby of the British Museum, named the dragonflies in the Dublin Museum collection, I find that we possess examples of at least two species which appear to be undescribed. It seems desirable, therefore, to publish descriptions and figures of these; they are both refer- able to the sub-family Libelluline. At the same time I take the opportunity of figuring and describing fully both sexes of an interesting species of Agrionid from Jamaica, which was founded forty years ago by the Baron de Selys-Longchamps on a single imperfect male specimen. My best thanks are due to my friend, Mr. R. J. Mitchell, who has kindly photographed the wings of the two new species. Family.—_LIBELLULIDA. LIBELLULIN A. Genus.—MISAGRIA, Kirby. Misagria funerea, Sp. nov. (Pl. XVI, figs. 5-9.) Male.—Length, 37 mm. Expanse, 66 mm. Pterostigma, 3°o mm. Head.—Face and mouth-parts yellow; clypeus and frontal tubercle, which is distinctly concave (fig. 5), bright metallic green; 1 Trans. Zool. Soc. Lond. xii., 1889 (pp. 259, 296). — a ee CARPENTEE—Some Dragonflies in the Dublin Museum. 485 occiput, blackish. Thorax, dull black, somewhat reddish beneath ; abdomen, entirely shining black. Anal upper appendages (fig. 7), slender and curved at base, enlarged and truncated at apex, a little longer than lower appendage ; aperture of second segment bounded in front by a conical “ hood,’ at sides behind by a pair of prominent lobes; appendages rather large, terminating in small hooks pointed backwards (figs. 8,9). Wings (fig. 6), hyaline, very slightly tinged with brown at base; pterostigma, blackish ; forewings, with fourteen antecubital and ten postcubital nervures ; triangle followed by one row of three cells, then two; hindwings, with eleven-twelve antecubital and ten-eleven postcubital nervures; lower basal cell with two nervures; legs, black, with coxee and insides of front femora yellowish. Nicaragua.—(Coll. Miss Hamilton). This species differs from I. parana, Kirby, the type of the genus in having the frontal tubercle bifid instead of convex, and the appendages of second segment much less conspicuous; but, I think, the agreement in wing-neuration is sufficient to warrant its inclusion in the same genus. It may be readily separated from IW. parana by its black colour and the smaller number of antecubital and postcubital nervures in both wings. Genus.—ZYXOMMA, Rambur.? Zyxomma multinervis, sp. nov. (Pl. XVI., figs. 1-4.) Male.—Length, 52mm. Expanse, 85mm. Pterostigma, 3mm. Head.—F ace and sides of clypeus, yellow; labrum, black ; mouth-parts brown; centre of clypeus and frontal tubercle, black. Thorax and three basal segments of abdomen pruinose ; remainder of abdomen, shining black. Hinder lobe of the second segment rounded ; prominent aperture, bounded in front by large spherical “hood”; appendages small, yellow, with recurved hooks (figs. 3,4). Paired anal appendages as long as the two terminal segments ; nearly straight, evenly dilated at apex ; lower appendage 1 « Tnsectes Neuropterés,’’ Paris, 1842 (p. 30). Kirby, Cat. Neur. Odonata, Lond. 1890 (p. 35). 436 Scientific Proceedings, Royal Dublin Society. three-quarters as long, very broad at base; upper edge, straight ; lower edge, evenly rounded to a blunt point (fig. 2). Legs, deep brown to blackish; coxee and inside of femora, pruinose. Wings (fig. 1), hyaline, slightly touched with brown at base, infuscated from inner edge of pterostigma to tip; pterostigma, black; forewings, with 14-15 antecubital, and 11 posteubital nervures, first four of the latter not continuous; hindwings, with 10-11 antecubital, and 12-13 postcubital nervures. Laloki river, British New Guinea (coll. Col. St. G. Smith). This is, I believe, the first Zyxomma recorded from any part of the Australian region. Z. petiolatum, Rambur, the type-species from India, has but 12 antecubital nervures in the forewing, Z. obtusum, Alb.1 from Sumatra, has 13 antecubitals, and only 7-9 postcubitals. Its anal appendages also differ in form from those of the present species. Family.—_AGRIONIDAs. CoENAGRIONINZ®. Genus. —TELEBASIS, Selys’ (Kirby*) (= Erythagrion, Selys'). Telebasis macrogaster (Selys). (Pl. XVI., figs. 10-15.) This dragonfly was described by the Baron de Selys Long- champs in 1857°, under the name of Agrion macrogaster, from a male which had lost its head, feet, and hinder abdominal segments. Later, the Baron, in his Synopsis of the Agrionine’, referred it, with doubt, to his genus Leptobasis. There are, in the British Museum collection, several specimens from Jamaica referred, doubtless correctly, to this species, and with these agree a male and two females in the Dublin collection. Fortunately some of the feet are preserved, and as they show small but distinct 1 Veth’s Midden-Sumatra, 1881 (Neuropt., p. 1). 2 Bull. Acad. Belg. (2) xx., 1865 (p. 378). ’ Cat. Neur. Odonata (p. 155). 4 Bull. Acad. Belg. (2) xlii., 1876 (p. 955). 5 Selys in Sagra’s ‘‘ Hist. Cuba ’’ (Insectes, p. 465). 6 Bull. Acad. Belg. (2) xliii. (p. 102). —_—S « ; * ; o CarPENTER—Some Dragonflies in the Dublin Museum. 487 accessory claws (fig. 10), the species cannot be retained in the genus Leptobasis. It must be transferred to that which the Baron de Selys Longchamps called first Telebasis, later Erythayrion, though it differs from the other species in the male, having the abdomen of a dark metallic bronze above, like the female, instead _ of a bright red. Male.—Length, 45mm. Expanse, 43 mm. Head, dark bronze above and in front; with orange trans- verse edge to occipital region; pale behind and beneath. Thorax, orange ; pronotum, with central longitudinal dark stripe, spread- ing transversely on hinder lobe; mesothorax, with central and lateral dark bronze stripes; thorax, pale beneath. Abdomen, long and slender, dark bronze above, pale beneath; hinder segments, entirely dark, nearly black; appendages of the second segment (figs. 13, 14), very prominent and complicated ; central organ membranous, and recurved at its extremity ; a pair cf palp- like structures directed backwards from the middle of second segment, and a pair of prominent, rather truncated, processes from hinder margin, projecting beyond third segment; upper anal appendages much shorter than lower, stout and conical as viewed from above, truncated and depressed as viewed from side, brown in colour; lower appendages, black, prominent, and forci- pated (figs. 11, 12). Female.—Length, 40mm. Expanse, 42 mm. In colour and markings closely resembling the male, but the terminal and abdominal segments are paler beneath; these seg- ments are greatly swollen, and bear two pairs of small appendages (fig. 15). In the wings of both sexes, the quadrilateral has (as noted for the male by the Baron de Selys) the upper side two-fifths as long as the lower in the front pair, three-fifths in the hind pair, and the postcostal nervure is much farther from the first than from the second antecubital. The number of postcubitals in our specimens is twelve in the front, which it varies from nine to eleven in the hindwings. 438 Scientific Proceedings, Royal Dublin Society. EXPLANATION OF PLATE XVI. Fie. : 1. Zyxomma multinervis,. male; wings. 2. os a ,, terminal segments of abdomen,magni- fied. 3. a, = ,, base of abdomen, magnified. 4, A 42 », ventral edge of second segment and appendages, more highly magnified. 5. Misagria fumerea, male; head, magnified. ” ” », W188. 3 PS ,, terminal segments of abdomen, ~ magnified, 8. - a ,, base of abdomen, magnified. », ventral edge of second segment and appendages, more highly magnified. claws of foot, magnified. from side, magnified. 4 wv : & r lit x3 male; terminal segments of abdomen from above, magnified. Te. 4 a ,, terminal segments of abdomen from side, magnified. 13. sf Ks _,, base of abdomen, magnified. 14. as ns », base of abdomen, more highly magni- fied. 15. ne female; terminal segments of abdomen pedeenn | LV. THE GEOGRAPHICAL DISTRIBUTION OF DRAGONFLIES. By GEORGE H. CARPENTER, B. Sc., Lond., F.E.S., Assistant Naturalist in the Science and Art Museum, Dublin. (Pirate XVII.) [Read DecEeMBER 16, 1896; Received for Publication DEcrmBer 18 ; Published Aprin 3, 1897.] Tue dragonflies are insects specially appropriate for study from a distributional point of view. They are an isolated group, so dis- tinct in structure and development from other insects which resemble them superficially, that most modern entomologists regard them as worthy to be ranked as a separate order (Odonata). Then they can be traced back to a somewhat remote geological period. Wemains of insects referred without doubt to some of the existing sub-families have been found in the Upper Lias of South ‘England, and are numerous in the (Oolitic) lithographic stone of Bavaria ; while wings from the Devonian and Carboniferous for- “mations are believed by Brongniart to have belonged to insects nearly related to dragonflies, to which he applies the name of Protodonata. In studying the distribution of the dragonflies, therefore, we have to deal with a group of animals which had become differentiated into their principal existing types at a period when the dominant vertebrates were the ichthyosaurs, plesio- saurs, and dinosaurs, and when neither the placental mammals nor the higher birds had yet been developed. It is of considerable interest to find how well the regions, into which the earth’s surface has been divided to indicate the distribution of those modern groups, suit that of this ancient order of insects. Students of the dragonflies from any standpoint owe adebt of SCIEN. PROC. R.D.S., VOL. VIII., PART V. 21 440 Scientific Proceedings, Royal Dublin Society. gratitude to Mr. W. F. Kirby for his invaluable catalogue’ of the order. The present paper has been compiled chiefly from that catalogue, the nomenclature of which has been adopted in spite of some highly inconvenient revolutions, necessitated by the appli- cation of the law of priority. The most important of these is the restoration of the name Agrion to the genus which Leach called Calopteryx, a new name, Cenagrion, being coined to replace Agrion as used by Leach and subsequent writers. The recognised division of the Odonata into six well-marked sub-families has been followed, and these are apportioned among three families—Libellulidea, A®schnide, and Agrionidze—as in the usual classification. Mr. Kirby’s catalogue was published in 1890. All genera described since, so far as I have been able to ascertain them, have been: inserted; and in reckoning the number of species in each genus I have also tried to incorporate the latest results, so that the tables — given below may be taken to represent our knowledge of the subject at the end of the present year (1896). Where the name in Mr. Kirby’s catalogue differs from that in general use, the latter is added in parenthesis. | The regions and sub-regions adopted in the tables of distribu- tion are, on the whole, those of Sclater and Wallace.” I have, however, reckoned the Mascarene division of the Ethiopian as a separate region, and it will be found that the dragonfly-fauna of Madagascar and the adjacent islands has no more affinity with that of Africa than with that of Oriental Asia. Also I have divided the Nearctic region as suggested by Dr. Hart Merriam,’ adding the Canadian sub-region to the Palearctic to form’a Holarctic region, and calling the rest of extra-tropical North America, Sonoran. While the distribution of dragonflies affords considerable support to this revision of the classic zoological regions, it must be admitted that several Holarctic genera range over the Sonoran. As a rule, however, the Holarctic genera do not range southward nor the Sonoran northward beyond Merriam’s Tran- 1<¢ A Synonymic Catalogue of Neuroptera Odonata.’’ London, 1890. 2«« The Geographical Distribution of Animals.’? 2 vols. London, 1876. 3 Proc. Biol. Soc. Washington, vol. vii., 1892, pp. 1-64. Also Natural Science, vol. v., 1894, p. 53. Carpenrer— The Geographical Distribution of Dragonflies. 441 sition Zone. Dragonflies are naturally apt to spread widely, and _ it is appropriate to consider a genus peculiar to a region when it only transgresses the frontiers for a short distance or, if a large genus, with but one or two species. The Manchurian sub-region of the Holarctic has a large Oriental element in its dragonflies ; indeed it is to some extent a transition zone between the two faunas. In dealing with the Malayan sub-regions I have regarded Celebes as Oriental ; its dragonflies seem to show more Oriental than Australian affinities. There is, however, much similarity between the Oriental and Australian dragonflies, a number of characteristically Oriental forms range into Papua and even into Australia and Polynesia. The distribution of the genera of each sub-family is shown in the following tables. The figure after each genus indicates the total number of known species, and the figures in the columns show the number of species found in each sub-region. By this means it is seen at a glance how widely each genus ranges, and in what districts it is most abundantly represented. At the end of the tabular view of the distribution of each sub-family I have pointed out what genera occur in or are peculiar to the various regions. A short summary of the distribution of dragonflies, compiled from tables furnished by M. R. Martin, is to be found in Dr. Trouessart’s excellent little book! on geographical distribution. It - will be seen that the statements there made regarding the absence xo. nny i of certain sub-families from various districts require modification. The Agrionines (Calopterygine) are represented in Madagascar (though only by one species) as well as in Papua. Libellulines occur both in New Zealand and Polynesia, and Auschnines in Polynesia and Madagascar. 1“ La Geographie Zoologique,’’ (pp. 275-6.) Paris, 1890. 212 PUElEO7Z Ni Le Se Lobel sddel db Tl ded i 1 aise ai Pe dl ee alec] leh esl liste a PP PD LT eS Ts alesse Tt Poh? Tose T°?) 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SS ee | | pe) | eee [een eee eae eee el cca Unf F — 16 —|°: is (eT) sTUTOTyyO.L0v TL | a a a ee pee) ee cere ee eee eed Stee Ven tT iJ/—-— lc oe: "+ (@) BLIsestyl ae see ee me lat oe ei (Re ea ee en ef ee | ae ed ee GN ae an 29 ee *(e) stowty Ne i We | Fear a pe fe eect | al Wt ctl | |i 2.0 ‘({) vIZoyPouL1oy J, wm I a | i | 29 “(@) vuLolstule FL S| | — | — op = eH He - —|—-|—|—]" eG *({) vsddoutprag a ey Ut ea tea [een | aml fe zs “(1) eydeqortd J, SET ty ee ed Pe ee Ne | Vcr Heft fa cep |e oF “ “(7) ekjeny Sy | Re a Vie i | lee oe *({) sdornp.10p Bee ere | | ey ree fe is ee le oe “({) viustydeyy SS ee a "s “(q) ergdoysoopeyy) tobe te a aa a aa ae eH ee *(9) vtoydouons y a fall ae a0 + €(g) BIMOXOSO N eT I I tr p—bm ae a da a ad a ae dd cd I I cd a “({) ByoreUTejo 247 }—lrt Pa e mee la a cd ae a a a et oe a a ad Og “(9 eer Sg es (a ea ee ae |e a ee enh ene ae ‘+ *(T) erpayedy e f—f—f — f= — ea a et a ed ed a a I a ** £(@) VEIO0S0 N a a i *(Z) STULeyy1OJOL Ne ee SSS aS Sa ee ae SS aC ‘(T) stot O[O FT SY Ne fet |e fn Me lf lhe) | | fe cy fe "+ (Tq) srereqzoape yy So) oN | fe PR fae lV pc fal ae iN | |e ac “(g) vraqnoydurd jy =|) = ff i |p a el a it ge }—!]—}—1l— | — ya a} ar ar ee ‘+ (4) sruroyy10ultoy, J, ee ee ee eee |e sre oa ‘(g) VLULOTOF, ws eee Id i fi fs a ee a eo a ae alle |p Oe OO “+ (QT) BIMOleg ns | fale He sil |) a pc cl ere Dee eC [A ae aa | ° “+ “(e) srmmeyyetd Se ae ee | Pe hele WG tS le | 1 “5 1) (ommnoay' ede wile Se ‘(1) eaysesod[o | fe Pe Tf ot a a a ad eo I @ ihe ou "+ “(e) sTuLayytO a a ee ea ae ad 20 § ( Z) stmoyyradary —Ir ft |—|—l—}—!—!l—-Te |-—I|— II —}—FJ—|]—!i—|/—-— fT" ose *(g) sturayjortATy — Pp ee he a a a a a ed et ae ae a od On *- (7) oureyuy S| pes fe |e (reece Fg vine fees fee eel een Per (en) cea Or cet (ae a9 ‘({) vsAdouvsorg =F — | — | — |} — J — JH FH fH fe i i ea fe de a ld od: ener =) erent Ny ea aR i] oe | - — “(g) stuoqjoyoLugQ a Ne ey | — | ee eee ed a cr sae “(3) BLUBULVILG AT Le ee Ae a Feed Ia Ta A |e (GON hee Roe eve (ra =| [Samet eat ee See os * (ZI) stareyjo1g, ee | <—oa| |e eT ——" —7F4 —— _—_— oe ae) _— Pee | eed ee a a “(7) xvTdtpor0ov yp fl ed — LIBELLULIDZ. Libelluline. NEOTROPICAL HOLARCTIC. ETHIOPIAN Bi ORIENTAL.” AUSTRALIAN. BS =A malig : e : 5 i F 5 3 a S a 9 -|s 3 a - GENERA. Stee | By EH eH) |e see 2 i gS as eylecal ees ENE 5 SEO csi >a |= Us | ats Ex | ee lt ce cee | pce Ua COU Wan |S irs = § aw S z g 3) ° pel ia) ea a Rn Ls} & v, ny as a Se oO eta | a | ned | ei ecoie H eecele [ie sig (Sea Nance s ; 3 pet |) oy ecb) Gehl beet Se O,a}/a]sa[2]/o]4/alal sel ala ee IP SEE Ee Pech eh |) te tl 2 Tholymis (3), .. +. oe | ea i] } SE Sa [ee ah oy) ST fe fof) es |] Pantala (2), oe ve | 1 1 2 27—|—|— 1 1 1 1 1] — 1 1 1 1 1}/—/—|— Hydrobasileus (2), 68 ee = | a | fal a P|] es | Camacinia (2), .. an pen, . a= = | =, | = 17 1)—j|—J— \ Antidythemis (1), ae ~f—] 21/—}—-}—]}-—J]-]- = | _ = Wea, ba: wo. oer | dh RI ae Bh 8 | | fi a fs | a a a rh al ae ea le Sel} Ga Tauriphila (3), f—j| 2|— 1] — | | Miathyria (4), | 2 3 | = "| a a ieee en |e Pseudothemis (1), Fc er | | 1] | | = 454 Scientific Proceedings, Royal Dublin Society. Of the fifty-five genera of Gomphine, eighteen are found in the NzorropicaL Rrcion. Sixteen of these may be reckoned as peculiarly Neotropical, including two (Progomphus and Gomphoides) which have each a species in the Sonoran. Except for four pecu- liar Chilian genera, the Cordulegasterine section is absent from the Neotropical Region. Henpetogomphus is divided between the Mexican sub-region.and the Sonoran; though it has but four species in the Uuited States to six in Mexico, its affinities suggest that it isa Sonoran genus invading the tropics. The Sonoran RxEGIon possesses eight other Gomphine genera (not reckoning the two Neotropical stragglers mentioned above), but only three (Octogomphus, Dromogomphus, and Teeniogaster) can be claimed as peculiar. lixcluding Macrogomphus, an Oriental genus with one species in Thibet, and Jctinus, an Oriental and Hthiopian genus with three species in China, the Horarcric Recion has twelve genera of Gomphine, of which four only (Davidius, Sieboldius, Vanderia, and Zorena) are peculiar. These are, all four, small genera, and it is noteworthy that the first and second are confined to the Manchurian, the third to the Mediterranean, and the fourth to the Canadian sub-region. The Eruiop1an Recion has ten genera, of which six are peculiar, but nearly all of these have only one species each. The Mascarene Recton has five species of the wide-ranging genus Lindenia (= Onychogomphus), and the peculiar genus /somma with one species. In the OrirnTaL Reetion are found eighteen genera, just the same number as the Neotropical possesses ; thirteen of these may be reckoned as peculiar to the region. The AusTRALIAN Reeton is very poor in Gomphines. The Austro-Malayan and Polynesian sub-regions are apparently devoid of these dragon- flies; and Australia and New Zealand have but five genera. Three of these are peculiar, and it is noteworthy that the Aus- tralian Petalwra and the New Zealand Uvropetala are allied to Neotropical genera confined to the Chilian sub-region, while the genus Hemigomphus has five Australian and one Brazilian species. The wide-ranging gomphine genera show many points of interest in their distribution. Lindenia (= Onychogomphus) is dominant over the Oriental and Ethiopian Regions, and spreads | 4 4 - ; CaRPENTER—The Geographical Distribution of Dragonflies. 455 into the southern Holarctic sub-regions, having nine Mediter- ranean species. Anisogomphus, with far fewer species, has a much more discontinuous range in the tropics, and invades only the south-eastern Holarctic districts. Diastatomma and Cordulegaster may perhaps be reckoned as characteristically Holarctic genera ; but in both cases the Canadian sub-region is hardly richer in species than the Sonoran. Both genera occur in most of the European and Asiatic sub-regions of the Holarctic. The large genus Aischna or Gomphus shows a somewhat similar range, but the great majority of its species are about equally divided between the Canadian sub-region and the Sonoran. A fair number of species occur in the European and Asiatic districts of the Hol- arctic, stragglers ranging as far south as Abyssinia in the Ethi- opian, and Assam and Madras in the Oriental Region. The range of Hagenius is very remarkable; one species is Neotropical and Sonoran, one Japanese, and one North Indian; but it should be mentioned that the two latter are doubtfully referable to the genus. Ictinus is widely spread over the Oriental and Ethiopian Regions, and has five species in Madagascar; as noted above, it invades the Manchurian sub-region of the Holarctic, aud there is also one species in Australia. Anotogaster, with two species in northern India and one in Japan, is hardly more Oriental than Holarctic. Striking facts in the distribution of Gomphine dragonflies are their absence from the Austro-Malayan and Polynesian sub- regions, and their scarcity in Madagascar and Ceylon. ‘The affinity of the southern Neotropical with the Australian and New Zealand gomphines has already been mentioned. The genera in question all belong to the division Cordulegasterina, which is absent not only from Austro-Malayan, but also from the whole Neotropical Region except Chili. Such isolation of animal groups at the extremities of the southern regions has often been invoked to support the theory of an ancient Antarctic continent. In the present instance, however, we fortunately have some evidence from fossils by which to cheek our speculations. The Gom- phinae are believed to be one of the most primitive of the odonate sub-families, and remains of dragonflies referable to them have been discovered in rocks as old as the Lias. Quite a number of SCIEN. PROC. R.D.S., VOL. VIII.) PART Ve 2K 456 Scientific Proceedings, Royal Dublin Society. species have been described from the Solenhofen lithographic stone, and among these are four referable to the genus Uropetala, now confined to New Zealand. It would seem, therefore, that we have here striking proof of the truth of Wallace’s' explanation of the discontinuous range of animals in far southern lands: that they are the last survivors of groups that at one time inhabited the great northern continents. Were fossil evidence available in other cases, such, for instance, as that of the earthworms common to New Zealand and Patagonia, it would possibly be found equally needless to imagine a sunken continent in order to explain the facts. 1 Op. cit., pp. 525, 526. eines cet st a ie — — ——« I —— — — —_— — — —_— _— G — — — — — I ——s — — — — 1 ee et lag — — T — — — —_ — — —_— G — —_— — — — hs NP) FS iiees ll iS —_— — — — G = — _— Gene ebony Ge 9G] = |e zlelelefelslo eel eo eee || oe Ie adler Mliget ollie ea eryen ee el ete lace a4 © 2 uy = @ 5 9 Loa lse open ale thal jacsieo us 208 aie dll Es eval ee SR 5 ‘NVITIVULSAV - “IVINSIHO oD ANGE VOSVH — — Hi — _— _ — — _ P — _—_ — —_— — — — ge _ — _— — — — — il -_—_— — ——— —_— —_ — — I — ol = PR ee all G — —_—_ _— _— {L —_— —_— SAI Hae | ee fp ae tele a rest nD 4 — iB | b> | b | Ealpse cow ae cae Onesie ecole saa cet Ode Go| eile oele dines 2 PIB IB de |F [e ! ‘NVIGOIHLE ‘OILOUV'IOH “‘BUlNyOSaT SN pile ei iieer uote lrg SGC Miatae a@l tele ay Teper eed eal | = afl eg Bel el] Bk Sad pa ih et Saal Skee havi er EM le lel talg | oO aN: Pda he cia AEA SOIL I Sl al Se ee ee ci ee ee ¢ I) vrqopydomeyg (1) vuyosema yy —|]": ‘(1) BuTpserpoyy — |(¢ A eeeneenkge See € — (eu Adeyjuvoerty, =) eqjyuvovudy G ) eudSeyyuvoetyo 7, “(@) erqotydouqosyy (1) vrqorydeyay, euqosesyey dary ) vuyosatped euyoserydury BIqULOTOOSMO FT ) vuqoseiseq o ‘(g) vrperedorty oe ‘* (Z) vuyoseqduoy ys ‘* *(T) ~vuoseoysny ‘(Z) vuyoseqyuLoy *({) uoaAqovag Teg) eurgoseetdyy pa eee “(bp) vutosay oe “() eupOsBrovuy * “(@) eutposnosr[( ‘(@) xeuvrmoy (5) xeuy (G 2) is oe ee ‘(g ¢) ee ee (g) “(I “uvipeuesy “NVAONOS “aRey[ay “URDIXOTT *uelpizerg “ERE ITD) “VIANAD “TVOIdOULOIN 2K 2 458 Scientific Proceedings, Royal Dublin Society. The NeorropicaL Reeion possesses eight of the twenty-four genera of this sub-family ; only three of these are peculiar, but one other enters no other region save the Sonoran. In the Sonoran Recion four genera occur (neglecting Holarctic incur- sors), one only of which is peculiar. The Horarcric Rzcion has eight A%schnine genera. Three only are confined to the region, but two others (Basieschna and Fonscolombia), which enter the northern Sonoran, may be reckoned with these. The Erutopran Recon possesses but four genera, one of which is peculiar. In the MascarENE Reocion the sub-family is represented by three species of the almost cosmopolitan Anaz, and two of the wide- spread Acanthagyna. In the Orrenrat Rucion, eight genera are found. ‘Three of these (Olgowschna, Cephaleschna, and Tetracanthagyna) are peculiar, and one other (Amphiceschna) which transgresses into the Austro-Malayan sub-region may be reckoned with them. Nine genera (excluding this just mentioned) inhabit the AusTRALIAN Recion; only three (all Australian) are confined toit. There appear to be no Aischnine dragonflies in New Zealand. Of the wide-ranging genera, Anaw is nearly cosmopolitan, but appears to be absent from Australia and New Zealand. Hemianazx has a very curious range—one South Huropean, and one Australian species. schna is spread over the whole of the Neotropical and Holaretic Regions, but is almost unknown in the tropics of the eastern hemisphere; there is one (doubtful) species in India, one in Australia, and two in the mountains of Hast Africa. Gynacantha has an interesting discontinuous range in the tropics, occurring in the Neotropical and Austro-Malayan Regions, while Acanthagyna is more widely spread, being found in the Neotropical Region (where it is almost confined to the Brazilian and West Indian sub-regions) in West Africa, and in the Indo-Malayan district of the Oriental Region, some of the species extending thence into Papua. A sur- prising fact is that, with such a range, the genus has not been found in Madagascar, but Mauritius and the Seychelles have a species each. Fossil Adschninee appear to be less plentiful than fossil Gom- phine. A single Anawz is recorded from the Oligocene of Rado- boj, Croatia ; and there are several extinct dragonflies referred to dischna, the oldest of which is from the Lias. A species has been found in Cretaceous rocks in Queensland. This fact seems to indicate that the scattered range of the few species of the genus now found in the old-world tropics is due to its almost total extinction over those regions, though in Kurope and America it appears to be fully holding its own in spite of its comparatively high antiquity. sr cles ea cc Uc se | ee fd) ea ae om Pe fl SP | oe — — — — il — — -_— — se a — —_ i a — — —_— — — — — _— I _ — — —|—/|—!|—]F a [eel et (a Sete sh te [NOi | oe Per) xe — —- — —_ — I — _— — Be | eee | oo a ee eget La |p a eS a Se | ry ll ca ng Pte ating ee a oe a — — _ —_— I —_— —_— — y rs ota? ie Bs es are cats Zz Se! uvisoudjog “URITeI{sny TRIN" 3snv fTeW-"Prr OPT “uojfag “weysOpulEy ‘ENGUVOSVM “IVINGIHO “UROL “F ueoLyy “Ss ‘NYIGOIHLE “(gon y = co eee ve ae g G I TES SIN uvodoing *URLIAqIS ‘OILOUV'TION - 393.00 (ep) os UL ‘uvipeursy “NVUONOS | | el erie SIM ae sea aval ca a a glee pete gS | ‘uvol[[uy Sa) are a lpalral ’ ’ earl |e "* “(T) erqatydoeye gq ee pe = “(g1) Bion mos ee ee ee ‘(9) aLoyyny i “(1) e1oyy, ,) xAaaydooyeyg er) SNIOMOLOLIL g) ey dAoourq yy 1) oSerpoquyTs 1) wrqorqdrcy “(T) Byqepeaa(y (qh) xAroyrydury I) vSuesopyg *(g) svrtazorqy = Nes ap ‘(g) strmyoorpa yy i "+ 5) vaydsicp le H(iy2)) (vod =) veydopnesy Ea [ne ‘(g) wino[dosty SEE vies his (2) aSurpedsy ‘(z) vaoprdvg “(q) vaydrep == || 0° ve ‘(gF) vuLejo FL a ono - o. “(F1) SIv'yT Sie fe eae ee) SION == || 98 oe *(e) stseqo.mo Ny el an ite ee (1) wovyg jae MI Gig on oe “(e) oyogy ==} ee of ‘([) snusapolosg = oe oi ee “(F) STRUTT == |[s9° a *({) vanourory BE ews ere es ‘@) oydeg — ee ee oe ve :) CUIUL YL) Saltese ** (e) vuoIe I =} 08 “g1) (xAroqdoyey =) mons y el {heh I} ° = i) ete | 8 iq 3 “VUMAUNATOD “TVOIAOULOAN 460 Scientific Proceedings, Royal Dublin Society. It will be seen that of the thirty-three genera included in this sub-family, nine are peculiar to the Nrorropican Recron, and all of these appear to be confined to the Brazilian sub-region. The Chilian sub-region seems, like Australia, Polynesia, and New Zealand, to be entirely without Agrionines. The genus Hete- rina ranges through the Mexican sub-region into the Sonoran, and as far as Merriam’s Transition Zone, and its range is over- lapped by that of the Holarctic genus Agrion, which comes south as far as Florida and Texas. Hence, so far as this sub-family is concerned, the Sonoran Rezeion, without characteristic genera of its own, is merely neutral ground between the Neotropical and the Holaretie; there is no more reason for annexing it to one than to the other. The Eruiorian ReGion is comparatively poor in this sub- family. Of its four characteristic genera, two (Umma and Sapho) are peculiar to West Africa; and one (Phaon) ranges into Mada- gascar ; the fourth (Libel/ago) is specially noteworthy as the only instance in the sub-family of discontinuous range; it has ten African species, and one in the Philippines. The Orienrat is by far the richest region in Agrionines. Thirteen genera may be reckoned as peculiar, including the large and important Lhinocypha, which just transgresses the limits, having two species in Thibet, and three in Papua. Two other genera (Matrona and Caliphaea) are common to the northern Oriental and southern Holarctic (Manchurian). In the Hot- Arctic Recion we have four peculiar genera—FEpallage in the Mediterranean sub-region; Archineura, Mnais, and Paleophlebia in the Manchurian, Archinewra being confined to China, and the two last-named to Japan. Then there is the typical genus Agrion or Calopteryx spread all over the Holarctic and Sonoran Regions. The distribution of the genera of this sub-family indicates a high degree of specialisation in the fauna of the different regions. The most notable fact is the almost entire absence of the sub- family from the Australian Region, only two Philippine species of the Oriental genus Rhinocypha ranging into Papua. In Mada- gascar the group is represented only by one widely-ranging Hthiopian species (Phaon iridipennis, Burm.). And in the West CarPENTER—The Geographical Distribution of Dragonflies. 461 Indies we find but one or two species of the widespread American genus Heterina. The Agrionine are considered to be among the most primitive of dragonflies, and all the fossil insects referable to the sub-family come from the Solenhofen lithographic stone, and thus carry us back to the Jurassic period. It is, therefore, exceedingly strange that they should be unrepresented at the present day in the Australian Region, Madagascar, and the West Indies, except by species which are evidently comparatively recent immigrants from the neighbouring great continents. For it is well known that these countries are specially characterised as the sanctuaries of primitive forms of life. Yet it seems probable that the Agrionine dragonflies, for some reason, have only lately extended their range into these districts. The genera peculiar to the Neotropical Region and their allies in the Oriental and Ethiopian appear to be the descendants of a primitive stock once widespread, for there are three Solenhofen species referred to Pseudophea. Then a newer stock seems to be represented by the genera at the head of the table—Agrion and its allies. These are mostly Holarctic and Oriental, and it is remarkable how many genera are represented at the confines of the two regions, suggesting that from the Manchurian district the insects spread westward to Europe and Africa, and eastward into North America. The last genus in the table, Pa/eophiebia, con- fined to Japan, is of special interest as the most primitive of living dragonfiies, combining the body of a Gomphine with the wings of an Agrionine.' 1D. Sharp: The Cambridge Natural History, vol. v. (p. 427). London: 1895. PPT Lb i a Sescateae PETS a eee Z ie) ealeocle a dias N a aq a 8 Je) H 4 — (4) » iS 5 Bt a ial rely foeielp es “NVITVULSOV ETM Per —m. —a, —— L as a at SS ee eee eee ee a s) — I — — a — — — — — — — — — — os —— —< — — —_ G — —_ —~ —_— — —_— — — — _— — —, —_~ — — —~ — — G — — — — — — —_ —— _— — — — =; — ——_ — = 1 — — —— ——o — — —— — =) — — __ — —< — — — — —— — — — —_— — —— G —— — — — ——e ——. — —— or ——s —— — — ~~ es —— LI = ET gst [ie | [a EY a Hare eee | Ped eae alse — — — —_— —_. — — — — —— — —— — —_— _™ Il oe —, —_ — I ——s, —— —_— —— ——_ — —— — — — — —_— — — —— — — — =— — ed et — If —- — — ew — _ — — — — — — —— — —= — — — — — — V —_— — —— —— — — —. — 9 cos 006, < (rsin Od): In the case of cylindrical coordinates we proceed in the same manner. In the same way if PP’ (fig. 4) be taken as an element of an electric current, it may be replaced by two elements of the same strength along PM and MP’, respectively, and the fundamental — formulee of Electrodynamics may be deduced at once. ee ee ee ee = a [ 475 ] LVII. REPORT OF THE COMMITTEE consisting of PROFESSOR W. J. POLLAS, LL.D., F.R.S., B. LLOYD PRAEGER, B.A., B.E., A. F. DIXON, M.B., ann ALFRED DELAP, B.A., B.E., appointed by the Royal Dublin Society to investigate the recent Bog-flow in Kerry. Drawn up by R. Luoyvp Prarcrer and Pro- FEssor Sotias. (Puates XVIII. anp XIX.) COMMUNICATED BY PROFESSOR SOLLAS, LL.D., F.R.S. [Read January 20; Received for Publication, January 22; Published Aprit 8, 1897.] Tus daily newspapers of Tuesday, the 29th of December, 1896, announced that, in the early hours of the morning of the previous day, a bog, situated at the head of the Ownacree valley, seven miles N.N.E. of Headford, near Killarney, had burst, and dis- charged a fluid mass, which, pouring down the valley of the Ownacree, had devastated the surrounding country in its course. Without loss of time the Royal Dublin Society appointed a committee, consisting of Professor W. J. Sollas, Mr. R. Ll. Praeger, Dr. A. F. Dixon, and Mr. A. D. Delap, to investigate and to report on the phenomenon. The committee left Dublin on the afternoon of Friday, January 2nd, and devoted Saturday, Sunday, and the early part of Monday to the work. They desire to acknowledge in this place the kind assistance rendered them by Mr. Maurice Leonard, 3.p., acting for Lord Kenmare, on whose estate the bog is situated. The following summary comprises the results of their observa- tions and inquiries, supplemented by information derived from the full accounts which appeared in the Dublin press. A dry summer had been followed by a wet autumn, and, about nightfall on December 27th, a heavy downpour of rain set in, accom- panied by a south-easterly gale. Somewhere between two and three o'clock the following morning, the edge of the Knocknageeha bog, which overlooks the Ownacree valley, gave way, and liberated a vast flood of peat and water. There was no immediate warning of SCIEN. PROC. R.D S., VOL. VIII., PART V. 2M 476 Scientific Proceedings, Royal Dublin Society. the catastrophe, and no one witnessed the actual rupture. That the flood of escaping fluid did not at once acquire its full force is proved by the testimony of Mr. Arthur John Keeffe, as given in the Freeman’s Journal of January 4th. He states that, driving to Killarney fair, his horse stopped near the bridge on the Quarry Lodge road, and could not be induced to proceed; he then jumped off the car, and found himself standing in mud knee-deep. After vainly endeavouring to cross the bridge, he retraced his steps and roused some neighbours. He returned with them in half-an-hour’s time, to find that he could not approach within, as he states, a quarter of a mile of the bridge. There is an inexacti- tude, however, about this statement, as the total width of the flood at this point does not exceed the distance mentioned, viz. one quarter of a mile. Although the outburst was clearly not instantaneous, it evidently proceeded with great rapidity, as is witnessed by the circumstances of a lamentable loss of life. The bog gave way along the line of a turf-cutting from 4 to 10 feet deep, parallel to which, and about 3800 yards below it, runs the Kingwilliamstown road. A small stream, coming from the bog, passes under this road. Close by this stream, on the lower side of the road, was situated the house of Cornelius Donelly, Lord Kenmare’s quarry steward; it was of the ordinary type, of one storey, with walls of rubble masonry and a thatched roof; it stood about 12 feet below the level of the road, and at a short distance from it, the interven- — ing space being occupied by a garden. The house was entirely swept away ; Cornelius Donelly, his wife, and family of six children ~ all perished; the bodies of.some of them, and those of their live- — stock, together with articles of furniture, were carried down the — valley, and were found at various points along the course of the flood, a portion of one of the beds being picked up, a few days later, in the Lake of Killarney—fourteen miles away. From the fact that the whole family perished, and that those bodies which — Pe ee Pe ee gn et te ee er ee were recovered were without clothing, it would appear that the s rapidity with which the flood rose was so great as to afford them — no chance of escape. The Flood.—After bursting from the face of the turf-cutting already mentioned, the first obstacle the flood encountered was — Report of Committee of Investigation on Bog-flow in Kerry. 477 the road leading to Kingwilliamstown, which ran on an embank- ment about 6 feet above the level of the cut-out bog; it over- whelmed this for a width of a quarter of a mile, and continued its course to the road to JSillarney, a short distance below, pouring as it passed, a small cataract of mud into the old quarry at the cross-roads. ‘The Carraundulkeen, a small streamlet, tributary to the Ownacree, passes under the Killarney road, through a culvert about 8 feet by 5 feet; this was speedily blocked with masses of turf, and the rising flood poured across the road, carry- ing away the tall hedges on both sides that stood in its course on its eastern side. On both this and the Kingwilliamstown road huge masses of the more coherent upper crust of the bog were left stranded. A short distance further down, on the northern side of the Carraundulkeen valley, is situated a valuable limestone quarry, which the flood filled to a depth of 15 or 20 feet; as 1t impinged on the lower corner of the entrance, it surged up in a great wave 3 or 4 feet above the highest level within the quarry, which is marked as a horizontal line along the quarry walls. _ Beyond the quarry it continued down the valley for a straight run of three-quarters of a mile, to enter, almost at right angles, the valley of the Ownacree or Quagmire river. Checked, as it encountered the opposing side of this valley, the flood rose along its middle line, where its velocity was greatest, 8 feet above its sides. A small cottage stands near by, and its floor is 5 feet below the maximum height of the flood. . It owes its escape to the fact that it is situated about 100 yards on one side of the middle line of the flow. After entering the main valley, the flood continued its career for a mile and a half to Annagh- bridge, where the Ownacree meanders through flat bog and meadows. ‘These, and the road which crosses the bridge, were inundated, and the muddy fluid broadened out into a black lake, half-a mile in length by 600 yards in breadth. A breach was made in the road close beside the bridge. On the margin of the submerged flat stands the cottage of Jeremiah Lyne; he and his family had a narrow escape. ‘The flood, in its downward course, encountered the back of the cottage, and rose against it 5 feet, sweeping two haycocks, which stood behind the house round to the gable. The family were awakened by water pouring in. They 2M 2 478 Scientific Proceedings, Royal Dublin Society. were unable to unbar the door owing to the pressure of 3 feet of fluid, and escaped by climbing through the window and wading to higher ground. Below Annagh Bridge, the force of the flood was less felt. At Barraduff Bridge, ‘‘ Six-mile”’ Bridge of the Ordnance map, where the Ownacree joins the Beheenagh river, the Ownacree is 20 feet wide, and the flood rose 8 feet; below the jsanction the stream is 30 to 50 feet wide, and the flood rose 6° “feet; at “Six-mile ” Bridge it rose to the top of the arches, 10 feet above its normal level; at the bridge two miles below Headford, the level of the flood was about 4 feet above the stream, and finally at Flesk Bridge, near the Lake of Killarney, one foot. The flood attained its maximum height during its first great outburst in the dark hours of Monday morning. At daybreak, the roaring flood of black fluid, bearing on its surface huge masses of the lighter crust of the bog, had already become confined to the central portions of the valley, but still ran across the road and over the site of Donnelly’s house. The flow, which continued with constantly diminishing violence for the whole of Monday, was not regular, but intermittent, swelling and diminishing as fresh portions of the bog gave way, and slid downwards into the torrent. Every fresh outburst was accompanied by loud noises, likened by bystanders to the booming of big guns or the rumbling of thunder. Over the sides of the valley the settlement of the peaty part of the fluid had already taken place, and, as drainage continued, increased somewhat in consistency. ‘The disruption of masses of bog continued at intervals down to Friday, January Ist. When we visited the scene on Saturday, January 2nd, the flow had lost its torrential character, but a turbid stream, many times increased beyond its usual volume, occupied the river bed. Mr. James Barbour, who visited the place on Saturday, January 8th, reports that one could then have stepped across the stream, so that by this time it must have shrunk to nearly its usual size. The Bog before the outburst.—The district in which the bog is situated forms the southern portion of a high and undulating area of Coal-measures, generally bog-covered, and attaining a height of over 1200 feet, some. miles to the north-west. That part of the bog in which the outburst took place is about 750 feet above the Report of Committee of Investigation on Bog-flow in Kerry. 479 sea; it forms the watershed, and drains eastwards into the river Blackwater, and west into the Ownacree. ‘To the north-east the bog descends in a gentle slope towards the Tooreencahill stream, a branch of the Blackwater; to the north-west towards the main branch of the Ownacree, and westwards towards the Carraundul- keen streamlet, into which it burst. Judging from the size of the valley in which this branch flows, it would appear that the greater part of the bog drained into the last-mentioned stream. At the inquest evidence was given that a “ wet vein’ existed in the bog continuing the direction of this stream. It is of interest to observe that the bog rests partly on Coal-measures, and partly on Carboni- ferous limestone, which is brought up by an anticlinal, and separated from the Coal-measures by a fault, which runs for some miles east and west, through the very middle of that part of the bog which lies adjacent to the outburst. The bog, like most others, possessed a convex surface; it extended in three arms, which sloped downwards in the three directions of drainage already specified. In all other directions it is bounded by gently rising cultivated land. It was not drained by any superficial streams, nor was any large amount of water discharged at any point from beneath. ‘The “‘ wet vein”’ already mentioned was evidently a line of drainage. The peasantry state that the surtace of the bog was excep— tionally soft; they admit, however, they could walk across it in the middle of winter. According to the evidence of Cornelius Sullivan (Freeman, December 31st), the place was ‘‘shaky in patches, and persons crossing the bog could avoid these.”’ The flora of the bog shows that it was no wetter than bogs usually are. The plants which form its surface are members of the normal bog- flora. The vegetation consists of a tangle of Calluna Erica (Ling), Evica Tetralix (Cross-leaved Heath), Narthecium Ossifragum (Bog Asphodel), Scirpus cespitosus (Club-rush), and Molnia varia (Purple Melic grass), with the usual abundant undergrowth of bog-mosses, of which Sphagnum rubellum is the prevailing species, while S. cuspidatum, var. plumosum, fills the numerous shallow pools, which, as usual, were scattered over the surface. ‘Tufts of the moss Racomitrium lanuginosum were frequent, and the lichen Cladonia rangiferina (Ikeindeer moss) was abundant, mixed with the hepatic 480 Scientific Proccedings, Royal Dublin Society. Pleurozia cochleariformis. The above list furnishes satisfactory evidence that the surface of the bog was not unusually wet; indeed, the plants characteristic of wet bogs, such as Andromeda polifolia and Schollera Oxycoccus (Cranberry), though searched for, were not to be found. The bog had been cut for turf in two places—on the north- eastern slope, which faces towards the Blackwater, where the cuttings were of no great extent; and along the western edge, where, as already stated, they formed an irregular line, running parallel to the Kingwilliamstown road. It was from the latter cuttings that much of the local fuel was obtained. As regards these, Timothy Carey gave the following evidence at the inquest :— “The edge of the bog was not firm; we could cut only a depth of four sods, and a breadth of four sods from the edge. You would sink in the bog if you went in further; after a while, when the exposed place dried, you could cut down four sods more, and then you came to the clay.”! “For the last few years, they could not cut deep in the bog; it had a habit of closing in.’” The cutting does not appear to have been judiciously planned, except at the southern end, where it extended in wedge-shaped gashes into the bog; but for the rest of the distance it was cut in an irregular line, transverse to the line of drainage. An evidently faithful description of the bog, as it existed in 1811, is given by Mr. Nimmo? in his account of the bogs of Kerry and Cork. It appears under the heading “ No. 6 or the Quarries Bog”; the area of which is stated to be 2103°6 Irish, or 8407°5 Hnelsh acres. “The bog is at a high level, being about 650 to 700 feet above the sea, and is in this place on the summit of the county; its waters passing on the east to the Blackwater, and on the west to the Awinegrea and Flesk to the Lake of Killarney. It is mostly pretty firm and requires little more than surface drainage.” ‘Under the estimate of the cost of a scheme for draining the bog, 1 Freeman, Dec. 81. 2 Trish Times, Dec. 31. 3 Appendix to Fourth Report of the-Commissioners appointed to inquire into the nature and extent of the several bogs in Ireland, and the practicability of draining and cultivating them: ordered by the House of Commons to be printed 28th April, 1814, p. 84. Pe ee eT eee Te a ee ee ee . — Report of Committee of Investigation on Bog-flow in Kerry. 481 QUARRY,LODGE 6, CARRAUNDULKEENG@ Li RY eel TT ene? Naaetey He As ay Z ES Gr ewveuimy ee \ Ds es me SCALE oF MILES fo} " I 1% 2 Fie. 1. Map showing the subsided portion of the bog, and the a:ea over which peat has been deposited in the valley of the Ownacree. The letters A to P indicate the directions in which the sections shown in figs. 2 and 8 were taken. 482 Scientific Proceedings, Royal Dublin Society. we find the following interesting item :—‘ Two cuts into a swamp on the summit, 304 perches at 3s. 6d., £53 4s.” | The Bog after the outbwrst.—My. Leonard states that on visiting the bog at mid-day on Monday, about eight hours after the out- burst, its surface for about a mile above the site of the turf-cutting was no longer convex but level. As the escape of fluid material continued, the surface correspondingly sank, till a shallow saucer- shaped depression was formed, opening by a narrow trough into the Carraundulkeen stream. At each side of the mouth of this trough there could still be seen the undisturbed ends of the turf- cutting; the central portion, for the width of a furlong, had dis- appeared. Looking eastwards from this point, a wide, broad valley appeared to extend upwards into the bog. On January 2nd, when we saw it, this depression was 7 furlongs in length by 5 furlongs wide, with a maximum depth of 28 feet. From careful inquiries it would appear that the former elevation of the centre of the bog above the undisturbed edge of the depression was about 7 feet, so that the total subsidence amounted to no less than 35 feet. The margin of this collapsed portion of the bog was clearly marked, so that we had no difficulty in tracing it on the 6-inch map, from which the plan (fig. 1) accompanying this Report is reduced. The slope near the side was comparatively steep, lessening towards the middle; the steep margin was marked by concentric fissures, which, when of sufficient width, were occupied by great masses of ‘sludge’? which had risen from below. Near the margin, the area of these crevasses, as compared with that of the still remain- ing upper surface, was about 1:3; the proportion increased to about 2:1 near the centre, where also the fissures were no longer concentric, owing to the fact that a definite flow of the whole mass of the bog had taken place down the valley. Over the two areas, marked on the map by close parallel lines, the surface had entirely disappeared. Walking round the margin of the depressed area, it was observed that, in addition to those portions which originally sloped towards the Ownacree, other adjoining areas, which pre- viously had sloped towards the east and north, had shared in the general subsidence, and now formed a part of the newly-formed valley which we have described as opening to the westward through the former turf-cutting. This curious feature will be ‘ r ' Report of Committee of Investigation on Bog-flow in Kerry. 488 clearly seen from the sections of the bog given in figs. 2 and 3. A striking indication of this reversal of slope was furnished by several shallow surface drains which had been cut in order _to dry the surface of the bog for turf-cutting at its eastern extremity. These, when made, had a slope of one in forty towards the Blackwater valley ; they were now broken across, so that what had been the upper half sloped with an equal gradient towards the Ownacree. It was along the southern edge of the basin that the greatest amount of marginal disturbance had taken place, the proportion of crevasses to crust here being quite 2:1. This appears to have been the shallowest portion of the bog; several ridges of the underlying gravel had somewhat disturbed the general subsidence of the peat. The portion overlying the erests of the ridges had remained 7m situ, while that on their slopes had broken away on both sides, and flowed down through the depression between them. Soundings with a pole in these depres- sions showed hard bottom at from 5 to 8 feet. This was the only place where an 8-foot pole gave an indication of bottom. Owing to the increase in the number and width of the crevasses, on entering the depression from its margin, it was quite impossible to make any observations for more than 20 or 30 yards inwards from the edge. But there appears to be no doubt that along the line of greatest depression, the thick covering of bog had been entirely removed ; in some places the hard bottom could be seen. Effects of the Flood.—Immediately above the Kingwilliamstown road we pass from the area of subsidence to the region of flow. The flood has left behind it, in the upper portion of the valley, a deposit of peat averaging 3 feet in thickness, here as everywhere contrasted by its black colour with the grass land or other surface on which it rests. Its compact convex margin, like that of out- poured oatmeal porridge, often 2 feet in height, serves equally well to define it; so that it was an easy task to determine and map the high-water level of the flood. The surface of the deposit was everywhere broken by great roots and trunks of Scotch firs, which, in their enormous numbers, bore convincing testimony to the evis- ceration which the bog had undergone. The appearance of this extensive sea of black peat, with its protruding stumps of blackened trees, overlying fertile fields, was a sight melancholy in the extreme. 484 CROSS SECTIONS 2) Oo Old_surface_ ~----- = -- 4 = = i) NORTH it ta w S S. + a as (e) <¢ NORTH WEST SOUTH EAST 0 5000 FEET | = Gee Sections through the bog of Knocknageeha. Vertical scale, 6 times the Horizontal 485 Bog-flow in Kerry. ton on of Investigat tlee o ; Report of Comm ‘qned yo ysodep a4} pur pooy oy3 Aq poureyze yy Soy oy} MoYs OF ‘satovua () aU} FO AOT[VA OY} S8O1O¥ SUOIJOIS-SSO1Q “POOF OY} JO Os1NOD OY pur vor PopIsNs oy} TSNOLY} WOTj0es [eutpuytsu0y ‘e ‘Ong 1334 001 a ae —_ 8NOILDIS SsouD 1344 008 0 0g AIDUDU PAO 2 noqv 00g wning NOILOIS TYNIGNLIONOT ante Sites s 1334 006 _—" 5 od 486 Scientific Proceedings, Royal Dublin Society. The presence of so much floating timber in the waters of the flood must have greatly enhanced its destructive power. One of the largest of these trees, a huge stump with roots 12 feet across, was seen lying some distance up the course of a tributary stream, and on the top of its overhanging bank, at a distance of two and a half miles from the scene of the outbreak. ) The erosive effects on the bed of the Ownacree are well marked. We observed places where it had been lowered 6 feet; e.g. at a spot about half a mile from Annagh-bridge; a lane, which had extended across this as a shallow ford, had been cut through by a trench, 20 feet in width and 6 feet in depth. In other places the stream has cut for itself a new course. The lamentable fate which overtook the Donelly family has been already alluded to. Many farmers have suffered serious loss by the tearing up and washing away of their potato pits, which were situated near the banks of the stream. ‘The filling up of the limestone quarry is a serious inconvenience; for, although the work of clearing it out has been already commenced, and it will ultimately be worked as before, it must remain useless for some time. No other quarry exists in the neighbourhood, and lime is the only manure in universal demand. ‘The roads can he cleared without much difficulty : the breaches made in them are not serious. The farmers will feel most seriously the loss of their land. On most of the holdings the best land was situated along the river banks; and, in the upper portions of the valley, this is now covered to a depth of 3 feet with a solid deposit of peat. At Annagh-bridge the average depth has decreased to 2 feet ; here the deposit is of a finer grain and more liquid. According to the inquiries made by the police, in the four townlands which occupy the east bank of the river between the scene of the outburst and a point a little below Annagh-bridge, close on 300 acres of land have been thus buried.’ The tenants being all small holders, the loss of their best grazing has ruined them. Premonitory Sounds.—Strange and contradictory rumours are prevalent among the peasantry as to whether any symptoms of the approaching catastrophe were noticed. Sergeant King, R.1.c., states positively that he and other officers on patrol heard rumbling 1 Freeman's Jowrnal, January 2nd. Report of Committee of Investigation on Bog-flow in Kerry. 487 noises some days before the occurrence. Further, it is certain that some of the peasantry were so alarmed by sounds, which they _ attributed to the “‘ banshee,” that the parish priest was sent for to _ pray with several families. The evidence as to whether the actual bursting of the bog was accompanied by sounds is conflicting. Some state that they were awakened by a loud roar; others, including Mr. Mac Sweeney, of Quarry Lodge, slept as usual. But this negative evidence is of little or no value ; for, in one instance, the flood passed within fifty yards of a cottage, breaking down and sweeping away the trees of the adjacent haggard, without arousing the occupants. The phenomena attendant on or preceding the catastrophe, to. which special attention may be directed, are the following :— 1. A dry summer was followed by a spell of wet weather, which commenced in September ; and heavy rain fell immediately before the outburst. 2. An earthquake, which had its epicentre situated in Wales, or on the borders of the principality, occurred on December 15th, and is said to have been felt in Miltown-Malbay and other places ‘in Ireland. This preceded the rupture of the bog by five days. 3. A fault trending from east to west crosses the collapsed area of the bog ; and the Coal-measures, which form high ground to the north, dip towards it, ¢.e. southwards. 4. The stream of the Carraundulkeen was continued as a “ wet line,” or line of drainage, into the bog. At the origin of this was. a swamp. 5. The neck of the bog was cut through by a working face, which thus crossed the line of drainage. 6. The centre of the collapsed portion of the bog stood, before the outburst, 7 feet higher than the sides. 7. The bog was disrupted along the line of peat-cutting, and liberated a deluge of water charged with peat. The volume of the discharged material we estimate to have amounted to about six million cubic yards. 8. As a consequence of this discharge the crust of the bog subsided ; so that, after the lapse of some days, its centre had 488 Scientific Proceedings, Royal Dublin Society. fallen 35 feet below its original level, forming a depression with a maximum depth of 28 feet. It is obvious that, before the outbreak, the condition of the bog was that of a viscous fluid enclosed within a resistant wall, The pressure of the fluid and the tension of the envelope were then in equilibrium. Owing to an increase in pressure or a decrease in the tensile strength of the containing wall, this equilibrium was destroyed, the envelope was ruptured at its weakest part, and the viscous fluid, under a head of pressure rushed down the inclined surface provided by the natural drainage of the country. Before entering further into the discussion of the causes which led to the outburst, it will be convenient to present here informa- ti onwe have collected concerning similar occurrences which have taken place in the past. We give first a list of those which have affected the bogs of this country; they are arranged in chronolo- gical order. Account oF Boe Fiows 1n IRELAND. A.D. 1697, June 7, Kapanihane Bog, Co Limerick, near Charle- zille-—This occurrence is so quaintly described in a letter dated June 7, 1697, that it is worth quoting verbatim et literatim :— “On the 7th Day of June, 1697, near Charleville, in the County of Limerick, in Ireland, a great Rumbling, or faint Noise was heard in the Earth, much like unto a Sound of Thunder near spent; for a little Space the Air was somewhat troubled with little Whisking Winds, seeming to meet contrary Ways: And soon after that, to the greater Terror and Afrightment of a great Number of Spectators, — a more wonderful thing happened; for in a Bog stretching North and South, the Harth began to move, viz. Meadow and Pasture Land that lay on the side of the Bog, and separated by an extra-_ ordinary large Ditch, and other Land on the further side adjoining to it; and a Rising, or little Hill in the middle of the Bog hereupon sunk flat. “This Motion began about Seven of the Clock in the Evening, fluctuating in its Motion like Waves, the Pasture-Land rising very high, so that it over-run the Ground beneath it, and moved upon . Report of Committee of Investigation on Bog-flow in Kerry. 489 its Surface, rowling on with great pushing Violence, till it covered the Meadow, and is held to remain upon it 16 Feet. “Tn the Motion of this Earth, it drew after it the Body of the Bog, part of it lying on the Place where the Pasture-Land that moved out of its Place it had before stood ; leaving great Breaches behind it, and spewings of Water that cast up noisom Vapours : _ And so it continues at present, to the great Wonderment of those that pass by, or come many Miles to be Hye-witnesses of so strange a thing.” This communication was accompanied by a map and detailed description by John Honohane.* a.p. 1708, Castlegarde Bog, County Limerick.—The Castlegarde bog, or as it was then called Poulevard, moved along a valley and buried three houses containing about twenty-one persons. It was a mile long, a quarter mile broad, and about 20 feet deep in some parts. It ran for several miles, crossed the high road at Doon, broke through several bridges, and poured into the Lough of Coolpish.” A.D. 1745, March 28.—Bog of Addergoole, Dunmore, County Galway.—About mid-day, after a heavy thunder-shower, about 10 acres of bog, the front of which was being cut for turf, moved forward and down the course of a stream, and subsided upon a low pasture of 30 acres by the river side, where it spread and settled, eovering the whole. The stream, thus dammed back, rose till it formed a lake of 300 acres, which, by the cutting of a channel, was subsequently reduced to 50 or 60 acres. This area, together with the 30 acres of meadow over which the bog spread has been destroyed for purposes of husbandry.’ A.D. 1788, March 27.—Bog near Dundrum, County Tipperary.— “A large bog of 1500 acres, lying between Dundrum and Cashel, in the county of Tipperary, began to be agitated in an extraor- _ dinary manner, and to the astonishment of and terror of neighbour- * Philosophical Transactions, vol. xix., pp. 714-716, October, 1697; and Boate, Molyneux, and others, a Natural History of Ireland, p. 113, 1755. 2 Dublin Evening Telegraph, 2nd January, 1897, 3Ouseley, Trans. R.I.A., vol. ii., Science, pp. 3-5, plate I., 1788. 490 Scientific Proceedings, Royal Dublin Society. ing inhabitants. ‘The rumbling noise from the bog gave the alarm, and on the 30th it burst, and a kind of lava issued from it, which took its direction towards Ballygriffen and Golden, overspreading and laying waste a vast tract of fine fertile land belonging to John Hide, Esq. Everything that opposed its course was buried in ruins. Four houses were totally destroyed, and the trees that stood near them torn up by the roots. ‘The discharge has been incessant since the 30th, and how far it will extend cannot at present be determined.” A.D. 1809, 16th December.—Bog of Rine,Camlin River, Co. Long- ford.—‘“ In the night, during a thunderstorm, about 20 acres of the bog burst asunder in numerous places, leaving chasms of many perches in length, and of various breadths, from 10 feet to 3 inches. The rifts were in general parallel to the river, but in some places the smaller rifts were at right angles to it; not only the bog, but the bed of the river was forced upward; the boggy bottom fillmg up the channel of the river, and rising 3 or 4 feet above its former banks. In a few hours 170 acres of land were by these means overflowed, and they continued in that state for many months, till the bed of the river was cleared by much labour and at considerable expense.” The bog had been an unusually wet one. It did not sink in any particular place. “Several earthquakes were felt in distant countries about 16th December, . . . and it is not absolutely impossible that a com- — munication may exist between them” [the earthquake and the bog-slide. } A.D. 1819, January.—Owenmore Valley, Erris, Co. Mayo.—“ A mountain tarn burst its banks, and heaving the bog that con- fined it, it came like a liquid wall a-down, forcing everything — along, boulders, bog timber, and sludge, until, as it were in an instant, it broke upon the houses [of a small village], carrying all before it, stones, timbers, and bodies, and it was only some days after, that at the estuary of the river in Tullohan Bay, the bodies of the poor people were found.””* 1 Gentleman's Magazine, vol. lviii., p. 355, 1788. 2 Edgeworth, App. § to 2nd Report of Bog Commission, p. 176, 1811. ° Otway, ‘‘ Sketches in Erris and Tirawley,” p. 14, 1841. 4 Report of Committee of Investigation on Bog-flow in Kerry. 491 A.D. 1821, June 26.—Bog of Kilmaleady, near Clara, King’s Co.—The excellent report on the outbreak of this bog, communi- - eated to the Royal Dublin Society by Sir Richard Griffith, has supplied us with the following excerpts :— “The bog of Kilmaleady, from whence the eruption took place, situated about two miles to the north of the village of Clara in the King’s County, is of considerable extent ; it may probably contain about 500 acres; in many parts it is 40 feet in depth, and is con- sidered to be the wettest bog in the country. It is bounded on all sides, except the south, by steep ridges of high land, which are com- posed of limestone gravel, and beneath of cavernous limestone rock, containing subterranean streams ; but the southern face of the bog is open toa moory valley, about a quarter of a milein breadth, which, for nearly half a mile in length, takes a southern direction in the lands of Lisanisky, and then turns at right angles to the west, and continues gradually widening for upwards of two miles. . . The bog of Kilmaleady, like all other deep and wet bogs, is composed for the first eight or ten feet from the surface down- wards of a reddish brown, spongy mass, formed of the still undecomposed fibres of the bog moss (Sphagnum palustre), which, by capillary attraction, absorbs water in great quantity. Beneath this fibrous mass, the bog gradually becomes pulpy, till, at length, towards the bottom, it assumes the appearance, and, when examined, the consistence, of a black mud, rather heavier than water. “The surface of the bog of Kilmaleady was elevated for upwards of 20 feet above the level of the valley, from which it rose at a very steep angle; and its external face, owing to the uncommon dryness of the season, being much firmer than usual, the inhabitants of the vicinity were able to sink their turf-holes, and cut turf at a depth, of at least 10 feet beneath the surface of the valley, and, in fact, until they reached the blue clay which forms the substratum of the bog. ‘Thus the faces of many of the turf-banks reached the unusual height of 30 feet perpendicularly : when at length, on the 19th day of June, the lower pulpy and muddy part of the bog, which possessed little cohesion, being unable to resist the great pressure of the water from behind, gave way, and, being once set in motion, floated the upper part of the bog, and continued to move with astonishing velocity along the SCIEN. PROC. R.D.S., VOL. VIII., PART Y. 2N 492 Scientific Proceedings, Royal Dublin Society. valley to the southward, forcing before it not only the clamps of turf, on the edge of the bog, but even patches of the moory meadows, to the depth of several feet, the grassy surface of which heaved and turned over almost like the waves of the ocean; so _ that, in a very short space of time, the whole valley, for the breadth of about a quarter of a mile between the bog-edge and the base of the hill of Lisanisky, was covered with bog to a depth of from 8 to 10 feet, and appeared everywhere studded with green patches of moory meadow. ... A considerable deposit of heavy, black bog-mud,... at present fills the bottom of the stream... “In the centre of the bog, for the space of about one mile and a-half in length, and a quarter of a mile in breadth, a valley has been formed, sloping at the bottom from the original surface of the bog to a depth of 30 feet, where the eruption first took place. In this valley or gulf there are numberless concentric cuts or fissures filled with water nearly to the top. “The valley between the edge of the bog and the road of Kilbride, for a length of half a mile, and an extent of between — 60 and 80 acres, may be considered as totally destroyed. It is covered by tolerably firm bog from 6 to 10 feet in depth, consist- — ing at the surface of numberless green islands, composed of — detached parts of the moory meadows, and of small rounded ~ patches of the original heathy surface of the bog, varying from — 2 to 10 feet in diameter, which are separated from each other by brown pulpy bog; and the bed of the original stream is elevated to — about 8 to 10 feet above its former course, so as to flow over the road. ... The whole distance which the bog has flowed is about 3 miles — in length, namely one mile and a half in the bog, and the same — distance over the moory valley; and the extent covered amounts to about 150 acres.’ : Sir William Wilde gives the following additional particulars — taken from the daily press of the time :— “At 7p.m., of the evening of the 26th of June, the south front of the bog of Ballykillion, or Kilnalady, gave way to a depth of 25 feet, and, with a tremendous noise, commenced to move down 1 Journal of the Royal Dublin Society, vol. i., pp. 141-144 and map, 1858. j Report of Committee of Investigation on Bog-flow in Kerry. 493 the valley at the rate of about 2 yards an hour, with a front _ 200 yards wide, and about 8 feet deep. ... It continued to move for more than a month. ~ © About the same time the Ferret bog, about 16 miles north- east of Kilnalady, was strongly agitated, boiling up to a great height.””! A.D. 1821, September. Joyce Country, County Gahvay.— “Upwards of a hundred acres of land, on which crops were growing and several families resided, were heard.to emit a sound resembling thunder; the earth then became convulsed, and even- tually this large tract moved down towards the sea, leaving the whole route over which it passed a complete waste.’” A.D. 1824, December 22. Bog of Ballywindelland, Coleraine.— A portion of this bog containing 80 or 100 acres gave way and passed into an adjoining valley; it gradually advanced on the firm land, during the day, at the rate of 2 feet per minute. A.D. 1831, January. Bog near Geevagh, Co. Sligo.— After a sudden thaw of snow, the bog between Bloomfield and Geevah gave way; and a black deluge, carrying with it the contents of 100 acres of bog, took the direction of a small stream, and rolled on with the violence of a torrent, sweeping along heath, timber, mud, and stones, and overwhelming many meadows and arable land. On passing through some boggy land, the flood swept out a wide and deep ravine, and a part of the road leading from Bloomfield to St. James’s Well was completely carried away from below the foundation for the breadth of 200 yards.’ A.D. 1835, Sept. 17. Fuairloch Moss, Randalstown, Co. Antrim. (A very large bog overlooking a valley.)—All day a portion of it swelled up till the convexity was 350 feet in height; at 5 p.m., with a sound like a loud, rushing wind, it sank several feet, and a collection of tufts, mud, and water moved N.E., not rapidly, and soon stopped. It swelled up again, and about midday on the 19th, it again burst with a similar noise, and the flow crept on till the 2lst, when it ceased 1 Census of Ireland for the year 1851, part v., vol. i., 1856, pp. 189, 190. 2 Thid., p. 90. 3 Tbid., p. 198. 4 Lyell, ‘‘ Principles of Geology,’’ 10th ed., vol. ii., p. 504. 2N2 494 —— Scientific Proceedings, Royal Dublin Society. till the 23rd, being interrupted by ditches; on the 23rd, at 3 p.m., it suddenly rushed forward. Continuing, it surrounded a cottage 10 feet deep, rose over the Belfast-Londonderry coach road, crossed it with a width of 300 yards, and poured over the far bank in a cascade, and continued down the valley till it reached the River Maine, which it dammed temporarily, and killed all the fish. The flow into the Maine did not cease till Sept. 28. The deposited area of bog was three-quarters of a mile long, and 200 to 300 yards wide, with a maximum depth of 30 feet. The place where the bog had swelled up 30 feet, afterwards sunk 20 feet below its original level, and a small pool occupied the hollow.’ A.D. 1840, January. Bog of Farrendoyle, Kanturk, Co. Cork. —The bog was 10 feet in thickness, resting on a substratum of yellow clay ; the pent-up water undermined a prodigious mass of bog, and bore it buoyantly on its surface; twenty acres of valuable meadow were covered, and a cottage was propelled and engulfed; a quarter of a mile of the road, from Kanturk to Williamstown, was covered 12 to 30 feet deep.’ a.p. 1870, December 14, 9 a.m. Bog, near Castlereagh, Co. Roscommon.—The bog is situated 5 miles north-east of Castlereagh, on the watershed of the river Suck and the Owen- —. na-foreesha, a tributary of Lough Gara; it overlies cavernous — limestone. The eruption took place from the face of a turf- — cutting, which was from 12 to 15 feet in height. A very rapid — flood of peat and water poured forth, bearing on its surface — large masses of the crust of the bog; it rose 10 feet over Baslick — Bridge, and left a deposit of peat, which covered 165 acres of low — ground and extended for some 6 or 7 miles down the valley of the — Suck. A valley was formed in the peat bog half a mile in length — and 20 feet deep. A.D. 1873, October 1. Bog 3 miles east of Dunmore, Co. Galway. — —The bog was connected with the Dunmore river by the — Carrabel, a small stream. It was considerably elevated above the 1 Hunter, Magazine of Nat. Hist, vol. ix., May, 1836, pp. 251-261. * Freeman's Jowrnal, January 3, 1840 (copied from the Cork Standard). 3 Report to the Board of Public Works, by Mr. Forsyth, 26th and 28th January, 1871. Report of Committee of Investigation on Bog-flow in Kerry. 495 surrounding country, its edges presenting the appearance of high turf banks. “A farmer digging potatoes suddenly observed a brown mass slowly approaching. Leaving his spade in the ground, he went for the neighbours, and on his return the mass of moving bog had half covered his potato field, and completely hidden his corn field from sight, except a few stacks which remained on a knoll, an island in the midst of a scene of desola- tion.”’! The bog slowly flowed down the valley of the Dunmore, burying three farm-houses, and covering about 3800 acres of pasture and arable land, 6 feet deep. The peat was cut along a perpendicular face, 25 to 30 feet in height, which extended down to the underlying gravel. It was from this cutting that the outburst took place. The flood of peat and water moved rapidly at first, but afterwards slowly, and continued in movement for 11 days. It carried away roads and bridges. The subsided portion of the bog extended eastwards from the face of the cutting for a distance of a quarter of amile; its greatest breadth measured also a quarter of a mile: down the middle, a valley from 20 to 25 feet deep was formed, and about the sides the crust was torn asunder. ‘The numerous crevasses so formed were filled to the top with black peaty fluid.’ a.D. 1888, January 25. Bog near Castlereagh, Co. Roscommon. —‘ The bog was situated between the villages of Moor and Bas- lick; in about two hours, it moved a mile in a south-westerly direction towards the River Suck; after a short interval, the movement continued, some 4000 acres of land were covered, three houses had to be deserted, several roads were blocked; the Ballinagare-road being covered 15 feet deep. leven or twelve years ago the Tulla bog, situated about a quarter of a mile from. the scene of the present outbreak, burst and discharged itself into the river Suck.’ A.D. 1883, January 30. Bog near Newtownforbes, Co. Long- Jord.—‘A. bog near Newtownforbes has commenced to migrate, covering turf and potatoes.’”* ! Savage, ‘‘ Picturesque Ireland,’’ pp. 234-285, illustr. (n. d.). 2 Report to the Board of Public Works, by Mr. Forsyth, 31st October, 1873. 3 Freeman’s Journal, January 27, 30, and 31, 1883. + Tbid., January 31, 1883. 496 Scientific Proceedings, Royal Dublin Society. A.D. 1890, January 27. Bog at Loughatorick North, Co. Galway. —The bogis situated in the townland of Loughatorick North, on the Slieve Aughty Mountains, nearly on the watershed, and 300 feet above Ballinlough Lake, which lies N.H., and into which the bog drains by asmall river. ‘The bog consists of two portions, separated by a narrow neck, where exposed rock was seen after the outburst. The upper and larger part is 70 acres in extent, the lower only 15 acres. The latter began to move 3 days before the upper portion: in its centre was a small lake to which an underground stream could be traced ; after the outburst, this lake became dry. Aftera fall of 4 i snow, a sudden thaw set in on the 24th January; three days later — a movement of the bog commenced, and continued till Ist February. Great masses of peat were carried away by the black flood into the Ballinlough Lake, which was nearly filled with peat and the out- washed trunks of trees. The lowlands were covered with peat over an area of 100 acres, and for a depth of 12 inches. ‘Traces of the flood were visible to a height of 6 or 7 feet on the trunks of trees which stood in its course. The upper part of the bog sub- sided from 10 to 15 feet; its margins were much rent with fissures." 1895, August 9. Dungiven Bog, Co. Derry.—The site was in the townland of Briskey, at the east slope of Benbradagh, an extensive mountain bog 10 to 380 feet in depth, sloping at a gradient of about 1 in 12. Where the burst occurred a small stream runs underground for about a quarter mile, the ground above it being firm, so that cattle grazed on it. On the evening — of August 9th there was a thunderstorm, but not accompanied by any excessive rainfall. The weather during the summer had been normal. In the night, probably before midnight, between 2 and3 | acres of bog gave way. For some 40 yards length at its lower end, the bog burst out entirely. Over the rest a tapering area 300 feet wide by 600 long, the ground subsided about 10 feet, leaving — great blocks of the solid crust, broken up in a fantastic way. A very considerable flood of water and peat poured down the stream, — which eventually joins the River Roe. No damage was done, as — the gradients are steep, and the land not under cultivation, but a 1 Report to the Board of Public Works, by Mr. A. T. Pentland, 24th November, 1890. Report of Committee of Investigation on Bog-flow in Kerry. 497 cottage situated beside the stream 1 mile below the scene of the ~ outburst narrowly escaped being washed away. A deposit of peat was left on the banks of the stream for a considerable distance. There is evidence of several similar slides having taken place in the district.’ Outside Ireland the bursting of bogs appears to be a pheno- menon of great rarity. Klinge, in a valuable Paper on bog eruptions states that, after a diligent search through European literature, he has been able to discover only two examples that did not occur in this country. To these we are not able to add more than two others. Abstracts of the accounts of these occur- rences are given below in chronological order. Account oF Boc-FLows ELSEWHERE THAN IN IRELAND. A.D. 1768, autumn. Stuckhauser bogs, Trewenfeld, Duchy of Oldenburg.—Lasius states’ that an outburst of this bog took place, similar to that of Tullamore, but of less extent; it lies over the ordinary marsh floor, which is impervious to water, and is more than 20 feet deep. ‘The summer was exceedingly wet, and doubtless this is the explanation of the occurrence.” A.D. 1772, December 16. Solway Moss, Cumberland, England.— Lyell states that the bog, on December 16th, 1772, having been filled like a great sponge with water during heavy rains, swelled to an unusual height above the surrounding country, and then burst. The turfy covering seemed for a time to act like the skin of a bladder retaining the fluid within, till it forced a passage for itself, when a stream of black half-consolidated mud began at first to creep over the plain, resembling in its rate of progress an ordinary lava-current. No lives were lost, but the deluge totally overwhelmed some cottages, and covered 400 acres. The highest parts of the original moss subsided to the depth of about 25 feet, and the height of the moss, on the lowest parts of the country which it invaded, was at least 15 feet. 1 Information supplied by Mr. H. C. Moore, C. E., Dungiven. 2 Lesquereux, Untersuchungen tiber Torfmoor: German edition by Lengerke, with remarks by Sprengel and Lasius, 1847, p. 165, Anmerk. 498 Scientific Proceedings, Royal Dublin Society. A.D. 1871, November 29. Stanley, Falkland Isles, off Cape Horn. —‘“ Just after midnight one of the inhabitants was awakened to find that his house was surrounded by a black moving mass of peat, several feet in height, and travelling down the hill at about four or five miles an hour: following up the course which the slip had taken, the hill presented a curious appearance ; from the peat- bank down to the brow of the hill, a distance of about 250 yards, the surface peat lay in confused heaps, direct from the opening of the bog. The water, or liquid peat, travelled over the ground faster than the heavier bodies, which were left standing 3 or 4 feet above the level of the ground. Proceeding to the top of the bog, I found a depression extending over 9 to 10 acres of ground, the edges cracking and filling up with water.” . . . An endeavour to drain the bog by cutting a trench did not succeed, ‘‘ owing to the soft peat welling up from the bottom and filling the trench again.” A.D. 1886, June 2. Stanley, Falkland Isles.—A second outbreak of the same bog took place 200 yards westward of the scene of the previous slip. A stream of half liquid peat, over 100 yards in width, and four or five deep, flowed suddenly through the town into the harbour, blocking up the streets, wrecking one or two houses in its path, and surrounding others, so as to imprison their inhabitants. One child was unfortunately smothered in the peat, and an old man is reported to be missing. ‘The slip is assigned to the unusually heavy rains which fell during the few previous days, and which the drains constructed by Mr. Bayley in 1878 proved insufficient to carry off. * On comparing these records with each other, and with the account already given of the recent catastrophe, a close general similarity will readily be perceived to characterize them. The recorded outflows differ partly in magnitude, but chiefly in the rapidity of flow of the escaping material. The rate of flow 1 Extracts from a letter by Acting Governor Bailey to Governor Callaghan. Quarterly Journal of the Geological Society, vol. xxxv., Proceedings, pp. 96, 97, 1879. 2 Extracted from a letter by Lieut. Governor of the Falkland Islands, Arthur Barkly, to the Rt. Hon. Earl Granville. Quarterly Journal of the Geological Society, vol. xliii., Proceedings, p. 2, 1887. fe ' : Report of Committee of Investigation on Bog-flow in Kerry. 499 is evidently a function of the slope of the ground and the viscosity of the fluid, and the latter depends on the ratio between the amount of water and of solid contents present in the moving material. A difference also exists in the proportion of solid erust to liquid contents. The largest proportion of solid material is met with in the flow of 1745. In this case the bog shifted bodily, and the movement might, with more justice, than in most instances, be compared to that ofalandslip. The late eruption of Knockna- geeha was one of the largest on record, and is also characterised. by the unusually large proportion of water present in the liberated material. Hence its rapid flow. SuMMARY oF Previous EXPLANATIONS OF BoG-BURSTS. In giving the following short review, we desire to acknowledge our indebtedness to Klinge’s valuable paper alluded to below. Leonard’ remarks that “a great quantity of water collects in damp years on the bottom of the bog, which water held down by the turf seeks a subterranean outlet.” Bronn’ points out the living peat bog may absorb from 50 to- 90 per cent. of water, and so swell to double its volume: it is to: this cause that the dome-like form is due. When the bog lies on an inclined plane, heavy rains will cause the bog to swell, and possibly burst. ' Lesquereux® states that if peat bogs are deep, and lie higher than the neighbouring country, and if the drainage is not properly attended to, water will accumulate at the bottom of the bog. As the surface does not rise any higher, and water is no longer absorbed by the vegetation, the lower layers of the peat become softened and converted into a kind of soup. ‘The crust of the bog bursts under the pressure of the contained fluid. Senfft* repeats Bronn’s view regarding excessive surface absorp- tion, adding that, if a bog swollen by rain is situated on a slope, it 1 Mineralogische Taschenbuch ftir das Jahr 1823, 3 Abt., p. 861. 2 Handbuch einer Geschichte der Natur. Bd. ii., Th. ii., Stuttgart, p. 496, 1843. 3 Untersuchungen ueber Torfmoore, p. 165, 1847, Anmerk. B 4 Die Humus-, Marsch-, Torf-, und Limonitbildungen, p. 102, 1862. 500 Scientific Proceedings, Royal Dublin Society. ; tends to bulge out like a bag down the slope, and finally bursts. He lays special stress upon the rapid bladder-like sveiee that sometimes precedes an eruption. | Noeggerath! says, if the felt-like covering of extensive bogs, highly strained by water and gas, suddenly breaks, mighty streams of mud pour forth. Kinahan’ has attributed some bog-slides to shrinkage cracks, formed during drought, and enlarged by the subsequent entrance of water. Klinge,? the latest investigator of these phenomena, propounds — an entirely new theory, and expresses views on the constitution of — peat bogs differing in some respects from those usually accepted. He labours to prove that the absorption of sub-aerial water, or the — development of large quantities of gas, are insufficient to account for the bursting of bogs. He regards mountain bogs as of two — different kinds, those which have grown in the uniform climate of — the western coast of Europe, characterised by a continual increase — in the degree of decomposition from their surface downwards, and those which have arisen under the influence of severe changes of climate; the latter consist of alternating layers more or less highly decomposed. The different layers have different saturation limits for water, and these limits once attained never alter. There is no vertical movement of water through a bog. ‘This view, the author asserts, stands in complete opposi- — tion to statements made by older writers as to the absorption by bogs of from 50 to 90 per cent. of their bulk of water. In support of his contention that peat bogs are impermeable, he — ‘appeals to pools on their surface, often 5 to 10 feet in depth, separated by peat-walls only 3 to 5 feet thick, and yet with — water levels differing from each other by several feet. The — dome-like form of mountain bogs he regards as inexplicable, — unless a high capacity for water in conjunction with imperviousness — be admitted for the peat. Excessive rainfall accumulates in pools — on bogs, which are drained by surface channels. Pools only © occur on bogs near the wet western coast of Europe. The author 1 Der Torf, 1875, p. 12. } 2 Valleys in their relation to Fissures, Fractures, and Faults: London, 1875, p. 10. — 3 Ueber Moorausbriiche, Botanische Jahrbiicher, Bd. xiv., 1892, p. 426. Report of Committee of Investigation on Bog-flow in Kerry. 501 makes an interesting observation on the dessicating effects of sphagnum on the air over mountain bogs. This is so great that onthe leeward of these bogs, at least in Norway and Nova Zembla, an aero-xerophytic (dry air) flora occurs. The immediate cause of an eruption of a bog is, according to - Klinge, the violent irruption of water into the bog from below. | In discussing Klinge’s views we may first point out that the mountain bogs of this country belong to his first class—those in which the decomposition of the vegetable matter increases from the surface downwards. The decomposed peat is heavier than water, and tends to accumulate at the bottom; the crust on which the growing plants are found is lighter than water, and floats on the top of the bog. It is between the crust and the lower layers that we should expect the most fluid portion of the bog to occur. We cannot agree that the crust is impermeable; the fact that bogs can be drained is opposed to such a view; nor do the pools which Klinge instances afford conclusive proof in its favour; they may be explained by a difference in permeability of the surround- ing peat, and that they are being drained of water, or have been supplied with it, it is possible, at different rates. The subject is discussed in the Report of the Commissioners on Bogs, some of the surveyors taking the same view as Klinge. Thus Mr. Townsend? states that strata of turf of a firm and close texture, impervious to water, exist in every bog; and he is “decidedly of opinion that the springs under the bog do not penetrate upwards through this substance, but that the wetness of bogs is caused by the rain-water falling on the surface, and lodging in the small cracks and indentures”’; the water slowly drains away by-the natural descent of the surface. A similar opinion was held by Mr. Longfield, who says that ‘the vegetable matter of which the bogs in his district (River Brusna) are com- posed is perfectly retentive of water, so much so that the numerous duck-pools and lodgments of water in bogs are almost all upon different levels”’; and he mentions “two considerable bodies of water at the distance of a few perches only from each other and yet differing 23 feet in level.’ Mr. Edgeworth remarks of certain 1 Second Report Commission on Bogs, Appendix No. 7, p. 154, 1811. 2 Tbid., p. 5. 502 Scientific Proceedings, Royal Dublin Socieiy. bogs in the district of the Inny and Lough Ree that “some drains — 6 to 7 feet wide, and as many deep, had been made from the — centre of the bog to its outlet: these were about 20 perches asunder, and although they had been finished for twenty years, and were not choked up, the bog did not appear to have been affected by them.’ The Commissioners remark on this subject that the lakes on bogs are situated in hollows, and the material forming the banks of these is more solid than that of the general crust.* We see no reason to doubt the correctness of the accepted view, — which regards a peat bog as consisting of a fluid interior, more or less viscous, and an outer felted crust. The closing up of drains and canals, cut into hogs, is a familiar phenomenon which supports this view. It has been remarked by Sir R. Griffith, who states that “every kind of bog drain will in time become narrower at the top than when originally formed; the drains made by the canal company. . . have now become considerably narrower at the top”’;? and by Mr. G. H. Kinahan, who informs us that on one occasion he opened a canal in the hard margin of a bog, 20 feet deep and 380 feet wide at the top; this, twelve years later, was — reduced to a depth of from 5 to 6 feet, and to about the same width. — Mr. Kinahan predicts that in ten or fifteen years’ time the site of — the recent debacle will be scarcely visible; the present depres- — sion in the bog will have become converted into a hollow from 10 to 15 feet below the level of the surrounding bog. Although the felted envelope of a bog is close enough at its margins to afford support to the fluid interior, it is often broken by — holes in the middle; into these the soft, black fluid of the interior — oozes up, as everyone who has traversed a wet bog is well aware. Through such openings rain-water may make its way, and join the liquid accumulation below the crust. All mountain bogs present very similar features; and the fact - which appears most wonderful is not that they burst, but that they do not do so more frequently. Evidently the crust, in its natural state, is, as a rule, equal to 1 Second Report, Commission on Bogs, p. 6, 1811. 2 Tbid., p. 6. 3 Tbid., p. 9. 4 | 4 | | j > Report of Committee of Investigation on Bog-flow in Kerry. 508 the task which the contained water puts upon it, and it is only when weakened by unusually deep cuttings that it gives away. If this cause be considered sufficient, it might be thought un- necessary to discuss the question further, yet we think that the eruption of water from below, as Klinge suggests, though not as he postulates sudden and violent, may sometimes, perhaps fre- quently, have played a chief part; that, indeed, not a decrease in the support afforded by the crust, but an increase in the pressure of the contained fluid may have been the last in a train of causes which brought about the catastrophe. In the present instance the whole structure of the country (fig. 4) would lead the geologist to ~ MIDDLE COAL Ww 35 , Soe egal eK4 Z roa Dp eee Pees NES Greate aay o DRY, a °bb SP Bag laofp hy 4 \ SS es In AP aden SS peewee oa > = = a SSO g DinGiat Le anchors \ bo? DRE yAdD PRI y A ee ae Y \ a Fie. 4. Geological Map, founded on that of the Geological Survey, showing the fault which underlies the sunken portion of the bog. Scale 1 inch to a mile. suspect the existence of springs: the southward dip of the beds forming the rising land to the northward of the bog, would convey subterranean water towards it from a large catchment basin; the fault underlying the bog would serve as a conduit, through which this water would rise beneath it. The water draining away from such a spring would give rise to the wet line in the bog. The existence of such a spring would also afford an explanation of the origin of the bog; about the waters escaping from it, bog plants 504 Scientific Proceedings, Royal Dublin Society. would naturally spring up, and would thence spread outwards and upwards; but since their growth would commence near the spring, it is there that we should expect to find the bog attaining its greatest height above the level of the surrounding country. That the water contained within many bogs is supplied by springs was fully recognised by careful observers as early as the beginning of the present century, as will appear from the follow- ing quotations :—‘“ The summits . . . of bogs are generally the deepest and invariably the wettest parts . . . large lakes covering _ the surface. . . . The summits are composed of fluid peat. The fluid peat at the summit is of so soft a nature that boring irons descend 16 to 18 feet by their weight alone. Over the fluid peat is from 1 to 2 inches of water. In summer the bog dries, but the summit continues wet for 200 or 300 acres, and supplies streams. Springs are often met with in the deepest part of the bog, rushing up sometimes with much violence, and often strongly impregnated with sulphate of iron, carbonic acid, and earth. The water of almost all the springs in the bogs deposits oxide of iron on the beds of the streams in passing from the source through the bog. There is a very strong chalybeate spring issuing from the fissures of a limestone rock, whose beds are vertical, in the bottom of a cut-out bog near Newpark. . . . I have observed of a deep drain, made several years ago, to take away the water from a lake in the bog of Moanahinch, that it still continues to discharge a consider- able quantity of water, although the lake has been drained... . This water issues from springs, which perhaps first formed the lake. There is also a constant discharge of water throughout the year from other lakes in the same bog near the summit, and consequently without any supply but from springs.”’ And the same writer concludes as follows:—‘‘ That the wetness of those bogs originates from springs within themselves, and that the principal springs must be at the summits.” Mr. Edgeworth also remarks, with reference to Ringowny bog, in the Inny valley, that it is “kept marshy by springs of its own, of which there 1 Aher., Appendix No. 2, Third Report, Commission on Bogs, p. 65. 2 Tbid., p. 66. Report of Committee of Investigation on Bog-flow in Kerry. 505: are several... . These springs are not concealed, but filled to the brim by water issuing from the gravel beneath them.””! Mr. G. H. Kinahan has also clearly recognised the connexion which exists between the loughauns or pools on the surface of a bog and subterranean springs.? The existence of springs has been recognised in the peat bogs of other countries, as in Norway. _ Thus Stangeland speaks of small tarns which occur in certain bogs, mostly those which lie in narrow valleys with an uneven ae ee bottom. These he considers must be caused by subterranean springs. It is worth notice in passing, however, that this author assigns another origin to the swamps which occur on many large bogs; these he regards as a necessary stage in the development of a bog, which occurs when it is large enough to receive and retain a great quantity of water. This accumulates in a superficial pool, and when the wind agitates the water, the peat moss, which is very sensitive to wave-motion, cannot thrive at the bottom of the pool. In dry seasons the pool becomes a black muddy surface, and in wet it forms a clear layer of water.® In view of the probability that much of the water discharged from the bog had its origin in springs, the occurrence of an earth- quake about ten days before the disaster should not be overlooked. The earthquake was felt from Kew, in Surrey, to as far west probably as Miltown-Malbay, its epicentre seems to have been situated near Hereford; and we might fairly expect that the disturbance which produced it should have continued along the ereat structural features trending east-to-west, which extend from Wales through the south of Ireland. Any change in the distri- bution of material along the fault, that we have several times mentioned as passing beneath the scene of the late eruption, would be likely to affect the subterranean drainage. The two views, one that looks for the cause of the outbreak in heavy rain, and the other which invokes the action of springs, and perhaps of earthquakes, are not mutually exclusive; both causes may have acted together, or sometimes one, and sometimes the 1 Second Report, Commission on Bogs, Appendix 8, p. 192. 2 Op. cit., pp. 108-109, ° Torvmyrer of G. E. Strangeland, Norges Geologiske Undersiigelse, Kristiania, 1892, p. 63. 006 Scientific Proceedings, Royal Dublin Society. other. Some outbursts, however, almost certainly owed their origin to the influx of subterranean water, e.g., that of Randals- town (September 17th, 1838), when the bog swelled up till its convexity was 30 feet in height, and after sinking, was again raised in the course of a few days. The question as to which of the two, in a given instance, is the correct explanation, is evidently not one of mere theoretical interest, for much will depend on our knowledge of the source of water issuing from bogs in devising plans for their drainage. This was clearly recognised by the surveyors employed on the Commission on bogs, as is shown by the following :— “‘To ascertain whether the wetness of these bogs originates solely from rain-water falling on the surface, or from springs in the interior of the bogs, or from both, is an inquiry of very great importance, and deserving serious consideration, as the system of drainage should be regulated thereby ; if, for instance, it was supposed to originate from rain-water only, shallow water surface drains would be sufficient, but should it be found to originate — from springs rising up through the bog, a system of deep drains calculated to intercept and convey the water of those springs to a more convenient outlet should be adopted.” Although a great work was accomplished by the Commission — on Bogs at the beginning of the century, little has been done since ; — a few organized attempts have been made from time to time to turn : some of our peat bogs to better use, but the want of success which ~ has generally attended them seems to have discouraged further — effort, and thus a possible source of vast national wealth has been — left to undeserved neglect. 4 ‘ 4 5 On the Continent it is far otherwise ; there the investigation of — peat bogs receives the attention that the importance of the subject , demands. So great is the interest taken in the subject in Germany, ~ that a society numbering more than 600 members exists there, having for its object the advancement of knowledge of peat culture, under which term more is comprised by German workers than might be supposed. This society publishes “‘ Mittheilungen” fortnightly ; those for 1896 make a volume of 476 pages in royal — 1 Aher, Third Report, Commission on Bogs, Appendix iii., p. 60.° ~ Report of Committee of Investigation on Bog-flow in Kerry. 507 octavo. roc. R.D.S., N.S., Vol. VIII. Plate XVI. Oxford Press Flate XVII. fly Faunas. £E guator FO \ | Oriental KZ Australian Ra eS ee eee ees Oe ee Se | | | | Map of the World; showing the pepe range of the Dragonfly Faunas. La BS GAS A i ba Bey be ee Seientifie Proceedings, Royal Dublin Society. mately vertical pull now withdraws the drill, retaining within it the excavated rock. It is evident that the saws will retain the final dotted position shown in the plan. When, in fact, the current is stopped, the spring pulling the drill upwards maintains. the vanes pressed against the base-plate above them and so fixes them in their position of extreme deflection. In this position the saws meet across the opening of the drill-shaft, and the loss oe the specimen is impossible. In place of cutting-saws, a cutting wire or r chain may be used. This wire may be lodged in a horizontal groove within the drill. at its lower extremity. When the drill has attained its lowest. position, the release of the fans effects the rotation of a loose collar which carries the fans, rotates on the drill-shaft, and is attached to one extremity of the cutting wire by means of a rigid extension. extending downwards in the inside of the drill-shaft. The rota- tion of the collar is thus accompanied by the gradual pulling of. the cutting wire into the diametral position. When this position. is attained the horizontal cut is complete. This form has the. advantage of requiring a drill of less thickness in the walls than the first form, but experiment alone will show how far it may be relied upon in the case of a hard rock. In many cases the rock beneath the sea is probably eovered with but a shallow thickuess of mud or sand. In such cases it- would be possible to modify the apparatus so as to enable it to bore through this covering.. Experience will probably show that. the electrical measurements and observation of the duration of- drilling will, at any rate, after a single trial of the rock, enable a a sufficient estimate to be made, by those at the surface, of the depth to which the drill has penetrated. An electrical release may then be employed to stop the vertical cut and liberate the vanes, and so commence the horizontal cut or simply reversion of the direction of rotation of the drill might be used to stop the vertical cut, and at the same time call the vanes and saws into. | operation. ‘I'he mechanism would be of the simplest kind. . But trial of the form first described, upon ground where bare rock is assured, will at once be a test of all such modifications so: far as their essential features are concerned. . [ 515 ] LIX. SHORT ACCOUNT OF AN EXPERIMENT TO DETERMINE THE EXACT POSITION IN A FOCUS TUBE FROM WHICH THE X-RAYS ARE EMITTED. By THE VERY REV. GERALD MOLLOY, D.D., D.Sc. [Read Drecemper 16, 1896. Received for Publication Maxcu 26 ; Published Jury 9, 1897.] I roox a deal board, 7 inches long by 5 broad, and three-quarters of an inch thick, into which I drove fifteen long slender nails, making three rows, with five nails in each row. The nails had small circular heads, and when fixed in position stood about one inch above the level of the board. This board I now attached to the back of a fluorescent screen E, by means of two elastic bands, as shown in figure 1 (p.516). The fluorescent screen was mounted on a stand A, the foot of which fitted tightly into a wooden socket F, at the end of an arm B, capable of moving round a centre C. The centre of motion C was simply a screw driven into the lecture table, and allowing the arm to move freely round in a circle. The Focus ‘Tube was now carefully adjusted so as to make the plane of the platinum plate vertical, with its centre in the hori- zontal line of the middle nail in the deal board, and in the vertical line passing through the centre of motion CO; and the fluorescent screen was made perpendicular to the arm B, so that in all positions of the arm, the screen and the deal board attached to it should be tangential to the circle described. When these arrangements were completed, I placed the wooden arm B in such a position that the plane of the fluorescent screen made an angle of about 45° with the plane of the platinum plate in the Focus Tube. The room having been then darkened, the current was ttirned on, and the shadows of the nails appeared on 516 Scientific Proceedings, Royal Dublin Society. the screen, as shown in figure 2. The shadow of the central nail appeared as a black spot a little larger than the head of the nail, and the shadows of the other nails went out symmetrically from. the centre: those above went upwards, those below downwards; those on the right went to the right, those on the left went to the left. The interpretation of these facts was very simple and clear: Figure 1. the area of radiation was small, as shown by the sharpness of the shadows, and the centre of that area was in the line of the central nail produced. The question now was, what would happen to the shadows if I moved the arm B round the centre CO, thus making the board of nuls revolve in a circle to which it would always remain 4 Mottoy—Source of X-Rays ina Focus Tube. 517 tangential. This was a question which it was easy to answer,’ with the arrangements before me. When I moved the arm, the shadows remained absolutely fixed, and the figure on the screen remained, in all positions of the screen, exactly what it had been in the first position I had tried. It followed, that the centre of the area of radiation was in the line of the central nail produced, for all positions of the board; therefore it was at the point where all these lines would meet, that is, at or about the centre of the platinum plate. Figure 2. Having thus determined the position from which the X-Rays were emitted, I next proceeded to determine the size of the area of radiation, by means of a pin-hole image. I placed a metal plate, with a small round hole pierced in it, in a vertical position, facing the platinum plate, and about six inches distant from it ; and I placed the fluorescent screen at the same distance from the metal plate, on the other side. When the current was then turned on, as before, and the room darkened, I got a luminous spot on the screen, which, under the geometrical conditions of the 1 Perhaps I should explain that the black patch close to the second nail from the right hand corner above, in the figure, is due to the presence of a piece of an old nail, which unknown to me was imbedded in the deal board. 518 Scientific Proceedings, Royal Dublin Society. experiment, must have been’an image of the area of radiation, and equal to itin size. This image I found to be irregularly circular in form, hazy and ill-defined round the edge, mt nal a aren of an inch in diameter.’ In connexion with this result, it is interesting to note a fact which must, I think, have fallen under the observation of most persons ite have worked at the X-Rays. There is always one small spot on the platinum plate which first begins to glow ; and it is not difficult so to regulate the current as to keep this spot glowing with a red heat, while the rest of the plate remains dark. This is evidently the area of fiercest bombardment, and it must be situated at or near the focus of the Cathode stream. It is irregu- larly circular in shape, ill-defined in its outline, and about a quarter of an inch in diameter. I think, therefore, we may infer that this glowing spot is, in fact, the area from which the X-Rays are emitted. [ 519 ] LX, A NEW METHOD OF CONFERRING DISTINGUISHING CHARACTERISTIC APPEARANCE UPON ILLUMINATED BUOYS AND BEACONS FOR HARBOURS, ESTUARIES, AND RIVERS. By JOHN R. WIGHAM, M.R.I.A., Member of the Council of the Royal Dublin Society. : [Read Junz 16; Received for publication Junz 18 ; Published Juty 21, 1897.] Most of the Papers which I have brought before this Society on the subject of Lighthouse Illuminants have had reference to improvements in the illuminating power of the great lighthouses on our sea-coasts. Most of these improvements have been adopted by the Lighthouse authorities of this country, the apparatus which I have described to this Society having been fixed at their lighthouses; for example, at the famous Eddystone, the Tuskar, Tory Island, Mew Island, Galley Head, Hook Tower, Haisbro’, Mine Head, Wicklow Head, Bull Rock, Howth (Bailey), Rockabill, Slyne Head, and other great leading and landfall] lights. <0 - Taih This Paper has no reference to these great lights, but to what may be termed minor lights. It has been found, of recent years, that lights fixed on the beacons and buoys which mark the rocks and shoals of our navigable rivers and estuaries, to show the safe channels by which these dangers may be avoided, if not as impor- tant to the mariner as leading and landfall lighthouses, yet possess for’ him great value, by enabling him to deal with these dangers at close quarters, when he has passed the greater liglits and has reached their shoreward side, where they are of little further use to him. Hence it is, that increasing attention is being given to the improving and. perfecting of these smaller lights, 520 Scientific Proceedings, Royal Dublin Society. placed on beacons and buoys, to guide him under such eireum- stances. I had the honour of reading a Paper before this Soest on the 22nd of January last* on a method which I had devised for using common petroleum as the illuminant for beacons and buoys, by which, at exceedingly low cost, a continuous light can be main- tained day and night for weeks or months without the necessity for the attendance of a light-keeper. I described in that Paper the method by which that form of light was, by means of a revolving wick, kept burning for that length of time, without attendance. These lights have been permanently adopted in Belfast Lough, and other places, and Sane been found suc- cessful. Lighthouse authorities have determined that, for distinctive purposes, two kinds of buoys shall be used in marking rivers, and the fairway of harbours and estuaries, viz. conical buoys and can buoys; the former to mark the starboard side in entering the river or harbour, and the latter the port side. This distinction is, of course, useful in the daytime when the buoys are perfectly visible; but to establish a similar characteristic distinction at night, it 1s, advisable to differentiate the lights on the buoys or beacons, and it has been suggested that bright, white lights should be used on the starboard side, and red on the port side. Some harbour authorities having called upon me to produce an’ occulting light which might be suitably used as marking one side of a river in contradistinction to fixed lights which might be used for marking the other, I devised the lamp here described. It will be seen by the simple plan of its construction that we can not only have occulting lights on buoys and beacons, but that we can. superadd the further distinction of colour, say, besides light and. dark alternately, we can have white and red, or red and dark, or, green and dark, or amber and dark, or any other variety that se be fixed upon. In this case the arrangement by means of rotating wicks, by which the light is maintained for a month together. without attendance, is the same as that described in my previous Paper. * Scient. Proc., Royal Dublin Society, vol. viii., Part v., p. 877. WicHam—Llluminated Buoys and Beacons for Harbours, &c. 521 The occultations are occasioned by causing the lamp itself to be ‘the motive power; the heat of the lamp acting upon the mica blades of a small fan which is caused continuously to revolve by the upward current of air resulting from the combustion of the lamp. Slight arms of steel which support the two screens of opaque, or coloured, or translucent material, such as talc, are so arranged that they balance each other and keep up, as they pass in front of the flame, a continual occultation and re-exhibition of the light. If it be desired to have a quicker repetition of the occul- tation than can be produced by two shades, three or four can be substituted for two, and thus the flashes will be rendered more frequent. an I exhibited on a former occasion, for the illustration of one of my Papers, a pulsating light, consisting of eight first order annular lenses, by which it was demonstrated that by the plan of rotation which I had devised the powerful light transmitted by these lenses was caused to remain in the eye as a continuous light, even when the lenses were continually revolving, and would other- wise cause intervals of darkness. I refer to this here merely because the same device is employed in this case. The effect of the continuous light which I have described was produced by the method by which the lenses were caused to revolve. They were mounted on a steel pivot, working on a piece of agate, causing so little friction that the great group of lenses (weighing about one ton) could be made to revolve by an exceedingly slight pressure, and hence great rapidity of revolution was practicable. The same contrivance is adopted in the case of the little lamp here described. ‘The pivot system is adopted also in this case, and so little friction is created that an exceedingly feeble upward current of air is sufficient to put the apparatus into motion. The sim- plicity of this device is its chief recommendation, for clockwork complications or other mechanical appliances would be quite unsuitable for the exposed positions in which such lights are placed. The balancing of the fan is so exact that, although the light may be fixed to a buoy which is subjected to the motion of the sea, the rotation is maintained with practical uniformity. Of course, if the lamp be used in a beacon which is perfectly steady, the rotation of the flashes is absolutely periodic; but even in the 522 ©. Scientifie Proccedings, Royal Dublin Society. case of buoys where the lamp, owing to the motion of the sea, is -unsteady, the flashes, for all practical purposes, are sufficiently regular and distinctive. Norz.—The Paper was illustrated by a working model showing ‘the movement to which buoys are subjected by the action of the sea, ‘and the gimbal arrangement by which that motion is neutralised and the flame of the lamp kept steady, an occulting apparatus ‘(showing white and red light alternately) being fixed in connexion with the gimbal arrangement. ' foes) ink NOTES ON A PAPER RECENTLY PUBLISHED IN THE ASTROPHYSICAL JOURNAL, by PROFESSOR E. HALE, of the Yerkes Observatory, Chicago, on “THE COMPARATIVE VALUES OF REFRACTING AND REFLECTING TELE- SCOPES FOR ASTROPHYSICAL OBSERVATIONS.” By SIR HOWARD GRUBB, F.R.S., Vice-President, R. D. 8. [Read May 19; Received for Publication May 21 ; Published SepremBer 14, 1897.] THe very first memoir in the first volume of the Transactions of the Royal Dublin. Society (New Series, 1877), was a Paper by the author on “ Great Telescopes of the Future.” That Paper was written at a somewhat critical period in the history of large telescopes, and was intended to draw attention to several advan- tages which reflecting telescopes possessed, more particularly for spectroscopic and certain lines of physical work, which advantages, in the opinion of the author, rendered it probable that the great telescope of the future would be of the reflecting and not of the refracting type. _ Glancing back for a moment over the past history of tele- scopes, it will be remembered that the development of the reflect- ing telescope got its first impetus from the failure of Sir Isaac Newton to achromatize telescopic objectives. Hven after “ Dolland ” -had perfected his great invention of the achromatic objective, re- -flectors were in considerable favour on account of the difficulty of procuring perfect pieces of optical glass, but as this difficulty decreased the reflecting telescope, then always made with metallic ‘mirrors, gradually lost ground on account of the difficulty of renewing the optical surface when tarnished. 1Vol. 5, No. 2, Feb. 1897. 524 Scientific Proceedings, Royal Dublin Society. About the sixties, the invention of Foucalt of using silvered glass mirrors, instead of metallic, gave the reflector a new lease of life, until it was found that the silver film was very perishable in the neighbourhood of towns. Moreover, the advance made in the manufacture of optical glass, has rendered it possible to obtain discs of a size almost comparable with the large reflecting telescopes. It was about this time that the author published the Paper referred to, thinking that the deserved popularity of the refractor had caused the many strong points of the reflector to be overlooked. The strongest advocates of the refractor have, undoubtedly, been in the New World, where most of the great modern refrac- tors have been built and installed, and it is therefore somewhat surprising, but at the same time gratifying to find from the Paper referred to in the title of this Paper, that American astronomers are becoming quite alive to the many strong points of the re- flector, and that a Paper from the pen of one so eminent in his profession as Professor Hale should contain such a remarkable confirmation of the views expressed in the author’s Paper referred to above, and published twenty years ago. Professor Hale, in his Paper, treats the subject in a far more exhaustive and complete manner than that which the author was able to do twenty years ago. He points out in the first place the actual necessity that exists for the building of telescopes larger than we have as yet attempted, if we desire to solve some of the great astronomical problems of the day ; he says :— “‘ But those who wish to materially reduce the probable error of wave length determinations of iines in stellar spectra, either for the purpose of increasing the accuracy of line of sight measure- ments or to render possible such detailed studies of certain lines as are now made in the solar spectrum, must be content to wait for the construction of telescopes much larger than the great instru- ments of the present day.” He then points out the particular classes of observations which the reflector is suitable for, and shows that that perfection of definition which the imperfection of our atmosphere renders impossible is not necessary in these particular observations. Grusps—WNotes on a Paper by Professor E. Hale. 525 Referring to the author’s Paper of 1877, he corroborates what is there said about the distinctive advantages of each form, and then enters into a most exhaustive and valuable examination of the relative light collecting powers of refractors and reflectors when used for visual work and when used for photographic work. An elaborate table is given of the various results of his analyses, and also a diagram which represents the same in a graphical form, which latter is here reproduced (see p. 526). An examination of this diagram will show that whereas the refractor is a more powerful light collector for visual rays up to about four feet in diameter, the reflector then, and for sizes over this aperture, becomes the more powerful in consequence of the fact that owing to the increased thickness of the glass the absorption of light is greater. The difference, however, is never very great for visual rays. In the case of photographic rays, however, the absorption in the case of the refractor is so great that at one metre diameter the reflector becomes 50 per cent. more powerful; at 2 metres it is 100 per cent. more powerful than a refractor of equal size; while at a little over 3 metres aperture the absorption increases at such a rate that no more light is collected by increasing the aperture. The conclusions, therefore, which Professor Hale comes to are as follows. He says: “ As regards the future development of telescopes in the direction of increased light-grasping power, the reflector promises far greater gains than the refractor, especially for spectroscopic work in the so-called photographic region. Indeed it appears from an inspection of the curves in the diagram that an increase in the aperture of an objective beyond about 350 centi- metres would be attended by no gain in the intensity of the photo- graphic image. In the case of reflectors, on the contrary, the light grasping power will continue indefinitely to gain with the aperture.” The author desires to take this opportunity of thanking Profes- sor Hale for his courteous reference to the Paper above referred to in the Transactions of the Royal Dublin Society. SCIEN. PROC. R.D.S., VOL. VIII., PART V. 2Q 400, 526 Scientific Proceedings, Royal Dublin Society. Di1aGRAM OF PLATE REPRESENTING THE VARIOUS RESULTS OF Proressor H. Haun’s Graruicat ANALYSES. 30) 20 100 5 4% g ? Ca “| 2 7 oe a“ s ony oe aes Be Z a= i / {JS 7 Ny |_| Yi ‘\ Y; ky) = Me y | vam = e/ As vu v wy My & 4 / As : tH / / " / dj 7 by 7 j i aay a iS i bis i y Nh ¥ he f / a c / |} ‘ 1s oN 73 ~ 7 a ie. 7 atone = / fractile s-— | Z bars. yi if -~ 3 Ve Beal 5 oo vet 200 300 ey LXII. A MECHANICAL CAUSE OF HOMOGENEITY OF STRUCTURE AND SYMMETRY GHOMETRICALLY INVESTIGATED ; WITH SPECIAL APPLICATION TO CRYSTALS AND TO CHEMICAL COMBINATION. By WILLIAM BARLOW. [Read Junz 16; Received for Publication Junz 18; Published Decumzzr 20, 1897.] From the early days of crystallographic study, attempts have from time to time been made to find some clue to the nature of the ultimate structure of crystals by means of artificial devices which imitate as closely as possible the various kinds of symmetry displayed by these bodies; these attempts have mainly consisted in packing together spheres, ellipsoids, and other regular bodies in a symmetrical manner, the methods employed being generally such that the packing is the closest possible, and the bodies packed together being all alike. In the meantime, however, evidence has been accumulating, notably in connexion with stereo-chemical investigations, that a regular repetition in space which portrays the homogeneity of structure of crystals should be that of groups composed of two or more individuals rather than that of single bodies as generally hitherto represented, and further that the bodies forming a group need not be similar. Thus, if we adopt the simile used by Lord _ Kelvin, and compare the homogeneous structure of a crystal to a regiment of soldiers in battle array,? we shall in many cases take a troop of cavalry rather than one of infantry for the comparison, 1 Comp. ‘‘ Molecular Constitution of Matter,’’ by Sir William Thomson, in Proc. Roy. Soc. of Edinburgh, vol. xvi. pp. 712-715. 2“«The Molecular Tactics of a Crystal.’”? Second Robert Boyle Lecture, 1893, p. 26. SCIEN. PROC. R.D.S., VOL. VIII., PART VI. 2R 528 Scientific Proceedings, Royal Dublin Society. and distinguish a man from his horse, while at the same time generally, in a sense, regarding them as one." Perhaps the simplest conceivable kind of closest-packing whial gives this diversity in unity of the elements of the structure, is that of a large number of spheres of two, three, or more different sizes ; and, as will be seen in the following pages, the variety of types of symmetry obtainable in this way, when a great number of different ratios between the sizes of the spheres are taken, is comparable to the variety presented by crystals. When further we find that numerous other facts concerning crystals are paralleled by the properties of closest-packed sym- metrical assemblages composed of balls of different sizes, we may be tempted to conclude that, in cases where closest-packing of balls all of the same size does not suflice, the real state of things is pictured in outline by the simple kind of closest-packing just referred to, and if this be so we shall conceive the ‘spheres of influence’ of the atomic properties or movements, whatever these may be, to be strictly spherical around certain centres, so that polarity in a crystal is traceable to the disposition and not to the forms of the spheres of influence of its ultimate parts. This is, perhaps, not unlikely, but it is proper to remark that the existence of the parallelism alluded to by no means establishes the propriety of using spherical balls in all cases. For every crystal not of the cubic system can be conceived to be deformed in such a way as not to alter the type of symmetry of its parts or properties, and since corresponding deformation of an assemblage of balls representing its symmetry would alter the spheres to spheroids or ellipsoids, we see that while the latter forms are not necessarily indispensable for the portrayal of the lower types of symmetry, they will always do as well as spheres so far as the geometry is concerned. An objection to the simple kind of closest-packing in question 1Tf the definition of homogeneity of structure suggested by the author (see Mineralogical Magazine, vol. xi., p. 120) is adopted, there are types of homogeneous arrangement whose representation would require the units of the troop to be no¢ all similarly orientated, and some which would involve the military inconvenience of each man being related similarly to more than one horse, and each horse related similarly to more than one man. Bartow—A Mechanical Cause of Homogeneity of Crystals. 529 is that the distance between the centres of two spheres of given sizes which touch one another is the same throughout an assem- blage of this kind whether the line joining them has in all places the same relation to the general symmetry or not. _ This arbitrary feature is obviated if, instead of rigid spheres placed against one another without pressure, we employ elastic deformable balls differing in material as well as in size, and subject the closest-packed assem- blage to some uniform compression which flattens the spheres at the places of contact. An assemblage thus constituted can be regarded as equivalent to a flock of mutually-repellent particles occupying the places of the ball-centres, and which is in equili- brium ;? provided that repulsion subsists only between near particles whose interaction is represented by the effect on one another of balls which touch. Hquality of lines whose situations are unlike is now avoided, and at the same time the polarity is still that of the disposition and not of the forms of the ultimate parts. The type of symmetry will not be materially affected by the modification referred to. In what follows we shall mostly content ourselves with the use of the undeformable balls, believing that the changes occasioned by using the elastic ones instead, would in all cases be quite symmetrical and immaterial so far as type of symmetry is concerned. The employment of spheroids or ellipsoids in place of spheres appears, as just remarked, to be unnecessary. _ For the purpose of imitating two of the principal universal properties of molecular matter, the balls employed will be (1) regarded as suffering contraction or expansion under change of‘ conditions, those of one size, composed of one material, changing at a different 1 Comp. Note 2, p. 550. 2 Some simple equilibrium arrangements for mutually-repellent particles of two kinds have been suggested by Lord Kelvin, the particles being under a constraint in addition to exhibiting repulsion. (See ‘‘ Molecular Constitution of Matter,’’ oe, cit., “pp. 699, 700.) It is conceivable that the spheres of influence around centres of force of one or more kinds found recurring throughout some uniform mass of matter appropriate to them- selves distinct portions of space as large as possible as a consequence of the interacfion of ‘the molecular movements or properties. And if this is the case, we appear to be furnished with a system of mutually-repellent spheres of influence whose stable equilibrium will be reached when the arrangement is a closest-packed one. 2R 2 530 Scientific Proceedings, Royal Dublin Society. rate from those of another material, and (2) it is postulated that ball can be attached to ball bya practically inextensible tie reaching from centre to centre through the place of contact, so that when tied in this way, the centres of two balls cannot get further and further apart under change of conditions, and thus the balls have, so to speak, to inter-penetrate between tied centres if they expand. The last-named postulate is intended to imitate to some extent the different kinds of aggregation of the ultimate parts of matter.’ The simple materials thus provided,’ the different balls of different materials,®> with their power of expansion and contraction under change of conditions, and their faculty of attachment to form groups, are now to be put together in various ways which fulfil the condition of closest-packing, this principle being the foundation stone of the present inquiry. The arrange-_ ments obtained will be compared with various phenomena of erystallization,* chemical isomerism, chemical combination, and diffusion. The work may be regarded as supplementary to the geometrical work on the nature of homogeneity which the author has already published, by which he has shown that every homogeneous struc- ture, whatever its nature, displays one or other of the thirty-two kinds of crystal symmetry.° The various effects producible will be found to range themselves under seven heads, viz. :— | I.—Symmetrical arranging of parts converting a fortuitous assemblage into a homogeneous assemblage and subsequent preser- vation of the homogeneity by the application of the ties, an effect 1 Where the linking thus defined is sufficiently complete to prevent any free move- ment of small parts of the assemblage with respect to one another, the assemblage will in the sequel, be said to be solid. 2 For a more precise statement of the concepts employed, see Appendix. 5 Sometimes it will be convenient to think of an artificial system as consisting of mutually-repellent particles instead of balls of different kinds (see above). 4 A reference to some of the conclusions as to crystals reached in this memoir was made by the author at the Cardiff Meeting of the British Association, 1891. Diagrams — showing some of the kinds of symmetry dealt with were published in Nature, 1883, vol. 29, pp. 186 and 205. 5 See Mineralogical Magazine, vol. xi., p. 119. Bartow—A Mechanical Cause of Homogeneity of Crystals. 581 which, since crystals are homogeneous structures,’ resembles that arranging of the ultimate parts of a body, and stereotyping of the arrangement, which constitute crystallization. IT.—Partial dissolution in a symmetrical manner of the ties which attach the parts of a linked assemblage, and subsequent partial destruction of the homogeneity, so that the assemblage breaks up into groups in each of which the parts are symmetrically placed with respect to one another, while the arrangement of the groups has become irregular, the groups thus resembling the theoretical molecules of stereo-chemistry. III.—Symmetrical intercalation of homogeneous assemblages whose forms are identical or appropriately related, comprising formation of twin assemblages, including under this head the symmetrical fitting together of enantiomorphous assemblages as well as that of identical assemblages; the formation of isomorphous assemblages and their intermixture, and the symmetrical inter- locking of unlike assemblages. Comparison to crystal-twinning, isomorphism, isogonism, and crystalloid structure, also to some kinds of diffusion. TV.—Interlacing of different kinds of groups or individuals, converting a fortuitous assemblage into an assemblage which approximates to homogeneity, but does not reach it, because the arrangements for closest-packing are not homogeneous ones. V.—Combination of two or more homogenous or approximately homogeneous assemblages to form a single homogeneous or approxi- mately homogeneous assemblage; an effect which, (a) in its most perfect form finds a parallel in that highly symmetrical inter- mixture of the combining atoms or complexes which must, it is evident, accompany or precede a chemical synthesis,’ and which 1 Homogeneous, that is to say, according to the definition given by the writer in his memoir: ‘‘ Ueber die geometrischen Higenschaften homogener starrer Structuren,’’ &e. Zeitschrift fiir Krystallographie, &c., 28, p. 1. Comp. Mineralogical Maz., vol. xi., p..120; or Zeitschr. fiir Kryst. 27, p. 450. * This effect is very closely related to that defined in I.; indeed these two effects may be said to overlap. Under head I., however, the salient point before us is the symmetry of arrangement which succeeds a more or less chaotic state, while under head V. it is the uniform intermingling of. different kinds of particles or elements in precise proportions which claims our attention. The latter condition is a result of the former which may survive the symmetry to which it owes its origin; it may exist continuously while the symmetry productive of it is intermittent and fluctuating. 02 Scientific Proceedings, Royal Dublin Society. (6), when the assemblage produced is only imperfectly homogeneous, may be paralleled by some phenomena of diffusion. VI.—Breaking up of an assemblage into two or more distinct assemblages; an effect resembling the disentangling of the separated atoms or complexes which commonly follows a chemical decomposition, and also resembling the crystallizing out of a con- stituent from a liquid or partially-liquid mixture. VII.—Exchange of the constituents of two or more assemblages so as to constitute fresh assomblages; an effect which finds a parallel in the re-arrangement or re-distribution which is one of the features of double chemical decomposition. The object kept in view throughout will be, not so much to ascertain with precision what particular relations between the parts lead to the formation of particular arrangements, as to show broadly that relations are conceivable which will lead to the production of the variety of results above enumerated as a direct physical con- — sequence of closest-packing carried out under the conditions indicated. As to the connexion between actual phenomena and the proper- ties of the artificial systems obtained in the way here described, I would say that so large a number of resemblances can hardly be — regarded as all of them mere coincidences, although some of them ~ may be, and that we are therefore justified in concluding that some ~ mechanical causes akin to those here traced are actually operating — in nature. | I.—Symmetrical arranging of parts, converting a fortuitous assemblage into a homogenous assemblage, and subsequent preservation of the homogeneity by the application of the ties; an effect which, since crystals are homogeneous structures, resembles that arranging of the ultimate parts of a body and stereotyping of the arrangement which constitute crystallization. (A.) Formation of homogencous assemblages when the balls, or mutually-repellent centres, are all of one kind. The simplest case is that presented when the balls are all similar and independent of one another. When this is so, it is not difficult to show that the relative Bartow—A Mechanical Cause of Homogeneity of Crystals. 5833 disposition of the ball centres which gives closest-packing, is one in which each ball is in contact with twelve others. For if a number of equal spheres be stacked together, twelve is the greatest number of them which can be in contact with any given sphere, and a closest-packed arrangement is realized by the sphere-centres of a stack consisting of plane layers triangularly arranged in which each sphere is in contact with six others, and the succeeding layers are so disposed that every sphere is also in contact with three others of the layer above, and three of the layer below it. But since there are two different positions in which a second plane layer can be deposited to fulfil this condition, it is evident that twelve contacts for each sphere can be attained in a variety 1 Kven this simplest of all cases of closest-packing has not, so far as I am aware, ever been exhaustively treated, or its various possibilities expressed algebraically. (See Lord Kelvin on the arrangements here referred to in ‘‘ Molecular Constitution of Matter,’’ by Sir William Thomson, Proc. Royal Soc. of Edinburgh, vol. xvi., p. 712, note *and p. 715.) As those who have employed the conception of closest-packing of similar bodies have contented themselves with a treatment which is comparatively rudimentary and not exhaustive, considerable difficulty must be looked for in any attempt to deal exhaustively with the closest-packing of bodies of more than one kind. I am, however, not without hope that, when the importance of the subject is realized, experts in analytical methods may he found who will indicate precise ways of arriving at some of the closest-packed arrangements described in the succeeding pages. I anticipate that should some of these arrangements prove not to be the closest-packed possible, the arrangements which supplant them will in all, or nearly all, cases be found to be homogeneous, and will therefore serve the purposes of the argument equally well. I may say that my general principle for getting closest-packing of the spheres is to produce a maximum number of contacts, so as to diminish, as far as possible, the amount of interstitial space. 534 Scientific Proceedings, Royal Dublin Society. of different ways. There are two, and two only, which give homogeneity of structure,’ viz. :— (a.) An arrangement in which the sphere centres occupy the centres of a symmetrically selected half of the cubes of a.cubic par- titioning of space. This is shown in figs. 1 and 2,’ and is of ‘the type marked 8a, in the lists of types of homogeneous structure given by the writer,? and has the generic symmetry of class 28 in Sohncke’s list of Krystallklassen.* The centres form a singular point-system,° each of them being the intersection of tetragonal, trigonal, and digonal axes and of the planes of symmetry. (6.) An arrangement in which the spheres of alternate layers are directly over one another, the pro- jection of the system being shown in fig. 3. The sphere centres then exem- plify that particular case of Sohncke’s system 02, which is obtained when the generating point lies at the point of intersection of one of the trigonal and one of the digonal axes of the system, and the distance separating successive layers of the system is such that each point is equidistant from twelve nearest points. Such a system possesses planes of symmetry in which the points lie, and also centres of inversion, and is a singular point-system. The type of homogeneous structure to which it belongs is that marked 24a,,° the ‘“‘ doppelte Systeme,’ of which are of the kind numbered 87a 1 See note 1, p. 531. 2 Fig. 2 has one corner of a cubic group truncated to show the triangular close- packed arrangement of the spheres in planes perpendicular to the cube diagonals. 3 Zeitschr. fiir Kryst. 23, p. 44. The references given here, and in subsequent examples to the lists contained in the author’s former works on homogeneous struc- tures, and to Sohncke’s list of the thirty-two classes of crystal symmetry are supplied for the convenience of those who desire to examine particular cases closely ; it is scarcely necessary for the purposes of the general argument that the reader should look them up, 4 Ibid., 20, p. 466. 5 Ibid., 23, p. 60. § Zeitschr. fiir Kryst. 23, p. 45. Compare Sohncke, Entwickelung einer Theorie der Krystallstruktur, p. 115; also Natwre, Dec. 20, 1883, vol. xxix., p. 186. Bartow—A Mechanical Cause of Homogeneity of Crystals. 535: in Fedorow’s list;1 it has the generic symmetry of class 9 in Sohncke’s list of ieretallle deen: g As a and 0 are just as closely packed, one as the ens it would seem, at first sight, that in every case where the centres are of a single kind, one of these arrangements is as available as the other. But this can hardly be the case, for it is conceivable that the initial disposition of the centres may by some means, perhaps fortuitously, be nearer to the one arrangement than to the other in some given case; and if this is so, the assemblage will pass more easily to the arrangement to which it thus already approximates, and on reaching it can experience no disposition to adopt the other. And further, a fortuitous arrangement ts, in some respects, nearer to form (a) than to form (b). For, in a, the planes most thickly set with ball centres have four different directions, viz., those per- -pendicular to the cube diagonals, while in 6 they have but one such plane direction. And if we suppose that, starting with a fortuitous arrangement, the first step towards closest-packing is the production of a large number of aggregations in which closest-packing prevails, but which are variously orientated, it is obvious that the passage to a continuous closest-packed arrange- ment which absorbs all these, will partly consist in reducing the number of the different orientations of the groups, and that, as the movements requisite to reduce them to four will be less, on the whole, than would be requisite to bring them to a single common orientation, the cubic arrangement marked a will generally be easier to reach than the hexagonal one marked 0.° If, as in the last case, the balls are all similar, but are aggregated to form a number of similar groups in which each ball is similarly linked to the remaining balls of its group, the conditions obviously become much more complex, and it is easily seen that the closest- packed arrangement will but rarely be of the type just named.* 1 Zeitschr. fiir Kryst., 24, p. 236. 2 Tbhid., 20, p. 460. 3 The argument is perhaps easier to follow if we think of the balls as shaken close together in a bag. 4 Tf the reader desires to study the simpler cases of arrangement before he addresses himself to the more complex, he should pass on at once to the cases in which the balls are of two kinds. (See p. 546). 536 Scientific Proceedings, Royal Dublin Society. If, for example, the similar centres are similarly linked together two and two, closest-packing gives different arrangements accord- ing to the distance apart of the two centres of a pair as compared with the distances separating nearest centres in different pairs when equilibrium is reached. The consideration of a few particular cases renders this clear. : Thus suppose :— (a) That the distance between the two centres of a pair is small’ compared with the distances between those of the nearest pairs when equilibrium is reached, so that the balls of the pair inter- penetrate one another very considerably. When this is so the arrangement which gives closest-packing will still, very approximately, be that of the simpler case given above, except that now the points midway between the two centres in each group or pair, instead of the centres themselves, will have the arrangement of the sphere centres in the assemblage depicting a closest-packed arrangement of unlinked spheres of a single kind. The assemblage will not, however, be homogeneous unless the relative orientation of the pairs conforms to the definition of homogeneousness above referred to. ‘The only relative orientation which conforms to this definition, and also has the symmetry of the regular form, is that in which the centres all lie on trigonal axes situated as in type 1 of my list? (System 58 of Sohncke), the line joining the two centres of a pair coinciding everywhere with such an axis. If the pairs have this relative orientation, a homo- geneous structure is presented which has the axes and coincidence- movements (Deckbewegungen) of type 1, and possesses in addition centres of symmetry (of inversion) lying at the cube centres of the space partitioning which I have employed to generate this system.® It is, therefore, a structure of the type numbered La, in my list,* and displays the generic symmetry of class 31 in Sohncke’s list of Krys- — tallklassen.? The two centres of a pair are equidistant from the centre of the cube in which they lie, and they are found on the single trigonal axis of this cube; their positions are not identically 1 Not infinitesimal. 2 Zeitschr. fir Kryst., 23, p. 6. 3 Ibid., 23, p. 7- 4 Tbid., p. 44. 5 Tbid., 20, p. 467. Bartow—A. Mechanical Cause of Homogeneity of Crystals. 587 alike, but enantiomorphously related. As they lie on axes they are singular points.’ If in the case under consideration a homogeneous arrangement is produced, it is probably this.’ Suppose next :— (0) That the distance between the two centres of a pair is relatively large, so as very nearly but not quite to allow the balls to take the arrangement prevailing when they are all indepen- dent.® In this case an arrangement approximating closely to the compact arrangement taken up by the balls when independent will obviously be produced ; it cannot, how- ever, be a homogeneous one belonging to the cubic system, because it is not possible to connect the points of the closest-packed cubic system above de- scribed, two and two in such a way that the arrangement of the ties shall comply with the definition of homo- geneousness and belong to the regular system. In some instances of this kind probably an arrangement of the balls according to the system 21 of Sohncke with centres of inversion, d.e., of type 49a, in my list* will result, the generic symmetry being that of class 12 in Sohncke’s list. The projection of a stack of spheres whose centres would have such an arrange- ment is shown in fig. 4, the balls being so placed as very nearly to have the alternative closest-packed homogeneous arrangement ‘ 1 Thid., 23, p. 60. Comp. Min. Mag., vol. xi., p. 182. 2 Other symmetrical orientations which are consistent with homogeneousness will be found to give a lower degree of symmetry and would probably not give such close packing. 3 A comparison of the specific weights of different bodies composed of the same atoms in the same proportions, but whose molecules are of different degrees of com- plexity, rather favours the conclusion that, in the solid and liquid states, if as the stereochemists suppose, the atoms have definite situations, the distances separating the nearest atoms of different molecules of a substance are frequently not very much greater than the distances separating the nearest atoms of the same molecule. * Zeitschr. fiir Kryst., 23, pp, 30 and 46. 538 Scientific Proceedings, Royal Dublin Society. shown by fig. 3.1. In such a grouping, the centres linked are in different layers, and the positions of the two ball centres of the pairs are identical;? they are singular points in planes of symmetry. The two projections of alternate layers are shown in the figure. Layers between which the linking obtains will be rather closer together than other succeeding layers.* The relative position of two linked balls is indicated by connecting with dotted lines the projections of the spheres whose centres pair together. Finally suppose— (c) That the distance between two centres of a pair is slightly but not much less than in the last case. | It is then conceivable that the closest-packing will be reached in a homogeneous arrangement belonging to the regular system whose axes are those of type 5 in my list* (system 62 of Sohncke), and which is obtained by placing a point on a trigonal axis very near either to one of the cube centres, or to one of the cube angles of the space-partitioning employed to generate this system,’ and generating a point-system by carrying out the coincidence-movements (Deck- bewegungen) of the samesystem. ‘The ball centres to be regarded as linked together will be those lying nearest to one another on the same trigonal axis. The structure obtained will be of the type numbered 5 in my list, and display the generic symmetry of class 29 in Sohncke’s list. The positions of the centres are all identical, and they are singular points lying on trigonal axes. Where, on stable equilibrium being reached, the distance between two centres forming a pair bears some other relation to the distances between the pairs than those prevailing in the three cases referred to, the closest-packed arrangement, towards which the assemblage continually approximates, will be in some cases. homogeneous, in other cases probably unhomogeneous. To be homogeneous it must, as we know, possess the coincidence-move- ments of some one of the 65 systems of Sohncke, and will generally be a specialized system of very high symmetry.” 1 See page 584. 2 4.e., not enantiomorphous. 3 If the layers were all equidistant, the symmetry would, ignoring the linking, belong to one of the hexagonal types. 4 Zeischr. fiir Kryst., 23, pp. 6and 12. ° [did., 23, pp. 7and 12. ° bid., 20, p. 466. 7 See ‘‘ Ueber die geometrischen Higenschaften &c.’’ Zeitschr. fur Kryst., 23, p. 1. Bartow—A Mechanical Cause of Homogeneity of Crystals. 589 Take next a case in which the ball centres, while all of one kind, are similarly linked to one another to form groups of three. Manifestly for each of the three centres of a group to be similarly placed with respect to the remaining centres of the same group, they must lie at the three angles of an equilateral triangle. Suppose— (a) That the distances between the three centres linked together to form a group are small as compared with the distances between the nearest centres in different groups when equilibrium is reached. As in the corresponding case of groups containing two balls, very close packing will be attained if the arrangement of the groups is that of the sphere centres in figs. 1 and 2, but this would not appear in general to be the closest-packing possible if we take the shape of the groups into conside- ration, 7.e., unless the distance between the centres of a group is so small as to make the shape of the group quite in- operative. It would seem that the closest-packing possible is attained when the disposition of the groups ap- proximates to the one referred to on p. 534 (and see fig. 3), and the orientation of the groups is such that the arrangement of the ball centres is that of a system 52 of Sohncke,' whose generating point lies on one of the digonal axes which intersects trigonal axes near to one of the latter, and on a line of intersection of planes of symmetry. ‘The structure presented is of the type marked 24a, in my list ;? and the generic system displayed by sucha system is the holohedral symmetry of class 9 in Sohncke’s list of Krystall- klassen.* The nature of the arrangement is shown in fig. 5, in which each group is seen to consist of three interpenetrating spheres which are in contact with the spheres of adjoining groups. The 1 See ‘“‘Entwickelung &c.”’, p.115. Compare Zeitschr. fiir Kryst., 23, pp. 23 and 25. 2 See Zeitschr. fiir Kryst., 23, p. 45. The ‘‘doppeltes System’’ is No. 87a of Fedorow, Zeitschr. fiir Kryst., 24, viii., Taf. vi. 3 Zeitschr. fiir Kryst., 20, p. 460. 540 Scientific Proceedings, Royal Dublin Society. projections of alternate layers are identical, so that two projections of succeeding layers suffice. The positions of the centres are all identical; they are singular points, and the digonal axes on which they lie are lines of intersection of those planes of symmetry which intersect trigonal and hexagonal axes. Suppose next— (3.) That the distances between the three ball centres forming a group are almost as great as the distances between the nearest centres in different groups when equilibrium is reached, so as very nearly to permit of the centres taking the arrangement of the sphere centres in figs. 1 & 2. If the distances referred to differ only infinitesimally, we shall get an unhomogeneous arrangement very closely resembling in structure the closest-packed arrange- ment referred to, but lacking its definite polarity. If they are not infinitesimal it would appear that the conditions may be such as to give the closest-packing in an arrangement depicted in fig. 6, in which the three centres grouped around a hexagonal axis and lying in the same transverse layer are rather nearer together than to centres in other groups; Fig. 6. as before the spheres interpenetrate in threes. The system has the axes of system 52 of Sohncke (Type 24 in my list) with centres of inversion on the hexagonal axes and situated midway between the layers of points. Its structure is therefore of the type marked 24a, in my list,’ and has the generic symmetry of class 9 in Sohncke’s list.2 The positions of the centres are all identical; they are singular points lying on those of the digonal axes which intersect nearest hexagonal axes and also on lines of intersection of planes of symmetry. Take next a case in which the centres, while all of one kind, are similarly linked to one another to form groups of four. 1 Zeitschr. f. Kryst., 23, p. 45. The ‘‘doppeltes System” is No. 88a of Fedorow (see Zeitschr. f. Kryst., 24, viii., Taf. vi.). 2 Zeitschr. f. Kryst., 20, p. 460. — Bartow—A Mechanical Cause of Homogeneity of Crystals. 541 Several different kinds of grouping of four ball centres are possible consistently with this; let us take the most symmetrical ease, that in which the centres lie at the angular points of a regular tetrahedron. Suppose— (A.) That the distance between two centres of a group is small as compared with the distances between nearest centres in different groups. ‘ As in the above cases in which a relation of this kind obtains, elose-packing will be attained when the arrangement of the groups is like that of the sphere centres in figs. 1 and 2, and an arrange- ment approximating to this would give the closest-packing possible in cases where the distance separating centres of the same group is relatively very small indeed. We see, however, that when, having this arrangement, the groups are orientated in such a way that the assemblage shall be a homogeneous structure belonging to the cubic system (?.¢., when the ball-centres lie upon trigonal axes) closest-packing is not attained; and therefore we conclude that in cases where the groups approximate to the arrangement referred to, the orientation is less regular than this, and the assemblage in consequence either unhomogeneous or of a lower degree of symmetry than the cubic. If the arrangement is homogeneous, but has some lower sym- metry than the cubic, the four centres of a group will not all bear the same relation to the structure. For example, if the symmetry is trigonal, we shall find not more than three of each group occupy- ing similar positions, and if three are similarly related the fourth will lie on some trigonal axis. Suppose next — (B.) That the ball centres of the same tetrahedral group are further apart than in the case of A, but still much closer together _ than centres in different groups. It would appear that cases now present themselves in which closest-packing is reached when the arrangement of the groups is that of the centres and angles taken together of the cubes in a 1 See p. 611. 542 Scientific Proceedings, Royal Dublin Society. close-packed stack of equal cubes (that of a kubisches centrirtes Raumgitter), and the arrangement of the ball centres is that of a system 56 of Sohncke (Type 10 in my list), whose generating point hes on a trigonal axis near to, but not at, a cube centre. Such a structure is of the type marked 10b, in my list.* The generic symmetry displayed is tetrahedral hemihedrism, being that of class 30 in Sohncke’s list. Suppose finally— (C.) That the distance between two of the ball centres forming a tetrahedral group is almost as great as the distance separating the nearest centres in different groups. The arrangement of the centres can now approximate very closely to that of the sphere centres of figs. 1 and 2. This is accom- plished if the centre points of the groups form a cubic space-lattice, and the arrangement of the centres is that of a system 54 of Sohncke (type 7 in my list) whose generating point lies on a trigonal axis at a distance rather less than d/4 from a cube centre where d is the diameter of a cube of the space-partitioning which I have employed to generate this system. (If the distance were exactly d/4 the particles would have the closest-packed arrangement shown in figs. land 2). The structure obtained is of the type num- bered 7b; in my list.* The generic symmetry, as in the last case, is tetrahedral hemihedrism, being that of Sohncke’s class 80. ‘There is, however, another arrangement of the tetrahedral groups of balls which gives equally close-packing with that just described. For a closest-packed cubic assemblage of spheres can be partitioned into tetrahedral groups in two different ways, 7.e., (a) one of the form just described in which the system, after partitioning, pre-— sents the type of symmetry No. 7b:, and (d) one in which each triplet of spheres forming a face of a tetrahedral group is fitted into a triplet of an adjoining tetrahedral group. ‘The arrange- ment of the ball centres, when the groups are placed in this way, is that of a system 63 of Sohncke whose generating point lies on a trigonal axis at a distance rather less than d/4 from a 1 Entwickelung &c.”, p. 157. Comp. Zeitschr. f. Kryst., 23, p. 20. 2 Zeitschr. f. Kryst., 23, p. 62. 3 Tbid., 20, p. 467. + Zeitschr. f. Kryst., 23, p. 52. BarLtow—A Mechanical Cause of Homogeneity of Crystals. 543 _ cube centre or a cube angle, where d is the diameter of a cube of one of the two space partitionings employed in this system. (As in the previous case, if the distance were exactly d/4, the balls would have the closest-packed arrangement shown in figs. 1 and 2). The structure is now of the type numbered 9a, in my list; the generic symmetry is the holohedral cubic; one half of the groups have their orientation opposite to that of the other half. The centre points of the groups lie, one set at half the cube centres of a cubic partitioning of space, the other set, which are oppositely orientated, at half the cube angles. Groups composed of four similar similarly-placed balls arranged in some other way, e. g., at the angles of a square, do not appear to be capable of very close-packing in a homogeneous manner when taken alone. Take next a case in which the centres, while all of one kind, are similarly linked to one another to form groups of six. Several different kinds of grouping of six centres are possible consistently with this;* let us take the simplest case, that in which they lie at the angular points of a regular octahedron. Suppose— (aa.) That the distances between the six ball centres linked together to form a group are small as compared with the distances between the nearest centres in different groups. As in the case of groups of four similar centres, if the distances between the centres of the same group are relatively so small that _ the shape of the groups does not affect their relative arrangement, we shall get closest-packing in an unhomogeneous arrangement in which the relative situations of the centre points of the groups approximates to that of the sphere-centres of figs. 1 and 2. Suppose— (6b.) That the distances between the six ball centres forming a group are larger than in case aa, so that the form of the groups affects their arrangement. Closest-packing will probably not now be attained in any homogeneous arrangement belonging to the cubic system ; for, if the groups, appropriately oriented, be arranged with their centre 1 See p. 612. SCIEN. PROC. R.D.S., VOL. VIII., PART VI. 28 544 Scientific Proceedings, Royal Dublin Society. points to form either (1) a regular octahedral space-lattice, or (2) a cubic space-lattice, or (8) a cubic centred space-lattice, the groups do not fit very closely together ; and these are the only three ways in which the ball-centres can be arranged so as all to occupy similar positions in the structure and to have cubic symmetry.” —_Closest- packing would appear, however, to be attained in trigonal sym- metry if the particles have the arrangement of a system which ~ has the axes of type 49 in my list® (system 21 of Sohncke), and possesses centres of inversion lying at the intersection of trigonal and digonal axes, and the generating point be so situated in a plane containing nearest trigonal axes of the same kind that groups of six points are traced from it which form the angles of regular octahedra. The structure is then of the type marked 49a, in my list. Fig. 6 will represent an arrangement of this nature, but the spheres will now interpenetrate in sixes, not in threes as in the previous case represented by this figure; and the layers will not now all be equidistant, the distance between consecutive layers, each of which contains half the centres of the same groups, being less than that separating layers not thus related. The symmetry dis- played by such a system is scalenohedral hemihedrism, being that of Sohncke’s class 12. Ifthe distance separating the nearest centres in the same group becomes equal to the distance between nearest — centres of different groups measured both in transverse planes of — particles and also between the nearest particles of succeeding — transverse planes, the arrangement becomes that of the very close- _ packed system referred to in page 534 and fig. 3. We might pursue the investigation for cases of centres all of — one kind linked to one another to form groups of more than six, but greater complication would then be encountered, because a greater number than six cannot be similarly placed with respect 14. e., (1) To form the centres of regular rhombic dodecahedra fitted together to fill space; (2) to form the centres of cubes thus fitted together; or (3) to form the centres and solid angies of such cubes, in other words to form the centres of cubo- octahedra thus fitted together. 2 Tt seems unlikely that closer packing will be attained in any homogeneous arrange- ment of the particles in which they have not this similarity of position. : 3 Zeitschr. f. Kryst., 28, pp. 80 and 31. Comp. Sohncke’s Entwickelung, &e., p. 129. 4 Zeitschr. f. Kryst., 238, p. 46. Bartow—A Mechanical Cause of Homogeneity of Crystals. 545 to one another without producing a hollowness of the grouping, @.e., the distance between the opposite centres of a group is then far greater than that separating nearest centres; and hollowness of the grouping seems inconsistent with close-packing, so that it would seem that the centres, where more than six go to form a single group, must occupy positions with respect to the structure which are not identical with one another. When this is the case our task is similar to the one before us when we come to deal with cases of balls of more than one kind. Enough has been said to show that, in the case of similar ball centres linked together in various ways, compact packing and homogeneousness of arrangement commonly go together, and we may regard the following proposition as established. Closest-packing produces, under the given conditions, a great variety of homogeneous arrangements of balls of a single size, when these balls are fitted together to form symmetrical groups consisting of two, three, four, or six balls, and the balls which form a group interpenetrate. The nature of the arrangement is in each case determined by the relation which subsists between the distance apart of adjacent centres of the same group and the distance between the nearest centres of different groups. The strict parallel as to general symmetry obtaining be- tween the various homogeneous closest-packed arrangements of centres of one kind, some of which have just been traced, and the various crystal forms of the elements is obvious, the linking together of two or more of the centres to form a group being paralleled by the supposed linking together of two or more similar atoms to form a molecule.’ 1Jt has sometimes been suggested that when atoms, whether of the same or different kinds, combine to form a molecule, the individuality of the atoms is lost, much in the same way that the individuality of a number of superposed movements of any kind is lost, and not separately discernible in the resultant movement. The objection to this view is that, in the case of a chemical combination, we can always, by analysis, recover the same identical combining atoms from the combination, while in the case of combined movements the identity of the component movements is completely lost, so that we can no more say that the resultant movement contains the movements whose combination produced it, than that it contains any other of the infinite number of conceivable groups of movements which would have this same resultant. And this objection is supported by the evidence we have that the presence in a number 282 046 Scientific Proceedings, Royal Dublin Society. (B.) Formation of homogeneous assemblages when the balls, or mutually repellent centres, are of two kinds. We now come to the cases of homogeneous arrangement brought about by closest-packing in which the balls are of two kinds only, and in some of which they are not linked together to form groups of any kind, while in others they are so linked. In these and other cases in which more than one kind of ball is present, and provided the centres are unlinked, the nature of the arrangement produced will depend on the relative sizes of the balls of different kinds.’ For the sake of simplicity, let us first suppose that the ball centres are all confined to the same plane, but free to move in this plane. If they were all alike and indepen- dent, they would evidently pack closest in the triangular arrangement, in which each centre is equidistant from six nearest centres, and they would dis- play a less compact packing in the quadrilateral arrangement, in which each centre is equidistant from four nearest centres. ‘But when two kinds of balls, one larger than the other, are present, the triangular arrangement referred to may not give close-packing at all, and the sizes may be so proportioned as to give closest-packing in the quadrilateral arrangement depicted in fig. 7; this packing being somewhat closer than would be of different compounds of a common constituent is very often the occasion of their possessing allied properties. It should be remembered, in connexion with the resemblance that has just been pointed out, that some. or indeed all, of the so-called elements may prove in the end to be compounds. Where this is the case the remarks made later respecting compounds will apply instead of what is said here as to the elements. 1Tf elastic balls are used and the closest-packed assemblage is compressed (see p. 529), the arrangement will also, in nearly all cases, be influenced by the repulsions found subsisting between the different ball centres, these repulsions, at least such of them as have any modifying effect on the form of the assemblage, having to form a system in statical equilibrium. { . ) } ; > Bartow—A Mechanical Cause of Homogeneity of Crystals. 547 attained by massing the two sizes separately in the triangular arrangement. Let us now pass to the consideration of cases of balls of two kinds not confined to the same plane, and all independent of one another. Suppose that the relation between the sizes of the two kinds is such that, when closest-packing is attained in a combination of the two, the centres of the large balls are found at the centres of a sym- metrically selected half of the cubes of a cubic partitioning of space, i.., having the arrangement which would be the closest-packed possible if they were present alone'—in other words, that the smaller balls are small enough to go into the interstices between the larger ones when the latter have the closest-packed ar- rangement referred to. It is then evident that the smaller balls are moperative ones—that they have no share in the production of thegeneral symmetry, but merely lie loosely be- tween the balls whose interaction de- termines it, and which therefore may be designated operative. The larger of the interstices are ~ equalin number to the closest-packed Fig. 8. spheres; and if, insuch anassemblage of spheres, the smaller-sized spheres are too large for the smaller interstices, while small enough for the larger, they will occupy the latter only. In an assemblage of mutually-repellent particles of two kinds corresponding to this,’ the relative positions of the particles exer- cising the lesser repulsions will be given by the centres of spheres just large enough to fit into the large interstices, the arrangement produced being that of the sphere-centres in fig. 8. In such an arrangement, the centres of one kind occupy the centres of half the cubes of a system of cubes into which space is divided, and those of the other kind the centres of the remaining half, each half system consisting of cubes in contact at their edges only. The 1 That of the sphere-centres in figs. 1 and 2. 2 See page 529. 048 Scientific Proceedings, Royal Dublin Society. structure is therefore of the type marked 6a, in my list.1 Hach kind of centre forms a singular point system,’ centres of both kinds lying at points of intersection of tetragonal, trigonal, and digonal axes, and also in planes of symmetry. The generic sym- metry is the holohedral cubic, being that of class 28 in Sohncke’s list.* The use of spheres somewhat smaller than those which would just fit into the larger interstices would still leave the arrange- ment referred to the closest-packed possible, so long as they are not small enough for more than one to go into one of these interstices. Corresponding to this we have the fact that the arrangement described is an equilibrium one for particles of two kinds, if when thus arranged the mutual repulsion between the particles of different kinds is either equal to or /ess than the repulsion between the particles of the same kind which have the closest-packed arrangement of figs. 1 and 2; provided the repul- sion between the particles which correspond to the smaller spheres, and also that between these particles and particles of the other kind are considerable enough to prevent more than one particle from occupying any of the larger interstices, and any particles at all from occupying the smaller ones. If spheres of two sizes are used, and the same arrangement of the larger spheres prevails, but the smaller spheres are small enough to go into the smadler interstices between the larger ones, closest-packing will be attained in some arrangement which is homogeneous so far as the disposition of the larger spheres is concerned if the arrangement of the smaller ones be neglected, but unhomogeneous if the smaller ones are taken into account, unless indeed the relative magnitude of the two kinds is such that the larger interstices are packed fullest when a number of the smaller spheres are arranged in each of them in a manner con- sistent with the homogeneity of the structure formed.* In these and in all other cases of assemblages consisting of more than one kind of ball, it is manifest that unless the different kinds are present in the numerical proportions in which they enter into the particular combination which gives closest-packing of 1 Zeitschr. fiir Kryst., 23, p. 44. 2 Tbid., p. 60. 3 [bid., 20, p. 466. 4 See note 1, p. 531. Pp Bartow—A Dechanical Cause of Homogeneity of Crystals. 549 them all, there will, when equilibrium is reached, be an excess containing one kind of ball less than is found in this combination, and that closest-packing applied to this excess will cause the balls composing it to take up the relative positions in which they occupy the least space possible! We see, therefore, that the numerical proportions in which different kinds of balls are present will determine how far uniformity of arrangement shall extend throughout the entire assemblage. Where there are but two kinds of balls, as in the cases referred to above, the combination ultimately produced will exhaust the stock of one kind, and the kind which is present in excess will be arranged just as the sphere- centres are arranged in the closest-packed system above referred to.” To proceed to other cases of equilibrium of two kinds of balls. Another case of holohedral cubic symmetry. The two sizes may be so related that the disposition of the centres when the most stable equilibrium is reached is that of the centres of spheres of two sizes, where those of one size occupy the centres of all the cubes of a cubic par- titioning of space, those of the other all the cube angles (fig. 9). In this case all the balls will be operative.? The type of homo- geneous structure to which such an assem- blage belongs is that numbered 7a, in my list.‘ Each kind of centre forms a singular point system,” centres of Fig. 9. ' As to the steps by which this ideally-perfect condition of most stable equilibrium will conceivably be reached in the case of an assemblage of mutually-repellent particles of two different kinds, patches of such a symmetrical combination as gives closest-packing will probably first appear at all places where the different kinds are in juxtaposition, then the two kinds will interpenetrate each other, and the patches of the compound assemblage formed will extend and combine till an arrangement is reached in which all of one kind of particle is in combination with the needful proportion of the other in a continuous mass as symmetrically arranged as possible. The remainder of the assemblage will consist entirely of the kind of particle which is present in excess arranged in one of the closest-packed forms for the uncombined state, probably in that depicted in figs. land2. There will, of course, be some irregularity and continual fluctuation at all boundaries. It is needless to add that, if change of state takes place before the ideally-perfect condition is reached, the process described will be only partially carried out. * See figs. 1 and 2. 3 See p. 547. 4 Zeitschr. fiir Kryst., 28, p. 44. 5 Ibid., p. 60. 550 Scientific Proceedings, Royal Dublin Society. both kinds lying at points of intersection of tetragonal, trigonal, and digonal axes, and also of the planes of symmetry. The two kinds are present in the same numerical proportions. The generic symmetry is holohedral, being that of class 28 in Sohncke’s list. A case of tetrahedral hemihedrism of the cubic system. Tf the radii of two sets of spheres are very nearly in the pro- portion requisite for the assemblage in which the larger spheres. have the closest-packed arrangement of figs. 1 and 2 and the smaller just fit into the larger interstices between them,’ but the smaller are just too large to allow of the larger spheres being in contact, a different arrangement gives closest-packing of the spheres. This arrangement is obtained if the larger spheres, which will be not quite in contact when arranged as in the closest- packed arrangement referred to, approach one another uniformly in groups of four, till the four mutually touch, while = the different kinds of spheres continue in contact. The assemblage formed in this way may be regarded as consisting of groups each composed of eight spheres, four of each kind tetrahedrally arranged (fig.10). In it each large sphere is in contact with six small ones, and also with three large ones, making nine contacts, and each small sphere has six contacts as in the previous case.” The type of Fig. 10. 1 See p. 547. 2 The centres of the spheres in a closest-packed homogeneous structure of this kind! do not precisely give a possible equilibrium arrangement for mutually -repellent particles. of two kinds, because the equality of the distances between the centres of the spheres: of different radius which touch one another would then involve equality of the repul— sions subsistizg between the two different kinds of particles placed at these centres, and this equality does not necessarily exist in the modified arrangement referred to. For each force which acts on a particle is not now, as in the previous case, balanced by a similar opposite force, and, for the forces which act on a particle to be in statical equilibrium, they must bear certain ratios to one another which depend on their mutual inclinations. And in the case before us these inclinations are such that the: pressures between nearest different particles, and therefore their distances apart, will have to form two different sets which are not alike, but slightly different one from the other. A slight modification of the arrangement of the sphere-centres is therefore necessary to obtain the actual equilibrium arrangement possible for two kinds of particles in the case under consideration, but this modification will be one which: ig quite symmetrical (compare p. 529). ee. ee ed —— elt Bartow—A Mechanical Cause of Homogeneity of Crystals. 551 homogeneous structure to which such an assemblage belongs is that _ numbered 7b; in my list... The generic symmetry is that of class 30 in Sohncke’s list.*, The two kinds of balls are, as in the last _ ease, present in equal numerical proportions ; each kind of centre forms a singular point-system, all centres lying on trigonal axes, and also in planes of symmetry. All the balls are operative.® There is an important difference between this case of closest- packing, and the cases for two kinds of balls previously given. In _ the latter no kind of partitioning of the structure into unit groups of balls is possible which is not arbitrary, and, owing to its incom- patibility with the coincidence-movements (Deckbewegungen), pro- ductive of a lowering of the type of symmetry. In the present case, partitioning into groups of the form A,, By, can take place without lowering the type.‘ Case of gyrohedral hemthedrism of the cubie system. Again, the radii of two different sets of spheres may be so pro- portioned that the closest-packed mixed’ arrangement is of the following kind :— Partition space with maximum regu- larity into similar plane-walled cells, whose centres are at the centres and angles of a cubical partitioning of space; these cells will be octahedra truncated by cubes in such a way as to reduce the octahedron faces to regular hexagons (fig. 11). Join three alternate angles of each of the hexagonal interfaces, selecting the angles symmetrically, and bisect the lines thus drawn. There are two ways of doing this (a and 4, fig. 11, in which only the bisecting points are shown). At the points of bisection of one set thus obtained, place the centres of spheres whose diameter is such that they touch one Fig. 11. 1 Zeitschr. fiir. Kryst., 23, p. 52. 2 Zeitschr. fiir Kryst., 20, p. 467. 3 See p. 547. 4 See Mineralogical Magazine, vol. xi., p. 130. Comp. post, p. 587. 5 Some sort of linking will most likely be requisite for this kind of packing to obtain; the massing of each set by itse/f in closest-packing will probably demand less space than any mixture of the two kinds of the nature here described. 5952 Scientific Proceedings, Royal Dublin Society. another, three and three in the planes of the hexagonal interfaces ; it will be found that the triplets of spheres thus obtained also touch one another in points which lie four and four in planes parallel to the square interfaces of the system. About each of the centres of the similar cells into which space has been partitioned, then group six equal spheres in close order, 7.¢., in octahedral grouping ; each octahedral grouplet to have its centre at the centre of the cell which contains it, and to have the same orientation as that of the latter, and the size of the spheres to be such that they touch the spheres already placed whose centres lie in the hexagonal interfaces. In the system thus formed every sphere of the central grouplets is in contact with four similar spheres, and four others, making eight contacts, and the spheres whose centres lie in the hexagonal — interfaces are each in contact with four of the same size, and two others, making six contacts... The type is that marked 13 in my ~ list,” and it has the generic symmetry of class 29 of Sohncke.* The two kinds of centres are present in the numerical proportions 1:2. Hach kind forms a singular point system, the less numerous — lying on tetragonal axes, the more numerous on digonal axes. There are two closest-packed arrangements of the same — spheres, one of which arrangements is the mirror-image of the other. One is obtained by taking points a, fig. 11, the other by taking points 6 for the places of the sphere-centres of one kind. — Case of dodecahedral hemthedrism of the cubic system. Within each cell of the space partitioning of the last example place the centres of twelve equal spheres at equal distances from the centre of the cell on lines joining this centre with the middle points of the twelve edges in which the octahedral faces meet, and let the equal distances referred to and the magnitude of the spheres be such that the latter touch one another, and also the spheres 1-As in the previous case, the centres of the spheres in the homogeneous structure thus described, will not precisely give a possible equilibrium arrangement for particles _ of two kinds, the necessities of statical equilibrium precluding this, but a slight modifi- cation of the arrangement of the sphere-centres which does not alter the type of symmetry will give a possible arrangement. * Zeitschr. fiir Kryst., 23, p. 22. 3 Ibid., 20, p. 466. BarLtow—A Mechanical Cause of Homogeneity of Crystals. 553 similarly placed in the nearest surrounding cells. Then, as in the last example, within the cavities which exist about the centres of the cells, insert octahedrally-arranged grouplets, containing six spheres each, of such smaller magnitude that they touch the spheres first placed. Hach of these smaller spheres will then be in contact with four of the same set and four of the larger set, while each of the larger spheres will be in contact with two of the smaller set, and eight of the larger set. The packing of such an assemblage is very close, but if we compare the shape of a single compound grouplet with the shape of one of the cells, it is easy to see that there is a slight openness of the packing at the square interfaces of the cells, that there is a hollow space between the four spheres lying on the one side of such a face and the four spheres lying on the other side. If now at each square interface the centres of two diagonally-placed spheres on one side and those of the two spheres opposite to them are symmetrically moved slightly towards one another, all four centres continuing in the same plane of symmetry, the hollow places in the arrangement can be contracted and a possible equili- brium arrangement? for balls of two kinds can in this way be obtained, in which the centres referred to form a series of similar twelve-point groups, which have planes of symmetry parallel to the cube faces. The type of the arrangement thus indicated is that marked ‘10a; in my list.” The generic symmetry is that of class 31 of Sohncke.* The two kinds of centres are present in the numerical proportions 1:2; each forms a singular point system, the less numerous centres lying on digonal axes and in planes of sym- metry and the more numerous in planes of symmetry. Case of holohedrism of hexagonal system. If a stack of equal spheres is made, consisting of plane layers triangularly arranged in contact, placed so that the spheres of the different layers are vertically over one another, a number of similar interstices are left between the spheres. Place now in these interstices smaller spheres whose radius is such that they 1 But see Note 5, p.551. ? Zeitschr. fiir Kryst., 23, p.45. 9 Lbid., 20, p. 467 - | A ? ii just fit into them. Hach large sphere will then be in contact with eight of the same size and twelve of the smaller size, and each — small sphere will be in contact with six of the larger spheres. Such an arrangement would appear to give closest-packing, for/y spheres of two sizes thus proportioned. The type of homogeneous structure is that marked 25a, in my list. The generic symmetry is that of class 9 in Sohncke’s list.” The two kinds of centres are present in the numerical proportions 1:2. Hach kind formsa singular point system, the less numerous kind lying at the point of intersection of hexagonal and digonal axes and planes of symmetry, and the more numerous at the points of intersection of trigonal and digonal axes and planes of symmetry. 004 Scientific Proceedings, Royal Dublin Society. Case of rhombohedrism. In the closest-packed arrangement of spheres of two different — radii, referred to on page 549, the centres of one set occupy the centres, and the centres of the other set, the angles of the cubes of © a cubic partitioning of space. Suppose now that we have two sets of spheres whose radii are nearly in the proportion requisite for this arrangement, but that the smaller are rather too small for the purpose. Closest-packing will then probably be attained in an — acute rhombohedral arrangement, in which each of the larger spheres is in contact with six of the same size and six of the smaller size, and each of the smaller spheres is in contact with six of the — larger ones, this arrangement being derived from the cubic one just referred to by a slight relative elongation of the assemblage in the direction of a cube diagonal and uniform contraction in directions — transverse to this. ; The type of homogeneous structure presented is that marked — 52a, in my list. The generic symmetry is that of class 12 in — Sohncke’s list. The two kinds of centres are present in equal — numbers. Hach kind forms a singular point system, the centres all lying at the points of intersection of trigonal and digonal axes and on lines of intersection of planes of symmetry. ta a , et, oe rT ee ae 1 Zeitschr. fiir Kryst., 23, p. 45. 2 Tbid., 20, p. 460. 3 Zeitschr. fiir Kryst., 28, p. 47. 4 Ibid., 20, p. 461. Barrow—A Mechanical Cause of Homogeneity of Crystals. 555 Case of hemimorphism of rhombohedral symmetry. If tetrahedrally arranged grouplets, each composed of four equal spheres in contact, be so placed at the centres of the cubes of a cubic partitioning of space that the axes of the grouplets coincide with the diagonals of the cubes, the grouplets being all similarly orientated, and if the spheres are of such magnitude that the grouplets touch one another, then it will be found that the spheres have the closest-packed arrangement of figs. 1 and 2. Suppose, now, that instead of all the grouplets being composed of spheres of the same size, half of them symmetrically placed—i. e., placed about the centres of one of the half systems of cubes which touch one another at their edges only—are composed of rather smaller spheres. The cubic arrangement will not now give closest-packing; for if the largest grouplets be placed as in the case just referred to, the smaller ones will be just too small to fill the spaces allotted to them. Closest-packing for a mixed assem- blage' will, however, probably be reached if, keeping the grouplets intact, a slight contraction of the assemblage along the direction of one of the cube diagonals be made so as to obtain additional contacts, still keeping the structure homogeneous.” The type of homogeneous structure thus obtained is that marked 51b,; in my list,? and it has the generic symmetry of class 19 in Sohncke’s list. The two kinds of centres are present in equal numbers. It is evident that in an equilibrium arrangement of this nature, centres of the same kind do not all occupy similar positions in the structure; one out of every four centres of each kind lies on a trigonal axis in which planes of symmetry intersect one another, and each of the remaining three centres of each group of four lies in a single plane of symmetry. While therefore all the centres form singular point-systems, two of these systems contain fewer points than do the remaining two. 1 See note 5, p. 551. 2 See note 1, p. 531. 3 Zeitschr. fiir Kryst., 23, p. 55. 4 Ibid., 20, p. 463. 5906 Scientific Proceedings, Royal Dublin Society. Case of trapezohedral tetartohedrism. Tf the radii of two sets of equal spheres are in a certain ratio, we are able to build them together into a very closely-packed homo- geneous assemblage of the type numbered 52 in my list,’ whose axes and coincidence-movements are those of system 22 of Sohncke. The arrangement of the centres of the two sets of spheres is diffi- cult to indicate on a diagram; the larger have their centres on digonal axes, and are therefore half as numerous as the smaller ones. Hach larger sphere is in contact, or nearly in contact, with fourteen surrounding spheres, each smaller one nearly in contact with ten.2 The generic symmetry is that of class 15 in Sohncke’s list of Krystallklassen. The two kinds are present in the numerical proportions 1 : 2 and the centres of the less numer- ous form a singular point-sys- tem. The balls may be all un- linked, or they may, consis- tently with the symmetry, be linked together to form similar groups of three, one of one kind and two of the other. If they are thus linked a slightly modi- fied arrangement will be ap- propriate, and groups of three interpenetrating spheres,* two of one size and the third of another, will be used to build up the type of symmetry. An arrangement of the sphere centres such as may be presented in this case is depicted in fig. 12, the methods employed by Sohncke 1 Zeitschr. fiir Kryst., 23, p. 32. 2 For the reason stated in a previous example, the centres of the spheres do not precisely give a possible equilibrium arrangement for particles of two kinds, but a slight modification of the arrangement of the sphere-centres which does not alter the type of symmetry, would appear to satisfy the necessities of statical equilibrium and give a possible arrangement. 3 Compare p. 530. Bartow—A Mechanical Cause of Homogeneity of Crystals. 557 _ to indicate that the centres are at different distances from the _ plane of the diagram being followed and no attempt being made to show the spheres themselves or the way in which they touch one another.’ We have in this case most of the symmetrical and other con- ditions which are met with in quartz-crystals, including a compo- sition and grouping which agree with the molecular composition of that body, and screw-movement axes which involve a spiral arrangement of the parts such as is requisite to account for the property of rotation of the plane of polarization. Case of bipyramidal hemihedrism. Take a stack of close-packed spheres, such as is described on page 534 and in fig. 3, and, keeping the spheres which are nearest to each hexagonal screw axis in contact both laterally and longi-. tudinally, separate the stack into strings of triads of spheres by slightly increasing the distances between the axes in a uniform manner. Orientate all the strings of triads uniformly about the respec- tive axes so as to bring some of the separated spheres again into contact. Finally, place in each of the largest interstices now left between the spheres a sphere of some other radius as large as possible. It is probable that such a value can be selected for the ratio of the sizes of the two kinds of spheres in an assemblage of the kind just described as will make it the closest-packed mixed arrangement for spheres whose magnitudes bear this proportion. The type of homogeneous structure produced in this way is num- bered 20a, in my list;? all the centres lie at singular points, the more numerous in planes of symmetry and the less numerous on tri- gonal axes. The generic symmetry is that of class 11 in Sohncke’s list of Krystallklassen. The two kinds of balls are present in the numerical proportions 2: 3. 1 Compare fig. 22, Taf. II. in Sohncke’s Entwickelung einer Theorie der Krystall- struktur. 2 Zeitschr. fiir Kryst., 23, p. 45. 558 Scientific Proceedings, Royal Dublin Society. A case of holohedral rhombic symmetry. Place a number of equal spheres in the same plane in triangular order in contact with one another. On this layer, place a second — layer composed of rather larger spheres half as numerous; the ~ most even distribution of these which brings them over the spaces between the spheres of the first layer is indicated in fig. 13, the centres of the first layer being indicated by the plain points, those of the second layer lying over the points marked with an asterisk. The latter centres are nearly equidistant, and slight relative movements would make them so. Consequently if an appropriate relation subsists between the radii of spheres of two sizes and the two kinds are linked into groups in some way, they will probably pack closest when the centres of alternate layers have ap- proximately the relative situa- tions shown in the figure. Neither of the two kinds of layers will, however, have pre- cisely the regular triangular arrangement, and the assem- blage, as a whole, will display rhombic symmetry. The type of homogeneous arrangement is numbered 53a, in my list.’ The generic symmetry is that Fig. 13. of class 6 in Sohncke’s list of Krystallklassen. The two kinds of balls are present in the numerical proportions 1 : 2. The positions in the structure oc-— cupied by the more-numerous are of two different kinds; all the ball centres form singular-point systems the points of which are on digonal axes which lie in planes of symmetry. It is inter- esting to notice how little removed the assemblage is from being hexagonal—one among many instances of a low type of symmetri- cal arrangement possessing features more or less similar to those of some higher type. oe SEO, EE ee eee 1 Zeitschr. fur Kryst., 23, p. 47. 4 Bartow—A Mechanical Cause of Homogeneity of Crystals. 559 : Case of holohedrism of the monoclinic system. The arrangement of alternate layers in a stack of equal spheres whose disposition is described in p. 534, is depicted in figs. 3 and 14. Such a stack can be partitioned into octahedral grouplets containing six spheres each, as indicated in the figure, each sphere being in contact with four others of the same grouplet, and the centres of the grouplets forming a triangular-prismatic space-lattice. Suppose now that, instead of employing equal spheres, we take spheres of two sizes, and form two sets of octahedral grouplets, one composed of the smaller spheres, the other of the larger, and pack the grouplets as closely together as possible, the general plan of the grouping of the spheres of two sizes on plane being of the nature indicated by the letters A, B, in the figure.? If the relative magnitude of the spheres of two kinds be such that the centres of one kind of similar groups in the same layer approximate closely to a square arrangement, the centres of the other kind of group falling therefore at the. middle points of the squares, it is evident that a very close-packed arrangement is obtained when the centres of the large grouplets of one layer lie about over the centres of the small grouplets of the succeeding layer. There will, however, be some slight racking or shifting over of the assemblage owing to the spheres employed being of two sizes. Thesymmetry of such an arrangement ismonoclinic. The type of homogeneous structure presented is numbered 63a, in my list.’ The generic symmetry is that of class 3 in Sohncke’s list of Krystall- Klassen. The two kinds are present in equal numerical proportions. * Probably a linking of the two kinds of balls to one another must be postulated to prevent closest-packing leading to the formation of two distinct assemblages one of each kind. * Zeitschr. fiir Kryst., 23, p. 48. SCIEN. PROC. R.D.S., VOL. VIII., PART VI. Tk 560 Scientific Proceedings, Royal Dublin Society. One out of every three centres of each kind lies in a plane of symmetry, and the centres thus distinguished, therefore, form two singular point-systems. The axes are parallel to the plane of the diagram and horizontal; the planes of symmetry are perpendicu- lar to the plane of the diagram through vertical lines. A. second ease of holohedrism of the monochiic system. If in a stack of spheres arranged for holohedrism of the hexago- nal system in the way described on p. 553, the smaller spheres are just too small to fill the cavities containing them, the grouping referred to will not give closest-packing, but if the system be canted over slightly, and the spacing of the spheres in the layers be very slightly modified in an appropriate manner, an arrangement which is probably a closest-packed arrangement can be obtained which is an example of holohedrism of the monoclinic system. The type of homogeneous structure is that marked 64a, in my list.1 The generic symmetry is that of class 3 in Sohncke’s list of Krystall- klassen ; the two kinds are present in the numerical proportions 1: 2. Centres of the same kind do not all occupy similar positions in the structure. C. Formation of homogeneous assemblages when the balls are of three kinds. Case of tetartohedrism of the cubic system. Partition all space into equal cubes. Place similar tetrahedral grouplets, each consisting of four equal spheres in contact with each other, so that their centres occupy the centres of the cubes. ; Similarly place tetrahedral grouplets composed of spheres of another size at all the cube angles. Finally place tetrahedral grouplets composed of spheres of a third size at all the middle points of the cube edges.” Tf all the grouplets are similarly orientated, and their axes have the four directions of the cube diagonals, sizes can be selected for the three sets of spheres which will give very close packing in the 1 Zeitschr. fir Kryst., 23, p. 48. 2 Or at all the middle points of the cube faces, the latter having the same situa- tions relatively to the cube centres as the middle points of the cube edges have relatively to the cube angles. BarLtow—A Mechanical Cause of Homogeneity of Crystals. 561 arrangement described. A yet closer packing is however, attain- able if all the grouplets of the third set experience a slight sym- metrical rotation about their centres, the rotation being of such a nature that all the four spheres of each of these grouplets continue to occupy similar positions in the four cubes which meet in the cube edge. In the closest-packed system of spheres of three sizes that can be arrived at in this way,! it will be found that each cubic cell of the space-partitioning contains a similar arrangement of the spheres, the sphere centres of the first and second sets lying, in each case, at the angles of a regular tetrahedron, and the sphere centres of the third set forming a “ 12—punkter” of Sohncke.? The type of homogeneous structure is that marked 7 in my list,° and it has the generic symmetry of class 82 in Sohncke’s list of Krystallklassen. The two sets of less-numerous centres form two singular point-systems whose points lie on trigonal axes. ‘he three kinds of balls are present in the numerical proportions 1:1: 3. There are two equilibrium arrangements of the same spheres, one of which is the mirror image of the other. Centres of the same kind occupy similar positions in these arrangements. Case of pyramidal hemihedrism of the hexagonal system. Arrange a plane layer of equal spheres touching one another, but with symmetri- cally-situated gaps as shown in fig. 15, the gaps having a triangular arrangement. 1 There will probably have to be some linking, see note 5, p. 551. 2 As in some of the previous cases, the centres of the spheres in the closest-packed homogeneous assemblage of spheres thus indicated will not precisely give a possible equilibrium arrangement for mutually-repellent particles, this beimg precluded by the . necessities of statical equilibrium. (Compare note 2, p. 550). 3 Zeitschr. fiir Kryst., 23, p. 18. 2T2 . 562 Scientific Proceedings, Royal Dublin Society. Over these gaps place equal spheres of greater size, and over the points midway between them a second set of equal spheres smaller than those over the gaps, the size of the spheres in the two sets being such that their centres lie in the same plane and that they are in contact. ; On the second layer thus formed place a third layer similar to the first and vertically over it, and then a fourth similar to the second in like manner, and so on. In such an assemblage each smaller sphere is in contact with five of the same size, two of the medium size and two of the large size; each medium-. _ sized sphere is in contact with pa a Ee six small and three large ; each large sphere with twelve small Ja and six medium-sized.1 The type of homogeneous structure presented is numbered 23a, in my list.” The genericsymmetry is that of class 11 in Sohncke’s list of Krystallklassen. The three kinds of centres are pre- sent in the proportions 1 : 2: 6. All the centres occupy singular points, those of one of the two less numerous kinds lying on hexagonal axes, those of the other on trigonal axes, and all in planes of symmetry. Case of pyramidal hemihedrism of the tetragonal system. Arrange a plane layer of spheres in close square order, but with gaps asshown in fig. 16. Over these gaps, and also over the ; 4 4 a points midway between them, place other spheres in contact with — those first placed of such radii that their centres all lie in the same plane, and that they touch one another. On the second layer thus formed, place a third layer similar to the first and vertically over it, and then a fourth similar to the second in like manner, and so on. 1 See note 5, p. 551. 2 Zeitschr. fiir Kryst., 23, p. 45. Bartow—A Mechanical Cause of Homogeneity of Crystals. 563 Each smallest sphere is then in contact with three of the same size, and two ofeach of the larger size. Hach larger sphere of either size is in contact with eight small, and four of the other larger size. The type of homogeneous structure presented is numbered 34a, in my list.” The generic symmetry is that of class 23 of Sohncke’s list of Krystallklassen. The three kinds of centres are present in the proportions 1:1:4.* Allthe centres occupy singular points, those of the less numerous kinds lying on tetragonal axes, and all in planes of symmetry. The foregoing examples of closest-packing of one, two, or three different sizes of balls must suffice. To give anything like a complete review of the ways in which a fortuitous assemblage may be converted into a homogeneous assemblage as a consequence of closest-packing, we shall have to deal with cases of the combina- tion of four, five, six, &c., different sixes, and ¢o greatly multiply mstances in which particles of more than one kind are linked together to form a number of similar groups. This additional supposition often leads to a considerable increase of complexity which makes the results difficult to trace, while at the same time the number of possible solutions is greatly multiplied. Several, however, of the eases above described have been, and others can, as will subse- quently be pointed out,‘ be treated as those of assemblages of identical groups of linked particles; and it is easy to see that in cases of more complicated assemblages of groups of linked particles, as well as in the simpler cases here given, closest-packing will frequently lead to homogeneity of arrangement. Without citing otker cases, enough has been said to establish the general conclusion that closest-packing of an assemblage of balls of one, two, three, &c., different kinds will, under the conditions defined, very commonly lead to the production of some homogeneous arrangement or arrangements, the variety of form possible being very great indeed. All homogeneous structures whatever have ! There will probably have to be some linking, see note 5, p. 551. * Zeitschr, fiir Kryst., 23, p. 45. 5 As a fact which may have some significance, it may be noted that several bodies which crystallize in the symmetry referred to have a composition of the form AB C4. 4 See pages 586 et seq. 564 Scientific Proceedings, Royal Dublin Society. been shown. by the author’ to possess the generic symmetry of one or other of the thirty-two classes of crystal-symmetry. In most of the instances of symmetrical arrangement above traced it is not easy to determine with certainty whether we have arrived at a system which can give stable equilibrium or not, but there is a high probability that in very many cases stable equili- brium is attainable in the arrangement described without any linking being premised, if certain appropriate relations between the repulsions be chosen. In any case we have established the following proposition :— That assemblages belonging to all of the thirty-two classes of erystal- line symmetry result from closest-packing of balls of different sizes, when the relations between the different radu take the widest possible range of variety, and cases of packing together of spheres formed into groups in the way premised are included, as well as the cases in which the spheres are unlinked. This proposition has, as has just been intimated, been established from a consideration of comparatively simple cases; the employ- ment of more complicated assemblages would lead to the same conclusions.” An examination of some results corresponding to the facts of stereo-chemistry which is undertaken later* will show that in some of these more complicated assemblages the centres of the same kind occupy enantiomorphously-similar, as well as identically-similar, positions, like the points of a Fedorow-Schonflies ‘‘doppeltes System.’ The spread of symmetrical arrangement in an assemblage. Crystal growth. Bent and branched crystals. If a process of close-packing, due to the interaction of its parts, is the agency by which an assemblage becomes arranged symme- trically, it is evident that the solidification, 7. e., complete linking up of the parts which produces a rigid homogeneous assemblage, is not strictly concurrent with, but subsequent in time to, the arrang- 1 Zeitschr. fiir Kryst., 23, p. 1. 2 See note 1, p. 533. 3 See pp. 582 e¢ seg. - 4 Zeitschr: fiir Kryst., 23, p. 41. Bartow—A Mechanical Cause of Homogeneity of Crystals. 565 ing process. For in order that the arrangement may take place as a consequence of the interaction of the parts which are taking up symmetrical situations, there must, it is manifest, be a more or less extensive tract of matter in an unlinked or partially unlinked, i.e., in a Sluid condition, in which symmetrical arrangement is being achieved, but not rigidity. There must, in other words, be a state, which may, however, be quite transitional, which is a symmetrically arranged fluid state. Again. Itfsuch a fluid tract be bounded on one side by a portion of the same assemblage, of the same composition, which has passed into the completely rigid state, but on the other sides is not so bounded : it is evident that at the side next to the rigid portion, if the latter have retained the same or nearly the same density, the parts or particles will, as they pack closely, take up positions in harmony with those of the particles composing the rigid portion, and will consequently here arrive sooner at a condition of stable equilibrium, and so experience less continual disturbance or re- arrangement than those do which are further removed from the solid portion. On the other hand, if the fluid tract be in contact with a solidified assemblage which is wnhomogeneous, it is evident that the condition of special tranquillity which prevails where the fluid and solid meet when they are congruent will not be experienced. As in harmony with these conclusions, one may cite the existence of crystalline liquids (krystallinische Fliissigkeiten), d.e., of a liquid state of some bodies in which a definitely arranged symmetrical structure, as evidenced by their polarizing properties, is associated with complete fluidity.!. And the rarity of this phe- nomenon can hardly be said to diminish its suggestiveness. For a single well-established instance of the production of crystal properties apart from rigidity suffices to show that the latter is not essential, and may in all cases follow, and not accompany, the arrangement of ultimate parts which gives crystal properties. Parallel to the above conclusion that if, in a homogeneous 1 Lehmann, ‘‘ Ueber fliessende Krystalle.”’ Zeitschr. fiir physikalische Chemie 4, p. 462 ; and by thesame author, ‘‘ Die Struktur krystallinischer Flissigkeiten.’’ The same Zeitschr., 5, 427. bd 7 566 Scientific Proceedings, Royal Dublin Society. assemblage of mutually-repellent particles, a portion have passed into the rigid state, we shall have a tract or film of the portion still fluid lying next to the solidified portion, and which is in @ more tranquil state, and further advanced towards stable equili- brium than the rest, we have the fact that it is the portion of the crystallizing liquid nearest to the crystal which commonly passes. to the solid state first. In other words, crystals grow by accretion, while amorphous bodies do not. The tract of maximum tranquillity and symmetry which we have concluded must lie next to solidified portions of the assem- blage will, it is evident, to some extent be broken up if the con- tinuity of structure of the solidified surface is partially destroyed by rupturing the solid and disarranging the broken portions. For a symmetrical arrangement of the film of liquid in harmony with one portion of the body will not then be in harmony with a neighbouring portion. A very significant fact with regard to crystals may be cited to compare with this. Tf a crystal, e.g., of ammonium chloride, be beaten out, and then placed in its solution and allowed to grow, it is found that the accretion at the boundary, where the solid particles are in contact. with the solution, takes place in skeleton form? showing that the disturbing influence of a fracture and displacement on the process of crystallization eatends to a considerable distance from the fracture im both directions in the adjacent film of solution. | The transition state, in which the symmetrical arrangement, but not the solidification of an assemblage is taking place, is. 1 The alternative theory of crystal formation supposes each particle added to the growing mass to take up its symmetrical situation not before, but at the time it is. . attached to the previous growth, just like a brick added to a wall in building. This. view seems perhaps at first sight to be countenanced by the discovery made by Wulff that better and more regularly formed crystals can often be obtained when a solution is in motion that when it is at rest. That it is not supported by the fact referred to is. — seen, however, when we consider that the places of minimum disturbance will still, notwithstanding the motion, be close to the crystal surfaces, and that while the disturbance operates to prevent irregular growth, it does not preclude the existence of Jilins of the crystallizing substance in a more or less liquid condition adhering to the already solidified crystal surfaces from time to time formed, and remaining undisturbed by the motions. (See Wulff, Zeitschr. fiir Kryst., 11, p. 120. * Lehmann ‘‘ Ueber fliessende Krystalle’’ Zeitschr. fiir physikalische Chemie 4, p. 467 and fig. 3. ———— eee Se 4 #44) Bartow—A Mechanical Cause of Homogeneity of Orystals. 567 necessarily one of gradual change from the moment when the first indications of orderly arrangement present themselves till the most perfect symmetry is achieved. And if the opposing forces, the arranging force and the disturbing force which produces fluid motions, are subject to any ebb and flow, it is conceivable that after some amount of orderly arrangement has been achieved the fluid motions, instead of uniformly subverting this symmetry, will merely so far break up the partially-arranged mass as to reduce it to frag- ments which roll upon and round-off one another; these fragments "preserving internally the degree of symmetrical arrangement which has been already imposed, and the space between them being occupied by less-regularly arranged aggregates of particles of the same or of some different composition. _ The rounded crystalline grains whose presence in many cases marks an intermediate stage of crystallization from solution, and which have been called giobulites and crystallites,) may be men- tioned in this connection as furnishing a possible parallel to the condition just traced, but the composition of the bodies referred to is very possibly, in some cases, due to impaired homogeneity, the nature of which we are about to consider.” Where a homogeneous assemblage in which, under slow change of conditions, a very gradual spread of solidification is taking place, is continuous, and but little disturbed by outward influences, we shall expect the accretion at the growing surfaces to proceed with ‘much uniformity, and especially that at every surface throughout which the conditions are uniform the growth or increase will also be uniform. And it is obvious that the extremely regular progress of crystallization in continuous masses subject to very uniform conditions and very slow change is entirely in harmony with this _ expectation. Further, if the general conditions change but slowly, consider- _ able disturbing movements of the liquid portion of a homogeneous assemblage may not prevent the accretion to the solid portion from being extremely uniform so Jong as the slowness of the change of 1 See ‘‘ Die Krystalliten’’ von H. Vogelsang. Bonn, 1874. 2 See p. 568. Compare Heinrich Vater “‘ Ueber den Einfluss der Lésungsgenossen auf die Krystallisation.’? Zeitschr. f. Kryst. 27, p. 477. 068 Scientific Proceedings, Royal Dublin Society. conditions is such that every part of the surface of the growing sole experiences on the whole the like conditions. If, however, the change is not sufficiently slow to give this uniformity of conditions in a fluid assemblage at different points — of the boundary of a solidified portion of it, some departure from uniformity of accretion is to be looked for. This will especially be so if the fluid assemblage which is of the same composition as the mass already solidified is more or less fragmentary and interspersed among portions of differently- constituted fluid assemblages which are not partaking in the solidifying change. For although in this case the place of maximum tranquillity, 7.e., the surface of the growing solid, will still be the place of growth, the relative rute of growth at different parts of this surface will be regulated chiefly by the relative distribution or — supply of the material for growth, and the supply of material — being different at different places the growth will be irregular As irregular growth thus caused is, however, a matter which : does not come within the scope of our investigation, this interesting topic must be dismissed with the remark that Lehmann’s investiga- tion of the nature and causes of the growth of skeleton crystals — seems to the author to be entirely satisfactory.2 This remark is intended, however, to apply only to the cases of irregular growth in which the structure is congruent—to skeleton crystals but not to bent or branched crystals. As we shall see immediately, closest-packing is capable of producing bent and branched assem- blages which are very nearly homogeneous, although it is of course impossible for them to be quite so. Impaired Homogeneity—Bent and Branched Crystals. We have hitherto in these pages regarded mixed assemblages — of balls which are subjected to a process of closest-packing as forming two great divisions—division 1, to which this section is — especially devoted, comprising all those in which closest-packing is attained in a homogeneous arrangement, and division 2 those — 1 Compare ante, note 1, p. 566. 20. Lehmann “ Ueber das Wachstum der Krystalle.’’ Zeitschr. fir Kryst., 1, p. 453, especially page 471. BarLtow—A Mechanical Cause of Homogeneity of Crystals. 569 which, while they may approximate to a general uniformity of distribution, cannot reach homogeneity, and are unable to arrive at stable equilibrium. Now, although it would appear that these two divisions embrace all possible cases of assemblages whose dimensions are large, a little consideration shows us that for thin assemblages, #.e., those in which either one or two of their three dimensions are small, slightly impaired homogeneity, not incompatible with stable equilibrium within the assemblage, may give closest-packing. The following will make this clear in a single instance :— If in a cubic partitioning of space spheres of one size be placed at the cube centres, and spheres of another size, bearing a certain proportion to the first, at the cube angles so as to form a stack such as is described on p. 549 (fig. 9), this stack may be regarded as made up of triangularly-arranged layers, each composed of one kind of sphere only; the planes of these layers are perpendi- cular to some one of the four directions of the cube diagonals, and alternate layers are composed of spheres of the same size. Suppose now that instead of spheres of two sizes only, four different sizes are used, and, instead of an infinite number of layers but four consecutive triangularly-arranged layers are present. It is then evident that if we preserve about the same proportion between the sizes of succeeding layers as prevails in the stack just referred to, but make the spheres of the third layer avery little smaller than those of the first, and those of the fourth with a similar relation to those of the second, closest-packing will be reached, not when the centres of the equal spheres of a layer lie in the same plane, but when they lie on some curved surface very approximately spherical, the four different surfaces traced by the centres in the different layers being practically concentric. Since the curvature of the layers is very slight, as compared with the sizes of the spheres, the departure from uniformity in the arrangement of a layer caused by its following a curved surface instead of a plane will be but trifling, even in the ease of layers of considerable extent. Further, if, instead of one set composed of four layers, the assemblage consists of several such sets, it is evident that an effect of the same kind may be looked for, although in this case, for the arrangement to be congruent, the conditions in each curved 570 Scientific Proceedings, Royal Dublin Society. shell composed of four layers will be slightly different. Where a limited number of similarly constituted shells are present in an assemblage of the nature indicated, there may be very little difference in the closeness of the packing of the different shells if the cncrements of the distances between similar ball centres found as we travel outwards from shell to shell, and caused by the increase of circumference, be compensated by an appropriate decrement in the radial distances and consequently in the thickness of succeeding shells; the solid contents of the spaces contained between the successive corresponding spherical surfaces being thus made equal. The other kind of wniform curvilinear distortion of a thin plate possible, viz. cylindrical curving is, it is evident, equally available with the spherical curving just referred to, when suitable homo- geneous assemblages are selected for modification.? . Besides these two kinds of distortion, Joca/ distortions piodicei local increase of closeness of packing are conceivable. The effect of these will naturally be the same as that of local shrinkages in thin solid bodies, and like these be productive of local torsional twists. Finally, a torsional twist, uniform along the length of a capil- lary assemblage of sufficient fineness, may increase closeness of packing in some cases. Assemblages consisting of large linked groups will especially lend themselves to the production of the modified homogeneity referred to. Thus wedge-shaped groups will be likely to pack closer when put together to form an arch if the assemblage is a thin one. A fundamental condition, in all cases, Siders is that the dis- tortion from the corresponding homogeneous arrangement shall not materially shorten or lengthen the distance separating two ball centres which touch one another. For, if it did, the centres could not continue to have approximately the same general arrangement throughout the assemblage. . Applying this condition, we see that if some of the lines which 1 The axes of an assemblage may be inclined to the axis of the cylinder. If they are, their directions will, after distortion, become screw-spirals. a Bartow—A Mechanical Cause of Homogeneity of Crystals. 571 join the centres of balls that touch in a thin assemblage lie in a parallel to the surface of the assemblage, we cannot have spherical bending of several layers, because this kind of distortion would involve material differences in the lengths of corresponding lines found in different layers. Such a situation of these lines does not, however, preclude cylindrical bending, provided their direction is that of the axis of the cylinder, for when this is the case their lengths will be unaltered by the distortion. It is not necessary, or indeed generally possible, that the curving of an assemblage shall present precisely the same degrees of symmetry as would be presented by the assemblage if undistorted, even when the modification of the latter by the limitation imposed on its extent is taken into account. Thus it is conceivable that the holomorphism of a thin assemblage may be impaired by a curvature which is concave towards one end of a holomorphic axis, and therefore convex towards the other end. For although symmetry will require that such a change shall be equally possible in either of the two opposite directions, its occurrence in the one direction in any part of the assemblage may preclude its occur- rence in the other in any other part of the same assemblage. Similarly a torsional twist experienced by an assemblage of small extent which is identical with its own mirror-image, may deprive it of the latter property, although the determination of the direc- tion of the twist—whether it shall be right-handed or left-handed, _ will depend on accident, or at least on external circumstances. A few words next with regard to the growth or increase of curved assemblages. The curvature of succeeding uniform layers of a curved assem- blage being necessarily different, it is evident that if a particular curvature gives closest-packing, and a very thin assemblage con- sisting of a very few layers and having this particular curvature be formed and solidified, layers added congruently to either face of such a nucleus will be unable to take up the closest-packed arrangement, those on the convex side having their dimensions along the surface rather too large, and therefore the distance between succeeding layers rather too small, and those on the concave side experiencing an unfavourable condition just the opposite of this. 572 Scientific Proceedings, Royal Dublin Society. Notwithstanding this, however, we must look for a congruen extension of the assemblage in both directions from the nucleus, because the irregularity and incompatibility which would other- wise be found at the junction of the solid and fluid portions would, at any rate so long as the number of added layers is few, be more prejudicial to closeness of packing at this boundary than the modi- fication imposed by the difference of curvature referred to; indeed we reach the important conclusion that if the curvature is infini- tesimal as compared with the distances between contiguous centres, a large number of layers may be added before the departure from the most favourable curvature becomes sufficient to prevent congruent accretion. Transition is thus possible from molecular thinness to microscopic or even macroscopic dimensions. Now a slight straightening of the nucleus will, it is evident, favour closest-packing of layers added on the concave side by approximating their conditions to those of the favourably arranged nucleus in regard both to the distribution of the centres and the curvature of the layers. Such a straightening will also favour closest-packing of layers added on the convex side, so far as distri- bution of the centres is concerned, but not in regard to the curvature of the layers, the latter becoming still further removed from the most favourable curvature. It is clear, therefore, that in many cases layers added on either side of the bent nucleus will, in striving after closest-packing, exercise some force tending to straighten it, and that as fresh layers are added, this will increas- ingly be the case. And if the solidified nucleus yields to some extent to the strain thus put upon it without being ruptured, its original curvature will be flattened. And further, if more layers are added at one part than at another we shall have the alteration of curvature different at different places. If, for example, the number of layers added is greater as we pass from one end to the other of a band-shaped assemblage whose most favourable curvature for closest-packing is a cylindrical bend- ing about an axis transverse to the band, it is evident that the band will take the shape of a watch-spring spiral. If, when a certain amount of bending has taken place, the: solidified portion of the assemblage breaks rather than bend any more, it is evident that the gradual growth of an assemblage will BarLtow—A Mechanical Cause of Homoyeneity of Crystals. 578 result in its sudden rupture when a critical point is reached. If, however, it will bend till all curvature is done away we may look for ultimate production of a rectilinear perfectly homogeneous condition of the assemblage as the result of the addition of a large number of layers. If it affords great resistance to bending we may have a case in which the assemblage grows considerably in every direction, while still a curved assemblage. If skeleton growth, 7.¢., discontinuous accretion, takes place along a bent surface of the solidified portion of an assemblage of the modified nature now under consideration, it is evident that the curved branches formed cannot be congruent, ¢.e., cannot form part of a homogeneous whole capable of a congruent filling in of the interstitial spaces. In other words, an unhomogeneous branched assemblage and not a skeleton homogeneous one will result. The facts concerning curved and branched crystals exactly parallel the conclusions reached above. Bending and branching oceur generally when the crystals formed are extremely fine or thin,’ and consequently only when the conditions are appropriate for the production of such crystals. According to Lehmann these conditions are either rapidity of crystallization, viscosity of the solution, or a low degree of solubility of the crystallizing eee in the solution. Thus he found that when a hot saturated solution of ammonium chloride, which has been suitably thickened with gum, is cooled, the quicker the crystals are formed and the more the viscosity is increased, the more delicate are the forms of the crystals. And he further found that in order to obtain skeleton crystals of potassium chloride out of aqueous solution, either an extremely thin stratum must be employed or, which attains the object more readily, the viscosity must be increased by the addition of gelatine. As an instance of the effect of a low degree of solubility, the same writer says of silver chloride, “ Small skeleton crystals can be easily obtained by rapid evaporation of its solution in ammonia or sodium chloride solution. Very fine large, well-formed crystals resembling those of ammonium chloride are produced by the 1 Thin, that is to say, as compared with their curvature. It must be remembered that the curvature, considered with regard to molecular magnitudes, is always extremely slight. 574 Scientific Proceedings, Royal Dublin Society. A solidification of the melted mass or when it is dissolved in melted e silver iodide. It may, however, be remarked that the skeleton cr ystals obtained in the way last mentioned are much more a massive than those out of aqueous solutions. Difficulty of solution — has therefore much. the same effect as viscosity, since it brings ; about the formation of more delicate forms.’” Lehmann tells us that ‘“‘ bending and branching arise almost — simultaneously.” They are of very common occurrence among cases where very great irregularity in the rate of growth at different : places is produced by one or other of the causes just enumerated. Thus, according to the same author, Isohydrobenzoindiacetate erystallizes out of alcohol in singular bent crystals resembling frequently a rolled up band. This form is, however, retained only so long as the crystals are sufficiently thin to show inter- ference colours. As they thicken they straighten themselves out more and more, and finally hecome fine regular rhombic crystals. Besides the bending described, a bending perpendicular to it generally takes place. Again, if a mixture of chromic chloride with mercuric chloride in aqueous solution is placed on an object glass under a cover and then evaporated till it becomes fairly thick, very long thin capillary crystals are formed as the cooling proceeds, which at first are curled up in spirals, but unroll themselves as they grow thicker. As a third striking instance, if a solution of wax in naphtha is rapidly cooled, radiated aggregations of very thin plates are at first formed ; these spherolites do not, however, continue long, but give way in the middle, extending themselves to form a ring which — then breaks up into several bow-shaped fragments. Hach in- dividual of these winds and bends itself as the growth proceeds till at length it again falls to pieces. And all this stretching and bending and fracturing takes place with such energy that the whole crystal mass in effecting these involved movements appears as though alive. As a final instance cupric chloride mny be mentioned. Com- monly this substance crystallizes out of acidified aqueous solution ; ly 'n 10, Lehmann “Ueber das Wachstum der Krystalle.’’ Zeitschr. f. Kryst., 1, pp. 457-459. Bartow—A Mechanical Cause of Homogeneity of Crystals. 575 in extremely fine needles which bend themselves somewhat vigorously, and then, while strong evidences of tension, sometimes resulting in rupture, show themselves, straighten themselves out. The larger crystals show brilliantly the progress of the formation of branches; directly they impinge on any obstacle, however in- significant, brush-like radiations are formed at the place.? Tetragonal well formed crystals of cromfordite (phosgenite) are sometimes met with which have a spiral twist.’ Dimorphism, Trimorphism, &c. The relative situations taken up by the ball centres of a mixed assemblage as the result of closest-packing depend, as we have seen, on what sizes are brought together.* It is evident, therefore, that where there is more than one kind of ball, if a change of con- ditions occurs which alters the sizes of balls of different kinds differently, the alteration produced may conceivably be such that closest-packing is no longer attained in the type of arrangement which originally gave it. And where this is the case, if the change be made gradually, it will be found that immediately a critical point is passed at which the type of arrangement origin- ally presented ceases to be the closest-packed equilibrium-arrange- ment, the assemblage will cease to approximate to this original type of arrangement, and will commence approximating to some other different type, viz. to that which after the critical point is passed becomes the one which now gives closest-packing. When- ever a critical point of this kind is passed, an assemblage will, therefore, take up a new type of arrangement, and if both before and after the critical point is passed, the same bodies constitute one homogeneous assemblage, the two assemblages thus presented will be dimorphous assemblages. At the critical point exactly the assemblage will of course be equally disposed to take up either arrangement, and consequently 10. Lehmann, ‘‘ Ueber das Wachstum &c.,”’ pp. 479-481. 2 There is an exceptionally fine specimen in the British Museum, London. 3 But see note 1, p. 546. Some effect in determining the nature of the arrange ment is also traceable to the linkage; and this applies to all linked assemblages whether they consist of a single kind of ball or of more than one kind. SCIEN. PROC. R.D.S., VOL. VIII., PART VI. 2U 576 Scientific Proceedings, Royal Dublin Society. if a fluid assemblage in this critical condition is brought into con- tact with a solidified portion of the same assemblage of practically the same density which displays one of the two dimorphous forms, it will adapt itself to, and become continuous with this form, to the exclusion of the other. Indeed a fluid assemblage capable of dimorphism, if it is anywhere near the critical condition referred to will show this readiness to adopt the arrangement of whichever of the two dimorphous forms comes in contact with it in a solid state. For in so doing it will bring about a closer-packing at the place of junction with this solid portion, than it would do if it were not congruent with the latter, even although the result of the con- gruence is that the fluid assemblage has not, when taken alone, the absolutely elosest-packed arrangement possible to it.’ An essential difference in the broad features of the various dimorphous changes of which assemblages of balls undergoing alteration in size are capable enables us to classify these changes under two distinct heads. Thus we have :— 1. Dimorphous change which consists in the uniform shrinkage or expansion or shearing in one or two directions of an assemblage taken as a whole, and which is wnaccompanied by any further re- arrangement or redistribution of the parts than this involves. 2. Dimorphous change which consists in a rearrangement or redistribution of the parts beyond what can be effected by any mere orthogonal projection, or successive projections, or simple shearing of the original assemblage.” An instance of a change of the nature included under the first of these heads would be presented if an assemblage consisting of two kinds of balls, or groups of balls, placed respectively at the angles and centres of a number of similar parallelopipeda fitted together to fill space without interstices in the most symmetrical manner possible, became so changed that the two kinds came re- spectively to occupy the angles and centres of similar cubes 1 Aneffect of the kind above described is also capable of being produced by an altera- tion in the ratio between the shortest distances separating linked and unlinked centres respectively, and the latter kind of dimorphism may be brought about in assemblages consisting of a single kind of ball as well as in those composed of more kinds than one, if an adequate change of conditions takes place. 2 Compare p. 590. BarLtow—A Mechanical Cause of Homogeneity of Crystals. 577 filling space as symmetrically as possible; thus experiencing a change from the asymmetric to the regular system.’ As an example of a change such as would come under the second head may be given that of an assemblage consisting of two kinds of balls present in the proportions 1:2 from the gyrohedral hemihedrism of the cubic system described on page 551, to the holohedrism of the hexagonal system described on page 553. Changes belonging to division 1 may, it is evident, take place in solidified assemblages without doing violence to the ties above defined which constitute their solidity, but it is hard to conceive of changes belonging to division 2 as occurring in a solidified homo- geneous assemblage without causing the destruction of these ties ; unless indeed the redistribution be of a trivial character. The changes comprised in division 1 can be subdivided into two classes. (a) Comprising all those in which the change on passing the critical point takes place smoothly, 7. e., not per saltum. (6) Comprising all cases in which on passing the critical point the assemblage is suddenly found out of equlibrium, and makes a change of form per saltwm to reach equilibrium in the new type of arrangement. The following will illustrate the nature of a change of class a. Suppose that we have a stack of spheres of two sizes such as is described on page 547, the larger spheres having the closest- packed arrangement of figs. 1 & 2, and the smaller spheres just fitting into the largest interstices left between these. If now, keeping the size of the smaller spheres the same,’ the size of the larger spheres be gradually diminished to a slight extent, so that they can no longer have as many contacts with one another, the stack will, it would appear, continue to be as close- packed as possible ¢f the separation of the larger spheres takes place in planes drawn through the sphere centres perpendicular to some one of the cube diagonals of the space partitioning, and the remaining contacts between these larger spheres be preserved intact. 1 This instance is given merely to show the kind of change meant, not as one likely to be realized. 2 As the effect under consideration depends on a relative change of size, this comes to the same thing as changing the size of both kinds. ae 2 578 Scientific Proceedings, Royal Dublin Society. Now the relative arrangement of the sphere-centres thus reached is produced by a uniform contraction of the cubical arrange-— ment in one of the four directions of the cube diagonals, the arrangement reached being therefore a rhombohedral one. The change experienced takes place smoothly without any discontinuance of equilibrium, and it is therefore of the kind marked a. To illustrate the nature of a dimorphous change of the class marked 6. Suppose that in the stack of spheres of two sizes which has become rhombohedral in the way just explained the ratio between the radii of the larger and smaller spheres con- tinues to fall in value, and passes the point at which the equilibrium arrangement becomes again a cubic one, viz. that described on page 549 (and see fig. 9). Now during all the previous change in the ratio of the radii up to this point the contacts between the larger spheres in the equilibrium arrangement have continued of the same nature, but directly this point, at which the arrangement a second time becomes cubie, ts passed, these contacts become broken, and it would appear that almost immediately after passing this point, for closest-packing to obtain, the larger spheres must approach one another in planes at right angles to one of the directions of the trigonal axes of the system till they come in contact in these planes. This involves a sudden uniform contraction of the system in all directions at right angles to such an axis and a uniform expansion in the direction of the axis. The changes of division 2 must, it is evident, be per saltum. If an assemblage passes two critical points in succession at each of which the existing type of equilibrium-arrangement is exchanged for a different type in one of the ways above described, we have trimorphism ; if three such critical points are passed, tetramor- phism. Turning now to the experimental facts we find that these are closely akin to the conclusions reached above. In the first place there is the fact that a mere dimensional change of a crystal which does not amount to dimorphism, ¢.g., an alteration of bulk caused by change of temperature, is different in different directions except in cases of crystals belonging to the regular system. And, just such a relation between form and dimensional change will be found Bartow—A Wechanical Cause of Homogeneity of Crystals. 579 in an assemblage consisting of two or more kinds of balls, if the different balls expand or contract at different rates when subjected to some external change of conditions. The behaviour of sulphur is just what one might expect of an assemblage of mutually-repellent particles when subjected to such changes of conditions as will produce polymorphism belonging to class 6 of division 1.1. Thus Lehmann says of this body :—“ Sul- phur, as we know, crystallizes from a melted mass, or out of a hot solution, in monosymmetric forms which, as the cooling proceeds, are transformed more or less rapidly into the rhombic modification, and conversely, the latter when heated passes to the monosymmetric form, as is perceived by the turbidity which displays itself, or still better by the change of colour of a thin lamina in polarized light. And it is easy to keep the temperature at such a point that the boundary of one or the other modification gives way at the slightest change in one or the other direction, .¢., as slight cooling or warm- ing occurs.’” And, quoting further from the same anthor:—“ If very hot melted sulphur is rapidly cooled the viscous modification is obtained. In a mass of this kind two kinds of crystals are gradually formed, the characteristically bent ones of a yet unknown modification, and monosymmetric ones which are more spherolitic. On being touched the first are rapidly transformed into the latter. And on being heated they disappear first, and therefore have the lower melting point. Ifrhombic sulphur is brought in contact with the viscous mass the rhombic crystals grow in the form of fine branched and bent skeleton crystals; they are, however, quite distinguishable from those of the unstable form just mentioned, especially when the warming takes place gradually, in which case they grow to fine pyramidal groups, while the latter develop to small leaf-like erystals.’” As another instance resembling the polymorphism of class }, division 1, we have ammonium nitrate which presents four forms, 1 This explanation of the properties of sulphur requires the presence in it of ut least two kinds of ultimate parts or particles. If this is regarded as an objection, there is the alternative that similar effects may arise from dimorphism due to linkage. (See note 1, p. 576). * Zeitschr. f. Kryst., 1, p. 112. 3 Tbid., 1, p. 128. 7 two rhombic, a rhombohedral and a regular form. In polarized light the crystals behave as altogether isotropic. If gradually — cooled, however, a change suddenly takes place at about 127°, and they become double-refracting, and asa less solubility is proper to the new form than to the regular one, the change of form is accompanied by increase of size in cases where the crystals are found in a solution. From the rudimentary form and the optical behaviour it can be concluded that the crystals obtained in this way are Frankenheim’s rhombohedra. Ifthe solution is further cooled, at about 87° needle-shaped rhombic crystals are produced. The regular situation of these with relation to the rhombohedral ones, as the latter are spontaneously transformed, furnishes an exceptionally good example of the phenomenon that when a transformation from one modification into another takes place, the newly-formed has in general a regular situation with respect to the older modification. Thus in the present instance the crystals are so placed that the vertical axis of the rhombic form, that which corresponds to the greatest extension, either has the same direction as that of a secondary axis of the rhombohedral form, or is at right angles to it, while the macro- or brachy-diagonal,! has the same direction as the principal axis of the rhombohedron.’ The readiness with which an assemblage of mutually-repellent particles, or spheres,’ will respond to a change of conditions past a critical point, and commence approximating to a different type of arrangement will, it is manifest, depend not only on what it comes in contact with, but will also partly depend on the amount of disturbance to which it is subjected.* And for comparison with this may be mentioned Lehmann’s remark with regard to the transformation from one solid modification to another. ‘ When a modification is heated while isolated it is sometimes possible to raise the temperature far above the point (normal critical point of temperature) at which, when in contact with a crystal of the 580 Scientific Proceedings, Royal Dublin Society. 1 It is impossible to determine which, as the prism of the rhombic crystal is nearly right-angled. ? 0. Lehmann ‘Ueber physikalische Isomerie’’; Zeitschr. £. Kryst., 1., p. 107; Comp. Pope’s translation of Fock’s ‘‘Chemische Krystallographie,”’ p. 158. 3 See p. 529, especially note 2. 4 Comp. No. 7 of Data, p. 688. Bartow—A Mechanical Cause of Homogeneity of Crystals. 581 modified sort, transformation commences, but mechanical shaking is generally competent to bring about the change.” Of other dimorphous substances whose behaviour would appear to resemble that which has just been attributed to dimorphous assemblages belonging to division 2, Lehmann speaks as follows :— “ oe _ . 588 Scientific Proceedings, Royal Dublin Society. in equal numbers arranged in the holohedral monoclinic symmetry — described on page 559 have its adjacent balls all linked together, this assemblage can, by a symmetrical breaking of the links compatible with the coincidence-movements (Deckbewegungen), be divided into identical grouplets, each consisting of an octahedrally- arranged group of six of the larger balls, to each of the opposite triangular ends of which is linked a triad of the smaller balls, thus making twelve balls, six of each kind, linked together in each grouplet. All the six balls of each kind are similarly placed in the grouplet. A partitioning into grouplets composed of half the number of balls, 7.¢., three of each kind, may equally well take place con- sistently with the coincidence-movements (Deckbewegungen). 4. Groups similar to one another of the composition 4B, may form an assemblage of type 10a, or one of type 52, and these groups may also be obtained from certain assemblages belonging to these types. Thus, if an assemblage composed of two kinds of balls, present in the numerical proportions 1 : 2, arranged in the dodecahedral hemihedral symmetry described on page 552, have its adjacent. balls all linked together, this assemblage can by a symmetrical breaking of the links be divided into identical grouplets of the composition AB,, the two similar balls being similarly situated. Again, an assemblage thus composed, with the trapezohedral tetartohedrism described on page 556, can also be divided into identical grouplets of the composition referred to. 5. Groups similar to one another of the composition A,B, may form an assemblage of type 62a. Thus an assemblage composed of two kinds of balls present in the numerical proportions 1: 2, arranged when closest-packed, according to type 25a,, as described on pages 553, 554, can, without _ much change of the conditions of equilibrium, have its parts so linked and allotted as to form groups consisting of two nearest — large balls, about which are grouped rectangularly four smaller balls, the six centres of a group lying at the angles of a right — octahedron derived from a rectangular parallelopiped, the larger ones at the vertices, and all the groups being similarly orientated. For the modification in the arrangement to be slight in such a j Bartow—A Mechanical Cause of Homogeneity of Crystals. 589 case, the distances between the centres of a group must be but little less than the corresponding distances between next centres of different groups. The modified assemblage which results will have angles slightly different from right angles, and will belong _ to type 62a,, so that it will display the symmetry of class 3 in Sohncke’s list ; the situations of the smaller balls will be singular points lying in planes of symmetry, but not all alike in the unbroken assemblage; those of the larger ones will be singular points on digonal axes and on planes of symmetry on the two sides of which the corresponding points are not directly opposite. In all the above cases the situations of all centres of the same kind in a group are identical, and consequently the ties which bind them are respectively similar and equivalent.” This, however,. is evidently not always the case, for we know that balls of the same kind may be differently situated in a homogeneous structure, and the same may hold true in a group. It has been concluded above that there are countless cases in which the principle of closest-packing, where balls of different kinds. are used, is productive of symmetrical assemblages, some of them capable, some incapable of being partitioned into units of a single. kind, without lowering the type of symmetry. And when assem- blages capable of this symmetrical partitioning are taken, and by some change of the external conditions their balls are aggregated into groups of a single kind, the balls of a group being linked with one another but not with balls of surrounding groups, a further application of the same principle will intermix these assem- blages with other balls or complexes of balls, that is provided the combination produces still closer packing. 1 Not, however, in all cases identical considered with respect to the unbroken assemblage. 2 Comp. theory of ring-formation in ‘‘ Handbuch der Stereochemie,’’ yon Dr. C. A. Bischoff und Dr. Paul Walden, Frankfurt-a-M., 1894, p. 50. The symmetry of arrangement of some of the groups here described, and of other groups constructed in a similar way, appears to be inconsistent with the diagrammatic linking together of atoms in a molecule ordinarily adopted, but it must be remembered that the basis of this graphic conception of links lies rather in a relation subsisting between the atom and the group in which it occurs than in one between the atom and individual atoms round about it. The graphic representations ordinarily employed may therefore very possibly express too much, and the method require some modification. See some remarks on valency made later, p. 681. 590 . Scientific Proceedings, Royal Dublin Society. Further, the more complicated assemblages produced in this — way can be subjected to symmetrical aggregation and partitioning, . and still more complicated groups obtained in this way; or a number of smaller groups of new patterns can be had by sym- metrically altering the linking. And then, by appropriate changes — of the external conditions, assemblages thus arrived at can be conceived to be broken up, and the various kinds of groups massed by themselves, all in obedience to the principle of closest-packing. In this way, by the action of closest-packing, with the aid of the additional hypothesis of symmetrical linking, very intricate results may be reached by a number of successive steps as the conditions change, and orderly complexity and highly specialized grouping, such as appeared at first sight impossible of attainment by any selective action of the principle referred to, is seen to be quite within the capacity of this agency for producing symmetry. As already noticed, a slight change in the relation between the balls may cause closest-packing to be attained in a different homo- geneous arrangement,’ and it is possible that in some cases two or more kinds of balls may be so related as readily to form a variety of different groups with but comparatively slight changes of the — general conditions.” Two kinds of balls may for example be so related as, under slightly different conditions, to form groups of all or most of the different kinds just referred to above, and also complex combinations of these groups. We may compare with this the complex isomerism displayed by the hydrocarbons, which may perhaps, as just hinted, be traceable to a species of polymorphism. It is important in this connection to distinguish between that kind of dimorphism or polymorphism which affects only the solid or completely-linked state, and dimorphism or polymorphism of the kind just referred to. In cases of the former the two forms become identical when they pass to the liquid condition, 7. e., they have the same grouping. In cases ofthe latter not only is the arrangement of the tranquil homogeneous assemblages different, but the grouping when they break up is different, although the consti- — tuents of the assemblages are the same. 1 See p. 575. 2 Compare p. 576. Bartow—A Mechanical Cause of Homogeneity of Crystals. 591 3. As to the effects produced by the presence of linked groups. We see that in most respects the groups will behave much as single unlinked balls would do—homogeneity and close packing will, as we have already concluded, frequently go together whether the balls of an assemblage are aggregated in groups or not. The same balls may, it is evident, under the same external con- ditions, take up two or more different relative arrangements in seeking equilibrium if some of them are linked together to form groups, and the grouping is different in different cases; and this will apply whether the balls are all of one kind or not, and whether in the different cases the groups contain the same sets of balls or not. Marked difference of behaviour of the same set of balls may be expected in different cases, especially when we compare a case in which few links subsist with @ case where there are many. Thus it is evident that the presence of links between balls will commonly prevent them from packing as closely as they otherwise would do, and that the more they are interlinked, the less free they will be to accommodate themselves to their surroundings, and the more the closeness of the packing will be likely to be impaired. And when a number of assemblages having similarity of composition, but differing in the amount of linking which obtains in them, are com- pared, the differences in the degree of closeness of the packing - which are thus occasioned may be revealed by differences in the susceptibility of the assemblage to some external influence. To compare with this we may cite the following from Lothar Meyer :—“ Experience has shown that the normal compounds always have a higher boiling point than those with side chains,’ and that the boiling point of the latter falls as the number of side chains increases. In the case of bodies having a similar constitu- tion, the addition of CH, raises the boiling point by from 18° to po 2 2 1 Ifthe resemblance here pointed out has any significance, it would seem to furnish some additional evidence as to the nature of these ‘‘ side chains ’’—to show that they have some of the properties of the links referred to in the text. * Lothar Meyer’s ‘‘Grundziige der theoretischen Chemie,” p. 84; or Bedson and Williams’ translation, p. 91. SCIEN. PROC. R.D.S., VOL. VIII., PART VI. 2X 592 Scientific Proceedings, Royal Dublin Society. Persistence of properties after change of state. When an assemblage is broken up into groups by the breaking of the ties which keep the groups fixed in the same relative situ- ations with respect to one another, disturbing movements may cause the equilibrium to fluctuate and produce a liquid state in which the groups move with respect to one another while the parts of the same group preserve the same constant arrangement. Compare Bischoff in Berl. Ber., xxiii., p. 620, and in ‘‘ Handbuch der Stereo- chemie,”’ p. 118; also Hantzsch’s ‘‘ Grundriss der Stereochemie,’’ pp. 67 and 101. SCIEN. PROC. R.D.S., VOL. VIII., PART VI. 24 3'G 608 Scientific Proceedings, Royal Dublin Society. Groups which resemble one another as to parts of them which are identical. Comparison with some cycle and non-cyclic combinations. There is a way in which groups which are not isomerides may be closely related, where the resemblance does not spring solely from an enantiomorphous relation, while, at the same time, such a relation is not excluded. Thus, instead of obtaining a number of different groups by changing the grouping of a given set of balls, we may fix upon some particular arrangement for a group, and then derive a series of related groups from it by substituting for one or more of its balls other different balls or complexes of balls, leaving the relative situation in the group of the remaining balls unaltered,! and waiving the question of the arrangement of the groups in the different assemblages. Groups obtained in this way will resemble one another as to all properties imparted solely by the identical portions common to them, but, in addition to this we have the interesting fact that under some conditions the number of dif- ferent groups obtainable from a given group by aspecified number of substitutions can be ascertained. For, if the general conditions are constant, or which amounts to the same thing, if we disregard any change of arrangement brought about by changes in these conditions, it is evident : 1. That the substitution for a particular ball in each group of a certain different ball or rigid complex will modify the conditions of equilibrium of an assemblage of similar groups im a definite manner determined by the action of the fundamental law of closest- packing, so that the position of the substituted ball or complex with respect to the remainder of the group may be regarded as fixed, and this will still apply if the substituted ball becomes attached to its group. 2. That when two or more of the same sort of original balls — are exchanged for others, and some of the balls left resemble those removed both in their nature and their situation, the exchange may be effected in a definite number of different ways depending on the nature of the grouping, the number of balls removed, and the number remaining which are similar to them. 1 We are not, for the moment, concerned as to whether this change can be made without travelling outside our data; some suggestions as to this are, however, made later. See p. 673. Bartow—A Mechanical Cause of Homogeneity of Crystals. 609 Now the variety of types of grouping possible in which some given number of similar balls can be grouped about a centre in similar situations in such a manner that the group is competent to form part of a homogeneous assemblage, is not very large, and the number of different ways in which a certain number of similar balls of any particular group of this nature can be exchanged for other balls or complexes differing from them is easily ascertainable. The following is a short enumeration of all the types of group- ing of similar balls possible, and it is accompanied by a statement of the number of different types obtainable by twofold! substitution, 7.e., of the number of different groups derivable by the exchange of two of the original similar similarly-placed balls for other balls or complexes different from them. In enumerating the groupings not only typesin which the similar balls occupy identical situations are given, but also those in which the situations are of two kinds enantiomorphously similar. The number of groups derivable in any case by the substitution of different balls or complexes depends not only on the arrangement of the balls some of which are removed, but also on the arrangement of other balls forming part of the same group, if any such are present.” It will be convenient to refer to the diagrams in Sohncke’s list of Krystallklassen contained in Zeitschr. fir Kryst., xx., p. 457. In every case in which the similar balls occupy identical situations in the group, it is manifest that, whatever the number or arrangement of these balls, substitution for one only will produce identically the same effect whichever of the similar balls is selected for removal. In cases, however, where the situations are of two kinds enantiomorphously similar to one another, single substitution of the same ball or complex can be made in two ways, resulting in two different groups which are enantiomorphs. ‘1. As to the number of different types of groups existing in which two balls are similarly situated, we see that two identical situations without other similar ones, can be found in groups of either one of the classes 3, 5, 6,7, 8, 9,10, 12, 18, 15, 21, 22, or 24 in Sohncke’s list just referred to, the required centres being 1 Threefold, fourfold, &c., substitution are also readily traceable, but the results would consume too much space here. 2 Compare Bischoff’s ‘‘ Handbuch der Stereochemie,’’ § 3, p. 635. 2Y¥2 610 Scientific Proceedings, Royal Dublin Society. singular points,! 7. e., lying in axes, or in planes of symmetry, or in both of these, except in the case of class 5. Groups belonging to classes 5, 7, 10, 15 or 22 are not identical with their own mirror-images, and consequently existin two enantiomophous forms. If the situations of the two balls are enantiomorphously similar they may be found in any group whose symmetry is that of either of the classes 1, 3, 4, 11, 14, 16, 23, or 25. Twotold: substitution in a group of either of these two sets, if the two balls or complexes substituted are both of the same kind, can, it is evident, be made in one way only. And if the two balls substituted are of two different kinds, and the situations of the original balls are identical, such substitution can still be made in only one way. Tf, however, the situations of the original balls are only enantio- morphously similar, as in the classes last mentioned, and the two balls substituted are of two different kinds, ¢wo different groups are obtainable from the original group, and these are enantiomorphs. 2. If a group contains ¢hree similar balls similarly placed, and no others occupying similar situations, it is evident that they must lie at the angles of an equilateral triangle, and that the number being odd, the existence of enantiomorphously similar situations for any of the three balls is precluded. And three identical situations, without other similar ones, can be found in groups of either one of the classes 13, 15, 16, 19, or 20 in Sohncke’s list, the required positions for the centres being singular points except in the case of class 20. Groups belonging to classes 15 or 20 are not identical with their own mirror-images, consequently exist in two enantiomorphous forms. T'wofold substitution in any such group containing three balls can be carried out in one way only when the substituted balls are both of the same kind. When they are of two different kinds the same is true in the cases of groups of classes 13 or 15, but two different groups are obtainable where the original group is of class 16, class 19 or class 20, and these two derived groups are enantiomorphs when the group from which they are derived belongs to class 19. 1 Compare Zeitschr. f. Kryst., 23, p. 60. Bartow—A Wechanical Cause of Homogeneity of Crystals. 611 3. A group containing four similar balls similarly placed will, if the situations of the four balls are identical, belong to one of the classes 6, 7, 21, 22, 23, 24, 26, 27, 80, or 82. If the similar situations of the four ball-centres form two sets of two points enantiomorphously related, it will belong to one of the classes 3, 8, 24, or 25. In all cases, except when the group belongs to class 8, 7, 8, 25 or 27, the situations of the ball-centres will be singular points. Groups of classes 7, 22, 27 or 32 are not identical with their own mirror-images, consequently exist in two enantiomor- phous forms. The number of different groups which can be derived by twofold substitution, z.e., by substituting two balls or complexes for some two of the four similar balls found in a group, is given below in two columns A and B, A giving the number obtainable when both substituted balls are alike, B the number when they are different from one another. If any of the derived groups are enantiomorphs the number of these is given. Those which do not pair as enantiomorphs are identical with their own mirror-images, except in cases where the original group is itself an enantiomorph. NuMBER OF GROUPS DERIVABLE. Description of group of similar similarly in B situated ball-centres before : ; substitution is made. Balls sub-| No. of ||Balls sub-| No. of stituted | Enantio- || stituted | Enantio- alike. morphs. || different. | morphs. Four-Ball Groups. 4a, Class 6, the four similar ball-centres lie at the angles of a rectangle, ; 3 — 3 — 46, Class 7, at either set of the alternate corners of a ard gay pee US (an enantiomorph), 3 _ 3 — 4c, Class 21, at the angles of a square, ‘ 2 — 2 — 4d, Class 22, at the ate of a ere le enantiomorph), ; 2 — 2 — 4e, Class 23, at the angles of a ie a enantiomorph), 6 2 _— 3 —_— 612 Scientific Proceedings, Royal Dublin Society. NumsBer or Grours DERIVABLE. Description of group of similar similarly A = situated ball-centres before ; : substitution is made. an Balls sub-| No.of ||/Balls sub-| No. of stituted | Enantio- || stituted | Enantio- alike. morphs. || different. | morphs. Four-Ball Groups—continued. 4f, Class 24, at the corners of a right tetrahedron,+ 3 1 pair 3 1 pair 4g, Class 26, at the angles of a square 2 — 3 1 pair 4h, Class 27, at the angles of a anu (an enantiomorph), 0 2 — 3 — 4i, Class 30, at the corners of a regular tetrahedron, . < : : 5 1 — 1 _ 4;, Class 32, at the corners of a regular tetrahedron (an enantiomorph), . 1 — 1 — 4k, Class 3, at the angles of a rectangle, 4 1 pair 6 3 pairs 41, Class 8, at the angles of a rectangle, 4 1 pair 6 3 pairs 4m, Class 24, at the angles of a square,” 38 1 pair 4 2 pairs 4n, Class 25, at the corners of a Ge. tetrahedron,? 2 4 1 pair 6 3 pairs 4. A group containing six similar balls similarly placed will, if the situations of the 6 balls are identical, belong to one of the classes 9, 10, 11, 12, 18, 15, 17, 18, 28, 29, 30, 31 or 32 in Sohncke’s list. If the similar situations of the six balls form two sets enantiomorphously related, it will belong to one of the classes 12, 14,16, or 19. In all cases, except where the group belongs to class 14, 15, 16, 18, or 19, the situations of the centres will be singular points. Groups of classes 10, 15, 18, 29, or 32 are not identical with their own mirror-images, consequently exist in two enantiomorphous forms. 1 The ball-centres lie in the planes of symmetry. The tetrahedron is not regular. 2 The ball-centres lie in digonal axes. 3 Not a regular tetrahedron. BarLtow—A Mechanical Cause of Homogeneity of Crystals. 613 The number of different groups obtainable by twofold substi- tution given under the two heads A and B as before, is as under :— NuMBER OF GROUPS DERIVABLE. Description of group of similar similarly iN B situated ball-centres before substitution is made. Balls sub-| No. of |/Balls sub-| No. of stituted | Enantio- || stituted | Enantio- alike. morphs. || different. | morphs. Six-Ball Groups. | 6a, Class 9, the six similar ball centres lie at the angles of a regular hexagon, 3 — 3 — 64, Class 10, the six similar ball centresilie at the angles of a regular hexagon (an enantiomorph), 3 — 3 — 6c, Class 11, the six efratlle ball’ AST TRE lie at the angles of a regular hexagon, 3 — 5 — 6d, Class 12, at the alternate corners of a right regular hexagonal prism, 4 1 pair 5 2 pairs 6e, Class 13, at the corners of a triangular right prism, 4 1 pair 5 2 pairs 6f, also Class 13, two and two in the sides of an equilateral triangle equidistant from the angles, ° 4 — 5 = 6g, Class 15, form a trigonal 6- -point-group which has no plane of symmetry (an enantiomorph), 4 — 5 — 6h, Class 17, at the angles of a regular hexagon, . 3 — 5 2 pairs 6i, Class 18, at the angles of a regular hexagon (an enantiomorph), . 3 — 5 — 67, Class 28, at the corners of a regular octahedron, 2 — 2 — 6%, Class 29, at the corners of a regular octahedron (an enantiomorph), y) — 2 — 67, Class 30, at the corners of a regular M octahedron, 2 — 3 1 pair 6m, Class 31, at the corners of a regular octahedron, 2 — 3 — 6x, Class 32, at the corners of a regular octahedron (an enantiomorph), 2 — 3 _— 6p, Class 12, at the angles of a regular hexagon, me 4 1 pair 6 3 pairs 6q, Class 14, at alternate angles of a regular right- -hexagonal prism, 5 , | 2 pairs 10 5 pairs 67, Class 16, at the corners of a triangular prism, 5 2 pairs 10 5 pairs 6s, Class 19, two and ‘two in the sides of an equilateral triangle equidistant from the angles, ‘ : 7 - : Nn 1 pair 10 5 pairs 1 The centres lie in planes of symmetry. 2 The centres lie on digonal axes. 614 Scientific Proceedings, Royal Dublin Society. 5. A group containing eight similar balls similarly placed will, if the situations of the eight balls are identical, belong to one of the classes 21, 22, 28, or 29. If the similar situations of the balls form two sets enantiomorphously related it will belong to one of the classes 6, 23, 24, 26, or 31. In all cases, except when the group belongs to class 6, 22, 23, 24, or 26, the situations of the ball-centres will be singular points. Groups of classes 22 or 29 are not identical with their own mirror-images, consequently exist in two enantiomorphous forms. The number of groups obtainable by twofold substitution given under two heads A and B as before, is as under:— NuMBER OF GROUPS DERIVABLE. Description of group of similar similarly A B situated ball-centres before ; substitution is made. Balls sub-)| No. of ||Balls sub-| No. of stituted | Enantio- || stituted | Enantio- alike. morphs. || different. | morphs. Hight-Ball Groups. 8a, Class 21, the eight similar ball-centres lie at the corners of a right pee prism, 6 1 pair 7 2 pairs 84, also Classes ‘21, on the four sides of a square equidistant from the angles, . 6 — 7 = 8c, Class 22, form an 8-point-group without plane: s of symmetry (an enantiomorph) 6 — Z = ae Class 28, at the corners of a cube, 3 — 3 == , Class 29, at the corners of a cube (an enantiomorph), 3 — 3 — 8f, Class €, at the corners of a rectangular parallelopiped, c 10 3 pairs 14 7 pairs 89, Class 23, at the corners of a square prism, ‘ 8 3 pairs 14 7 pairs 8h, Class 24 (for form see Sohncke’s fig.), 10 4 pairs 14 7 pairs Si, Class 26, on the four sides of a square ; equidistant from the angles, : 8 2 pairs 14 7 pairs 87, Class 31, at the corners of a cube, 6 4 1 pair 6 3 pairs 6. A group containing twelve similar balls similarly placed wili, if the situations of the twelve balls are édentical, belong to one of the classes 9, 10, 28, 29, 30, 31, or 382. If the similar situations of the balls form two sets enantiomorphously related, it will belong to one of the classes 11, 12, 13, or 17. The situations of the ball-centres in groups of classes 9, 28, 29, 30, and 31 are Bartow—A Mechanical Cause of H omogencity of Crystals. 616 singular points. Groups of classes 10, 29, or 32 are not identical with their own mirror-images, consequently exist in two enantio- morphous forms. The number of groups obtainable by twofold substitution, given under two heads A and B as before, is as under :— Description of group of similar similarly situated ball-centres before substitution is made. Twelve-Ball Groups. 12a, Class 9, the ball-centres lie at the corners of a regular hexagonal prism, 120, also Class 9, two and two on the sides of a regular hexagon cauidisin from the angles, : 12c, Class 10, form a 12-point- group of the hexag onal system which has no planes of symmetry (an enantiomorph), 12d, Class 28, at the middle points of the 12 edges ofa cube, 2 12e, Class 29, at the middle points of the 12 edges of a cube (an enantiomorph), 12f, Class 30, form a specialized regular 12- point-group whose points lie in planes which pass seuss opposite edges of acube, . 129, Class 31, form a " specialized 12- -point- group whose points lie in planes through principal axes, . 12h, form such a 12-point-group further specialized so that each point is equidistant from 5 nearest points, which consequently lie at the angles of aregular pentagon; other balls if present oe arranged in this higher symmetry, + : 122, Class 32, form a 12- -point- eroup “with- out planes of pomeey (an enantio- morph), . 127, Class 11, at the corners of a regular hexagonal prism, . 12%, Class 12 (for form see Sohncke’s s fig.), 127, Class 13 (for form see Sohncke’s fig.), 12m, Class 17, on the sides of a regular hexagon equidistant from the angles, NumsBer oF GROUPS DERIVABLE. A Balls sub-] No. of stituted | Enantio- |} alike. morphs. 9 2 pairs 9 au 9 = 5 1 pair 5 = 7 2 pairs 7 2 pairs 3 pes 7 — 12 5 pairs || 14 5 pairs 14 5 pairs 12 3 pairs 11 11 11 'Balls sub-| No. of stituted | Enantio- different. B morphs. 4 pairs | 11 pairs 11 pairs 11 pairs 11 pairs 1 Although a group of this kind can form the unit of a homogeneous assemblages, the symmetry of the group is not such as can be possessed by the assemblage. 616 Scientific Proceedings, Royal Dublin Society. q 7. A single type of group containing sixteen similarly-placed q balls, in which the similar situations of the balls form two sets — enantiomorphously related, belongs to class 21, the situations of the balls not being singular points, and the form being identical with its own mirror-image. NuMBER OF GROUPS DERIVABLE. A. B. Balls substituted No. of Balls substituted No. of alike. | Enantiomorphs. different. Enantiomorphs. 20 | _ 7 pairs 30 15 pairs 8. A single type of group containing twenty similarly-placed balls can be obtained by occupying the twenty similarly-situated points lying midway between every nearest three points of the specialized 12-point-group referred to under 12 h. above,’ the form obtained being identical with its own mirror-image. NuMBER OF GROUPS DERIVABLE. A. B. Balls substituted No. of Balls substituted No. of alike. Enantiomorphs. different. Enantiomorphs. 6 1 pair 7 2 pairs 9. A group containing twenty-four similar balls similarly placed will, if the situations of the 24 balls are identical, belong to one of the classes 28 or 29. If the similar situations of the balls form two sets enantiomorphously related it will belong to one of the classes 9, 80, or 81. The situations of the ball-centres in class 28 are singular points. Groups of class 29 are not identical with 1 When a homogeneous assemblage is built up of such groups, although the twenty balls oceupy similar positions so far as a single group is concerned, they will not all occupy similar positions in this assemblage. Bartow—A Mechanical Cause of Homogeneity of Crystals. 617 their own mirror-images, consequently exist in two enantiomor- phous forms. The number of groups obtainable by ¢wo-fold substitution given under two heads A and B as before, is as under :— NuMBER OF GROUPS DERIVABLE. Description of group of similar similarly situated ball-centres before substitution is made. A B Balls sub-| No. of ||Balls sub-| No. of stituted | Enantio- || stituted | Enantio- alike. morphs. || different. | morphs. Twenty-four-Ball Groups. 24a, Class 28, the 24-ball-centres arranged to form a specialized 24-point-group whose points lie in planes drawn through the cube centre perpendinuies to the three principal axes, 16 4 pairs 23 8 pairs 245, also Class 28, 24-point-group whose points lie in planes drawn through opposite cube edges, : c ; 16 5 pairs 23 10 pairs 24c, Class 29, form a 24-point-group without planes of symmetry (an enantiomorph) 16 — 23 — 24d, Class 9 (for form see Sohncke’s fig.), . 30 11 pairs 46 23 pairs 24e, Class 30 (for form see Sohncke’s fig.), 26 10 pairs 46 23 pairs 25e, Clsss 31 (for form see Sohncke’s fig.), 26 11 pairs 46 23 pairs 10. A group containing forty-eight similar balls, the similar situations consisting of two sets enantiomorphously related, can be formed of class 28, and the number of groups obtainable by ¢wo- fold substitution from such a group is :— NuMBER OF GROUPS DERIVABLE. A. B. Balls substituted No. of Balls substituted No. of alike. Enantiomorphs. different. Enantiomorphs. 56 23pairs 94 | 47 pairs In precise harmony with the conclusion stated above, that in 618 Scientific Proceedings, Royal Dublin Society. a group of similar identically-situated balls substitution for one only will produce identically the same effect whichever of the similar balls is selected for removal,’ we have the fact of the presence in some combinations of similarly situated atoms, é.e., of atoms whose — ties are similar; the proof of this being that there is but one mono- substitution product of such combinations, e.g., of methane, and that this is the case notwithstanding the employment of methods which ensure that different atoms and not the same atom are dis- placed in a series of displacements of a single atom.” That the atoms have distinct spheres of influence, and, although similarly related to the combination in which they occur, are not without relative arrangement of some kind is in evidence. Thus we have two and not merely one tetra-substitution derivative ab cd of Methane.° Corresponding to the limited number of ways in which double substit ution can be made in the simpler groups, as shown by the tables given above,* we have the facts referred to by Lothar Meyer as follows :— “ = time at similar surfaces. And to compare with this we have evidence, ¢.g., in embedded twins such as the Karlsbad twin of orthoclase, that larger faces often grow faster than the smaller ones of the same kind. 1 See p. 576. 2 See Pope’s Translation of Fock’s ‘‘ Chemische Krystallographie,’’ p. 152, where other similar instances are given. Bartow—A Mechanical Cause of Homogeneity of Crystals. 643 twin individuals in a nucleus, whatever its development afterwards, is at first a principal plane of each individual, and the networks _ of centres found in planes parallel to it display the same angles sameways orientated in both individuals... A kind of twinning is, however, conceivable in which this is not the case. For, if after a twinned nucleus has been produced by a change of external conditions in the way above explained, this change immediately proceeds further, so that the individuals forming the twin seek to pass by distortion to a yet lower kind of symmetry, and the accomplishment of this further change for one individual would involve a distortion in the separating plane different in direction from the distortion in this plane which would be involved by the corre- sponding change in the other individual meeting it at this plane, the following results must be looked for when the twinned nucleus is partly solidified :— . A condition of strain at the separating plane and in its immediate vicinity where the individuals will be mutually restrained from compliance with the demands of the further change of conditions, but, especially in cases where the plane is very small, a rapid approximation to the newly-acquired symmetry, and consequent falling off in strain as we pass away from this plane. As a consequence of this, two individuals of a twinned nucleus - will be more or less contorted near the place of contact, and, where the symmetry with respect to the plane is of a low order, will be also bent. Where there is no bending, a principal plane direction of each individual will still remain parallel to the separating plane, but the angles of the structure of one individual in this plane-. direction will cease to be identical in orientation with those of the structure of the other individual. Where there is bending in addition, no principal plane direction of either individual will continue parallel with the separating plane. Notwithstanding the contortion of the nucleus thus brought about, layers subsequently deposited may be expected to be laid comformably with the homogeneous symmetry reached by the free ends of the individuals, any irregularity of growth caused by the contortion rapidly dying out; the growing individuals will thus extend themselves to meet one another unconformably, so far as internal structure is concerned, as in the case of individual 7 erystals attached to one another unsymmetrically. Even, how-— ever, where there is bending, the relative orientation of the in- dividuals will preserve its symmetrical character, because the distortion of the structure of one individual of the nucleus will be accompanied by the similar distortion of that of the other. i For comparison with examples of the first kind, in which there is no bending, we may mention the Carlsbad twin of orthoclase,’ and for comparison with the results of twinning accompanied by bending of the nucleus, the anorthic twins of pericline and those of anorthite. 644 Scientific Proceedings, Royal Dublin Society. Secondary twinning. A word may appropriately be said here about an important property of some assemblages whose parts are competent by a mere linear distortion to pass to a different symmetry. This property may be described as follows :— Besides the kinds of twinning just referred to, another kind of twinning which is also produced by a shear is conceivable, in which, however, the origin of the disturbance of the original equilibrium-arrangement, instead of being found in a dimorphous change, 7.¢., in an alteration of the relations subsisting between the parts, originates in some external deforming agency, the kind of internal symmetry towards which the system tends in obedience to the principle of closest-packing continuing the same after the disturbance. This secondary twinning can occur in an assemblage whose parts are so related as to be geometrically competent by a linear distortion, or simple shear, to pass to a different order of symmetry, in the cases where this different symmetry has a plane of symmetry not found in the undistorted assemblage. For where this is the case the return distortion of the derived symmetry, which would eliminate the plane of symmetry and produce the initial arrangement, must be inclined to this plane, and must, therefore, owing to the presence of the latter, be one of a pair of enantiomorphously related distortions equally possible, and the angle between the directions of which is bisected by the 1 See Maskelyne’s ‘‘ Morphology of Crystals,’’ p. 176. Bartow—A Mechanical Cause of Homogeneity of Crystals. 645 direction of this plane. And these two distortions will, it is evident, owing to the symmetry, affect similarly the system of points lying in the plane of symmetry. Consequently if one half of an ideal assemblage possessing the derived higher symmetry, lying on one side of the acquired plane of symmetry, experiences one distortion, while the other half ex- periences the distortion enantiomorphous to it, the points lying in the plane of symmetry will be able to obey both distortions at the same time, 7.e., they will be distorted in precisely the same way by each of them. Therefore, since all planes of points parallel to one another are similarly affected by any uniform linear distortion of an assem- blage, every plane of points parallel to the plane of symmetry will experience the same change whichever of the two enantio- morphously related distortions it is subjected to. Therefore, finally, if those planes of points composing the original assemblage whose plane direction would become that of the plane of symmetry if a distortion to the derived symmetry took place, are capable of sliding on one another, 7. ¢., of under- taking a simple shear in any direction, it follows that twinning of the assemblage can be produced by such a shear if it affects the part of the assemblage lying on one side of some one of the planes of points referred to, and not the part on the other side. Or, if the movement is accompanied by a slight temporary increase of the distances separating the moving layers, it can equally well take place if the plane separating the hali of the assemblage affected by the shear from the other half has instead a certain direction which, when distortion to the derived symmetry has taken place, would be perpendicular to the plane of symmetry. This will be easier to follow in the particular case treated of below. The shifted portion of the assemblage will be the enantio- morph of the unaltered portion unless these two portions are identical with their own mirror-image, and therefore with one another, when they will merely occupy enantiomorphously similar positions with respect to the separating plane. The following is an example of a rhombohedral assemblage possessed of the property referred to. 646 Scientific Proceedings, Royal Dublin Society. Partition space into equal similar obtuse rhombohedra by ‘ drawing three sets of parallel planes in an appropriate manner. At the points of bisection of all the rhombohedron edges place 4 eentres of equal spheres whose magnitude is such that they touch — one another. With their centres at all the rhombohedron angles place a second set of equal spheres of such a radius as to touch the spheres first placed. ; Finally, with their centres at all the rhombohedron centres place a third set of equal spheres which are also of such a radius as to touch the spheres first placed. The spheres at the rhombohedron angles are then each in contact with six spheres; those at the rhombohedron edges, and those at the centres are each also in contact with six. If we regard such an assemblage as made up of layers of balls lying in planes parallel to the rhombo- hedron faces it is seen that it has the property referred to above, and is capable of distortion to a rhombic form, a face of the rhombohedron be- coming the base of the rhombic prism. The kind of movement is diagram- matically indicated in fig. 19, the shifted portions of each layer being supposed kept in contact with the un- shifted portions of the same layer at one end during the shear. This condition involves a slight temporary separation or widening of the distance between the layers, at least in the neighbourhood of the separating surface of the twins formed. The type of homogeneous structure presented is that numbered 52a, in my list... The generic symmetry is that of Class 12 in Sohncke’s list.” The three kinds of balls are present in the numerical proportions 1 : 1:3. The resemblances to the details of the case of the artificial twinning of Iceland spar are here very close, the atoms composing this substance having indeed the numerical proportions referred Hig. 19. 1 Zeitschr. fiir. Kryst., 23, p. 47. 2 Tbid., 20, p. 461. P ; ‘ ; Bartow—A Mechanical Cause of Homogeneity of Crystals. 647 - to. It is, however, unlikely that we have before us the precise arrangement prevailing in this body, because a division into unit groups of the assemblage in question would necessarily be an arbitrary one on account of the very specialized situations occupied by the balls. The direction adopted for the shear agrees better with the cleavage direction of Iceland spar than does the one it is usually supposed to take. If, instead of independent balls we have groups of balls, and the groups have some simple rhombohedral arrangement, there is still no need to suppose rotation of the groups with respect to the moving planes in which they he, provided each of the latter is a plane of symmetry of each of the individual groups which it intersects. Many peculiarities of crystal growth and of crystal-twinning and grouping are no doubt traceable to the partial application or distribution of the external forces or conditions of various kinds prevalent during the process of crystallization, e. g., there is some- times a tendency for a crystal to grow faster in some particular direction when, so far as symmetry is concerned, there are other similarly related directions equally available. All such cases are outside the scope of this investigation, for there are no analogies to peculiarities of this kind in the interactions of the parts of a homogeneous assémblage, these conforming strictly to the sym- metry. . Formation of isomorphous assemblages and their intermixture—Re- semblances to isomorphous, isogonous, and nixed crystals, and to crystalloids,® also to some kinds of diffusion. A few words will now be said as to the nature of the likeness of their parts and their conditions which will cause two homo- geneous assemblages, composed wholly or in part of different constituents, whether groups are present or not, when in equili- brium—(a) to have corresponding angles between planes of centres 1 In the usually received explanation of the nature of the artificial twinning of Ice- land spar, rotation of the molecules is resorted to; this is unnecessary, all that is requisite is change of orientation of their situation relatively to the assemblage, and this, in the case referred to, is accomplished by the simple shear. 2See note 1, p. 620. 648 Scientific Proceedings, Royal Dublin Society. equal, 1.e., to be isomorphous or isogonous ; (b) in addition to this to be capable of being intercalated in such a way that variously-shaped masses of the two assemblages have their corresponding planes of centres similarly orientated. We have already distinguished operative from inoperative balls in an assemblage,” operative balls being those on which the general form of the assemblage depends, and inoperative balls those which lie between the operative ones without doing anything towards regulating the relative situations of the latter. Bearing this in mind, the following proposition is evident :— If in two different assemblages the operative balls are the same, and, where more kinds than one are found, are present in the same proportions, the arrangement of the operative balls will, af the conditions are the same, be identical in both assemblages, and, unless a difference in the arrangement of the inoperative ones sufficient to produce a difference in the generic symmetry exists, the two assemblages will be completely isomorphous.*? They will also be capable of being intercalated in any proportions without any lessening of the closeness of packing. The inoperative balls may obviously be either entirely or partially different in the two assemblages. Far less resemblance than is here postulated will, however, suffice to make two assemblages practically isomorphous, and far less will too suffice to make them capable of becoming intercalated in such a way that the masses of different kinds have their corres- ponding planes of centres similarly orientated. For, on the one hand, they will be practically isomorphous if the inclinations of the planes of centres to one another in one assemblage be the same as the inclinations of corresponding planes to one another in the other assemblage, and that even 1 The term isomorphous is sometimes applied to two crystals when one has hemi- hedral or tetartohedral symmetry and the other has not, so long as all corresponding angles are the same: e.g., dolomite and calcite. Compare Groth’s ‘‘ Physikalische Krystallographie,’’ p. 278. The term isogonism has been suggested to cover cases in which the resemblance is incomplete and only extends to some of the crystal zones. See Fock’s “‘ Chemical Crystallography,” Pope’s translation, p. 167. 2 See p. 547. 3 Thus, as Dumas puts it, one may in a building substitute one stone for another, and yet the building may retain its form and general properties. —_——s- =~ oo So Bartow—A Mechanical Cause of Homogeneity of Crystals. 649 if the arrangement of the balls and the linear dimensions are different. On the other hand, they will be capable of the kind of inter- calation referred to, if in a roughly intermingled collection of two different kinds of assemblage, where both are about to solidify, it is found that at boundaries between the different kinds very close packing indeed is attained when the two adjacent structures are similarly orientated. For if this is so a bounding plane-layer of the growing solid composed of the one assemblage is capable of receiving an accretion either of another layer of the same kind of assemblage, or of a suitable layer of the other assemblage. If two intercalated assemblages are so related as to be capable of subdivision into space-units' which are identically shaped or very nearly so, or indeed if the shape and size of an aggregate formed of a finite number of contiguous space-units of some kind of one assemblage are identical with the shape and size of an ageregate formed by the same or some other finite number of contiguous space-units of some kind in the other assemblage, it is evident that there may be extremely little disturbance of regu- larity at ad/ the boundaries between the two kinds. Tf, however, while accretion of one kind of assemblage on the other readily takes place over small portions of some of the bounding surfaces of the growing solid, the space-units are not congruent, and this will generally be the case, it is evident that the regularity at the boundaries between the different kinds will be merely an initial one, 7.e., found only at the points at which the accretion of one kind on the other makes a fresh start, and that, like the surfaces between the differently orientated individual assemblages of a mass solidified before the arranging sought to be accomplished _ by the principle of closest-packing is completed,” or the more or less irregular surfaces at which in most cases individual twin- assemblayes meet during the continuance of their growth, the boun- dary formed as two assemblages of different kinds grow side by side will be a surface of some kind where they meet unconformably. Nevertheless this want of congruence at some boundaries will be quite consistent with the property that all corresponding directions in the two 1 See note 1, p. 586. 2 See p. 620. 3 See p. 623. 650 _ Scientific Proceedings, Royal Dublin Society. kinds of assemblages display similar orientation. There will, no doubt, in such a case be some mutual local accommodation of the arrangements of the parts of the assemblages where the two kinds — meet, but this will not be likely to disturb parallelism of the contact layers. Not only isomorphous assemblages but also assemblages dis- playing less similarity, provided they contain similar planes of — centres which will fit sufficiently well together to pack very closely, may become intercalated in a more or less symmetrical manner if the conditions of solidification are favourable, but we see that with a less correspondence of parts than is requisite for isomorphism the symmetry, except in cases of slight admixture, will be greatly deteriorated, and probably in few cases will there be uniformity of orientation of all the distinct fragments of the same kind of assemblage throughout any considerable space.+ For two assemblages to be absolutely isomorphous as a con- sequence of partial identity of composition,” it is not necessary for their like parts to behave identically under the same exernal con- ditions, the corresponding balls need not be precisely the same, it is only necessary that the operative statical system of interacting parts in the one assemblage, or some symmetrical system equivalent. to it, shall bear the same proportions as those in the other assem- blage do, so as to make corresponding angles the same in the two equilibrium arrangements. ‘This is a much less specialized con- dition for isomorphism than the one stated first. It is important to notice that the equality of corresponding angles just referred to may be associated with the exhibition of different types of symmetry. For this will be the case if in two assemblages in which the distances in three principal directions between the principal singular points’ bear the same ratios in . 1There may, however, occasionally be enclosure of a large number of isolated fragments, and perhaps of a continuous mass, of the one assemblage within a con- tinuous mass of the other assemblage throughout which uniformity of oricntation prevails. Compare note 1, p. 631. 2 Cases of isomorphism may arise from fortuitous relationship between the different sets of principal or singu.ar points found in different assemblages, but these, which we necessarily be of very infrequent occurrence, will not be considered here. 3 See note 1, p. 627. eS Bartow—A Mechanical Cause of Homogeneity of Crystals. 651 both,’ the positions occupied by single balls or by the centres of highly symmetrical groups of balls in one assemblage are occupied in the other by groups whose type of symmetry is low enough to impose a lower symmetry on the latter assemblage. Suppose, for example, to take a very simple case, that in two homogeneous isomorphous assemblages the singular points have the same relative arrangement, both containing balls of a certain kind situated at the centres of equal regular hexagonal right prisms of a particular pattern filling space in the most symmetrical manner possible, but that while in the one assemblage the remain- ing balls consist of triads of another kind of ball with their centre- points at the points in which six prism corners meet, in the other assemblage they consist of right tetragonal groups each composed of four balls of a third kind with the group centres placed in the same way as those of the triads.’ It is then manifest that if the principle of closest-packing requires the groups to be orientated in the most symmetrical way possible, the inclinations of the principal planes of points to one another will be the same in the two assemblages, which will be capable of intercalation in any proportions, but that the symmetry of the one containing the triads will be of a higher class than that of the other, the former having the symmetry of type 25a, the latter that of type 23b,, in my tables of homogeneous structures.* The isomorphism displayed by two allied assemblages will commonly not be perfect if the balls which are unlike in them are not absolutely inoperative in the sense above defined; and whether they are so or not, if the balls common to both do not behave identically under the same external conditions, but are of different magnitude* according to the nature of the balls with which they are associated in the two cases, it is very unlikely that the equality of corresponding angles will, except in the regular system, be 1 The ratios referred to appear to be the same as what are called by Tutton “ dis- tance ratios,’’ by Muthmann ‘‘ topic ”’ or “ topical axial ratios.’’ See Zeitschr. fiir Kryst., 22, p. 497, and Journ. Chem. Soc., vol. lxy., p. 628. We see that for their determination it is mot necessary to partition homogeneous structures in any way. 2 Neither arrangement is capable of being so linked as to form groups of a single kind without deteriorating the symmetry. It would, of course, be easy to instance others which are capable. 3 Zeitschr. f. Kryst, 23, pp. 45 and 52. * See page 529. 652 Scientific Proceedings, Royal Dublin Society. absolute ; there will be some difference in the conditions of equili- brium because the changes in the operative bails brought about by the substitution of one set of inoperative balls for another are — not strictly proportionate.’ If the presence of the balls which differ in two assemblages — whose composition is partially the same, effects any material — alteration in the conditions to which the similar balls are exposed so as to make them behave quite differently in the two assemb- lages, isomorphism will manifestly not be producible by the simi- . larity of these bails. In other words, there must be enough resemblance between the unlike balls to preclude them from disturbing the similarity of conditions requisite to the like balls that they may behave sufficiently alike in the two cases. If, owing to some difference in the conditions of equilibrium of two identical assemblages they are dimorphs, or if two assemblages capable under certain conditions of isomorphism or partial isomor- phism and intercalation, as just explained, are subject to conditions in which similarity of arrangement of their principal centres or singular points does not prevail, it is evident that certain layers may still display identity or similarity of arrangement in the two assemblages and cause the inclination of some principal directions to be the same in both, producing isogonism or partial correspondence less complete than that above denominated isomor- phism, but of the same character. And with reference to the intercalation of similarly-orientated isomorphous assemblages :— Where the supply of material present at a growing surface is of various sorts it is evident that the average proportions in which the constituents of different kinds are added will depend, not only on the proportions in which they occur in the supply, but also on the relative rates at which the different kinds are prepared to solidify at any given point. If one kind can assume tranquillity more readily than another we shall expect the accretion of the former kind to be thereby promoted. As the mixing of two or more kinds in the same layer may in 1 This is perhaps expressed more clearly if, instead of balls of different sizes, we speak of mutually repellent particles of different kinds (see note 3, p. 580). Bartow—A Mechanical Cause of Homogeneity of Crystals. 653: many cases be a hindrance to tranquillity, there will probably be a tendency to form distinct layers of each kind, the growing portion at any point remaining disturbed, and therefore unsolidified, till the more or less fortuitous movements taking place have resulted in perfecting the uniformity of the layer. So long as the proportions of the different assemblages present in the unsolidified mass are unaltered, and the conditions remain the same, an average uniformity of composition, or general homogeneity of the growing mixed solid should result; if, on the other hand, the proportions, or the conditions, or both change gradually, a gradual change of average composition may be expected to occur. Where the fitting together of the corresponding planes of balls of the different assemblages produces less closeness of pack- ing than the fitting together of the planes of balls of one of the assemblages taken alone, it is evident that retardation of solidification will tend, by giving additional time for the carrying out of the arranging process, to diminish the number of separate fragments of the two assemblages and increase their size, and indeed ultimately to cause them to mass themselves separately. The facts with regard to isomorphous crystals bear a close resemblance to the properties of isomorphous assemblages which have just been deduced. . Thus in the large majority of cases isomorphs have a similar chemical constitution’ and a large proportion of common consti- tuents. And the constituents in which they differ have in general similar properties and appear to exercise a similar influence on the common constituents.” The isomorphism of crystals is seldom, if ever, absolute, so that when accurate measurements of corresponding angles are made differences are revealed, the amounts of which are ordinarily 1 Fock’s ‘‘Einleitung in die chemische Krystallographie,”’ p. 65; or Enlarged English translation of same work (Pope), p. 98. 2 ©omp. Mischerlich’s definition ‘‘that only those substances are to be designated isomorphous which possess, in addition to an analogous chemical composition, a similar crystal form, and which crystallize together in variable proportions.” The equality of molecular volume of isomorphous compounds so commonly observed. will naturally be traced to the similar influence exerted by the allied though different constituents. 654 — — Scientific Proceedings, Royal Dublin Society. . a of the same order as the chemical differences between the substances compared. In the systems of low symmetry, these differences are not generally of such a simple character as those which appear when a body is subjected to a single linear distortion, they are traceable to slight differences in the dimensions in different directions of the space-lattices formed by the most symmetrical singular points or centres in the respective isomorphs.’ They are ordinarily most evident in a certain principal zone, whilst — between the corresponding angles of other zones nearly perpen- dicular thereto practically-complete identity subsists.’ It is generally the case that the similarity of form is greater , the nearer the compared bodies are related chemically. As we should expect from the similarity of form, and the 1 capacity to crystallize together, isomorphous crystals commonly — have similar cleavage. This similarity can scarcely be appealed to as throwing any additional light on the matter, but it is per- haps significant that the correspondence is not particularly great in some cases, é.g., when we compare aragonite, strontianite, ceru- — site, and witherite ; the occasional occurrence of such divergences is to be anticipated if the constituents which differ occupy definite situations in the structure. The more or less considerable dissimi- larity of the etched figures on isomorphous crystals* would seem — to point the same way; for it is easy to see, and indeed to show experimentally, that if two similarly arranged homogeneous struc- : : tures be built up of different mixed materials in such a way as to — give great differences of the same property, cohesion, pyroelec- tricity, or some other, in different directions in the same structure, the materials can be so selected and the common arrangement — have such a configuration as to give widely-diverse sets of direc- tional relations in the two systems, notwithstanding that the arrangement is the same in both. A very similar line of argument may be adopted with reference 1 See note 1, p. 651. 2 Fock’s ‘‘ Hinleitung in die chemische Krystallographie,’” p. 65; or Pope’s trans- lation of same, p. 92. 3 A case of great dissimilarity is given in Pope’s translation of Fock’s ‘‘ Chemische Krystallographie,’’ p. 102. Cases in which the dissimilarity of the etched figures is such as to place the crystals in a different class of symmetry are referred to presently. Bartow—A Mechanical Cause of Homogeneity of Orystals. 655 to the often great want of correspondence between the optical properties of two isomorphous crystals. The fact that the densities of isomorphous mixtures are weighted-means of the densities of their constituents militates against the supposition that there is any change in the relation of the parts of these constituents such as would alter properties; whatever change exists, the parts of a chemical molecule which enters into a mixture must be supposed to persist and perform the same functions as they do when unmixed.? Perhaps the evidence which most strongly supports the view that the dissimilar constituents in two isomorphous bodies occupy definite similar situations, being symmetrically and regularly in- terspersed each throughout the compound of which it is a consti- tuent in a similar manner, is afforded by the valuable researches of Tutton. This resourceful and original investigator has made a series of measurements of the isomorphous crystals of the monosym- metrical double sulphates of the composition R, SO,, R” SO,, 6H,0. Each of the 22 salts measured contains, as the metal R, one of’ the three alkali metals—potassium, rubidim, or caesium ; the salts may hence be arranged in series of three, containing the same dyad metal R”’, but different monad ones. The measurements show that all the geometrical properties of the rubidium salts are intermediate between the corresponding properties of the potas- sium and caesium salts respectively. ‘The same is also true of the facility of crystallization and the crystalline habit assumed by the rubidium salts. Since the axial angles of the rubidium salts are very approximately a mean between the corresponding ones of potassium and caesium, and the same relation approximately sub- sists between the atomic weights, the probability suggests itself that the differences observed in the properties are due to the sur- 1 Comp. Tutton. Journ. Chem. Soc., 1894, p. 628. 2 See Retgers on the specific weight of isomorphous mixtures. Zeitschr. f. phy- sikal. Chemie, vol. iii., p. 497. Similar relations subsist for other properties. Comp. Brauns’ ‘‘ Optische Anomalien der Krystalle,” p. 205. This author notes, too, that mixed crystals whose constituents when crystallized alone give, the one negative, the other positive crystals, can contain such proportions of the two constituents as to be isotropic. J0., p. 237. SCIEN. PROC. R.D.S., VOL. VIII., PART VI. 3B 656 Scientific Proceedings, Royal Dublin Society. vival of some property or properties of the respective elements in the compounds into which they enter.’ Mixtures of the monoclinic and anorthic felspars furnish striking examples of the crystallizing together, in what must be regarded as isomorphous mixtures, of substances belonging to dif- ferent crystal systems; and the extremely close resemblances which compounds may display and yet be of different systems is yet more strikingly exemplified by the arsenious and antimonious oxides, which, until a few years ago, were regarded as furnishing an exceptionally good example of an isodimorphous group with erystal form and cleavage practically identical. The latter com- pounds have been shown by des Cloizeaux to belong to different crystal systems.’ To compare with our conclusion that assemblages which are not isomorphous, but which are nevertheless capable of quasi homogeneous intercalation, may exist, we have the fact that in recent years a number of substances have become known which are not chemically analogous, and do not possess isomorphous forms, but which yet form homogeneous solid solutions.* The following are some other less-conspicuous properties of isormorphous homogeneous assemblages to which observed phe- nomena furnish resemblances. We may have two assemblages whose composition is such, that when exposed to similar conditions of a certain kind they are isomorphous, but which under another set of conditions attain equilbrium in different symmetries, one or both of the assemblages being therefore dimorphous. And since we hayé already concluded — that an assemblage, if sufficiently near a critical point, may have its symmetry determined by the symmetry of a small solidified por- tion of similar composition which comes in contact with it,* we see that in a rough mixture of the two assemblages the order in which the two kinds commence to solidify may suffice to determine whether they shall be isomorphous and crystallize together or not. 1 Journ. Chem. Soc., 1893, p. 887; or Zeitschr. f. Kryst., 21, p. 491, &c.; also Journ. Chem. Soc., 1894, p. 628; or Zeitschr. f. Kryst., 24. p. 1. * Bull. Min., vol. x., p. 303, 1887. 3 Pope’s translation of Fock’s ‘‘ Chemische Krystallographie,”’ p. 141. 4 See pp. 576 and 581. Bartow—A Mechanical Cause of Homogeneity of Crystals. 657 And again, if the properties of an assemblage are influenced by the mere presence of another assemblage intermixed with it, the priority in crystallization of one of the assemblages, which has just been referred to, may depend on the proportions in which they are roughly intermixed, or the same cause may in some other way determine which of two dimorphous forms one of them shall assume, and consequently whether they shall be isomorphous or not. It has just been said that the proportions in which the con- stituents of different kinds are added to a solid surface growing in a mixed collection of isomorphous assemblages, will depend, not only on the proportions in which they occur in the mixture, but also on the relative rates at which the different kinds of assem- blage are prepared to solidify at any given point. It may be added that the greater any discrepancy of form between two assemblages which are nevertheless practically isomorphous and capable of close-packed intercalation as above explained, the more subject to fluctuation will be the conditions of solidification of a mixed mass of them as the proportions of the two kinds present are changed. For we have already concluded that in a solidifying assemblage the place of maximum tranquillity is the place of readiest solidifi- cation,’ and if the assemblages intercalated do not fit together very well, the places of their junction will be places of less tran- quillity, and the effect of these on each kind of assemblage present will vary according to the proportions in which they occur. Suppose that we take a series of mixtures composed of different proportions of two isomorphous assemblages which are capable of solidifying together, but between whose forms there is some con- siderable discrepancy, the series being arranged so that succeeding terms contain more and more of one constituent, and less and less of the other, one assemblage unmixed standing at one end of the series, and the other assemblage also unmixed standing at the other end. It is then evident that when we examine the behaviour of the combinations forming such a series near the solidifying point, we can discriminate at least two classes of cases :— 1 See pp. 565 and 623. 658 Scientific Proceedings, Royal Dublin Society. 1. Cases in which the influence of one assemblage A on the - general symmetry of disposition of the constituents of the mixed solid is predominant, these cases lying together at one end of the series. 2. Cases in which the influence of the other assemblage B is thus predominant, these cases lying at the other end of the series. Now it is conceivable that if the discrepancy between the two con- stituent assemblages thus capable of intermixture is sufficiently great, the necessity for closest-packing will require one or other assemblage to predominate locally in the solidifying mass. For where there is such a discrepancy there will be a struggle in the mixed solidifying mass between its constituents, each seeking to impose on the mass. the arrangement proper to itself when unmixed, and the result will be that that form of arrangement which gains the upper hand will greatly favour the accretion of the constituent having this arrangement in preference to the other constituent, and will thus ensure a considerable preponderance of it throughout those portions of the mass in which it is thus in the ascendant. In such a case we must not look, as we pass along the series referred to, for a group of terms lying between the two classes named, and which belong to neither of them, but for a group of terms in which both classes appear side by side, one compensating the other, the liquid mixtures from which this group is formed being on the one hand richer in kind B than is the limiting case, with its maximum quantity of B, of those which furnish solely the symmetrical form dictated by A, and on the other hand richer in kind A than is the limiting case, with its maximum quantity of A, of those which give solely the form dictated by B. We shall not, of course, expect these limiting solid combinations to contain similar though opposite proportions of the two assemblages; it may be much easier for A to solidify than for B. The series of differently proportioned solid mixtures formed from such a series of liquid mixtures will in such a case contain a gap extending from the term with the greatest proportion of B capable of being contained in a mixed solid which has the general form of A, to the term with the greatest proportion of A capable of being contained in a mixed solid which has the general form of B. Bartow—A Mechanical Cause of Homogeneity of Crystals. 659 The above corresponds extremely well with the facts concerning a series of isomorphous mixtures of the chlorates of potassium and thallium completely investigated by Bakhuis Roozeboom.? Both these substances crystallize in the monosymmetric system, possess similar crystalline forms, and give rise to isomorphous mixtures, not however in all proportions. The following table gives the experimental results :— ONE LITRE OF SOLUTION CONTAINS 38 Cae Miligram Ce ee F' | TIclo, | KCl0s wae ee eae 1 | 25-637 = | eae =| spa 0 0 2 | 19:637 | 6-884 | 68-27 | 56:15 | 194-42 | 45:13 | 9-00 3 | 12-001 | 26-100 | 41-73 | 212-89 | 254-62 | 83-61 | 19-61 4 | 9-036 | 40-064 | 31-42 | 326-79 | 358-21 | 91-23 | 25-01 5 | 7-885 | 46497 | 27-42 | 379-26 | 406-68 | 93-26)) 36-30 and 6 | 7-935 | 46-535 | 27-60 | 379:57 | 407-17 a 97°93 7 | 6706 | 46-410 | 23°32 | 378-55 | 401-87 | 94-20 99-28 8 | 6-723 | 47-109 | 23°37 | 384-25 | 407-62 | 94-27 99-60 9 | 4-858 | 47-312 | 16-89 | 385-91 | 402-80 | 95-81 99-62 10 | 2-769 | 47-134 | 9-63 | 384-46 | 394-09 | 97-56 99°67 11 a Ty Aa-995 — | 407-22 | 407-22 | 100-00 100-00 Experiments 1 and 11 were made with solutions of the pure salts. The mixtures deposited in experiments 7-10 were scale- shaped crystals similar in appearance to those of potassium chlorate ; experiments 2-4 yielded much smaller, acicular crystals resembling those of thallium chlorate. Both kinds of crystals were obtained side by side in experiment 5 ; after removing them, and allowing the 1 Zeitschr. fiir physik. Chemie, vol. viii., p. 531. Compare also, for other cases in which two kinds of mixed crystals are deposited by a mixed solution, Rammelsberg’s observations published in Poggendorf’s Annalen XCI., p. 321; and also Retger’s observations in Zeitschr. f. physik. Chem., vol. ili., p. 542. 660 Scientific Proceedings, Royal Dublin Society. mother liquor to evaporate the same two kinds of crystals separated and the solution preserved its composition unchanged as is shown by No. 6. Such behaviour is, however, only possible if the deposited crystals have the same average composition as the dissolved matter.* In connection with the argument here submitted that the conditions competent to produce isomorphism and intercalation of similarly-orientated homogeneous assemblages are so little special- ized, it is interesting to notice that during recent years a considerable number of examples have been recorded of substances which form isomorphous mixtures, but are at the same time very slightly, or not at all related in a chemical sense.’ It is conceivable that in some cases one of two kinds of assem- blages entering into a series of intercalated mixtures may always, whatever the proportions in which the assemblages are intermixed, take the lead in solidifying, and when this is the case, and there is some small discrepancy between the forms of internal symmetry of the two assemblages, which may or may not affect the angles between the planes of centres, we may find that the assemblage which thus takes the lead causes some modification of the form of the other assemblage, the latter accommodating its symmetry to that of the earlier solidified one to which it attaches itself. The entire mixture of assemblages will, in such a case, as to some of its properties, present a resemblance to the kind of assem- blage which thus takes the lead. : In this connection a case may be mentioned in which the optical properties of a mixed crystal resemble those of one of the constituents only, thus furnishing an exception to the laws of Mallard and Dufet. The tartrates of ammonium and thallium are completely isomorphous, both belong to the mono-symmetric system, show nearly identical angles, and crystallize together in all proportions. The ammonium salt has a cleavage parallel to the basal plane, the optic axes lie in the plane of symmetry, and the optic axial angle is 42°38’. The thallium salt, on the other hand, shows no cleavage, the optic axial plane is perpendicular to the 1 Pope’s translation of Fock’s ‘‘ Chemical Crystallography,’’ p. 121. 2 Ibid. pa Lele BarLtow—A Wechanical Cause of Homogeneity of Crystals. 661 plane of symmetry, and the axial angle is 593°. The isomorphous mixture of the two salts, however, invariably show the same cleavage and optic axial plane as the ammonium salt; a mixture containing 88°7 per cent. of the thallium salt was, moreover, obtained, in which the optic axial angle was found to be 48° 31’, being thus completely identical with that of the pure ammonium salt. A resemblance of a lower order than isomorphism is con- ceivable between assemblages which have some constituents the same and similarly arranged or grouped in both. For although the congruence may not be adequate to produce equality of all corresponding angles or any intercalation, the arrangement may be so far alike in both as to come under the same type of symmetry and to have some axial lengths in one equal to some in the other. An illustration will, perhaps, make this plainer :—Suppose that an assemblage, when closest-packed, is found with its unit-groups arranged in rhombic symmetry in parallel layers in such a way that when it is partitioned symmetrically in the simplest manner possible, the cells are right-rhombic prisms, each containing a unit-group. And suppose that a second assemblage is composed of unit- groups, each of which consists of the same constituents arranged in the same manner as in the first-named groups, and in addition to these some other constituents ; the portion of a group which is the same forming the larger part of it, and the additional constituents being placed at opposite ends of the group. It is then conceivable that the second assemblage when closest- packed will also be capable of symmetrical partitioning into cells which are right-rhombic prisms, and that the only difference between the partitioning of the first and that of the second assem- blage will be that the prismatic cells of the latter will be rather longer than those of the former, the cross sections being identical. In such a case there will be aremarkable morphotropic relation- ship between the assemblages, for two out of the three axial directions will furnish the same values in both, and so consequently will the zone containing these two directions. 1 See Wyrouboft’s researches in Zeitchr. f. Kryst, 13, p. 648; also Pope’s transla- tion of Fock’s ‘‘ Introduction to Chemical Crystallography,” p. 138. 662 Scientific Proceedings, Royal Dublin Society. To compare with the above we have the very remarkable resemblances obtaining between a new addition-compound of camphorie acid with acetone and camphoric anhydride, which have been traced by Pope.’ Both erystallize in the ortho-rhombic system and display the same axial values in two directions, while they differ as to the third: the cleavages too, the planes of which belong to the zone throughout which the angular values are the same in both, correspond very closely, and so do the optical characters and the face-markings on the crystals. The kind of relation just referred to is very suggestive in connection with homologous series of carbon compounds, it being possible to form series of groupings of balls, each term of which is derived from the previous term by adding balls symmetrically at the end so as to elongate the group without altering its general character. The fitting of similar groups together side by side, as well as many features of the groups taken individually, will be found to furnish great similarities if the different types forming such a series are taken successively, and the geometrical features compared. If only one, or a few of the equivalent atoms in a compound are replaced by others, the crystalline system generally changes, and usually in such a way that the new system possesses less symmetry than the old. The influence of substitution on the crystalline form of benzene and its derivatives has been the most completely investigated. In the case of substitution of hydroxl- or nitro- groups for hydrogen atoms in the benzene molecule the length of only one axis changes considerably, those of the two others remaining practically constant.’ In connection with the consideration of the effects of partial similarity of composition and grouping on the general symmetry of an assemblage, it is very important to observe that groups are conceivable in which a high symmetry would be presented were it not for some slight defect in form or arrangement, and it is evident that, in the case of such groups, closest-packing may be attained by the 1 Transactions Chemical Soc., 1896, p. 1696. 2 Pope’s translation of Fock’s “‘Chemische Krystallographie,’’ p.176. Comp. Groth’s Zeitschr. f. Kyrst., 8. p. 284. Comp. also ante, p. 619. es Bartow—A Mechanical Cause of Homogeneity of Crystals. 663 _ formation of an assemblage which treats this slight deformity as non- eaistent. To make this plainer by means of an example :—Suppose that a linked group has cubic symmetry, except that out of twenty-four outermost balls but twenty-two or twenty-three are similar and similarly situated, dissimilar balls making up the twenty-four and occupying places which are symmetrically situated, or nearly so; it is then conceivable that the closest-packing of a number of groups of this description may be one which disregards the slight irregularity and puts the groups together with their centres at the points of a cubic lattice, and with their pre- dominating symmetrically arranged balls forming, as far as they go, a system in cubic symmetry. In a case of this kind the positions of the irregularities will not be symmetrically distributed; in other words the groups, when the deformities are taken into account, will be found variously orientated and the assemblage will not be strictly—v. e., mathema- tically—homogeneous, although, owing to the average effect of the deformities being the same in corresponding directions, the general symmetry will not be appreciably impaired. Large groups will be more particularly liable to function as though of a higher symmetry than they actually possess in the way just described. To compare with this we have the observation frequently made with reference to carbon compounds and their derivatives, that the higher the symmetry of the parent substance the less is the change in crystalline form caused by substitution. Thus the cubic form of ammonium alum is unaffected by the entrance of a methyl group in place of an atom of ammoniacal hydrogen, whilst such a substitution in an orthorhombic or monosymmetric compound would lead to a considerable alteration in crystalline form. If the parent substance contains several equivalent hydrogen atoms, it not infrequently happens that the symmetry of the system is decreased by substitution for one of these atoms; but that, as several or all of the hydrogen atoms are displaced, the products again crystallize in the same system as the parent substance.’ 1 See Pope’s translation of Fock’s ‘‘ Chemische Krystallographie,’’ p. 181. L Including the departure from strict homogeneity just referred — to, we have now dealt with four distinct ways in which assemblages may fail in homogeneity and yet exhibit a related orientation and symmetry of their parts, such as are found in crystals. They are :— 1. A want of uniformity in the arrangement of the inoperative constituents which does not extend to the operative ones, the latter, when taken alone, displaying homogeneity of arrangement.’ 2. A bending or twisting of thin assemblages whose parts are so related that they pack closer when thus curved than they do when homogeneously placed.? 3. A more or less irregular intercalation of two different con- gruent or partially congruent assemblages, in which, however, one or both preserve the same orientation of corresponding parts.° 4. A lack of symmetry in the unit-groups composing an assemblage which is not sufficient to prevent them from perform- ing the same functions as would the more symmetrically-shaped groups which they nearly resemble. ‘To make the assemblage perfectly homogeneous it would, therefore, merely be requisite to correct these slight departures from regularity without changing the rest of the structure. The positions of the defects with respect to the group-centres present a haphazard variety within the limits prescribed by the arrangement of the perfect portions of the assemblage. The intercalation of differently-constituted fragments of homogeneous assemblages in the ways above described will, obviously, be likely in many cases to modify the effect of change of conditions. Thus it is obvious that if, under change of tem- perature, one constituent does not change its bulk at the same rate as the other, a condition of strain must be looked for in the mixture which is not found in either constituent taken alone, and that the effects of this strain will, so far as the qualities of the constituents are concerned, be anomalous and not to be accounted for by any addition or subtraction of their individual properties. To compare with this we may mention the observation of Brauns that while pure crystals of alum, lead nitrate, and barium 664 Scientific Proceedings, Royal Dublin Society. 1 See p. 548. 2 See p. 568. 3 See p. 649. \ Bartow—A. Mechanical Cause of Homogeneity of Crystals. 665 nitrate are always isotropic, the crystals of these substances which contain isomorphous admixtures are double refracting.’ Also the fact that a small addition of ammonia alum to potash alum develops optical properties in the mixture which are wanting in the pure substances ; in particular lamellar polarization investi- gated by Biot. It should also be noted that the nitrates, which are double- refracting and are mixed crystals, fly into small pieces when subjected to pressure, but that the isotropic pure crystals are not nearly so brittle.’ Finally, we have the important fact that the behaviour of mixed crystals when subjected to change of temperature resembles that of cooled glass,? and can also be closely imitated with gelatine models,* strong evidence being afforded in this way that the effect is one proceeding from strain.* There are cases in which bodies are mixed crystals and also contain water of crystallization,® and any optical anomalies which they display may, therefore, be connected with either or both of these properties according to the conditions prevailing when the observation is made. The intimate relation between external form and anomalous optical properties which is probably traceable to strain, comes out prominently in the garnets which, as a rule, are mixed crystals composed of several related compounds.’ 1 Brauns, ‘‘ Optische Anomalien,’’ p. 50. Neues Jahrbuch, 1885, 1., pp. 96-118. Comp. also Brauns, Joc. cit., p. 206. 2 Brauns, Joc. cit., p. 225. As to sudden fracturing during growth of mixed erystals, see [bid., 255. 3 Brauns, Joc. cit., p. 224. *In particular such an imitation has been produced by Klocke, Klein and Ben Saude, see Jbid., p. 256. > Ibid., p. 257; and, in particular, see also Lehmann’s ‘‘ Molecular Physik,’’ 1., _p. 450. § Thid., pp. 240, 340. Comp. p. 640 above. 7 Tbid., pp. 245, 251, 253, also 357. 666 Scientific Proceedings, Royal Dublin Society.' Intercalated symmetrically-joined assemblages, of which one is liquid — while the other is linked into a continuous whole. Comparison to erystalloids’ and colloids. Of two assemblages which are mutually intercalated with con- gruent boundaries, in the way above described,’ it is conceivable that one may be liquid, 7.e., may be lying in small unlinked patches among patches of the other which are linked together, and this may have come about in one of the following two different ways :—(a) The assemblage which does not solidify may have reached a sufficiently tranquil homogeneous condition to enable it to fit in symmetrically with patches of the other assemblage, while the latter arranges itself more or less symmetrically as the con- ditions admit and solidifies, growing by accretion in the ordinary way ;° or (b) The solidification of both intercalated assemblages may take place as the mass grows, and liquefaction of one of them may be a subsequent occurrence. In either case a sponge-like structure is obtained.* If the two assemblages are isomorphous, so that in becoming intercalated they can each preserve their continuity of symmetrical arrangement, and present the same orientation of their corresponding structures, they will, like the more regular of the combinations above described, in which both constituent-assemblages are solid, have corresponding planes of particles sinularly orientated in the two assemblages. Since one of the constituents is liquid the mass will display some of the properties of a liquid,’ while the existence of the solid constituent will impart to it some of the characteristics of a solid. When from a mass thus constituted some of the tranquil liquid assemblage is, by degrees, abstracted, the solid skeleton framework 1 See Note 1, p. 620. 2 See p. 649. 3 See p. 566. 4 Since these pages were written the author’s attention has been directed to the experiments made by Biitschli, which support the view that substances which display imbibition have acellular or sponge-like structure. See O. Bitschli: ‘‘ Ueber den Bau quellbarer Kérper und die Bedingungen der Quellung.’’ Abhandl. der Gesellse. der Wiss. zu Gottingen, 1896. Bd. xt. 5 Comp. p. 682. BarLtow—A Mechanical Cause of Homogeneity of Crystals. 667 of the other assemblage will be squeezed together, and some con- siderable disturbance of the symmetrical arrangement of the parts will ensue, because the constituents forming the framework through being linked together are unable to alter their relative situations sufficiently to produce a fresh homogeneous arrange- ment; in other words, the symmetry of the framework will have to suffer distortion. The general distribution and the general outlines of the mass will, however, continue of much the same kind and form. If the mass before the abstraction of some of the liquid portion displays anisotropic properties, the diminution of internal re- gularity caused by this change will impair these properties, anisotropism requiring uniformity of the conditions at correspond- ing points, 7.e., at points which in the unaltered structure have similar surroundings similarly orientated. With regard to any change in the general form arising from the same cause, the maximum distortion will be found at the outer boundaries, because there the conditions around a given point are least symmetrical owing to the absence of ties in one direction ; it will diminish inwards and at the centre will be a minimum. Again, if before the withdrawal of the removable portion parallel layers of the linked portion are found in which none of the former is contained, so that these layers are unchanged by the process, it is evident that the crushing together will almost certainly be less in the direction of these planes than in other directions. Finally if the portions which have been removed, or portions of a similar assemblage, be supplied to a shrunken framework? we shall expect the advent of these constituents to restore the linked framework to its primitive condition, and therefore rather to increase than to diminish the symmetry, and if anisotropism is present, to intensify it. There is considerable resemblance between the properties thus traced and the behaviour of erystalloids. 1 The way in which the loose particles penetrate the shrunken assemblage is re- ferred to in a subsequent section. See p. 682. 668 Scientific Proceedings, Royal Dublin Society. Thus these bodies allow the liquid which they absorb to” behave within them much as it does when outside. They are not quite homogeneous but show some difference of 3 constitution as we pass from the centre to the outer boun- daries. ‘This is made apparent by the remarkable fact that the crystalloid when placed in a solvent begins to dissolve at its centre, at which a vacuole is formed which gradually grows in size till only the edges of the crystalloid remain undissolved.’ Further, while to the superficial observer they often appear quite as regular as crystals, angles of these bodies which according to the law of zones should be equal, differ by several degrees, and the angles vary according to the nature of the medium in which the erystalloids lie.’ The double-refraction of crystalloids is always very slight.‘ Crystalloids not already saturated show imbibition; placed in certain liquids they swell up to a bulk which is many times as great as that they have in their dried condition, and they do this without losing their regular form.’ In some cases the extension takes place i in a certain direction, but not in directions at right angles to this. Thus in the case of erystalloids of Brazil nuts there is no appreciable increase of - dimension perpendicular to the principal axis, and maximum ex- tension takes place in the direction of this axis.° Partial destruction of symmetry of arrangement by the action of an acid is revealed by the fact that too high a proportion of acid produces convexity of the faces of some crystalloids.” Also by the fact that crystalloids of Brazil nuts through imbibition of an acid suffer important modification and become incapable of restoration to the form and magnitude they had prior to imbibi- 1 Lothar Meyer says: ‘‘It is very noteworthy that in many cases precisely the same phenomena can occur in the interior of the liquid taken up as in that remaining outside, for example, the same diffusion movements. (Lothar Meyer’s ‘‘ Grundziige der theoretischen Chemie.’? 2nd Edition, p. 119.) Bedson & Williams’ translation, p. 129. 2 Schimper, ‘‘ Ueber die Krystallisation der eiweissartigen Substanzen.” Zeitschr. £. Kryst., v., p. 182 and p. 160. Comp. Jbid., p. 157. 3 Ibid., p. 133. 4 Tbid., p. 135. 5 Ibid., p. 188. 6 Tbid., p. 150. 7 Tbid., p. 151. Bartow—A Mechanical Cause of Homogeneity of Crystals. 669 tion, their faces becoming crooked or approximating to the spherical. To compare with the conclusion reached above that the re-in- troduction of abstracted portions of an intercalated assemblage may restore internal regularity and anisotropism, if the latter subsisted ; we have the fact that in some cases imbibition appears to increase the regularity of the internal arrangement of the parts of a crystalloid. Thus when crystalloids of musa or sparganium swell up in pure water the double-refraction materially increases. In the case of the former the phenomenon is very striking, for placed between crossed nicols when dry, or with oil, the light trans- mitted is very faint, but when so placed after imbibition it shows a brilliant white; and if a quartz plate is used which gives red, we get instead of the slight change of tint produced by the crystal- loid before imbibition, vivid yellow, white, blue-green, or green according to the position.’ The permeability of the sponge-like framework by a given set of constituents will, according to the above, depend principally on whether their entry will increase the closeness of packing, and in this connection may be mentioned the experimental observation of Tammann that what determines whether or not the respective molecules of a number of liquids shall penetrate a given membrane is not their relative size, as has been supposed by Traube and by Ostwald. We have said that when the framework is squeezed together the maximum distortion of parts will take place near the outer boundaries, because the conditions are there least symmetrical. From the same cause some parts of the shrunken framework will be more prepared to pack closely with the incoming liquid than will other parts, the distribution of this difference being dependent on the outer form of the mass of the framework. To compare with this we have the fact that if erystalloids of musa hilléi are treated with weak acid, so that a minimum 1 [bid., p. 153. 2 Ibid., p. 154- 3 Tammann, ‘‘ Ueber die Permeabilitat von Niederschlagsmembranen.’? Nach- richt der Géttinger Gesellschaft der Wiss., 1891, p. 213. Comp. Walden, “ Ueber Diffusionserscheinungen yon Niederschlagsmembranen.”’ Zeitschr, f. physical. Chemie, 1892. Bd. x., p. 699. 670 Scientific Proceedings, Royal Dublin Society. of imbibition is attained, they display while swelling a remark-_ able quite symmetrical star-shaped form. This is, however, of — short duration, the faces of the crystalloids being quite plane when the process is completed.’ If the process of formation of intercalated solid and liquid assemblages, just described, is not sufficiently uniform and gradual for the combination produced to display uniformity of orienta- tion throughout any considerable space, shrinkage and imbibi- tion may nevertheless take place, much as in the cases above referred to, and we may have mixtures or intercalations of prac- tically amorphous assemblages possessing the qualities referred to above. And as resembling these less regular mixtures, the gelatinous bodies known as colloids may be instanced. | Increase of disturbance and the strain occasioned by the intus- susception of portions of a liquid assemblage may, it is conceiv- able, rupture a sponge-like framework of the kind referred to and reduce it to fragments, which, although no longer able to impart to the mass the properties of a solid, may have considerable magnitude as compared with the distances apart of the ultimate constituents, and may hinder very materially the relative move- ment of its parts. To compare with this we have the interesting fact that colloids will not diffuse in colloids. | A. further reference to crystalloids is made presently in con- nection with a certain kind of diffusion.’ Intercalation or intermingling of two fluid assemblages. Comparison to solutions. When two assemblages which pack closer when apart, and are at the same time so related that layers in one are more or less compatible with layers in the other,? do not either of them sohdify when they come in contact, there will, nevertheless, as in the cases above dealt with, be some amount of intercalation or intermingling as a consequence of local disturbances.* And indeed 7 these 1 Schimper, ‘‘ Ueber die Krystallisation,’’ &c. Zeitschr. f. Kryst., v., p. 154. 2 See p. 682. 3 Comp. p. 649. 4 See Appendix, p. 687. Bartow—A Mechanical Cause of Homogeneity of Crystals. 671 disturbances be sufficiently consideradle, intercalation will, it is evident, take place even where there is very little or no compatibility be- tween the assemblages coming together.’ The mixture will in the latter case be such as is obtained by shaking together different ingredients whose forms are incom- patible ; there will be more or less uniformity of distribution but no symmetry, and in no such case can there be absolute homogeneity. Since the packing is closer when the two kinds of assemblage ‘do not intermix, the principle of closest-packing will, in the cases supposed, be continually to some extent undoing what intermix- ture the disturbances have accomplished, and producing here and there small patches of each kind unmixed with the other, which patches will however speedily be shaken to pieces again while fresh ones are formed. The amount of fluctuation going on will prevent any appreciable uniformity of orientation of the patches being exhibited, but it is easy to see that some of the features displayed will be very like those above traced in cases of mixtures which solidify. Unless some separating influence is at work, intermixture of this kind will tend to produce uniformity of distribution of the patches of one kind of assemblage throughout patches of the other; in other words intermixture in all proportions. Separating influences are, however, conceivable, which will remove portions of one or the other kind. of assemblage when a certain relative proportion of it is exceeded, the result being to limit the proportions in which the two assemblages can intermiz. Thus, for example, in cases where one kind of assemblage would, if found alone, experience a change to the solid state, but is capable of remaining liquid when finely divided and distributed through the other assemblage, it is clear that intermixtures composed of the two kinds in which the predominance of the former is beyond a certain limit will contain patches of the latter large enough to be unaffected by the proximity of the first-mentioned kind. Where this is the case these patches will pass to the solid state, and so the proportion of the kind in excess in the liquid mixture will be reduced till solidification can no longer occur. 1 Comp. Lothar Meyer, ‘ Grundziige der theoretischer Chemie,’’ p. 128. 2 See pp. 657-659. SCIEN. PROC. R.D.S., VOL. VIII., PART VI. 3C 672 Scientific Proceedings, Royal Dublin Society. Or, as another example, suppose the two assemblages to be subjected to a uniformly applied force of attraction which affects them differently, so that when the patches of one of them exceed a certain size they have a relative motion with respect to those of the other, which causes them to pass to and assemble themselves at one end of the mixture, leaving only the patches of less magnitude mingled with the other assemblage at the opposite end. A large class of cases of solution, or diffusion of one liquid in another in variable proportions, may be cited as resembling the sort of intermixture here treated of. For comparison with the ease last alluded to, an instance of a pair of liquids commonly spoken of as not intermixing, may be referred to, e.g., water and ether. The two liquidsin these cases form two saturated solutions. which are moreover in equilibrium together. Thus in the case referred to, we have—l. A saturated aqueous solution of ether ; 2. A saturated etheral solution of water, and both solutions have the same vapour pressure.* Other kinds of diffusion are referred to later.’ Let us pass on to the consideration of the fourth class of effects mentioned at the opening of this memoir. IV.—The interlacing of different kinds of groups or individuals con- verting a fortuitous assemblage into an assemblage which approximates to homogeneity, but does not reach it because the arrangements for closest-packing are not homogeneous ones. This effect of the law of closest-packing is, in all probability, precisely that already treated of in dealing with thin curved assemblages ;* it is likely that in all cases where the closest-packed arrangement is not a homogeneous one, it will be some such symmetrical departure from homogeneity as that already shown to be productive of curved assemblages. A mass of similar assemblages of the kind referred to, if the curved fragments be of smai/ extent, will be practicaily 1 As to saturated mutual solvents see Duclaux, Ann. chim. phys. (5) 7,267, 1876. Alexejew Wied. Ann. 28, p. 305, 1886. Comp. ‘‘Die Phasenregel” von Dr. W. Meyer- hoffer, p. 40 and Lothar Meyer, ‘‘ Grundztige &ec.,”’ p. 119. 2 See page 679. 3 See p. 569. Bartow—A Mechanical Cause of Homogeneity of Crystals. 673 amorphous, 7. e., destitute of any qualities depending on direction, but at the same time it will present general uniformity of distribution of the constituents. We shall indeed picture a mass of similar curved assemblages, just like a single continuous assemblage, as continually striving after that relative arrangement of the parts composing it in which it occupies least space, but that owing to inability to reach stable equilibrium it continually fluctuates from one imperfectly symmetrical closest-packed arrangement to another as itis shaken up by passing disturbances. The different consti- tuents will be very evenly distributed and a like relation of parts will frequently be found repeating itself in various places in the mass. If a collection of very minute assemblages thus circumstanced be solidified we shall look for the production of a practically homo- geneous amorphous solid, destitute of any appreciable symmetry, and therefore paralleled by the amorphous or non-crystalline state of bodies. It should be remembered, however, that we have concluded that some thin curved assemblages are convertible by accretion, under favourable conditions, into homogeneous assemblages,’ and it is conceivable that this may always or nearly always be the case. With this we may compare Lehmann’s conclusion that the amorph- ous state is due to hindrances which prevent the molecular forces from achieving the degree of symmetry of arrangement which they would otherwise attain.’ The next effect to be considered is :— V.—Combination of two or more homogeneous or approximately homogeneous assemblages to form a single homogeneous or approximately homogeneous assemblage. Resemblance of this effect («) when in its most perfect form, to that highly- symmetrical intermixture of the combining atoms or com- plexes which must, it is evident, accompany or precede a chemical synthesis; (4) when in its. less perfect form, 7.c., where the assemblage produced is only imperfectly homo- geneous or is fluctuating, to some phenomena of diffusion. If in an assemblage composed of one or more different kinds of 1 See p. 572. 2 See Lehmann in Zeitschr. f. eee 1, pp. 116, 117, and comp. Pope’s translation of Fock’s ‘‘ Chemische Krystallographie,”’ p. 61. 302 674 Scientific Proceedings, Royal Dubiin Society. balls, or mutually-repellent particles, the arrangement is the closest-packed possible, and this assemblage is brought in con- tact with another differently-constituted assemblage which is also in this condition, and 7f an intermingling of the assemblages enables the balls, or particles, to pack still closer, then it is evident that in obedience to the principle of closest-packing, the two assemblages will combine to form a single assemblage.’ The process will commence at the boundary where the two assemblages touch, and they will gradually interpenetrate one another.” If closest-packing is reached in a homogeneous arrangement, the resulting compound assemblage will, under sufficiently favour- able conditions, be homogeneous, and therefore display one of the thirty-two kinds of symmetry proper to crystals ;* if not it will be amorphous. The two assemblages will ultimately combine in the propor- tions in which they pack closest, and if there is an excess of one of them over the quantity requisite for this combination, the excess Will remain uncombined.* : Moreover, it is not necessary to suppose that all parts of any considerable portion, either of the constituent assemblages before the combination, or of the resultant assemblage afterwards, reach a condition of equilibrium simultaneously ; the combination will still take place if disturbances are occurring which prevent any great continuity in either time or space of the symmetrical arrange- ments towards which the principle of closest-packing is continually urging the mass. We may have, instead of very perfect homo- geneous assemblages whose continuity is unbroken over a con- 1 The conditions are taken to be uniform throughout 'the mass. If they are not we may have closest-packing reached in one kind of arrangement at one place, in another kind at another. 2 This is better understood if we take mutually-repellent particles and not balls. Compare note 1, p. 549. 3 Zeitschr. f. Kryst., 23, p. 1. 4 While the mass remains fluid there will be no hard and fast boundary between the combined and uncombined portions thus produced; particles at the edge of the combined portion will continually fall out of combination again, while, to compensate this, particles at the edge of the uncombined portion will become combined ; there may also be transitioual combinations. See below, p. 680. Bartow—A Mechanical Cause of Homogeneity of Crystals. 675 siderable space, a number of similar but not continuous assemblages variously orientated and in a state of fluctuation, but every portion of which now and again becomes very homogeneous indeed, and these fractional assemblages may consist either of unlinked balls (or mutually-repellent particles) or of groups, or partly of each. And where the arrangement of the constituents is thus fluctua- ting about an ideally symmetrical one, it is evident that some of the properties of the ideal arrangement will be wanting, while others will be present—those relating to orientation, which depend on extensive continuity of a single homogeneous assemblage, will not be traceable, while those which depend on local symmetry or configuration of the groups apart from orientation, or on mere evenness of distribution, will display themselves. If no change of state’ occurs to stereotype the arrangement reached in the homogeneous condition which from time to time recurs in the different parts of the mass, the making and unmak- ing of this highly symmetrical disposition may go on continually, wherever the materials for it are present; without leaving any permanent trace beyond the achievement, where the conditions are uniform, of a practically uniform intermixture of the different balls, or mutually-repellent particles, or groups, in more or less definite average proportions. A fluctuating mass, such as is here conceived, will not, however, owing to the many irregularities produced by the disturbances, attain as a whole the definite combining proportions found in a tranquil homogeneous assemblage, but if the particular homogeneous arrangement thus momentarily and locally brought about 1s one at which a linking together of previously unlinked balls or mutually- repellent particles occurs, and this change of state does not occur where the regularity falls short of this, the mass may, at least partially, notwithstanding the disturbances, pass by degrees, as here and there the requisite arrangement is produced, into a new permanent combination of a definite symmetrical character. A simple assemblage may undergo a change of state analogous to that here attributed to a compound assemblage. For suppose that a number of grouplets, all of the same kind, are momentarily 1 This investigation does not explain, but merely premises change of state. Compare note 2, p. 687. 676 Scientific Proceedings, Royal Dublin Society. or permanently arranged by the action of the principle of closest- packing to form a homogeneous structure, and that the nature of the arrangement produced is such that these grouplets are found placed around axes of revolution of the homogeneous structure, i. e., 80 that each grouplet is related to the other grouplets ranged with it around the same axis, or point of intersection of intersecting axes, in a different manner from that of its relation to any of the other grouplets. We then see that a linking together or poly- merisation of the grouplets to form larger groups may occur wherever the arrangement is sufficiently perfect, and without destroy- ing homogeneity. Permanent combinations brought about in the way above de- scribed will differ in character according to the nature of the change of state which occurs. If the fresh linking which takes place is, although symmetrical, not such as to constitute a con- tinuous mass, it will merely produce new groups of one or more different kinds (polymers), which will be thrown into various orientations by the passing disturbances and yet strive again and again to recur to the closest-packed symmetrical disposition of which they are capable.’ If, on the other hand, the linking is con- tinuous, it will result in the production of a continuous solid homogeneous assemblage capable, under favourable conditions, of symmetrical growth by accretion.® ; And when a solid assemblage has resulted and afterwards experiences a change of state which liquefies it, 7. ¢., breaks it up into isolated units, its properties thus brought to light will depend on the way in which the links break—we may have sufficient links surviving to connect all the particles contained in a unit of the mass so that but one kind of group is produced,’ or we may have some of the links which bind the various parts of a unit together too weak to survive the passage out of the solid state, in which case two or more different kinds will be produced.® Again, a combination different from those just described is conceivable in which one of the combining constituents consists of a solid assemblage 1. e., of one in which the linking of the parts prevents any permanent alteration of their relative situations. ’ 1 Compare p. 585. 2 Compare p. 584. 3 Compare p. 565. “See p. 584. Compare Min. Mag., vol. xi., p. 130. 5 Compare p. 619. Bartow—A Mechanical Cause of Homogeneity of Crystals. 677 In this case the other constituent will consist of balls suffi- ciently small to be inoperative in the sense above defined,’ or at least so small as not to be prevented from entering the interstices of the solid constituent. Finally, in a combination of two fluid assemblages there are two ways in which the balls or groups forming one constituent can be conceived to be related to those of the other, and this is the case whether the intermixture is accompanied by change of state ornot. Hither the balls of both constituents may be operative or those of one constituent may be all inoperative. And a complete gradation is conceivable from extreme cases of the first kind, in which each constituent is equally concerned in determining the kind of arrangement to be displayed by the compound assemblage, to cases in which nearly or quite all the general arrangement is done by the balls of one constituent only, the other, in obedience to the principle of closest-packing, just filtering into the available inter- spaces without producing any material permanent effect on the arrangement of the balls among which it intrudes itself. The rate at which intermixture proceeds will, it is evident, largely depend on the nature of the relation just referred to. Local disturbances, whether brought about by external causes— as stirring or shaking—or by changes occurring within the assem- blages themselves, or arising partly from both sources, will, it is evident, on the one hand, promote intermixture and render its progress more rapid, but on the other hand, they will, if they continue, hinder the intermixture from becoming completely symmetrical or homogeneous. Disturbance followed by a gradual passage to tranquillity will best promote the formation of a homogeneous intermixture by the action of the principle of closest- packing. ; Deferring the consideration of one or two details of the in- termixing of assemblages for a moment, let us now compare the processes thus traced with actual phenomena. We have just seen that in the presence of the disturbances referred to, permanent combination in precise proportions will only occur where the local attainment of perfect homogeneity brought 1See p. 547. This is more readily understood if we take mutually-repellent particles instead of balls. 678 Scientific Proceedings, Royal Dublin Society. about by the principle of closest-packing is immediately productive of a change to the linked condition not produced by any less close and symmetrical juxtaposition. Now, in order that the new molecules formed when a chemical synthesis takes place may all have the like composition, it is manifest that the atoms which combine to form them must, as an antecedent condition, by some means or other come to be distributed through space in the precise proportions obtaining in these molecules. Consequently this uniform intermixture of the combining atoms or complexes which accompanies or precedes the act of chemical synthesis may be instanced as greatly resembling the combination in precise pro- portions of two fluid assemblages which paves the way for a change of state as described above.’ This change of state, which stereotypes the homogeneous arrangement reached by the assemblage, has its representative in the chemical change or act of synthesis whose occurrence is. evidenced by change of properties and manifestation of energy, The intermixture which accompanies or precedes the produc- tion of definite compounds containing water of crystallization, or of those double salts whose constituent salts are held together so loosely that the tie does not survive the passage to the liquid state, also furnishes a resemblance to the symmetrical intermixture leading to change of state above referred to; the only difference is that in the fluctuating or liquid state there will be at least two kinds of separate groups present in a compound assemblage which is paralleled by the last-named cases, and not one kind of group only.” The change known as polymerisation resembles the symmetrical compounding of groups occurring in a simple assemblage in the way above described, e. g., 38C,H,O = C;H,.0; 3 mols. acetaldehyde = 1 mol. paracetaldehyde. When the homogeneity produced locally is not stereotyped as. it arises by a contemporaneous change of state, and thus the 1 See note 1, p. 675. * Comp. Pope’s translation of Fock’s ‘‘ Chemische Krystallographie,”’ pp. 36, 37, &c. Bartow—A Mechanical Cause of Homogeneity of Crystals. 679 passing disturbances continually cause lapses to irregularity, the effects which must evidently be produced find a very close parallel in certain phenomena of diffusion where there are limits to the combining proportions. For in the case of the hypothetical com- bination, as in that of diffusion, we shall have intimate intermixture in practically uniform proportions throughout, without any de- finite orientation, and a saturation-point whose position will practically be definite, and depend on the amount of disturbance prevalent,' as well as on the nature of the ideal equilibrium ar- rangement. The rate at which intermixture takes place will, as has been said, largely depend on whether operative? constituents are to be found in both combining assemblages or not, and on the part the latter respectively take in determining the nature of the ideal equilibrium arrangement. We can conceive of assemblages composed of linked groups whose forms are such that the different groups fit together so ill that the law of closest-packing affords great resistance to inter- mixture in any proportions regular or otherwise. And this is paralleled by some of the cases in which liquid bodies will not diffuse into one another.’ Comparisons may be instituted with the diffusion of gases as well as with the diffusion of liquids. _ There are also resemblances to the case of a solid assemblage receiving within its interstices inactive constituents in obedience to the law of closest-packing. Thus we have the common pheno- menon of solid bodies taking up small quantities of water or certain other liquids, without material change of properties ; in some cases the liquid previous to its absorption being gaseous, as in the case of hydrogen occluded by platinum or palladium. In cases of the latter kind the comparison is instituted with the subsequent intermixture, and not with the change of state. Having thus indicated the general resemblances subsisting between actual phenomena of combination and intermixture and the behaviour of our hypothetical assemblages, a few additional 1 In the case of diffusion, the vigour. of local disturbances is probably traceable to temperature conditions. (But see Appendix, note 1, p. 688.) 2 See p. 547. 3 Comp. pp. 670 and 672. 680 Scientific Proceedings, Royal Dublin Society. details of the action of these assemblages when combining may be given, and a few further resemblances pointed out before quitting this part of the subject. It has been stated above that two assemblages will ultimately combine in the proportions in which they pack closest; this refers to the completed process, there may, and indeed generally will be transitional combinations, some of them homogeneous, and which, as compared with the constituent assemblages unmixed, produce increased closeness of packing, but not the closest possible. Suppose, for example, to take a very simple case, that a set of unlinked balls A, mixed with a set of unlinked balls B, pack closest when they are homogeneously arranged in a certain way which employs the two kinds in the numerical proportions 1: 2. It is then evident that other homogeneous arrangements of the balls are possible into which they enter in equal proportions, and that one of these may, while it doesnot give such close-packing as that of the arrangement just referred to, give closer-packing than is attained by the balls when unmixed. Also that during the process of intermixing to produce the closest-packed arrangement, the balls may here and there fall into this less closely-packed arrangement. And although if its attainment anywhere is not accompanied by a change of state which stereotypes it, such an arrangement will prove but a temporary one, 7 will be made per- manent if a change of state fixes it as it is here and there produced. Any hindrance to the achievement of the closest-packing possible, such, for example, as a scanty but widely disseminated supply of some of the materials, will be likely to favour the pro- duction of this less closely-packed combination.” _The closest-packed arrangement will be appropriately called saturated, and transitional combinations unsaturated,’ the properties expressed by these terms being closely paralleled by the properties of chemical atoms thus named, both in cases of chemical synthesis, and also in those of diffusion. 1 This is somewhat analogous to the accidental twinning above referred to. See p- 620. 2 The method of production of a second combination from the same constituents which is here described must not be confounded with that based on change of conditions. (Comp. pp. 575 and 678.) 3 Comp. p. 607. BarLtow—A. Mechanical Cause of Homogeneity of Crystals. 681 The attempt made to formulate a general law respecting the combining properties of different chemical atoms which shall assign to each kind its definite value, or “‘valency,’’ with respect to other kinds has, it is well known, met-with but very limited success, and it cannot therefore be regarded as surprising that among the geometrical properties here traced no general law of valency of the various kinds of balls finds a place. It is true that in any given combination each kind of the hypothetic balls can, when the conditions are given, be seen to have its own proper com- bining proportion, but it is not easy to see how the proportion observed by a given kind in one combination will be related to the proportion observed by the same kind in another different combination. It is interesting to notice that increase of disturbance will diminish the efficiency of the principle of closest-packing, 7.¢., will hinder it in availing itself of the compatibility of units for fitting close together when appropriately intermixed ; and that resembling this we have the fact that increase of temperature diminishes the number of chemical bonds of substances capable of combination, and weakens their exhibitions of affinity, so that above a certain limit of temperature there is no strictly chemical action. Further, that change of temperature in the other direction greatly compli- cates the chemical effects.* In this connection we may call to mind the fact that the sta- bility of some of the carbon compounds which produce rotation of the plane of polarization is destroyed by a moderate rise of tem- perature.” Where the interpenetration of two assemblages depends on the closeness of packing being increased by the intermixture, it is evident that portions of a third assemblage present in one of the two assemblages which intermix may occupy some of the inter- stices and hinder the process; it may also disturb the symmetry, and in this way prove a hindrance. In connection with this may be cited the observation of Arrhenius, that the presence of a percentage of alcohol in 1 Compare Bischoff’s ‘‘ Handbuch der Stereochemie,’’ p. 42. 2 Ibid., p. 87. 682 Scientific Proceedings, Royal Dublin Society. water considerably lowers the rate of diffusion of a diffusing body.? | The action of the principle of closest-packing may cause an assemblage which consists of, or contains a linked framework’ to exhibit a selective action on assemblages brought in contact with it. Thus for closest-packing to obtain, a certain set of balls may have to occupy the interstices among the balls of such a framework, and to quit the interstices of another assemblage in contact with but outside it. In this connection we may recall the phenomenon of the re- moval of dye-stuffs by the action of crystalloids. Fuchsine blue, in particular, is greedily taken up by many crystalloids, so that in twelve hours a brightly-coloured solution of this substance may be rendered entirely colourless by the action of these bodies lying ro Tt We come now to :— VI.—The breaking up of an assemblage into two or more distinct assemblages ; an effect which resembles the disentangling of the separating atoms or complexes that commonly follows a “‘ chemical decomposition,’ and also resembles the crystal- lizing out of a constituent from a liquid or partially liquid mixture. If an assemblage composed of two or more different kinds of units, whose arrangement at the time of its formation was the closest-packed possible, is subjected to a change of conditions such that this arrangement ceases to be so, it is evident that, if the state of the assemblage as to linking permits, it will in obedience to the fun- damental law of closest-packing break up into two or more assem- blages of different kinds. The re-arrangement of the parts to form these separate assem- blages will be such as to give closest-packing under the new con- ditions, and these assemblages will be homogeneous or amorphous at the behest of the principle of closest-packing. ———s 1 «Untersuchungen tiber Diffusion von in Wasser gelésten Stoffen.’’ Zeitschr. f- physikal. Chemie, 1892, Bd. x., p. 51. 2 See p. 666. ° Schimper, ‘‘ Ueber die Krystallisation der eiweissartigen Substanzen.’’ Zeitschr. f. Kryst., 5, p. 156. Bartow—A Mechanical Cause of Homogeneity of Crystals. 688 As in the case of assemblages combining, it is not necessary to suppose that all the parts of any considerable portion of the changing mass reach a condition of equilibrium simultaneously ; the effect will still take place if the passing disturbances are such as to prevent any great continuity in either time or space of the new symmetrical arrangements produced. And as was just now pointed out, if any particular homogeneous arrangement momen- tarily and locally brought about is one at which linking occurs, and this change of state does not occur where the regularity falls short of this, the mass may at least partially, notwithstanding the disturbances, pass by degrees, as here and there the requisite arrangements are produced, into new permanent combinations, of definite symmetry." We find a resemblance to the process just described in the orderly separation of different kinds of atoms which follows a chemical decomposition, the mass breaking up into less complex substances of a definite composition. Also, in the orderly arrangement arrived at by the atoms of a body as it crystallizes out of a liquid or semi-liquid mixture. VII.—The exchange of some of the constituents of two or more as- semblages so as to constitute fresh assemblages; an effect which resembles the redistribution of the atoms which occurs in a chemical double decomposition. If two assemblages, each of which is composed of one or more different kinds of balls} whose arrangement is the closest-packed possible, are when brought together capable of closer-packing if a redistribution of the balls is made by which two fresh assemblages are formed, it is evident that, unless the linking in the original assemblages prevents, the action of the principle of closest-packing will produce such a redistribution. In some cases the effect may be produced by a combination of all the constituents to form a single assemblage, followed by a separation along fresh lines, while in other cases an actual inter- change takes place at all points where the parts in juxtaposition have not the closest-packed arrangement possible for them; one 1 Comp, p. 674. 684 Scientific Proceedings, Royal Dublin Society. kind filtering in one direction, another in the opposite direction at the same time, and the process continuing until the arrangement ~ throughout is of the closest-packed nature. If the constituents — dislodged are, before the change occurs, linked to other parts of — the same assemblage, the readiness with which the links break will do something towards determining which of these two alternatives prevails in any given case. As before, it is not obligatory to suppose the newly-formed assemblage to be continuous ; it may be produced in comparatively minute fragments as here and there the requisite symmetry is from time to time reached, and then stereotyped by the formation of links. The readiness of a compound assemblage to effect exchanges of this kind with other assemblages will depend on whether its con- stituents are loosely or closely packed, in other words on the extent to which some constituent of it is saturated with the others. This corresponds very well with the facts concerning double decomposition. Thus in speaking of certain cyclic compounds, Bischoff says, that the dimethylene. complex is very unstable and is broken by hydrogen bromide, bromine, and even by iodine. Trimethylene is alone decomposed by hydrogen bromide, not by bromine. Finally tetramethylene and hexamethylene are very difficult to break or not to be broken up.’ Inversion by exchange. Suppose that a certain collection of balls is so constituted as to find equilibrium in two slightly different homogeneous assemblages under some slight variation of the conditions, and that when these assemblages break up into groups as a change to the partially- linked or liquid condition® takes place, these groups are in both cases all of one kind and the composition the same in both cases ; and suppose further that the two assemblages of groups A and B are so related that the only material difference in the arrangement, apart Jrom the linking, is that one kind of ballin A occupies entirely different situations from those it occupies in B, and that the unoccupied points in B, which correspond to the places of these balls in A, and also the unoccupied points in A, corresponding to the places of the same balls in 1See p. 680. * Bischoff’s ‘‘ Handbuch der Stereochemie,’’ p. 51. °% Comp. p. 583. Bartow—A Mechanical Cause of Homogeneity of Crystals. 685 B, are places of most open or loosest packing, then it is evident that the following reciprocal relation between the two assemblages may be looked for:— When two parallel exchanges of the kind above referred to are effected between a third assemblage and the two kindred assem- blages respectively, the balls newly arriving in A are likely to fill the blanks whose positions correspond to points already occupied in B, and the same balls newly arriving in B are likely to fill the other kind of blanks corresponding to points already occupied in A, and if in the assemblages formed the influence of the newly-arrived balls predominates, the result will be that the new assemblage formed from 4 will resemble B, while that formed from B will resemble 4. And this will be the case whether or no the original balls whose positions were different break away and are expelled by the action of the principle of closest-packing, 7. e., whether the re-arrangement is of the nature of a metathesis or a synthesis. It is perhaps interesting to notice that if the positions of the balls thus exchanged are singular points they will, when occupied, probably be the centres of the respective groups, and as a conse- quence, the parts of the assemblages turned towards the centres of the groups in the one will be found turned towards the outer boundaries of the groups in the other related assemblage. A resemblance to the effect above described is found in the behaviour of the isomeric acids, fuwmaric acid, and maleic acid, the former combining with bromine to produce bromo-maleic acid, and not a derivative of fumaric acid—and the latter, in conjunction with the same element, forming bromo-fumaric acid. It is easy to see that if two assemblages are related in the way just described and intermixture of either of them with some third assemblage effects the transformation to the form of the other, this intermixture need not necessarily be followed by a linking in of the new constituent, as in the case just treated of, and if there is no such linking in, avery small quantity of the third assemblage may, by travelling about effect the transformation of a large quantity of whichever of the two assemblages is less stable into the more stable form; there will also be the converse transformation, but naturally the one named will predominate. . Resembling this we have the fact that mere contact with some 686 Scientific Proceedings, Royal Dublin Society. substances effects the spontaneous transformation of certain ethylene compounds into their isomerides. Thus the presence of traces of iodine causes the quantitative transformation of ethylic maleate into ethylic fumarate.* APPENDIX. The main ideas which form the basis of the foregoing inquiry viz. closest-packing, mutual repulsion of particles, ties or restraints on this mutual repulsion, are all old conceptions—they have been used by earlier writers and are still adopted by living scientists.” Nevertheless it seems desirable to put them collectively, as employed in the present case, into the shape of definite concepts clothed in precise language. The following is an attempt to do this, but the writer wishes it to be understood that the list of postulates here given is intended as 2 minimum one—that it is not to be regarded as complete for any purpose except the production of the effects under consideration, and that it is put forward merely as a proposal, for the purpose of eliciting the criticisms and suggestions of those who, in explaining or eluci- dating phenomena, have adopted the same or similar concepts. Proposed Concepts. 1. Particles or centres of influence which are mutually repel- lent. - 2. Kach particle to be destitute of polarity so that its influence on surrounding particles is not affected by turning it about its centre. 3. Different kinds of particles to experience different degrees of repulsion from the same particle at the same distance. 4. The mutual repulsion which any two of the particles exer- cise to diminish as the distance between them increases, and to be always some inverse function of this distance such that when the 1 Hantzsch, loc. cit., p. 83. 2 Comp. ‘‘ Molecular Constitntion of Matter,’’ by Sir William Thomson, in ‘‘ Pro- ceedings of the Royal Society of Edinburgh,”’ vol. xvi. p. 693; as to closest-packing, see p. 712; as to mutual repulsion of particles of more than one kind, see pp- 699-700 ; as to constraints, see p. 699. Bartow—A Mechanical Cause of Homogeneity of Crystals. 687 distance separating them increases beyond a certain limit the mutual repulsion falls very rapidly either to zero or to a com- paratively low value. The position of this limit to depend on the nature of the particles and the conditions affecting them at the moment. 7 5. A general force of compression’ to be applied to every assemblage of particles so as to limit the space allotted to it. 6. Every assemblage of particles to be capable of passing into a state in which movement of some or all of the particles with respect to one another is so restricted as to be almost negligible; in other words, into such a state as would be produced by con- necting some or all of the particles closely contiguous to one another by very slightly elastic strings drawn straight, similar lengths being employed to connect similar pairs of particles. And such a change of state may or may not be accompanied by a change in the mutual repulsions exercised by the repellent par- ticles; and the latter change, if there be one, may consist in an increase or a decrease of these repulsions. And every assemblage thus changed to be capable of passing partially or entirely out of this state of restricted movement back to the condition in which the movement is unfettered.? And the connection established between the particles is to be regarded strictly as a property of their conditions, and as enduring only so long as the conditions capable of producing it endure, so that a fluctuation of the conditions might produce alternate tying and untying of the links connecting the particles of an assemblage. 7. All assemblages of particles are supposed to be continually exposed to small (inconsiderable) local passing disturbances ade- quate to displace any equilibrium which is not the most stable 1 Any other restraint or attraction which, while preventing indefinite expansion, permits the interaction of the mutual repulsions, will do equally well. Compare Boscovich, ‘‘ Theoria Philosophie Naturalis redacta ad unicam legem virium in natura existentium.’’ Where ail space is occupied by particles sufficiently near together to repel one another, no restraining force besides inertia may be necessary. 2 This investigation does not throw any light on the causes or nature of change of state, or the causes of change of volume of matter, but merely premises that such changes of the assemblages of particles as are here defined can be brought about, and traces some of the effects consequent on these changes. SCIEN. PROC. R.D.S., VOL. VIII., PART VI. 3D 688 Scientific Proceedings, Royal Dublin Society. possible, and, as it were, to shake the particles into new situa- tions, and in this way facilitate their taking up relative mean positions which give stable equilibrium.’ The linking premised in No. 6 will, however, where it is present, limit or prevent this effect. 8. In some cases these disturbances ‘are increased so as to pro- duce a retrograde condition and disturb existing equilibrium. Tt is evident that in all cases whatever, in which stable equil- librium is attainable, the arrangement of particles whose nature has been thus premised will, if we neglect the small disturbances, ultimately come to be such that the pressures subsisting between them, together with the external force of compression, form a system in stable equilibrium.” And as, according to one of the data just given, the mutual repulsions fall off rapidly when the distance separating two particles passes a certain limit, this statical equilibrium may be regarded as that of the stronger repulsions, i.e., of those between particles whose distances apart are within these limits, the weaker repulsions, if any, subsisting between the particles whose distance apart exceeds these limits being negli- gible. Thus all repulsions between the particles, except those between each particle and the particles closely surrounding it, are to be taken as negligible. Fundamental Law of Closest-packing. Whether the particles are all of one kind, or of two or more different kinds, the effect of the mutual repulsions, under the con- ditions stated, exclusive of No. 8 above, will be to continually 1 The small movements of the particles may be oscillatory ; indeed the interaction of the repulsions will, if the particles have inertia, cause them to be so, but it is not necessary for our present purpose to attribute any persistence or regular periodicity to any of the oscillations, although the existence of some kind of regularity is not pre- cluded. The origin of the disturbances is immaterial; one thing is however clear: the inter- action of the hypothetic particles will, if they have inertia, cause a disturbance occurring at any point to be communicated to other points around by wave-movements of some kind. 2 Tf the attainment or persistence of complete equilibrium is prevented by the passing disturbances referred to, the given conditions will nevertheless be found continually removing the traces of every slight retrogression thus caused and striving after the equilibrium arrangement. (Compare p. 674). Bartow—A Mechanical Cause of Homogeneity of Crystals. 689 modify at every part of an assemblage any subsisting arrangement of the particles in such a way as to produce closer-packing, until an arrangement is reached which gives at every part the closest- packing attainable. For while the most obvious way of describing closest-packing is to say that it consists in getting the greatest possible number of certain bodies into a given space, if, instead of making the nwmber we make the size variable, we can define it as the packing of the largest sizes of a number of bodies of certain patterns into a given space, e.g., if the balls contained in a bag all swell uniformly the bag will be closest-packed when the maximum enlargement of the balls has taken place. And the effect of the hypothetic repulsions in making the particles get as far from con- tiguous particles as possible, can be regarded as equivalent to the swelling of spheres described about the latter as centres. As only the repulsions between near particles are operative, each part of the assemblage affects other parts not in immediate proximity to it only so far as its changes affect the general pressure, or set up travelling waves of fluctuating pressure; and although no doubt, in most cases, the united effect of the particles everywhere packing as close as they can will be to make the assemblage, as a whole, ultimately occupy the least space possible under a given pressure,' this is not necessarily the case always when we are dealing with assemblages the movements of whose particles are gradually becoming restricted in the manner defined.” The effect referred to, which we may call the law of closest- packing, may be stated concisely thus. Every assembly of mutually-repellent particles whatever, which Julfils the above definitions, will continually approximate to, or strive after, that relate arrangement of the particles composing tt in which it has come at every part to occupy a minimum space under a given general pressure, or average repulsion between the particles. And this will be true whether the assemblage is capable of ultimate stable equilibrium or not, and even if the disturbances referred to are such as to undo what is accomplished of closer-packing as fast as it is achieved. 1 See No. 5 in the above list of Data. 2 Compare conclusions as to bent and branched crystals, p. 568. 690 Scientific Proceedings, Royal Dublin Society. INDEX. Accretion, growth by, 565, 566. Anomalies, optical, in crystals, 629 e¢ seq. Appendix, 686. Bent crystals, 568. Benzene-nucleus, effect of presence of, 592. Branched erystals, 573, 575. Chemical compounds, nature of liquid-, 584, 673. Cleavage, 581. Closest-packing, law of, 688. [532. Closest-packing of units of a single kind, two kinds, 546. three or more kinds, 560. Combination of assemblages, 589, 673. Concepts, 529, 686. Crystallizing out, 682. Crystalloids and colloids, 666, 682. Curved crystals, 568. ®. Decomposition, chemical, 682, 683. Diffusion, 670, 679, 682. Dimorphism, 575, 623. Doppelte Systeme of Fedorow, 564. Double salts, 619, 678. Elastic balls, closest-packing of, 529, 546 note 1. Enantiomorphous centres, 564. Enantiomorphous groupings, 593. Gases, diffusion of, 679. Globulites, 567. Groups of a single kind, 585. Growth by accretion, 565, 566. Iceland spar, artificial twinning of, 646. Isogonism, 648, 661. Tsomerism, 590, 598, 597, 605. Isomorphism, 647. Kelvin (Lord), on homogeneity, 527, 529,, 533, 686. Linkage, 530, 563, 589, 591, 676. Liquid crystals, 565. Mixed crystals, 647, 656, 665. Partitioning into groups, 582, 585. Polar properties, pyro-electric, electric, &c., 582. Polymerisation, 678. Polymorphism, 575, 623. piezo- Racemation due to homogeneous mixture, 596, 603. Repulsion, centres of, 529, 686, 687. Rotation of plane of polarization by liquids, 592. Saturation, chemical, connected with close-packing, 607, 680. Solutions, 670. Stability connected with close-packing, 681. Substitution, chemical, geometrical possi- bilities in, 608. Symmetry, types of, cubic, holohedral, 533, 5438, 548, 549. dodecahedral-hemihedral, 536, 562. gyrohedral, 538, 551. tetrahedral, 542, 550. tetartohedral, 560. hexagonal, holohedral, 534, 539, 540, 553. pyramidal- hemihedral, 557, 561. » rhombohedral, 537, 544. hemimorphic, "555. tetartohedral, 556. tetragonal, pyramidal-hemihedral, 562 rhombic, 558. monoclinic, 559, 560. Ties, 530, 563, 589, 591, 676. Twinning, 620-647. Unhomogeneous assemblages, 543, 568, 649, 663, 664, 672. Valency, 681. Vicinal faces, 638, 634, 636. Water of crystallization, 619, 678. Zeolites, 640. [ 691 ] LXIII, ARRANGEMENT OF THE CRYSTALS OF CERTAIN SUBSTANCES ON SOLIDIFICATION. By FRED. T. TROUTON, D.Sc., F.R.S. [Read NovemBer 17; Received for Publication NovemBer 19; Published January 31, 1898.] In the case of certain substances, an arrangement of the crystals on solidification would appear probable from the following conside- rations :— The substances are those whose conductivity for heat varies with the direction the heat is travelling in the crystal. Suppose a mass of the molten substance beginning to solidify in consequence of heat escaping through its boundary, crystals will begin to form at the boundary. The axes of these incipient erystals may, in the first instance, lie equally in every direction. However, those crystals whose axes of best conductivity lie parallel to the flow of heat will now allow heat to pass out faster than those in any other direction, and, consequently, at these points more rapid solidification will take place than elsewhere. Now it would appear to be a justifiable assumption to make, that this solidifying matter will, in general, add itself to these parti- cular crystals, or at least take up sensibly the same axial direction through the well recognized tendency of substances, on crystal- lizing, to follow any example ready to hand. If this be so, those crystals with their best conducting axes normal to the isothermal surfaces, or surfaces across which the heat is flowing, will grow the fastest by a kind of “survival of the fittest”; and under suitable conditions an arrangement of the crystals may prevail with the axes lying parallel. Such an arrangement of a mass crystallised from fusion is often to be observed on fracture. Though the relative conductivities, in different directions, of a SCIEN. PROC. R.D.S., VOL. VIII., PART VI. 3E : 692 Scientific Proceedings, Royal Dublin Society. great number of crystals have been determined, it so happens that few of these are available for the purpose of testing this question, as most of these substances are not such as readily yield crystals from fusion." The conductivity of ice has been determined by G. Forbes to be greater in the direction of the hexagonal axis than at right angles to it, in the proportion of 22 to 21. Under favourable conditions even this slight difference would appear to be sufficient to determine the arrangement of ice-crystals, so as to have the best conducting axis parallel to the flow of heat. Mr. M‘Connel’ and others have drawn attention to the curious hexagonal arrangement of vertical crystals to be observed in the ice formed on a sheet of water under particularly calm conditions. On the other hand, bismuth, which crystallizes in the same system, was found by Jannetaz to have a conductivity less in the hexagonal axis than at right angles, in the ratio of about 2 to 3. It is not difficult, as is well known, to get crystals of bismuth formed at a surface through which heat is passing out, by allow- ing a vessel of the molten material to cool down a certain amount, till crystals have formed over the sides of the vessel, and then to pour the rest of the still molten bismuth out. The crystals so obtained are rhombohedrons, and are seen, in the great majority of cases, to point with one corner inwards. The rhombohedron is so nearly a cube that it is only by exact measurement it can be ascertained whether it is the corner at the hexagonal axis (which would not agree with the above supposition), or one of the others — which would permit the maximum rate of dissipation of energy. Several of these crystals were measured with the goniometer, and in each case the corner pointing inwards was that agreeing with our theory. Tt is obvious that further observations are most desirable — before accepting any conclusion of this character, but this can only be effected on the accumulation of further thermal con- ductivity data for crystals. 1 The author hopes, when opportunity offers, to make determinations of the relative conductivities of certain crystals, such as, say, sulphur, &c. 2 Nature, vol. xxxix. a [ 698 ] LXIV. PHELLIA SOLLASI: A NEW SPECIES OF ACTINIARIAN FROM OCHANIA. By ALFRED C. HADDON, M.A., D.So., Professor of Zoology, Royal College of Science, Dublin. [Read NovemBer 17, 1897; Received for Publication Novemser 19, 1897 ; Published Frsruary 10, 1898.] My friend Dr. W. J. Sollas, F.R.S., Professor of Geology at Oxford, asked me to identify one or two sea-anemones that he had collected in the lagoon at Funafuti, Hllice Group, W. Pacific, in 1896. They all belonged to the same species. Their anatomy has been studied by my friend and former pupil Dr. Katharine Maguire, and from the information she has supplied me I am able to determine the systematic position of this new form. Phellia Sollasi, n. sp. Form.—In the preserved specimens the body is fairly cylindrical with an expanded base in some specimens. The surface is thrown into folds of contraction, but no warts, suckers, or other prominences are visible. There is a thin cuticle. The disk is largely covered by the contraction of the upper portion of the column. Tentacles short, stout, entacmzeous, in three or four cycles, from about 48 to 54 in number. They are evidently very con- tractile, judging from the radiate grooves at their apices. Colour.—No observations were made as to the colour of the living polyp. Dimensions.—The height of the preserved specimens varies from about 15 mm. to 23mm. The average diameter of the column is from 8 to 10 mm. Habitat.—Coral reef, Funafuti, Ellice group. This actiniarian belongs to the family Sagartidee as it possesses numerous and characteristic acontia. The Sagartide have not yet been satisfactorily subdivided, but 3 E2 694 Scientific Proceedings, Royal Dubhn Society. as the typical sub-family, the Sagartinze, have numerous perfect — mesenteries which bear gonads, as do also the other well-developed — mesenteries, this species cannot be placed among them. Nor can it be located in Carlgren’s sub-family Metridine in which the chief mesenteries are sterile. Both these sub-families possess cinclides. — The Chondractininee have only six perfect mesenteries, but these are sterile. The anatomy of only one or two species of Phellia has been — —_—— studied. Andres (“ Le Attinie,’”’ 1884, pp. 78, 74) gives diagrams — of the general structure of Phellia limicola (Andr.), and quite recently Kwietniewski has described Phellia ternatana, n. sp. (Zool. Anzeiger, 1896, No. 512; “ Actiniaria von Ternate,” — Abhandl. Senckenbergischen naturf. Gesellsch. xxiii., 1897, p. 821); and he alludes (p. 827) to P. ambonensis, and P. decora (?), Klunz., from Ambon and the Red Sea respectively. I have also studied an undescribed species of Phellia from Torres Straits. In all of these there are only six pairs of perfect mesenteries, and these alone are fertile. The present species agrees with the above-mentioned five species in this respect, and therefore I have no hesitation in placing it in the genus Phellia. In the present state of our knowledge, I consider the presence of gonads in the six pairs of primary mesenteries in Phellia, and — their absence in the Chondractinine, to be of sufficient importance to place that genus in a distinct sub-family, for which Verrill’s (1886) name, the Phellins, may very well be retained. Kwietniewski considers the Chondractinine as a synonym of the Phellinz, which he defines as—“20|T9V| ww \oqdaiero| — | 9 | IN ] OM | %D | ° “m) Aresuny “vary ‘opTIory GAT ‘uoIy *g (») wyqnqd ‘wnosnyy qa | yw | ww |sn0|T8v| — | Fda} 1*%D |] — | 9 | IN | Of | BD | eoUeDG Jo oSoT[oD [ehoy *(G) VIUTSITA *Z FT files CON oon TON ee te ene Nore OM alle AO) Girma tne ee “(q) (1) BIULsarA *T ‘SNOUT OLMOTLAPL “pray “mOIT ‘aLVG GONV ANINNOD ENTS *‘minissejog *mINIpOS -reddoy PASS) OSoULSULT LHe) “manim0149 HeqoD eoENi “mINIO[e_D ‘SHLIVOULAN AGNV ‘SALITOWACIS ‘SNOUI OINORLANW JO NOILISOdNOO HHL —— q 706 Scientific Proceedings, Royal Dublin Society. | List oF IRON LINES MEASURED AND IDENTIFIED IN THE SPECTRA oF Merroric Irons: WAVE-LENGTH ACCORDING TO KAYSER AND RUNGE’S MEASUREMENTS. DN ry r X 5371-60 4045-90 0813-12 38682°35 5330-90* 4005-33 3799-68 3680-03 E 5269-65 3969-30 3798°65 3647-99 5169-09 3930°37 © 37907138 3631-62 5110-50 3928-05 3788-01 3618-92 4482°35 3923-00 3765°66 38608°99 4461-75 3920-36 376390 3087-10 4427-44 3906758 3108.36 3086°24 4415-27 3899-80 3749-61 N 3581-32 4404-88 8895°75 3748-39 3570°23 4383-70 3887717 3745°67 3065°50 4376-04 3878°82 3743°45 300862 4325-92 38/2°61 3737-27 3526-50 Ni here. G 4307-96 8867°33 3735°00 3521756 4294-26 3860-03 8732754 3513°91 4271-30 38856°49 M 3727-78 3497-92 4250-93 3850711 { 3727713 3490-65 4216-28 3840°58 3722°59 8476°75 4202-15 3834°37 3720-07 3475°52 4143°96 3826°04 3709°37 3465°95 4132°15 8824°58 8708-03 O 3441-07 4071-79 L 3820°56 3707718 3440°69 4063°63 3815°97 3687°77 Lines or Nicket 1n Merroric [rons: WAvVE-LENGTHS ACCORD- Inc To LivEInGc AND Dewar. r r r r 8857°8 38565°7 3461-1 3390°4 3806°6 8547°5 3457-9 3380-0 3783°6 38523°9 38452°3 33/373 3775°0 8519°1 3445°7 Ba 8}. 3618°8 8514-4 8436°7 3368-9 3612-1 3509-7 R 3433°0 3836074 Appear as 7" 3609°8 8492°3 8423-1 on one line. 3097°0 3483°1 38413°8 38319°7 8071°2 3471-9 38412°9 8815°1 Lingss oF Cospatt 1n Merroric Trons: Liveinc anp DEWAR’S WAVE-LENGTHS. x N 4119°4 3533°6 3995-4 3529-9 3575°7 3529-0 } Very (sirong. 3575°3 3526-9 Possibly two 3569-7 3502°2 ponehe * Not identified on Kayser & Runge’s map: possibly it is 5330°15, but in our spectra there is a diffuse band of rays hereabouts, and apparently several feeble line or edges of bands, which are difficult to measure. = Analysis of Iron Meteorites, Siderolites, and Meteoric Stones. 707 Lines oF THE ALKALI Merats 1x Mereoric Irons: Kayser AND RUNGE’S MEASUREMENTS. Sopium. Porassium. N RuBIDIUM. X 5896-16 } { 4047-36 \ 4201:98 5890°19 i 4044-29 4215°72 3303°07 Lanes or orHeR Merats 1n Mereoric Irons. GALLIUM. COPPER. SILVER. LEAD. Xr Xr Xr 4171°8 3274:09 3382°98 4057-97* 4032°7 3247°65 3280-80 3683-60 36389°70 A calcium line was observed, wave-length 422691. This was believed to be caused by dust. There is an iron line at 4227°60 (K. & R.), but it does not appear in flame spectra. In the meteoric irons from Arva, Hungary, in which there is troilite, and in the specimen from Cafion Diablo, Arizona, there is a trace of manganese. The lines just visible are those with wave-lengths 4033 and 4030 (Liveing and Dewar’s numbers are 4032-0 and 4029°5). The nickel and iron lines are strong in all the specimens. The alkali metals are weak, potassium being found in traces only. These spectra disclose a marked difference between meteoric iron and telluric metal, not only in the presence of a large proportion of nickel in the former, but in the absence of manganese, an element which is invariably contained in the latter. The presence of gallium in variable proportions in the iron meteorites is remarkable. The only one in which its occurrence was at first doubtful was that from Thunda, Windorah, Queens- land. Cobalt occurs in all specimens except in one from Virginia, but it does not appear in the meteoric stones. The meteoric stones all contain chromium in variable propor- tions, and manganese in traces only. The meteorite from Atacama consists of a honeycombed mass * This line is shown as 43857 in the plate 7, Phil. Trans., vol. 185, 1894, by an error of the engraver. SCIEN. PROC. R.D.S., VOL. VIII., PART VI. 3F 708 Scientific Proceedings, Royal Dublin Society. of iron, the spaces being filled with a yellow crystalline mineral (olivine?) which was examined separately from the iron, and found to contain the following constituents, the bases being separated from the silica. Composition oF THE Non-Metatiic Portion or THE [Ron MeETEOoRITE FROM ATACAMA. Alkali and Alkaline Earth Metals.—Sodium, potassium, mag- nesium, calcium, and a trace of strontium present as oxides or silicates. Heavy Metals—Iron, nickel, chromium, copper, silver, lead, and a trace of manganese as oxide or silicates. Professor Norman Lockyer has examined the photographie are spectra of iron meteorites, Phil. Trans., vol. 185, p. 1028, using as poles pieces of the meteoric irons from the British Museum, known as the Nejed and Obernkirchen meteorites. The range of spectrum was from about 5892 (D) to 3933 (K). In addition to iron the following substances were declared to be certainly present :— Manganese, cobalt, nickel, chromium, titanium, copper, barium, calcium, sodium, and potassium. Others were said to be probably present, namely, strontium, lead, lithium, molybdenum, vanadium, - didymium, uranium, tungsten, yttrium, osmium, and aluminium. The general conclusions arrived at were that the two meteorites agreed very closely in composition, that there was a very consider- able similarity between the spectra of the meteorites and that of the Sun, the lines having the same relative intensity as those in the solar spectrum. The presence of copper was supposed to be probably due to copper wire being used to bind the pieces of iron to the poles of the are lamp, as neither flame nor spark spectra confirmed the presence of copper. It may here be remarked, however. that the most prominent lines in the spectrum of copper lie in a region far beyond K in the ultra-violet, and were therefore not within Lockyer’s range of observation, when produced either by are, spark, or flame. There were 43 lines for which no origin was suggested, 29 being apparently coincident with lines in Kayser and Runge’s iron spectrum. It was shown that the chief chemical differences between the two meteorites was a preponderance of Analysis of Iron Meteorites, Siderolites, and Meteoric Stones. 709 calcium in the Nejed meteorite, and of nickel, barium, and stron- tium in that from Obern Kirchen. A line at 4171-2 is described as “unknown,” and one at 40351°4 is doubtfully ascribed to iron. The former is certainly, and the latter probably, a gallium line, wave-lengths 4171°8 and 4082:7. The substances which yield spectra in the oxyhydrogen blow- pipe, capable of being photographed are those which are easily volatilised at a temperature of about 1800°C., as one of us has already shown (“‘ Flame Spectra at High Temperatures, Part I., Oxyhydrogen Blow-pipe Spectra,’ Phil. Trans., vol. 185, p. 161, 1894), and they form a very large proportion of the metallic elements and their compounds. When examined by this method over a wide range in the ultra-violet, most substances yield characteristic spectra. CoNncLUSIONS. 1. The composition of different meteoric irons is very similar, though the proportions of the constituents differ to some extent. 2. We find that copper, lead, and silver are common constituents of meteoric irons, and that they occur in variable proportions. We have already shown that this is the case with iron ores of different varieties, and different kinds of manufactured irons. 3. Gallium is a constituent in varying proportions of all meteoric irons, but not of all meteorites. It occurs in one of the siderolites we have examined. 4, Sodium, potassium, and rubidium, are constituents of meteoric irons, but only in minute proportions. 5. Chromium and manganese are found in meteoric stones, but not in the irons, though very minute traces of manganese have been detected in two of our specimens. 6. Nickel is found as a principal constituent in all meteorites, meteoric irons, and siderolites. Cobalt occurs in the two latter varieties only. : The chief points of difference between telluric and meteoric iron is the absence of nickel and cobalt in any considerable propor- tion from the former, and the presence of manganese; while meteoric irons contain nickel and cobalt as notable constituents, and, except in minute traces, manganese is absent. 3 F2 710 Scientific Proceedings, Royal Dublin Society. DESCRIPTION OF PLATES. Tur three Plates reproduce the flame spectra of six Meteoric Irons and three Siderolites. Along the middle of each flame spectrum is a spark spectrum of two alloys, which yield lines of air, cadmium, lead, tin, bismuth, and silver, the wave-lengths of which are accurately known. The wave-lengths of the lines in the flame spectra are easily deter- mined from a curve of wave-lengths drawn from the lines in this spark spectrum. The principal lines of the elements present cannot be marked on every spectrum, but they are indicated by the symbols or names of the elements on different plates, thus :— On Plate XXII.: sodium, calcium, lead, nickel, rubidium, potassium, silver, gallium, and copper. On Plate XXIII.: cobalt and iron. On Plate XXIV.: manganese. Puats XXII.—Meteoric Irons :— Spectrum 1. Virginia (1). 5 2. Virginia (2). os 3. Arva, Hungary. Puatz XXIII.—Meteoric Irons :— Spectrum 1. Tolucca, Mexico. a 2. Cation Diablo, Arizona. oy 3. Thunda, Queensland. Pratt XXIV.—Siderolites :— Spectrum 1. Atacama, Chili. 3 2. Estherville, Iowa. a4 3. Imilac, Chili. Dba uaa LXIX. ON THE MOUNTING OF THE LARGE ROWLAND SPECTRO- METER IN THE ROYAL UNIVERSITY OF IRELAND. By W. E. ADENEY, D.Sc., F.LC., Curator in the Royal Univer- sity, anv JAMES CARSON, A.R.C.Sc.1., C.E. [Read Fesruary 16; Received for publication Frsruary 18 ; Published Aprin 7, 1898.] Tue working parts of this instrument were obtained from Mr. J. A. Brashear, of Allegheny, United States of America. They consist of two interchangeable inverted | steel rails, each of about 23 feet in length, and each haying the upper edge planed to an inverted (\ section, with top truncated. These rails were supplied with saddles of cast iron, into which the rail was fixed, and which were provided with levelling and lateral adjustment screws. One of these saddles takes one end of each rail at right angles, one to the other, and also carries the mounting for the slit. The ‘‘diagonal beam” is an iron girder consisting of a tube about 3” diameter (t, fig. 1), trussed with 2” rods (r, fig. 1), the struts being placed at angles of 120° round the tube. Fixed to each end of the tube is a cast-iron palm (g, fig. 1), which is provided with a small range of adjustment in the direction of the length of the girder. These palms are provided with vertical axes, which form the connexion with the carriages (1, fig. 1), which run on the rails. On the one palm is fixed the grating holder (a, fig. 1), and on the other the camera. These parts are similar in structure to those described and illustrated by Ames in the Astro-Physical Journal, p. 28, January, 1892. The concave grating, which was also obtained through Mr. SCIEN. PROC. R.D.S., VOL. VIII., PART VI. 3G 712 Scientific Proceedings, Royal Dublin Society. Brashear, has a focal length of 21°5 feet; the ruled space is about 6 inches long, bearing 14,488 lines to the inch. The spectra on one side of the grating are all bright; the first order on the other side is somewhat brighter than the others. Mr. Brashear remarks, in a letter to one of us, that ‘“‘ Professor Rowland states all the lines are clear and sharp,” and adds, “You are very fortunate in getting this grating, for no one knows when we will get another.” Our own experience with the grating fully corroborates these remarks. ‘The definition of the spectral lines afforded by it is remarkably fine; and we feel it due to Mr. Brashear to express here the thanks, which have been conveyed to him by letter, for the trouble and care he has so courteously taken to furnish this University with such a very fine instrument. For various reasons we decided not to erect the spectrometer in a dark room, but determined rather to set it up ina room open to day- and sun-light, and to endeavour to devise the light-tight connexions between the working part of the instrument, which then become necessary for photographic, as well also as for eye, observations. A raised floor, 30 feet by 30 feet, and about 9 feet high, was built at one end of the Physical Laboratory of the University, the floor being supported on steel girders, the ends of which were built into two opposite side-walls of the laboratory, while the central portions were supported by steel columns resting on concrete foundations. The spectrometer was mounted on this raised floor in the fol- lowing manner :— Two red deal beams, each 12” by 3”, and of sufficient length to carry the steel rails, were mounted true and level on cast-iron standards bolted to the floor. To these were bolted the saddles mentioned above, and on these were fixed the rails. The latter were very carefully adjusted, so as to be exactly level, straight, and at right angles to one another. The beam on which the grating rail H was mounted also served as a basis for a light-tight wooden structure running along its whole length, and completely enclosing both the rail and grating. ApEnrY & Carson—The Rowland Spectrometer, R. U. I. 718 Fig. 1 shows this structure in section, with the rail, carriage, and grating indicated in position inside. D a Fig.1. NS K, cH ——————— R a M represents a cast-iron standard. B QOH ft @ 34 the beam 12” by 3”. #8 the saddle. “3 the rail. 5 sheeting of 2” cedar wood. 55 framed top fastened to © and supported by brackets. The panels in this are represented by movable lids (D). AA are pieces secured, one to B and the other to c, and grooved for the reception of sliding doors, each about 2 feet wide, by means of a series of which the side of the rectangular box could be closed in from either end, making the whole completely light-tight. This construction was necessary, inasmuch as the girder passed out through this side, and at a varying angle, and different position, with every movement of the grating carriage along u, and with the corresponding movement of the camera along the other rail H’. 3G 2 714 Scientific Proceedings, Royal Dublin Society. One end of this rectangular structure or box was permanently closed, and a short piece of brass tube made to slide through a hole in the end at the proper height for the slit. This brass tube was supplied with a boxwood flange fitting light-tight against the slit mounting, so that all the adjustments of the latter were outside the wooden rectangular box. The other end was closed by a sliding door. A light-tight connexion had now to be established viohieeey this wooden box and the camera at the other end of the girder, and inasmuch as the girder not only moved from one end of the tube to the other along the rail u, but at every new position on the rail made a different angle with it, it was impossible to accomplish this connexion by anything in the nature of a bellows. After much consideration the following method was decided on, and works admirably in practice :—On the iron tube of the girder was fixed, by means of wooden supports and clamps, a wedge- shaped rectangular tube of wood, a little wider than the grating at one end, and the width of the camera at the other, and about four inches deep. Part of this is shown in fig.1 as K. The end came to within about 13” inches from the face of the grating ec. Fig. 2 shows a section, which represents the construction for about one-half of its length from the grating end, the remainder being without the grooved slides (a). The tube is shown in plan in fig. 3. Apenry & Carson—The Rowland Spectrometer, R.U. I, 715 The opening (B) was in that side of the tube nearest the rail, and was necessary when the camera was close up to the slit; since the light from the slit would otherwise be cut off from the grating by the angle of the tube coming between them, as shown in fig. 3 in plan. An arrangement for wholly or partially closing this opening at will was provided, in the shape of a door sliding in the grooves AA. In order to close up the space below the tube x, inasmuch as the sliding doors referred to as moving in the grooves Aa in fig. 1 could not come beyond the points of intersection of the tube k with their plane—namely, 1 in fig. 3—and inasmuch also as the lower grooved piece (A, fig. 1) had to be at sufficient distance below to clear the lowest point of the tie-rod r, the simplest way that could be thought of by the authors was to suspend a loose bag or tube of felt cloth from the lower edges of the sides of x, letting it hang down and enclose the girder and its tie-rods. This is shown at c in fig. 2, but is supposed to have been re- moved in fig. 1, so as to show the tube and tie-rods. The outer end of the bag, or the end nearer the camera, was closed up, and the other came well within the plane of aa, fig. 1. This was found to answer admirably, and by the aid of a cloth thrown across K,and loosely tucked in against a on the top, and the sliding doors and the felt bag at the sides, no difficulty has been experienced in obtaining a perfectly light-tight joint in all positions of x. The camera is connected to the other end of x by a few inches of bellows, which allows for the focussing adjustment. 716 Scientifie Proceedings, Royal Dublin Society. The spectrometer, mounted in the manner here described, has: now been in use for more than a year, and has been thoroughly tested. It has been found most convenient both for making eye- piece observations, and for taking photographs; it has also been found completely light-tight. In proof of this last statement, we- may mention that we have exposed rapid photographie plates in the camera of the instrument for upwards of six hours, on bright sun-lit days, during the course of an investigation we have been, and are at present, making, in conjunction with Professor Hartley, F. R.S., upon the ultra-spark spectra of the elements, and have experienced no difficulty whatever from‘ fogging.” Buea eG LXX. NOTES ON CERTAIN ACTINIARIA. By DR. KATHERINE MAGUIRE. (Puatze XXTIVa.) (COMMUNICATED BY PROF. A. C. HADDON.) [Read January 19; Received for Publication, January 21, 1898; Published July 23, 1898.] (a).—Tue Anatomy oF Puerria Sotzast, Happon. Turovucu the kindness of Professor Haddon I was given four specimens of this species to examine; they were brought by Pro- fessor Sollas from Funafuti in 1896. The specimens were pre- served in spirit, and the colour, of which no note had been taken, was completely lost. Form.—The preserved specimens are more or less cylindrical ; one is barrel-shaped ; none of them are completely retracted. The tentacles are set in three rows on a circular disc; they are simple, conical, and blunt at the apex, from which radial longitudinal strie run down the wall. The arrangement is entacmzous; the number in one specimen is forty-eight, of which the six inner are larger than the others. In another specimen there are fifty-four tentacles, of which the twelve inner are the largest. The body- wall is opaque. The surface of the column is transversely grooved ; but there are no warts, tubercles, nor acrorrhagi; the pedal disc is well marked in two specimens. The mouth is linear; in two specimens the gullet is everted, showing two gonidial grooves. In the smallest specimen whitish threads hanging from the mouth proved to be acontia. Size.—The length of the preserved specimens is 15-23 mm.; the average diameter of the column is 8-10 mm. Internal Anatomy.—On longitudinal section, the mesoglea of _ the lower three-fourths of the body-wall is seen to be much thicker 718 Scientific Proceedings, Royal Dublin Society. than the upper one-fourth. The longitudinal muscles of the primary mesenteries form well-marked swellings which are easily seen by the naked eye. Of the two specimens examined with the microscope, one (the smallest) was stained in borax-carmine, imbedded in paraffin, and cut transversely in series. The larger specimen was cut in two, the lower half was stained in carmine, and cut transversely, two portions of the upper half were also stained in carmine, and cut longitudinally. The transverse sections of the larger specimen, through the - gullet show two pairs of directives with four pairs of lateral com- - plete mesenteries, making six pairs of primary mesenteries. There are six pairs of secondaries bearing mesenterial filaments and acontia. ‘T'welve pairs of tertiaries without filaments, and three pairs of fourth-cycle mesenteries which do not project above the endoderm. Below the gullet, the number of mesenteries of the fourth cycle increases, and ovaries are found only on the primary mesenteries including the directives. Lower down, the number of fourth-cycle mesenteries is further increased. Mesenterial filaments and acontia are present along Fie. 2. Phellia Sollast.—The cesophageal region of Phellia Sollast.—The same below the cesopha- the large specimen. gus, showing gonads on primary mesenteries. with the gonads on the primary mesenteries. In the lower sections, the lateral primary mesenteries incline towards each other, but do not fuse. The small specimen is not so well preserved. It was pro- truding acontia through its mouth, and the gullet is everywhere Macuire—WNotes on Certain Actiniaria. 719 filled with a mass of partly broken down acontia. The number and arrangement of the mesenteries are almost identical with those of the larger specimen. But below the gullet, one of each of the two pairs of lateral primary mesenteries leans over towards the corresponding adjacent mesentery on the same side (that furthest from the directives). Lower down, these mesenteries fuse completely, forming a lateral chamber on each side of the animal. The primaries and secondaries bear mesenterial filaments and acontia. There are no gonads in this specimen. In both specimens, ‘the muscles have the usual Hexactinian arrangement. The retrac- tors are well developed on the primary mesenteries, forming a well- marked pennon. The parieto-basilar muscle is fairly developed. ETGao Phelita Sollas7.—Small specimen, below the cesophagus, showing fusion of lateral primary mesenteries. Sphincter.—The sphincter extends through about the upper third of the body-wall. It is mesoglceal, occupying at its commencement the inner rhalf of the mesogloea which is here very thick; though the muscle has sunk into the mesoglea, it is not sudounied by it, but is still directly continuous with the endoderm, where the body-wall is thick. Higher up where the wall is thinner, the muscle is much reduced, only a few strands, which are separated from the endoderm, being visible. There is a stronger portion forming a small prominence in the body-wall at the base of the outer tentacles ; here the muscle _ occupies almost the whole thickness of the mesoglea, but the lower part, where the body-wall is thick, is much the best developed. The endodermal circular muscle persists inside the sphincter. 720 Scientific Proceedings, Royal Dublin Society. Histology. Ectoderm.—There is a thin cuticle on the lower three-fourths of the capitulum; it is absent on the thin upper part of the wall. The ectodermal surface is everywhere exceedingly irregular, giving rise to numerous ectodermal lacunz in the: mesoglea. The general character of the ectoderm shows nothing unusual. On the tentacles, there are numerous stinging cells, both thin and thick walled. Ectodermal muscles are only present in the tentacles and disk, where they are well marked. No cinclides could be seen. Mesoglea.—The mesogloea of the body-wall shows an inner deeply stained dense layer; made up of fibres running both trans- versely and longitudinally, and an outer layer not stained so deeply, made up of fine fibres which cross each other, forming a loose reticular structure. The mesogloea of the tentacles contains numerous cells. The ectodermal muscles, which are very well marked, sink somewhat into the mesogloa, but are not enclosed by it, and cannot be called mesogleeal. A few strands of muscle are prolonged from the sphincter into the mesogloea of the disc, but in other places the mesogloea of the disc is thin, and there is no mesogleal muscle. In all sections of the upper part of the body-wall, irregularly rounded bodies of varying size are seen, mainly in the mesoglea, but in some places in the endoderm. These bodies stain deeply with carmine, and are made up of fine granules, most of which are very small and highly refracting, a few of them are larger, and may be also highly refracting, but are occasionally much darker than the other granules. Some of the smaller bodies seem to be made up of a few of these granules surrounded by dense deeply stained mesoglea, but other small ones do not differ in any way from the larger and presumably older bodies. I have de- scribed these with the mesoglea, as they are a striking feature in sections of the body-wall, but they also occur, though not so frequently inthe endoderm. The mesoglcea of the gullet and septa shows no special features; the mesoglveal strand of the acontia is almost circular. Endoderm.—The endoderm is of the usual type; gland cells are not very abundant. Alge are everywhere present. The Macuire—WNotes on Certain Actiniaria. Gon endodermal muscle of the body-wall is well developed; that of the tentacles and disk is not well marked. Mesenteries.—The arrangement of the muscles has already been described. The central glandular streaks of the mesenterial filaments are well developed; they contain large glandular cells. both granular and homogeneous, and thick walled stinging cells, The ciliated lateral streaks are poorly developed. The acontia, which are borne like the mesenterial filaments by the primary and secondary mesenteries only, are fairly abundant. In trans- verse section, they are nearly circular; they show numbers of very large thick-walled stinging cells, and a few fine granular gland-cells. The gonads are found on the first cycle of mesenteries, between the retractor muscles, and the mesenterial filaments ; they have the usual structure. Two points of interest to be noted in this species are the coalescence of some of the mesenteries, and the granular bodies in the mesogloea and endoderm. With reference to the coalescence of mesenteries, this condition has been described and figured by Rt. Hertwig (Report on the “ Challenger’ Actiniaria, 1882, p. 83, plate vii., fig. 2) in the primary mesenteries of Chitonanthus (Phellia) pectinata Fusion of the secondary mesenteries is described by the same author (loc. cit., p. 37, pl. vill., fig. 5) in Tealia bunodiformis. In both these cases, fusion occurred between mesenteries of the same pair, not of different pairs as in this species. Hertwig regards it as a temporary condition; and it seems probable that it must be so, as in Phedlia Sollasi the primaries are alone fertile; and in the larger specimen containing gonads, the mesenteries were not fused. Coalescence of primary mesenteries (directives) with each other, and with several pairs of secondary mesenteries, has been described and figured in Bunodes thallia by G. Y. and A. F. Dixon (Proceedings, Roy. Dubl. Soc., 1889). A similar condition has also been noted by G. H. Parker in Metridium marginatum (Bull. Mus. Comp. Zool., Cambridge, Mass., xxx.,.1897, p. 267). 1 This species is certainly not a Phellia, as Hertwig supposed. Haddon regarded it as a Hormathia; but MeMurrich (Proc. U. 8. Nat. Mus., 1893, pp. 189, 209) places it in his new genus Chitonanthus. 722 Scientific Proceedings, Royal Dublin Society. As regards the granular bodies, Hertwig (doc. cit., p. 82, pl. viii., fig. 1) makes the following statement about Chiton- anthus pectinata, ‘in it (the mesoglea), there are small roundish concrements which are strongly coloured by carmine, and the structure of which recalls that of granules of starch; they are made up of indistinct concentric layers, frequently appear in section like a figure 8, and are limited to the superficial layer of the mesoderm.”’ He makes no conjecture as to their nature. It seems likely that the granular bodies found in Phellia Sollasi may be of the same nature as those in Chitonanthus pectinata ; they are not identical with them, as they are not in the least like the figure, and are not apparently made up of concentric layers, though a different method of preservation might make a difference in their appearance. The only other references to such structures that I can find are in M*Murrich (‘‘Albatross ” Report, Proc. U.S. Nat. Mus., 1893, p.177), where he describes “ granular, spherical, or oval bodies in the ectoderm of the dise of Sagartia lactea’”’; they stained deeply, and he believed them to be glandular ; he gives no figure, but the description, though not the situation, resembles the bodies in Phedlia Sollasi. 8. J. Hickson (Quart. Journ. Mier. Sci., vol. 37, pt. 4) describes and figures dark homogeneous bodies seen in and among strands of endoderm cells; in the mesoglea of Alcyonium, he thought they were probably parasitic sporozoon. I should be inclined to regard the bodies seen in Phedlia Sollasi as due to a parasite more likely vegetable than animal. (6).— Tue Anatomy oF PARANTHUS CHROMATODERUS. Entacmea chromatodera, sp.n., Schmarda, 1852, p. 1d. Actinia chromatodera, Schm., Heller, 1868, p. 19. Paractis rugosa, sp.n., Andres, 1880, p. 314. Through the kindness of Professor Haddon, I was given six specimens of this species to examine. External Characters.—These are described from the living animal by Andres, Le Attinie, 1884, p. 256. The specimens I examined were preserved in alcohol; the colour is lost. Size: height 30-40 mm.; average diameter of column 12-18 mm. One specimen is completely retracted. The shape of most of the specimens is cylindrical; one is urn-shaped. Macuire—WNotes on Certain Actiniaria. 723 The surface of the column is smooth. The ectoderm is trans- parent, showing the insertion of the mesenteries, and the gullet which reaches about half way down the column. The tentacles are arranged on a circular dise in about four cycles; they are very numerous, nearly 200 in one specimen, small conical, all similar. The mouth is an elongated slit; there are two gonadial grooves. ‘The pedal disc is well marked in most of the specimens. One,specimen was stained in carmine, imbedded in paraffin, and cut transversely. Sections through the gullet show two pairs of directives with four pairs of complete lateral mesenteries, making altogether six primary mesenteries, all of which are sterile. There are six pairs of secondary mesenteries bearing ovaries and mesenterial filaments. Twelve pairs of tertiary sterile mesen- teries. Twenty pairs of sterile mesenteries of the fourth cycie; these are very small, and not raised above the endoderm (fig. 5). Sections below the gullet show the same arrangement; the primaries bear mesenterial filaments, but no gonads. The number of mesenteries is the same. The shape of the mesenteries was a good deal affected by pressure, the specimen being distended by ova; but there is no doubt that some pairs both of primary and secondary mesenteries are of unequal length. A second specimen was also cut transversely, showing the same number and arrangement of the mesenteries as the former; but in this specimen the primaries, including the directives, were fertile ; and some pairs of the secondary mesenteries (but not all) seemed to be also fertile: mesenteries of the third and fourth cycles as in the former specimen. Sphincter.—The sphincter (fig. 4) is present in the upper part of the column only; it is mesogleal, occupying the whole thickness of the mesogloea, and ceasing abruptly at the oral disc. It does not taper much at its lower extremity, but is of the same width throughout. Ectoderm.—There is no cuticle. The ectoderm of the column and disc is of the usual type. ‘There is no ectodermal muscle on the column. The ectodermal muscles of the tentacles are well developed; that. of the dise is fairly developed. There are nume- rous thin-walled stinging cells in the ectoderm of the tentacles; thick-walled stinging cells are not so common; in other parts of 724 Scientific Proceedings, Royal Dublin Society. the ectoderm, these cells are not numerous. The ectoderm of the gullet contains the usual gland-cells. Mesoglea.—The mesoglea is everywhere rather thin. That of the column is dense, made up of fibres running both circularly and longitudinally ; it stains very deeply with carmine. There are no mesoglceal muscles except the sphincter. The mesogloea of the mesenteries also stains deeply. Endoderm.—The endoderm is of the usual type. Zooxanthelle are everywhere present.1 The endodermal circular muscles of the column and tentacles are well marked. The muscles of the mesenteries have the usual hexactinian arrangement. The re- tractors form a well-marked pennon on the primaries and secondaries. The parieto-basilar muscle is present on the mesenteries of the first and second cycles. Mesenterial filaments are borne by the primaries and secondaries; the glandular streaks are best developed; they contain many thick-walled stinging cells as well as gland-cells. The filaments were, on the whole, not numerous or well developed ; but both the specimens examined were distended with ova. No acontia are present. The ovaries are of the usual structure, and contain numbers of nearly mature ova. P. chromatoderus is the only representative of the genus Paranthus, which was established and placed with the Paractidze by Andres on external characters only (‘ Le Attinie,” 1884). The Paractidee have been variously defined by Hertwig. Report on _ the Actinaria (“ Challenger” Hx- pedition), 1882, p. 41; Andres, “Te Attinie,” 1884, p. 200 ; Danielssen, “ Actinida’’ (Norske Nordhavs. Expedit.), 1890, p. 8; Paranthus chromatoderus.—Vertical section Carlgren, ‘Studien uber Nor- ofepperpetofesluna-vallshowingmesoyias! Gischo Actinion,” 1, 1893, D. 64 see p. 731.) M°Murrich, Report onthe Actinize (‘‘ Albatross’ Expedition), Proc. U. S. Nat. Mus. xvi., 1898, 1T notice that Simon (Beitrag zur Anatomie u. Systematik der Hexactinien, Inaugural Dissertation der Universitat Miinchen, 1892, p. 45) says, in his definition of the Paractide, ‘‘ Zooxanthelle in this family have so far not been recognised.” Macurre—WNotes on Certain Actiniaria. 725 p- 160. The latter simply separates the Paractidee from the Sagartidze by the absence of acontia; and with this definition, P. chromatoderus seems to agree very well. Fig. 5. Paranthus chromatoderus.—Transverse section through part of cesophageal region of column. (For Lettering see p. 731.) (c)—Tue Anatomy or Actinia EQUINA (Linn.) var. MESEMBRYANTHEMUM. So many figures and descriptions of the external characters of this Actinia have been given by Gosse, Andres, and others, that Ido not propose to describe anything but the internal anatomy, about which more information is required. The methods used were the following :— Some specimens were hardened in formaldehyde four per cent., and examined macroscopically. This reagent destroys the colour, 726 Scientific Proceedings, Royal Dublin Society. but does not make the specimens brittle, so that they could be cut easily without injuring the septa. For microscopic work, one of — the specimens hardened in formaldehyde was also used; it had been in the reagent for some weeks, having been fixed in five per cent., and transferred in a few days toa four per cent. solution; it was stained in borax carmine, dehydrated with absolute alcohol, and imbedded in paraffin ; this specimen shows the histological details very well, though the ectoderm was not stained as deeply as usual ; the cilia were very distinct. It does not seem to have suffered from dehydration in any way, and the cells are not much vacuolated.* One large specimen was fixed and hardened in a mixture of three and a-half per cent. each of bichromate of potash and formaldehyde (this mixture keeps badly) as a fixing reagent; it acts slowly and does not cause very complete contraction. Asa hardening reagent for general use, specimens may be left in it for from ten daysto a fortnight, and a much longer time may beallowed to elapse without overhardening; the fluid must, of course, be changed from time to time. This specimen was cut up into four, and after three days two parts were transferred to nitrate of silver seventy-five per cent. solution, to try if Golgi’s reaction could be obtained. These were afterwards dehydrated with alcohol imbedded in paraffin, and cut; but the chromate of silver had only formed a coating on the outside, though the tissues were in a good state of preservation. Carlgren (1893) also failed to stain Actinia after Golgi’s method. The two other pieces which had been hardened for about a fortnight in bichromate and formal- dehyde were washed in water for twenty-four hours, stained in borax carmine, dehydrated for several days in alcohol (in the dark), imbedded in paraffin, and cut—one part longitudinally, the other transversely ; this method of hardening is admirable for the histological details; the cilia are unusually well seen (perhaps this. is due to the formaldehyde as they are very distinct also in the sections hardened in it). Some specimens were also stained with methylene blue, the living or recently killed animals being put into a solution of ‘75 per cent. sodium chloride and methylene blue, and left for twenty-four hours; the specimens were then 1 Some other specimens hardened in formaldehyde did not stain well. I believe prolonged after-treatment with alcohol is advisable to ensure uniform results with formaldehyde material. Macurtre—Wotes on Certain Actiniaria. eT fixed in platinic chloride four per cent. solution for twenty-four hours then transferred to alcohol and imbedded in the usual way. ‘The platinic chloride fixes the stain very well; and it had penetrated to the endoderm in the superficial parts, such as the tentacles, but it was mainly taken up by the epithelial cells, and did not show any details of the nervous system. An adult specimen hardened in four per cent. formaldehyde, and examined macroscopically showed the following arrangement of the mesenteries. In section through the gullet, there are alto- gether twenty-four pairs of complete mesenteries, including two pairs of directives ; from embryological considerations, it is obvious that every fourth complete pair of mesenteries from each directive must be a pair of primaries. The secondaries and tertiaries can be determined in the same way. Thus of the complete mesenteries there are :— Primary, six pairs. Secondary, six pairs. Tertiary, twelve pairs, making twenty-four pairs of com- plete mesenteries. Of incomplete there are :— Fourth cycle, twenty-four pairs. Fifth cycle, thirty-eight pairs, making sixty-two pairs of incomplete mesenteries, eighty-six pairs in all. In the lower half of the column, the mesenteries were the same, except for the fifth cycle, of which there were apparently only thirty-six pairs. All mesenteries, except the fifth cycle, bear mesenterial filaments. Ina large adult examined microscopically, there are in sections through the gullet :— Primary mesenteries, 6 pairs (2 directives) ; Secondary ,, 6 pairs ; Tertiary 9 12 pairs, making twenty-four pairs of complete mesenteries ; Fourth cycle, - 24 pairs; Fifth cycle, | - 24 pairs; making forty-eight pairs of incomplete mesenteries, seventy-two pairs in all. Lower down the number of fifth-cycle mesenteries was, as far as they could be counted, the same. All mesenteries bear mesenterial filaments, except those of the fifth cycle. SCIEN. PROC. R.D.S., VOL. VIII., PART VI. 3H 728 Scientific Proceedings, Royal Dublin Society. Though both these specimens contained numbers of embryoes, neither of them had attained the full number of the fifth cycle of mesenteries. In the specimen examined microscopically, the fifth cycle seemed to be developing from one pair of directives, where all the cycles were complete, towards the other where the fifth cycle . was undeveloped. This was not so clear in the macroscopic specimen, though the cycles near one pair of directives were all complete, while one of the fifth was wanting to one side of the other pair of directives. Sphincter.—The sphincter is a diffuse endodermal one, being merely a thickening of the endodermal muscle lying between the marginal spherules and the outer row of tentacles. Histology. Eictoderm.—There is no cuticle. The nervous layer is every- where well developed... The usual gland-cells are present. Thread-cells are very abundant in the tentacles and marginal spherules; they are scarce elsewhere. ‘The ectodermal muscles of the oral disc and tentacles are well developed: these are the only places where ectodermal muscle fibres occur. The gullet has the usual structure. The marginal spherules are placed just outside the sphincter. In longitudinal sections they are often irregularly quadrangular, the external angle being the most acute. The ectoderm is much thicker here than on other parts of the disc. In some sections it can be seen to form three layers : (a). A layer of delicate fibres with a few scattered small cells. (b). A layer two or threerows deep of fusiform granular cells very closely set ; there are also a few thread cells and a few supporting cells. (c). The outer layer, one row of cells deep, consisting almost entirely of thick-walled thread-cells set evenly side by side; there are also a few fusiform granular cells like those of layer (2). At the edges of the spherule, the ectoderm is much like that of the disc, only somewhat thicker, and with more numerous thread cells. The mesogicea and endoderm have the usual structure. MacuirEe—WNotes on Certain Actiniaria. 729 Mesoglea.—The mesogloea is not very thick; it never contains muscle; it is fairly homogeneous. Sections hardened in formalde- hyde show numerous cells. Endoderm.—The endoderm has the usual structure. It con- tains large quantities of gland-cells, both granular and homo- geneous, especially on the surfaces of the mesenteries. That lining the column and the tentacles contains numbers of alge. The endodermal muscle of the column is very well marked, and so are those of the tentacles and disc. Mesenteries.—The numerous gland-cells on the surfaces of the mesenteries have been already mentioned. The muscles have the usual hexactinian arrangement; the retractors do not form a well-marked pennon, but are distributed fairly evenly along nearly the whole length of the mesenteries. The parieto-basilar muscle is present and forms a well-marked swelling on all the mesenteries, except those of the fifth cycle. It is very close to the body- wall in sections high up, but is much further in lower down. The mesenterial filaments are numerous at all levels of the Actinia. Those in sections through the gullet show the lateral ridges well marked; lower down, these ridges are much lower, and the cells contain numerous alge. The central streak contains the usual gland-cells, and a few thick-walled thread-cells. No gonads were developed in any of my specimens, though I examined them both in winter and spring, and many of them were full of embryoes. Milne-Edwards (Hist. Nat. des Coral- liares, 1857, p. 240) states:—“ The production of well-developed young in the interior of the gastric cavity is a very well-known phenomenon in Actinia equina, and it appears to begin before the reproductive organs have arrived at maturity.” Since this Paper was written, I have seen an account of the anatomy of Actinia equina, by T. A. Simon (Beitrag zur Ana- tomie und Systematik der Hexactinien, Inaugural Dissertation der hohen philosophischen Facultét der Universitat Munchen zur Erlangung der Doctorwiirde, 1892, pp. 42-45). I can corroborate a great deal of what he says, but in some points my specimens seem to have differed from his. In his account of the sphincter, on p. 43, he says: “The strong fibrillar mesogloea is at its (the sphincter’s) site thickened to more than double, so that one can see 3H 2 730 Scientific Proceedings, Royal Dublin Society. something of it with the naked eye.”” In my specimens, this thickening of the mesoglcea at the site of the sphincter is very trifling ; indeed, scarcely noticeable. Further on, p. 44, still speaking of the sphincter, he says :—“ The mesoglcea does not rise as in A. sulcata and Antheopsis roseirensis into more or less high folds, but preserves an entirely smooth surface towards the epithelium ; moreover the muscle fibres grow deeply into it, and appear at times to become wholly mesogleeal. One may regard the singular condition of this sphincter as being in a certain sense a transition or middle stage between an endodermal and a meso- gleeal sphincter ; the latter is at once attained if one thinks of the base (Fussteil) of the muscular twigs as absent.” I can find nothing in any of my specimens, when the sections are vertical, which would justify me in saying that the sphincter in Actinia equina is anything but endodermal. Oblique sections either of the sphincter or the tentacles often give the effect of mesoglceal muscle. . Speaking of the ectodermal muscles of the oral disc, on p. 44, he says:—“ They attain their greatest height in the middle between the insertion of two septa, and form here in tangential sections through the disc, pretty, rosette-like structures ; the radial - swellings of the dise apparently rise from these.’”’ These “ rosette- like structures” are seen in tangential sections of my specimens, but I believe they are due to the sections passing somewhat obliquely through the base of a tentacle of a different cycle from those obviously cut in the section, as on following these ‘rosettes ”’ through several sections, they pass gradually into sections of tentacles. On p. 45, the statement is made that “ zooxanthellae were observed nowhere in the bodies”; in all the specimens I examined down to embryoes of the 8+ 4 stage, the endoderm is everywhere crowded with zooxanthelle. I notice, on p. 46, that “‘all the septa, except the directives, bear gonads’’; also that all the septa are. covered with mesenterial filaments ; it is evident that Simon’s specimens were older than mine, as in the largest I was able to examine the fifth cycle of mesenteries bore no filaments, and were incomplete in number. Simon does not state the exact number of fifth-cycle mesenteries found in his specimens, but, as he says “they are regularly arranged” (p. 45), I conclude that they had attained their typical number of forty-eight. Macuire—Notes on Certain Actiniaria. vol EXPLANATION OF PLATE XXIVa. ar. mest., ect., end., . end. Mm. end. sph. m., Sf. mest. Le) MES.» « mes. sph. m., Fig. 1. Phellia Sollast. LETTERING ON THE FIGURES. directive mesentery. ectoderm. endoderm. endodermal muscle. endodermal sphincter muscle. mesentery of fourth cycle. granular bodies in mesoglea. mesogloea. mesogleeal sphincter muscle. mest. fil., par., p. b. m.,. @S., @S. Gl. Oa, ¢ mar. sphr., « pp. mest., .« S. mest. t. MeSt., « ae lower end of the cesophagus. marginal spherule. mesenterial filament. parapet. parito basilarmuscle. cesophagus. cesophageal groove. ovaries. primary mesentery. secondary mesen- tery. tertiary mesentery. tentacle. Transverse section of half the column at the [Through an oversight on the part of the artist, a tertiary mesentery has been omitted in fig. 1; it should have been inserted in the space between the two pairs of 2. Phellia Sollast. lateral primary mesenteries. | Vertical section through the upper part of the column-wall and tentacles, showing the mesogleal sphincter. 38. Phellia Sollast. 4, Actinia equina. Lower part of section granular bodies in the mesoglea. enlarged, showing Vertical section through the margin of the disc, showing a marginal spherule and the endodermal sphincter. i. 1782.4 LXXI. ON THE OCCURRENCE OF ANATASE (XANTHITANE ?) AND BROOKITE IN THE QUARTZITES OF SHANKILL. By PROFESSOR J. P. O’REILLY, C.E., Royal College: of Science, Dublin. (Puarz XXV.) [Read Marcu 16, 1898; Received for Publication Marcu 18, 1898; Published June 11, 1898.] Tue outcrop of Cambrian strata, with accompanying quartzites, which forms the mass of Carrickgollaghan, the most northerly outcrop of this formation in the vicinity of Dublin, extends in a N.E./S.W. direction from Phrompstown in the 8.W., to quite near the village of Shanganagh in the N.E., and is represented on the Geological Survey Map No. 121 with a total length of very nearly two miles in the direction mentioned, and a greatest breadth of about 4th mile at a point lying about 4rd of the total length from its S.E. extremity. Along the south-eastern margin is shown on the map an out- erop of quartzite; and a mountain road runs along it, from where it meets the Old Connaught-road at Shankill Castle, to where the formation terminates in the S.W. The characteristics of the formation are given in the explana- tory memoir to the sheets 121 and 130 (1869), p. 23, wherein it it is stated that the country included in the two sheets is divided into districts of which the first (a) is the ‘“ Carrickgollaghan District,” which is thus described :— “The quartz rock of Carrickgollaghan Hill occurs in the form of a narrow ridge striking N.E./S.W., one mile and a-half in length, with a maximum width of 250 yards. At the S.W. extremity, where it also attains the greatest elevation of 912 feet, light-greenish and grey sandy slates, like Cambrian rocks, show themselves in the ground on the northern side, and, taken together with the quartz rock, would point to the Cambrian as being the group to which these rocks most probably belong. O’Rettty— Anatase and Brookite in Quartzites of Shankill. 738 “Blue and black slates are seen on its southern side, the discerned dips on the latter being to the southward at 30°. A bed of greenish felspathic ash occurs in the black slates at the southern boundary of the quartz rock, which fact, together with their colour and character, would group them in the Lower Silurian, rather than with the Cambrian rocks of the district. At the distance of 250 yards N.W. of the summit of Carrickgollaghan, there occurs a thin band of grey quartz rock about + mile long and 40 yards wide, having smooth greenish-grey slates at either _ side of it. This and the former quartz band appear to belong to a boss of Cambrian rock, which probably rises through the dark Silurian slates and schists.” At p. 14, in the general description of the ground, it is stated :— ** At Carrickgollaghan, a boss of Cambrian slates and quartz rock appear through the Silurian rocks within half a mile of the surface edge of the granite. This is the closest surface approxima- tion of the Cambrian to the granite, the width of the Silurian band being elsewhere never less than two miles, one half of which is metamorphosed into mica schist.” It is further added :— “The relations of the Silurian to the Cambrian are everywhere very obscure, and to the north of Roundwood are absolutely un- determinable.” At p. 9, under the heading “ Formations or Rock Groups entering into the Structure of the District,” is mentioned “quartzite or quartz rock.” Of this rock it is stated :— “Here and there throughout the Cambrian rocks, there occur great belts and groups of beds of quartz rock. This has generally some shade of brown or yellow, sometimes becoming reddish, sometimes almost white; when examined with a lens, it is seen to be made up of minute granules of quartz, bound together by a siliceous cement, into a smooth, almost compact stone, intensely hard, but rather brittle.” At p. 10 is the statement :— “Tt is jointed in every direction both by large visible joints and smaller imperceptible ones, which cause it to break up into small angular fragments. The original bedding of the rock can hardly be discerned in it, and its stratification can only be de- termined by following its upper and under surfaces, and tracing 704 Scientific Proceedings, Royal Dublin Society. their junction with the slates and sandstones above and below. Some of the grit stones are so siliceous, and some of the quartz rocks become so granular, that it is not always easy to determine whether to call any individual mass of rock a siliceous grit or quartzite. The principal masses marked on the map are very decided in character, and have always been called quartz rock by every geologist who has examined them. They vary in thickness from twenty to several hundred feet.” The facility of approach afforded by the road from Shankill Castle, across the hill, already referred to, along with the excellent quality of the quartzite as a material for road-metal, has led to the opening up of quarries along the outcrop which borders this road; and in these quarries, may be examined, as well the rock, as the systems of jointing and fissuring to which it is subject. As might a priori be expected, certain directions of jointing dominate, and have already been noticed for this locality in a paper read by me before the Royal Irish Academy in 1889. (“On the Directions of the main Lines of Jointing observable in the Rocks about the Bay of Dublin, and their relations with adjacent Coast Lines,” part i1., p. 245. See also Proceedings Royal Irish Academy, 2nd ser., vol. iv., Science.) The more important jointings are further characterised by being filled to a greater or lesser extent with a silicate of iron and manganese, dark-brown to black in colour, and intimately associated with quartz crystals. The jointings thus marked may be referred to four principal directions :— (No. 1.) N. 6° : 15’ W.—Corresponding to the coast line direction between Six-mile-point and Ballygannon (lower New- castle district). (No. 2.) N.37°: 34 E.—Corresponding to the general direction of the 8.E. edge of Carrickgollaghan Hill. (No. 3.) N. 62°: 30° W.—A well-marked system of jointing, according to which there had evidently been repeated movements, having given rise to breccia formation along the joints, with inter- position of the iron-manganese silicate already referred to. This direction corresponds very exactly with that of Glencullen Valley, in the part of it which traverses the granite formation. (No. 4.) N.70:47’ W.—Corresponds to the systems of jointing O’Re1tty— Anatase and Brookite in Quartszites of Shankill. 735 which traverse Bray Head, also mentioned in the papers already referred to. The quarry nearest to Shankill Castle (the entrance to which is from the road leading to Old Connaught) was being worked for road metal about ten years ago, and in the southern end of it, the quarrymen came on a joint filled with a soft yellowish earth, having a soapy feel, which they had not met with before, and which presented itself in such quantity that one of the men (Jos. Mills, of Shanganagh village) subsequently informed me that a ton of the earth might easily have been secured at the time. The sample which he brought me, at the time of the discovery was, owing to pressure of other business, put aside for future examination. This only took place last year, and meanwhile the quarry had been completely abandoned for years, so that no further traces of the joint, or of the contained earth could be found, and only an approximate direction of the joint in which it occurred could be determined. This direction would (according to Mills’ indication) be about N. 6°-7° E., and would correspond to a system of jointing which shows itself in the quartzites lying to the east of the Sutton Coast- guard Station (and quite under the Martello Tower) with marked frequency. Circumstances having led me to examine the sample in question, I first “‘ panned” a certain quantity of it, and was surprised to notice inthe ‘‘ tail” or heavy remaining residue, certain minerals, in a sufficiently crystallized state to allow of their further examination. Nearly the whole sample was therefore carefully panned, the heavy part separated, and this carefully classed according to size, and hand-picked, when necessary, under the lens. I was thus able to obtain a sufficient quantity of these crystals to allow of a deter- mination of their characteristics being satisfactorily made. A large quantity of quartz crystals were separated out, more or less cariated and imperfect; along with these occurred crystals of a somewhat metallic lustre, presenting forms referable to the tetra- gonal system, being for the most part doubly terminated tetra- gonal pyramids, with oscillations of the upper and lower faces as shown in the plate (fig. 2). With these occurred, a mineral having also a submetallic lustre, a brown colour, a platy structure, and evidently of nearly the same density as the former. 736 Scientific Proceedings, Royal Dublin Society. After careful examination and measurement of the middle edges of the first-mentioned mineral it was set down as anatase. The density was determined, and gave a mean result of 3°587, which is distinctly lower than that of anatase proper, which is given in Zirkel’s “ Mineralogy,” as 3°83 to 3-93. It is to be remarked, however, that it was very difficult to obtain crystals so perfectly free from adhering parts and particles of quartz, as to allow of their being taken as perfectly pure. Hence, how- ever careful the hand-picking, some adhering quartz remained on the crystals examined for density. This, of course, operated to lower “ pro tanto” the density below the normal figure. In order to clear up this apparent discrepancy, a sufficient sample of hand- picked crystals was entrusted to Mr. W. L. Warren, F. C.S. for careful analysis. His report gave the composition of the crystals (No. 1) as below. Thinking that the alumina therein shown might have proceeded from minerals which had either accompanied the sample, or were adherent to the erystals as hand-picked, a further portion was very carefully hand-picked under the lens and this further sample entrusted by me to Mr. Warren, who reported as composition the analysis (No. 2) as below. (No. 1). (No. 2). Percentage. Percentage. Si0., . S : 3°30, 4 ‘ ‘4 3:07 AleoOs, . : = l22865 : 5 =) 13:02 HeO are . = | Lo7205 = : . 10°40 Fe203, . s : 1°05, : 3 4 6:01 C205 : : 2°29, tee 6 5 2°16 MgO, . : 5 4°42, : 2 4°42 WinQe seu) Me . traces : : . traces Wi@y, : a O02: 6 ; . 60°81 (K20 and Na2O) . 0-06, 0 é : 0°12 Combined Water, . 0-06, 5 ‘ : — 99-96 100°01 The main difference from one sample to the other was in the iron; and it was concluded that the alumina found was present as an essential constituent of the mineral. Assuming this for the present, it is evident that the composition shown is different from that of any known Silico-titanate, such as mentioned by Dana in his “ System of Mineralogy ” (edit. of 1892), and, if confirmed, may represent a new mineral, or mineral variety, O’Rem1ty— Anatase and Brookite in Quartzites of Shankill. 737 that is, an anatase in which a certain amount of TiO, is replaced by alumina, as it is frequently by Si0,. Keiihawite bears to it aresemblance only in so far as it isa titano-silicate of CaO, Al.O;, Fe.0;, and Y.O; the density being 3°52 to 3°77, but the crystalline form (monoclinic) and the other characteristics differentiate it markedly. It suggested, however, that the alumina might be accompanied by some of the rarer earths. An analysis was undertaken for the determination of the presence of such rare earths, but the results were negative. In the same edition of Dana, mention is made, on p. 716, of a mineral called Xanthitane, of which the following details are given by Eakins whose analysis thereofis also given. He considers it as an alteration product after Titanite. He gives the colour as light yellow, and says it was mixed with impurities to an undetermined extent. He calls it a clay containing titanium in place of silicon, and states that the analysis given is of a material obtained from Green River, Henderson Co., N. C. (U.8.A.). It isinteresting to place his analysis side by side with that of the Shankill anatase by Mr. Warren. Xanthitane. Shankill Anatase. Percentage. Percentage. S$i02., . 5 5 1-76, ; a 3°30 Al2,03, : . . 17°59, . . . 12°86 FeO, . : : — : ‘ a l5=20 Fe203, . < ; 4:46, 3 4 . 1:05 CaO : ‘ 0-90, ‘ ‘ : 2°29 MgO, . 4 . _ traces, : é : 4°49, MnO la: : : —_ 9 3 . traces TiO 5 . 61°54, 3 3 - 60°72 Ph20;, 4 ° = 4: We O e 3 —_— H20, 5 A 9°92, : ; 5 0:06 (K20 and Na20), . = ey ; ; 0:06 100°34 99-96 There is an evident resemblance between these two analyses, so much so, that it might be presumed that the yellow earthanalysed by Eakins from Green River, Henderson Co., U.S., was most probably the product of the decomposition of an anatase mass having origi- nally had the same composition as that of the Shankill specimen or nearly so. Subsequently to the analysis of the crystals, Mr. Warren made 738 Scientific Proceedings, Royal Dublin Society. an analysis of the yellow earth as originally found, but freed from the larger parts. The following was the results reported by him, showing the presence of the TiO, in notable quantities in the fine part of the clay and to a certain extent accounting for the colour of it :— Percentage. He MUR TLaan yt WORE Lea een TAN Gola WZ Fe20s, 5 5 o 5 3 O 5 6°75 FeO, . i : . ” 7 x , — Al,03, 5 ‘ ° . ° . fs 35°45 CaO, . ‘ ‘ : 5 ‘ Z 0°65 ~ MgO, . 6 : c 2 : : 5 0-99 Na,20, 5 = 5 . ° = 5 e 0:10 TiO2, ° . . . ° . : . 6°22 Combined H20, . ‘ Bi F 6 : 5°46 100:02 A sample of the same clay was also submitted to Mr. H. Ramage, assistant chemist in the Royal College of Science, Dublin, for examination by the spectrographic method so re- markably applied by him in collaboration with Professor W. H. Hartley, F.R.S., to the determination of the presence of certain of the rare elements in minerals and ores, as detailed in their Paper published by the Chemical Society (see Transactions, 1897, p. 583; and Proceedings, Royal Society, 1896, 60, p. 35; 1897, 60, p. 393). Mr. Ramage’s results were as follows :— In the precipitate containing the iron alumina, &c., were found iron aluminium ; copper ; nickel; silver ; gallium ; calcium ; lead ; chromium ; (traces of); sodium; and potassium. In the residue containing the alkalies, were found—sodium ; potassium ; rubidium ; caesium ; lithium; calcium ; strontium ; copper ; iron (traces of) ; manganese.’ Along with the anatase minerals occurred small crystals of brookite (Pl. XXV., fig. 1), presenting the usual characteristics of that mineral, and forming light-brown plates, striated, and of a sub-metallic lustre ; in some cases showing sufficiently well-defined crystalline forms to allow of these being determined ; moreover, 1 Silica and titanic acid were not looked for, but only those bases present in small quantities. By the ordinary method of analysis, gallium as sesquioxide would be precipitated along with the alumina. O’Rettty— Anatase and Brookite in Quartzites of Shankill. 739 the density was found to be 3°928 (mean), which quite agrees with the mean value of the densities indicated for that mineral, viz. ~—638'8 to 41. There is room for considering the probable origin of these titanic acid minerals as they occur in the Shankill quarries, and the clays therein found. It is to be borne in mind that minute erystals of rutile have been shown by microscopic examination to be present in most slate rocks, and, furthermore, that the presence of titanic acid has been proved by chemical analysis of various samples of the rocks of Bray Head, mostly as traces. It might therefore be assumed that the quartzites so characteristic of Bray Head and Carrickgollaghan would also show traces of that mineral, and its general diffusion through the whole of the strata of the *“‘Carrickgollaghan district,” in minute quantities only determin- able by very careful analysis. However, in the case of the Shankill quartzites there is evidence of thermal action in the abundant deposits of a ferro-manganese silicate along the main lines of fracture, as already mentioned, and in the cariated character of the quartzites in immediate contact with these ferro-. manganese silicates, as well as the altered texture of these quartz- ites, which are so friable and ‘‘ rotten” as to be useless for the purposes of road-metal. The examination of these particular quartzites in thin section, while showing the granular texture of the rock, points to a certain alteration in the structure of the quartz, such that it assumes the appearance of calcedony under polarised light, not to the point of showing the aggregation cross. on rotation, but an extinction seemingly due to the development of a fibrous structure which bears a certain relation to that of ealcedony. Another character of certain of the quartzites of Bray Head, points in this direction, that is, a relatively low density. Thus a specimen of quartzite from Windgate (Bray Head) analysed by Mr. Shegog (formerly Assistant Chemist in the Royal College of Science, Dublin), and marked by me No. 23, BH, gave a density, as determined by him, of 2°605, which corresponds well with that of calcedony, as given by Dana, viz. 2°6-2°64, that of quartz being given by the same author as 2°653- 2-654. It is right to add that the quartzite in question only contained 90°63 per cent. of Si0,, but the other constituents indicated in the analysis might, with reason, be looked as tending 740 Scientific Proceedings, Royal Dublin Society. rather to raise the value of the density than to reduce it. The analysis is as follows :— Percentage. Si02, . ‘ : : , 5 - $ 90-63 Al20s, : : i 5 ; ‘ 3 1-79 Fe203, : 4 6 5 ° - : 0°34 CaO, . 5 , 4 : 4 ; F 4°45 MgO, . : ‘ : : ‘: = i 0:14 LiOz, NazO and K,0 \ 9-51 calculated as Na,2O, cease’ 99°86 This caleedony character of the quartz may reasonably be taken as pointing to extensive thermal action along the main lines of fracture, and would receive a certain amount of illustration from the similar phenomena presented by certain quartzite beds which occur in the Carboniferous formation of St. Etienne (Loire), and which I was enabled to examine and have explained to me by Monsieur de Grand d’Eury during an excursion to that mining district with the French Association for the advancement of science, which took place last August. In this case the alteration of the rock into calcedony is manifest and clear in all its stages, and as I was informed by M. de Grand d’Hury, accompanied by the concentration of titanic acid in certain zones and the consequent presence of the minerals therein usually representing that acid. It is worthy of note that the district of St. Etienne possesses several gaseous mineral springs of noted quality in the country, which may be taken as the residual efforts of the forces which have left such marked results in the alterations and derangements of the strata so well studied by the eminent geologist already mentioned. It would be desirable that the whole of the quartzites of the Co. Wicklow and of the neighbourhood of Dublin be examined carefully and comparatively from the point of view of constitution and the alterations which they have undergone at their contacts with other rocks in different localities of the districts mentioned. EXPLANATION OF PLATE XXyYV. Figs. 1. Brookite, from Quartzites, Shankill, Co. Dublin; forms pre- sented: ¢=2P 0; y=1 Pm; e=P2; I= Po. 2. Anatase, from Quartzites, Shankill, Co. Dublin. Forel LXXTI. ON SOME MINUTE ORGANISMS FOUND IN THE SURFACE- WATER OF DUBLIN AND KILLINEY BAYS. By HENRY H. DIXON, D.Sce.; anv J. JOLY, D.Sc., F.R.S., Hon. Sec. R.D.S. (Puates XXVI. and XXVIII.) [Read Frsruary 16; Received for publication Frpruary 21 ; Published Aveusr 8, 1898.] Last summer we started tow-netting in Killiney Bay in the hopes of finding coccoliths, and adding something to_our knowledge of these peculiar bodies. Our first observations were made by skimming the surface-water with a funnel-shaped metal surface-dredge. This consisted of a truncated cone made of tinned iron. The wide end of the cone, which was trailed foremost through the water, was covered with a piece of brass-wire gauze, having 50 meshes to the linear inch. The narrow end was closed by a much finer piece of gauze, having 350 meshes to the inch. This latter piece of gauze was carried on the end of a short brass tube, which fitted into the truncated end of the conical dredge with a bayonet joint. The whole was floated by means of two wooden wings, extending from the sides of the cone. In use, a constant stream of water was kept up through the funnel by means of the motion of the boat from which it was trailed, and when it was raised for examination, the water con- tained in the funnel was allowed to run out through the fine gauze. In this way, none of the smaller organisms, which had got into the funnel, escaped through the coarse gauze; when all the water had run through the gauze, the brass tube carrying it was taken out, and the material caught on it was washed off and bottled. In this manner, very concentrated samples of the smaller surface-organisms were obtained. ‘The larger, such as jelly-fish, &ce., were excluded by the coarser gauze in front. 742 Scientific Proceedings, Royal Dublin Society. Although this apparatus allows the very minute bodies sus- pended in the surface-water to escape, it affords beautiful samples of Foraminifera, Diatoms, Crustacea, Infusoria, Peridiness, &e. ; and we were rewarded by soon finding specimens of the bodies we were looking for—the coccoliths. These occurred, not free; for they are so minute as to easily pass through the meshes of the finer gauze, nor yet aggregated in coccospheres, as Wallich! described having found them in shoal-water off the south coast of England, but implanted on an ameeboid protozoan, resembling a Difflugia in appearance. This protozoan occurs in great quantities in the surface-water off the coast of Dublin and Killiney Bays. It is urn-shaped (fig. 8), and narrows suddenly to the aperture which is surrounded with a collar of hyaline siliceous material. Lobose pseudopodia are extruded through this collar in life, and its internal edge is orna- mented by a circlet of minute teeth, standing up from it obliquely. The urn-shaped covering of the organism is covered with thin flat grains of sand fitted into each other with nicety. Among these grains, fragments of sponge spicules may occasionally be seen, and, besides these, an odd coccolith was often observed implanted in the test. In fact, we estimated that about 25 per cent. of these Difflugia possess one or two coccoliths. Fig. 8 shows a coccolith, i situ, on the Difflugia. The coccolith frequently occupies a position on the shoulder of the protozoan, or it may be closer to the collar. More rarely it is found on the converging conical end of the test. This find encouraged us to pursue our search. For it appeared probable that the coccoliths had been acquired by the protozoan in the same manner as the grains of sand, and that, like the latter, they were floating free, suspended in the sea-water. If this surmise as to the relations of the two organisms was correct, it must follow that examination of the most minute solid constituents of the sea-water would reveal the presence of free coccoliths in considerable numbers. To test this question, two litres of sea-water were allowed to stand twenty-four hours in a tall, narrow jar; the upper portion was then siphoned off, leaving about 200 c.cs. of the lower 1 Ann. and Mag. of Nat. Hist., 1868. _ Drxon & Joty—On Some Minute Organisms. 743 portion. This was treated in a centrifugal apparatus. By this means the water was cleared of all turbidity, and its solid contents were thrown to the bottom of the test tubes of the centrifuge, in the. form of a compact mat of whitish gray material. Examination of this material showed at once that coccoliths abounded in the free state in the sea-water. Their numbers, indeed, exceeded all anticipation, for there were about 100 on each slide prepared from the precipitates which formed in the centrifuge. An estimate of the actual number present in the sea is equally astonishing. A sample of water taken 3 miles off the coast, on a calm day, afforded 200 coccoliths in each cubic centimetre. The estimate was made by permitting the solid matter of a large volume of water to settle. The clear upper fluid was then siphoned off, and the remainder with the solid contents of the whole was vigorously shaken up. The number of coccoliths in a drop of this latter was then estimated by means of a divided stage (such as is used in counting blood-corpuscles). From this the number present in the original volume is obtained. Several closely agreeing estimates of the number present in the same sample gave the above-mentioned remarkable result. The centrifuge was an efficient way of getting large numbers of coccoliths, but all the solid matter suspended in the water was so closely compacted by its action that a clear view of the contained organisms was often difficult to obtain from this material. Later on, we found that the simplest manner of obtaining these bodies was straining large quantities of sea-water through fine silk; a procedure which, in the anticipation of finding but very few specimens, we did not at first adopt. The silk should be stretched as a diaphragm across the lower end of a wide glass tube (the chimney of an argand-burner answers well for this purpose), and while the latter is held in a vertical position, sea-water is poured in above. After many gallons have passed through, the silk is removed, and washed in a small quantity of water, and the washed-off precipitate bottled. We found this method more satisfactory than towing the strainer in the water. In the latter ease a backwash, which may lead to the loss of much of the material gathered, is always liable to occur. These methods supplied us amply with material to study the form and manner of occurrence of the coccoliths. These SCIEN. PROC. R.D.S., VOL. Vill., PART VI. 3 if 744 Scientific Proceedings, Royal Dublin Society. problematical bodies consist of two very thin elliptical valves, about -015 mm. in length. The valves are saucer-shaped; and one which is slightly larger than the other partially includes the smaller. ‘The central portion of the outer valve is re-entrant, so as to form a short, funnel-shaped collar, connecting it with the inner valve. The bottom of this funnel-shaped depression in the convex surface of the outer valve is an elliptical plate, which also TS HANS MAO SZ Gs C f (a) Coccolith seen from above, larger valve (dz) Seen from above, smaller valve upper- turned upwards. most. (4) Viewed obliquely, larger valve upper- (e) Seen obliquely, smaller valve turned most. upwards. (c) Seen in longitudinal section, smaller (7) Seen in profile, smaller valve above. valve above. forms the bottom of the smaller saucer-shaped valve. This plate is thicker than the rest of the valve, and is perforated. The perforation may be single, when it is an elongated oval (the length of the oval lying longitudinally in the coccolith}, or it may be double when there are two D-shaped holes placed back to back, as if the oval perforation had been converted into two by the deposi- tion of a bridge of material across its centre. A reference to the Dixon & Joty—On Some Minute Organisms. 745 foregoing figures will explain the form of the coccolith. It will be noticed that the connecting stalk between the two valves is much shorter than that given in the figures of Biitschli, and that it is scarcely correct to describe these bodies as*resembling a shirt-stud in shape.’ The coccoliths dissolve quickly in dilute hydrochloric acid, and are partially and much more slowly attacked by strong caustic potash. The latter reagent does not appear to be able to com- pletely dissolve the central parts, more especially of the small valve, or, at least, cannot do so with any celerity. The absence of the appearance of free gas upon attack with acids hardly negatives the generally accepted view that these bodies are calca- reous. In all these tests we have frequently had characteristic Diatoms present in the same field ; and whereas the siliceous valves of the Jatter were unaltered by the acid, the coccoliths were quickly dissolved. In the application of the caustic potash test, diatom- valves were also present, and these showed complete resistance to the caustic alkali. The appearance of a coccolith in polarised light is characteristic. Between crossed nicols, the thin flange of the large valve appears inactive; the entire inner ellipse, on the other hand, exhibits a dark cross, the arms, in some cases, revealing a certain amount of spiral bending. A somewhat complex crystalline structure is thus suggested. That there is some organic matter present between the valves appears suggested by the granular appearance often presented in the annular chamber, embracing the central connexion, and also by the fact that, upon solution in dilute acid, just such a ring of granular particles is thrown down, and alone remains to mark the spot where the coccolith had been. This ring assumes a tawny yellow or brownish colour when acted upon by iodine. Or, again, if the coccolith be treated with strong /iguor iodi, the valves dissolve, and this ring remains as a dark granular ellipse. From these observations, it would appear that a ring of (residual ?) protoplasmic matter surrounds the central connexion. In many specimens of free coccoliths we have seen a slimy, possibly proteid, mass depending from the smaller valve, or enveloping the 1Biitschli: Protozoa. Plate I. Wyville Thomson. The Depths of the Sea, p. 413 312 746 Scientific Proccedings, Royal Dublin Society. entire concave surface of the coccolith (fig.2). But in this we never were able to detect any marked movement, nor other definite sign of life. Neither were we able to observe nucleus nor any evident chromatophores. Although the free coccoliths are so abundant we were able to find but few coccospheres. After many prolonged searches we have only come across a half-dozen or so. The coccoliths aggre- gated on these presented, as a rule, a much less battered appear-- ance than those free in the water—a fact which is suggestive that. the coccospheres are the source of the coccoliths. The observation of Wallich, that a membranous covering envelops the coccosphere,! seemed to us supported by the appearance of these bodies. The whole contour is singularly spherical, and such that the component coccoliths appear as if fitted together, at least partially, by pressure from without. Upon treatment with dilute acids the coccospheres dissolved, and a globule of pale brown or yellowish proteid matter remained behind, agreeing with the observations of Wyville Thomson® and others. Our observations up to the present are hardly such as to give us any advantage over previous observers in forming an opinion as to what may be the nature of coccoliths and coccospheres. ‘Two: suggestions present themselves. ‘The first, the already well-known one, that the primary body is a small and abundant alga, which secretes upon its surface the shield-like coccoliths. These, upon the death of the coccosphere, are liberated. As will be seen further on, other spherical bodies of almost the same dimensions are present in the water, and these secrete each characteristic forms of investing shields. A class of minute alge (?) should, if this suggestion prove true, be recognised which might embrace eoccospheres and rhabdospheres, as well as two organisms to be described later. Or, again, it may transpire that the coccosphere is a reproduc- tive stage in the life-history of coccoliths (these latter being inde- pendent individuals). The coccosphere might then be regarded as somewhat homologous to the plasmodium of the Myxomycetes, formed by the adhesion of a number of independent organisms, or it may prove rather to represent an auxospore, such as is found in 1 Ann. and Mag. of Nat. History, 1860. 2 Loc. cit. Drxon & Joty—On Some Minute Organisms. 747 the Diatoms, differing, however, from them in the fact of its giving rise to a number of individuals. In order to ascertain if coccoliths are widely distributed around our coasts, we examined specimens of the solid matter found in the sea-water, with a positive result, off the following places :— Sligo, Slyne Head, Tralee, Smerwick Harbour, Dingle Bay, Valencia, Waterville, Kenmare River, Dublin, and Weymouth. We did not find any in water gathered in Loch Inver nor Port Stuart.' Again, the coccoliths are present at different seasons of the year. This fact we have ascertained in part by fresh specimens, and in part by specimens which have settled down with other solid matter off algee, gathered in different localities and preserved in Spirit :— Spring, 1894, . Smerwick Harbour, Dingle Bay. (Spirit specimens.) Summer, 1896, . Kenmare River. (Spirit specimens.) Summer, 1897, . Dublin Bay, Killiney Bay, Valencia, Sligo. (Spirit and Fresh.) Winter, ’97-’98,. Killiney Bay, Waterville, Dingle Bay, Kenmare River, Slyne Head, Wey- mouth. (resh.) A coccosphere was found in water taken at Weymouth in the winter. The coccoliths obtained in Killiney Bay in winter seemed to be more battered than those caught at the same locality in summer. Coccoliths have been frequently described as occurring in various geological deposits. We have found them in chalk from Newhaven, and also in commercial whiting. The latter is almost exclusively formed of these peculiar bodies. In both these, how- ever, other organisms are to be seen resembling coccoliths in their 1 Since the above was written we have found several coccoliths on the tests of Difflugia, but none free, in samples of sea- water from Portrush. 2 Cretaceous, upper greensand immediately above the Gault; coccoliths and rhab- doliths were found in the Hearthstone, Bletchworth, Surrey. W.M. Holmes: Proc. and Trans. Croydon. Micr. and Nat. Hist. Club, 1892-93, pp. 17-20. Coccoliths are also said to be found in Palzozoic rocks. Nicholson and Lydekker, Paleontology, vol. ii. 748 Scientific Proceedings, Royal Dublin Society. general appearance, but sometimes rather larger or smaller, and differing from them slightly in their structure. Sometimes they are quite circular. In specimens of Severn mud (obtained in excavating the tunnel), and also in mud obtained from borings in the bed of the Liffey, we have found examples exactly resembling recent coccoliths. Another peculiar locality, in which we discovered coccoliths, was the muds used to bind together the Papyrus mss. in making the mummy-cases which were found by Mr. Flinders Petrie at Fayyum. With the coccoliths we obtained a large number of minute organisms. One of the most abundant was the Difflugia-like organism on which our first coccolith was found. Although so abundant, we have not yet succeeded in identifying it with any previously described protozoan. It resembles the genus Difflugia in having lobose pseudopodia, and being enclosed in an urceolate test indurated with particles of sand. But the marine habitat and the very definite annular collar have not before been observed in this genus, so far as we are aware. It is true that Pritchard’ says that Bailey obtained a specimen from a depth of 2750 fathoms, which he called Difflugia marina. But its marine habitat led the discoverer to doubt its being a Difflugia. In any case, it is de- scribed as having a chitinous test divided into quadrilateral areas. The empty test almost exactly resembies that figured by Claparéde and Lachmann’ as belonging to Tintinnus ventricosus; but of course the structure of its inmate makes it impossible to classify it with the ciliate Infusoria. We would provisionally suggest the name Diffiugia thalassia. We may add, as further connecting it with the genus Difflugia, that we have found several specimens united in pairs by the foramina in conjugation exactly as Leidy* figures this process in Difflugia (fig. 9). Fig. 5 represents an organism of which we found two or three: specimens. With a low objective it resembled the antenna of an insect in general appearance, being jointed, the joints of which it was. composed diminishing uniformly from the greatest to the smallest. On closer examination it was found that the larger joints resembled 1 [Tnfusoria, p: 554. 2 Etudes sur les Rhizopodes et les Infusoires. Dixon & Jory—On Some Minute Organisms. 749 Difflugia in form and size. They were also incrusted with minute granules of transparent sand. We figure it here, as it may possi- bly be found to be a stage in the reproduction of Difflugia. If this turn out to be correct, it is a catena of Difflugia similar to what is well known as occurring in Ceratium tripos. Of course this is mere speculation, as we have not yet had opportunity of seeing the further development of this unknown structure, if further development it has. Besides the tests or loricee of the Difflugia, the tests of several other protozoa are found in the surface-water of the locality. The most numerous of these was, perhaps, Tintinnus campanula, a beautiful bell-shaped infusorian. The test, like that of Difflu- gia, is inlaid with particles of sand. These are, asa rule, much thinner than those on Difflugia. We never found a coccolith in the test of this infusorian. When found, the test was most usually empty ; however, on several occasions, we found it tenanted by the living infusorian, which exhibited all the characteristic energetic motions of the genus. Again very frequent in occurrence were other small tests resembling that of Difflugia in shape, except that they were not constricted at the aperture, and had no distinct collar. There were at least two species of these, one tapering almost uniformly from the widest place (fig. 7), and the other slightly constricted above the widest place, and then slightly expanding again, to finally taper toa delicate point. Both these tests were occasionally found inhabited by a heterotrichan infusorian. The latter seems identical with Tintinnus annulatus, as described by Claparéde and Lachmann. The former (fig.7) we propose to call Tintinnus conicus. Of the Foraminifera we found many examples, notably speci- mens which appear to be Rotalia veneta, Globigerina bulloides, Milliola, sp., Textulania picta. The Diatoms were very varied; among the more interesting were the following :—Actinocyclus undulatus, Actinoptychus sena- rius, Coscinodiscus radiatus, Melosira nummuloides, Arachnodiscus, sp., Pleurosigma, several sp., Cheetoceras, 2 sp. Another group, which was very numerously represented in the surface-water, was the Peridinese. Ceratiwm tripos vied with Diffugia thalassia to outnumber it in the plankton of the locality. Besides C. tripos (fig. 11) and its variety macroceras, C. fusca, C. 750 Scientific Proceedings, Royal Dublin Society. biceps (fig. 12), CO. fusus (fig. 18), C. divergens (fig. 16), (both in the motile and spore-producing stages), C. michaelis, and two species of — Dinophysis, apparently D. norvegica and D. acuminata (fig. 14). To these may be added Prorocentrum micans (fig. 17). Of the Radiolaria we found only Dictyocha trifenestra (fig. 15). In addition to the forms just described, and which can be more or less easily referred to known groups and genera, we came across, in this investigation, several organisms which, so far as we know, have not been described. Among these were two or three specimens of a minute sphere (fig. 1), somewhat larger than a coccosphere (7.e. about 05 mm. in diameter). It consists of a mass of protoplasm, carrying in it yellow-brown colouring matter, and eovered by a delicate pellicle, in which are supported a number of T-shaped spicules. On treatment with dilute hydrochloric acid, the pellicle remains, but the spicules dissolve. The spicules seem each to arise from an oval plate carried in the pellicle. From the peculiar spicules we may call this an “ Echinosphere.”’ About the same size as the Hchinospheres, and occurring also in the same sporadic manner, was another spherical body (fig. 3). In this the protoplasmic basis was covered over with oval scales of calcium carbonate. A short conical point rose from the centre of each scale, and projected from the surface of the sphere. From the peltate scales, we term this a ‘ Peltasphere.” This body we also found in surface-water gathered off Valencia Island. Within the ‘ Peltasphere,” one or more greenish granules could be observed. In much greater abundance than the Hchinospheres, or Peltaspheres, were two cyst-like structures, resembling Hhrenberg’s Xanthidia and Pyxidicula. Ehrenberg described these from the chalk, and, so far as we know, they are not described as being recent. ‘The forms resembling Pyxidicula are spherical shells of a chitinous substance, golden brown in colour. Their surface is finely punctate. ‘They are about -084 mm. in diameter (fig. 10). Sometimes they are complete, and contain coarsely granular protoplasm within them, which appears to have an inner and more delicate pellicle covering it inside the chitinous shell, some- times they are irregularly ruptured, or opened with a circular or tri-radiate slit. These Pyxidicula seem to us to be, in all pro- bability, encysted protozoa. Dixon & Jotry—On Some Minute Organisms. Vol The Xanthidia-forms are more definite. We have only observed empty cysts. These are spherical chitinous shells from which arise a number of short, stout, tubular spines, each appa- rently broken irregularly at the apex. The Xanthidia of the chalk have been described as the zygospores of Desmids. The occurrence of pelagic organisms of this form removes the necessity of the unwelcome dilemma, of assuming a partial freshwater origin of the chalk (!), or of presupposing marine Desmids.* In conclusion of this, which must, at best, be only a prelimi- nary sketch, we wish to express our thanks to Dr. E. Perceval Wright for calling our attention to a great mass of literature on this matter, especially Dr. Wallich’s Papers, dealing with the Rhizopoda, and also for giving us the opportunity of consulting many of the works needed in his own resourceful library. 1 Wallich, ‘‘ North Atlantic Sea-Bed,’’ 1862, states that he detected Xanthidia in the stomachs of Salpz in the Indian and Mid Atlantic Oceans in 1851. [ExpLaNaTIon oF PuatEs. 752 9. 10. 11. 12. 13. 14. 15. 16. fe Scientific Proceedings, Royal Dublin Society. EXPLANATION OF PLATES. Pratt X XVI. . Echinosphere. x 580. . Coccolith with proteid slime attached. x 1000. . Peltasphere. x 580. . Xanthidia. x 420. . Chain of urceolate chambers, each of which resembles an individual Diffiugia thalassia. x 160. . Test of Difiugia thalassia seen obliquely from below, showing the siliceous collar and delicate teeth. x 310. . Test of Tintinnus conicus. x 580. . Difiugia thalassia with pseudopodia extended. On the test is seem a coccolith among the grains of sand. x 310. Two individuals of Difiugia thalassia in conjugation. x 310. Various forms of spherical tests resembling Pyxidicula. x 310. Prate XXVIII. Ceratium tripos. x 310. Ceratium biceps, x 810. Ceratium fusus. x 310. Dinophysis acuminata. x 580. Dictyocha trifenestra. x 420. Ceratium divergens. x 310. Prorocentrum micans. x 580. eas LXXIII. AN IMPROVED FORM OF HYDROMETER BY WHICH THE SPECIFIC GRAVITY OF LIQUIDS MAY BE ACCURATELY DETERMINED AT ANY TEMPERATURE. By rue REV. H. O’TOOLE, of Blackrock College, County of Dublin. [Read May 18; Received for Publication Junz 28; Published Juny 29, 1898.] In numerous manufacturing processes, in commercial transactions, and in scientific investigations, an accurate knowledge of the specific gravity of the liquids used is a matter of the highest im- portance. This knowledge affords, in many cases, the readiest means of identifying a given liquid or of detecting in it the pre- sence of a foreign substance. More important still it enables us in the simplest manner, to estimate the value of alcoholic, sac- charine, acid, or other similar solutions: for the density of such solutions depends on the amount of alcohol, sugar, acid, &c., which they contain. It is not therefore to be wondered at that so many methods of determining specific gravity should have been proposed. Here, it will not be necessary to speak of methods requiring the use of sensitive balances or other delicate apparatus. These may be useful or necessary for special purposes, but are not of general application. In practice some form of hydrometer is almost in- variably used. ‘The common hydrometer consists of a long thin stem with a weighted bulb at one end; when placed in a liquid it floats vertically, and the distance to which it sinks, as,sshown by a scale on or inside the stem, indicates the density of the liquid. The simplicity ofthis instrument is its principal reeommen- dation, but, unfortunately, what is gained in simplicity is lost in accuracy. ‘The indications given are only to a certain extent approximate, as a little consideration will show. The scale, when most carefully made, is obtained by marking on the stem the points to which it sinks when immersed in liquids of known den- sities, and the intermediate densities are then marked off by some method of approximation. As the calibration is made for some particular temperature the indications will be incorrect if the 754 Scientific Proceedings, Royal Dublin Society. liquids are at any other temperature. This is a great draw-back ; — for, in practice, it is very troublesome to bring liquids to a given temperature, especially if they are hotter than the standard and have to be cooled. Perhaps the most serious, because altogether unavoidable, source of error is that due to capillarity or surface tension. All estimations of density are based on the supposition that the distance to which the hydrometer sinks is due to its weight alone; but this is not quite correct. ‘The reading of the instrument is also affected, and to a very appreciable extent, by the capillary attraction of the liquid. As this capillary attraction is generally different for different liquids, it follows that a hydrometer will necessarily indicate different densities when placed in liquids having the same density, but differing in capillarity. From all this it is apparent that specific gravities determined by the common hydrometer must, in the majority of cases, be considered as little better than fair approximations. Nicholson’s hydrometer, though it has no scale, is still adversely affected by capil- larity. Indeed, this source of error was pointed out by Nicholson himself: more- over, the instrument loses nearly all its value from the fact that its weight must be known, and as this weight is lable to change through use, a delicate balance must be at hand to determine it when necessary. The hydrometer (see figure) which the writer proposes is free from the above- mentioned defects. It has no arbitrary scale ; its weight need not be known; the effect of capillarity is totally eliminated, and it may be used for any temperature. The illustration shows clearly the shape of the instrument. The method of using it is very simple. It is immersed in any liquid, and weights put on the dish at top until it sinks to a marked point between the second and third bulbs ; additional weights are now put on until it sinks to O’Toorr—An Improved Form of Hydrometer, Ete. 755 a second marked point between the third bulb and the dish. These additional weights are evidently, according to the well- known law of Archimedes, the weight of a volume of the liquid equal to the bulb between the two points. In this way the weights of the same volume—the volume of the bulb—of any two liquids may be determined with extreme accuracy, and their relative densities may easily be calculated. The fact of having two standard points completely eliminates the effect of surface tension, so fatal to the accuracy of all other forms of hydrometer. It has a great advantage in that it requires only two spindles of convenient size for all liquids from the heaviest to the lightest : Twaddell’s form of the common hydrometer requires six spindles for heavy liquids alone, and as many others would be required for light ones. The proposed hydrometer should prove useful in junior ex- perimental classes; it 1s inexpensive; a beginner can obtain with it the most accurate results, and, above all, the accuracy of the result will depend entirely on the worker. INDEX LOW VOLUME VT LT: Acanthodide, Fossil Fish-Remains of the Coal Measures of the British Islands, Part II. (Davis), 279. Acrozoanthus, branched Worm-tubes and (Happon), 344. Actiniaria from Torres Straits (Happown and SHACKLETON), 116. Actiniaria, Notes on (Macurre), 717. Adeney (W.E.). On the Chemical Ex- amination of Organic Matters in River Waters, 337. —— Note on the present Condition of the Water in the Reservoir at Round- wood, 208. On the Reduction of Manganese Peroxide in Sewage, 247. Adeney (W. E.) and Carson (James). On the Mounting of the large Row- land Spectrometer in the Royal Uni- versity of Ireland, 711. Agriculture, Distribution of Drift in Ireland in its Relation to (Kizroz), 421. Alpine Flowers, (Jory), 145. Anatase and Brookite in Quartzites of Shankill (O’Rertty), 732. Andesite, Basaltic, of Glasdrumman Port, Co. Down, derived Crystals in (Coxe), 279. Andesite, Pitchstone and, from Ter- tiary Dykes in Donegal (Soxtuas), 87. Annelids, Irish, in the Museum of Science and Art, Dublin (M‘Inrosu), 399. Bright Colours of Bacilli, Suggestion as to a possible Source of the Energy required for the Life of; Cause of their small size (StonEy), 154. Ball (V.). On the Gold Nuggets hitherto found in the County Wick- low, 311. Barlow (William). A Mechanical Cause of Homogeneity of Structure and Symmetry geometrically investi- gated ; with special Application to Crystals and to Chemical Combina- tion [with an Index], 527. Beacons and Buoys, Method of Using Common Petroleum as the Illuminant for, by which a continuous Light may be maintained (W1cHAM), 377. Bodkin (Richard C.). The Automatic Image-finder, 281. Bog-flow in Kerry, Report of the Com- mittee of Investigation (PRAEGER and Souas), 475. Booth (William). On Hamilton’s Sin- gular Points and Planes on Fresnel’s Wave Surface, 381. Bourne (G. C.). On the Post-Embry- onic Development of Fungia (4d- stract), 244. British Islands, Fossil Fish-Remains of the Coal Measures of the (Davis), 279. Brookite, Anatase and, in Quartzites of Shankill (O’Rert1y), 732. Buchanan (Florence). Note on the Worm associated with Lophoheha prolifera, 432. Report on Polychets collected during the Royal Dublin Society’s Survey off the West Coast of Ire- land. Part 1. Deep-Water Forms, 169. Buoys and Beacons, New Method of Conferring characteristic Appearance upon illuminated (W1eHam), 519. 758 Cambrian Rocks of Howth, on Pucksia Mae Henryi, a New Fossil from the (Soxzas), 297. Cameron (Sir Charles A.). Note on the Action of Phosphine on Selenium Dioxide, 11. Canes Venatici, (Witson), 696. Carpenter (G. H.). On some Pycno- gonida from the Irish Coasts, 195. The Geographical Distribution of Dragonflies, 439. On some Dragonflies in the Dublin Museum of Science and Art, 434. A Collection of Lepidoptera from Lokoja, West Africa, 304. Report on the Zoological Collec- tions made in Torres Straits by Pro- fessor A. ©. Haddon, 1888-1889. Pyecnogonida (Supplement), 21. Carson (James) and Aprenzy (W. E.). On the Mounting of the large Row- land Spectrometer in the Royal Uni- versity of Ireland, 711. Coal Measures of the British Islands, Fossil Fish Remains of the (Davis), 279. Cole (G. A. J.). On derived Crystals in the Basaltic Andesite of Glasdrum- man Port, Co. Down (Adbstract), 279. —— On Hemitrypa hibernica (M‘Coy), 132. Crystals, Arrangement of the, of cer- tain Substances on Solidification (Trovton), 691. Crystals, a Mechanical Cause of Homo- geneity of (BARLOW), 527. Spiral Nebula in Davis (James W.). On the Fossil Fish- Remains of the Coal Measures of the British Islands. Part 11. Acantho- didex. (Abstract), 279. Delap (Alfred). Bog-flow in Kerry (PrarceER and Sorzas), 475. Depastrum cyathiforme, Notes on (Dixon, G. Y., and Dixon, A. Fras.), 180. Dixon (A. F.). Bog-flow in Kerry (PraErcerR and Soxuas), 476. Dixon (A. Fras.) and Dixon (G. Y.). Notes on Depastrwm cyathiforme, 180. Dixon (G. Y.) and Drxon (A. Fras.). Notes on Depastrum eyathiforme, 180. Index. Dixon (H. H.). On the Germination of Seedlings in the Absence of Bac- teria (Abstract), 28. Dixon (Henry H.) and Jouy (J.). On some Minute Organisms found in the Surface-Water of Dublin and Kil- liney Bays, 741. Donegal, Graphitic Schist from (Moss), 206. Donegal, Pitchstone and Andesite from Tertiary Dykes in (Sonus), 87. Dragonflies, Geographical Distribution of (CARPENTER), 439. Dragonflies in the Dublin Museum of Science and Art (CaRPENTER), 434. Drift in Ireland, Distribution of, in its Relation to Agriculture (KriRoe), 421. Duerden (J. E.). Trish Coast, 405. Survey of Fishing Grounds, West Coast of Ireland, 1890-91. Notes. on the Hydroida and Polyzoa, 325. The Hydroids of the Keclipses, Total Solar; Selection of suit- able Instruments for Photographing the Solar Corona during (Taytor), 272. Kozoonal Structure of ejected Blocks of Monte Somma (Lavis and Grecory),. 280. Field-Geology, Use of the Protractor in (HaRKER), 12. Flowers, Bright Colours of Alpine (Jory), 145. Fossil Fish-Remains of the Coal- Measures of the British Islands (Davis), 279. Fresnel’s Wave Surface, Hamilton’s. Singular Points and Planes on (Bootx), 381. Fungia, Post-Embryonic Development of (Bourne), 244. ‘“¢Garnet’’ Spot on Jupiter, Rotation Period of the (RamBavT), 389. Gas, Kinetic Theory of, regarded as Illustrating Nature (StonEy), 351. Germination of Seedlings in the Absence of Bacteria (Dixon, H. H.), 28. Gladstone and Dale, Law of, as an Optical Probe (Soxnas), 157. Index. Glascott (L. 8.). A List of some of the Rotifera of Ireland, 29. Gold Nuggets hitherto found in the County Wicklow (Batt), 311. Gregory (J. W.) and Lavis (H. J. Johnston). On Kozoonal Structure of the ejected Blocks of Monte Somma. (W\& : bee Mes | ) a ? ~ ann’s wW) QaP ) a rs ha aT Ye amdiol i r nA gnAnat oat aaf ah? panne DARA NLL er | rinle! | “He 4, Ap galanaate oanha Sanny , ake ‘ . \iapaee ayy be Reals ike Pete eel POLL mae Aa, "¢ t Pi Td egrsan- , Ap mh Ar ‘ AY a a ot . Liltt ee at BA. ailasea ni: al) ale! TARIARAL GL) Sat Abana Aipasen: aA niahaaains De althi° 0 TELA _. 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