VOLUME XXXVIII. NUMBER 561.
New Series. Volume XII. Part 4.
Entered at Stationers' Hall.

APRIL, 1915.

Focsded bv Richard A. Proctor, 1SS1.
Articles :— Plainly Worded. Subjects :— Exactly Described.

ONE SHILLING NET.

Registered for Canadian and

Newfoundland Magazine Postage.

C. BAKER'S LARGE
DISSECTING MICROSCOPE.

In Case, £2 9 6

With Aplanatic Lenses X 10 and X2U
Extra „ „ X 8 „ X15

Catalogue po?t free on request.

244, HIGH HOLBORN, LONDON

£3 6 O

each 11 o

Newton & Co. s Vitascope

Invaluable to the Botanist op Naturalist.

This Entirely Novel Instrument, designed at Naples University, removes the difficulty
of examining and observing living insects, and watching their movements, in the garden

or house, under high magnification, without remov-
ing them from their natural surroundings, disturbing
or frightening them. The " Vitascope " is neither a
microscope nor a telescope, but a combination of
both instruments. It can be used in the hand, or on a stand,
at will, and fills a long-felt want in Natural History Research.
The magnification can be varied from 12 to 60 diameters.

L>n'po Q>1 ,' with Table Stand (as illustrated) in case
rl ",s ** ■/ complete. Tall Garden Stand, SI- extra.
Descriptive Pamphlet post free. Sole Makers: NEWTON & Co.

NEW AUSTRALIAN BRANCH.

Temporary Address; NEWTON <S Co.,

do BANK OF AUSTRALASIA,

MARTIN PLACE, SYDNEY, N.S.W.

s>--
NEWTON & CO., K.n^^VLTfh^^l.en,. 72, WICMORE ST., LONDON, W.

Telegrams: "Newtobar, Wes'io, London."] Established over 200 Years. \Telephont: Mayfair 2339.

A most acceptable Gift at any time.

KNOWLEDGE VOLUME FOR 1914

Containing 440 Pages with 425 Illustrations, many being Full Page Plates.
Bound in Blue Cloih, Gilt Design and Lettering, 15/- net, post free within the United Kingdom.

Publishing Office : AVENUE CHAMBERS, BLOOMSBURY SQUARE, LONDON, W.C., or through any Bookseller.

Just published. 15/- net. 500 pp.
Numerous illustrations.

Dante and the
Early Astronomers.

By M. A. ORR

(Mrs. JOHN EVEKSHED. Kodalkanal).

A study of the ideas of the early astronomers, and
their relation to mediaeval thought, as revealed in the
numerous astronomical references found in Dante's
works.

A

NORTON'S STAR ATLAS

and Telescopic Handbook.

5/- net. 10 Charts, covering the
Star sphere, showing nearly all
objects in Webb's Celestial Ob-
jects to 7th magnitude, and
Smyth's Celestial Cycle.
Prepared with greatest care by
A. P. Norton, B.A.
Positions for ioii.

GALL & INGLIS, 31, Henrietta St., London, W.C.

w

CHEMICAL, PHYSICAL, and

SCIENTIFIC 'APPARATUS,

CHEMICALS. REAGENTS,

J.Woolley,Sons&C2d

Victoria Bridge, Manchester.

CATALOGUES ON APPLICATION.

Prism Binoculars

FOR SALE AND WANTED

CLARKSON'S,

338 High Holborn, LONDON, W.C.

(Opposite Cray's Inn Road.)

" Knowledge " may be obtained through any Bookstall or Newsagent
Offices: — Avenue Chambers, Bloomsbury Square, London, W.C.

KNOWLEDGE.

April, ilJi5.

IMPERIAL
COLLEGE

OF SCIENCE AMD TECHNOLOGY

SOUTH KENSINGTON, LONDON, S.W.
Department of Zoology.

The following Courses of Advanced Lectures will be delivered
in the Department after Easter : —

(1) A Course of about 20 Lectures with Practical Work on

" PROTISTOLOGY,"

By C. CLIFFORD DOBELL, M.A.

On Mondays, Wednesdays, and Fridays at 10 a.m., beginning

Friday. April 23rd.

(2) A Course of about 16 Lectures with Practical Work on

"ECONOMIC ENTOMOLOGY,"

By Professor H. MAXWELL LEFROY.

On Wednesdays and Fridays at 2 p.m., beginning Friday,
April 23rd.

(3) A Course of about Seven Lectures, beginning Monday,
April 26th, entitled —

"INTRODUCTION TO THE STUDY
OF HEREDITY,"

By Professor E. W. MacBRIDE, D.Sc, F.R.S.
On Mondays at 5 p.m.

(y.B. — This Course is a continuation of t/u Cow se delivered previous to Easter.)

For Terms and Fees apply to the Registrar.

BIRKBECK COLLEGE,

BREAMS BUILDINGS, CHANCERY LANE, E.C.

COURSES OF STUDY (Day and livening) for Degrees of the
UNIVERSITY OP LONDON In the

FACULTIES OF SCIENCE & ARTS

(PASS AND HONOUKS)
under RECOGN1SKD TEACHERS of the University.

SCIENCE.— Chemistry. Phyilci, Mathematics (Pure and Applied).
Botany, Zoology, Geology.

ARTS Latin, Oreek, English, French. German, Italian. History,

Geography. Logic, Economics. Mathematics (Pure and Applied).

Evening Courses tor the Degrees In Economics and Laws.

POST -GRADUATE AND RESEARCH WORK.

cvseinNAi tnirq • lnay: Science, «17 10s. I Am, £10 IOb.

Si-SMUIMAL rtfci . \/ivening._ Sc-mKCt ArlN or Kconomics, £5 5a.

MATRICULATION COURSES AND ACCOUNTANCY.
Prospectuses post /ree. Calendar 3d. [ly post sd.it from the Skchetarv.

GRESHAM LECTURES.

The Gresham Lecturer on Astronomy, Mr, ARTHUR R. HINKS, M.A., F.R.S. ,

will deliver a Course of Four Lectures on

THE SUN

On TUESDAY, WEDNESDAY, THURSDAY, & FRIDAY,
13th, 14th, 15th, 16th APRIL, 1915,

At Six o'clock in the Evening,
At GRESHAM COLLEGE, BASINGHALL STREET, E.C.

THE LECTURES ARE FREE TO THE PUBLIC.

OUR INFORMATION BUREAU

will be found to be of great use to Foreign and Colonial readers. Oftentimes
information is desired which is unobtainable locally, and in such cases, whether the
information is of a Literary, Scientific, Trade, or other character, we undertake, for
a small fee, to supply the information desired, if at all obtainable ; and in order to
introduce our Bureau to the notice of the readers of Knowledge we will, for a limited
period supply such information at the rate of 6d. per enquiry. Stamps (Foreign or
British) will be accepted in payment of the Enquiry Fee, and replies will be forwarded
by the earliest possible mail. We also act as Buying Agents for readers resident in
the provinces or abroad. Full particulars sent gratis.

E. GEORGE & SONS, 23 Jacob Street, London, S.E., England.

TELESCOPES.

THE "LORD BURY" TELESCOPE, bronzed brass, in sling case £4 4 0

Size, closed, 10 inches; extended, 31 inches. Diameter of Object Glass, Ig inches.

Magnifying power 25 diameters, increasing by pancratic tube to 35 diameters.

Angular Field 150. Lateral Field at 1,000 yds. =262 yds.

Will show a Flagstaff at 22 miles. I Will make out Wild Fowl at 16 miles.

,, read name of Lightship at 9 miles. ' ,, show time by Church Clock at 6 miles.

THE STEWARD
PRISM BINOCULAR

£5 15 0 in sling case.

Central focussing adjustment. Sealed bodies.
Suitable for use in hot climates.
Magnifying Power x 8 diameters.

Angular Field .. . . 5=>

Either of the above sent post free on

receipt of remittance.
Illustrated Catalogue, Part I, post tree.

J II QTFWADIl I \t\ Opticians to the British and
• D. (J I Ci W« rtlili, LIU. Foreign Governments,

406 STRAND; 457 WEST STRAND, LONDON, ^f

WATKINS and
DONCASTER,

NATURALISTS

and Manufacturers of

Cabinets and
Apparatus ss

- FOR -

COLLECTORS OF INSECTS, BIRDS'

EGGS AND SKINS, MINERALS,

PLANTS, Etc.

Lovers of Birds who wish to
encourage them to nest in their
gardens or shrubberies should
apply for our Price List of Nesting
Boxes.

A LARQE STOCK OF INSECTS,
AND BIRDS' EaflS AND SKINS.

SPECIALITY.— Objects for Nature
Study, Drawing Classes, &c.

Birds, Mammals, etc., Preserved and Mounted by
First-class Workmen true to Nature.

V**~ All Books and Publications on Natural
History supplied.

36, Strand, London, W.C.

(Five Doors from Charing Cross.)
PT CATALOGUE POST FREE*

April, 1915.

KNOWLEDGE.

SCIENCE PROGRESS t'hn= TWENTIETH CENTURY.

A QUARTERLY JOURNAL OF SCIENTIFIC WORK AND THOUGHT.
Edited by SIR RONALD ROSS, K.C.B., F.R.S., N.L., D.Sc, LL.D., VI. D., F.R.C.S.

176 Pages. Illustrated.

APRIL.

Some Aspects of the Atomic Theory. Prof. F. Soddy,
F.R.S.

The Electrical Properties of Conductors at Very Low
Temperatures. Francis Hyndman, B.Sc.

The Anthocyan Pigments. Arthi r K. Everest, M.Sc, Ph.D.

Vertebrate Palaeontology in 1914. R. Lydekker F.R.S.

The Prevision of Earthquakes. Charles Davison, ScD.,
F.G.S.

Is the Organism a Thermodynamic Mechanism P

James Joh\stosk, D.Sc.

5s. net.

Notes: The British Science Guild and the Fight for
Science The Fools' War The Quality of the
German Lie A Converted Pacifist Our Unspeak-
able Cranks and other Notes.

Correspondence: Elementary Logic (A. Sidgwick)—
Party Politics and Scientific Representation
i \. J. Gray, Se. retary "I he Pr .porti

Essay-Reviews: Character and the Emotions iDR. F.
W. Moii. F.R.S.) -Plagiarism in Science (The Editor)—
Mathematical Text-books (Amateur)— Fact and
Fancy in Hematology ill. C. Ross).

Reviews of Thirty-three Books on Mathematics,
Physics, Chemistry, Geology, Palaeontology,
Zoology, Botany, and Applied Sciences. Index.

JOHN MURRAY, ALBEMARLE STREET, LONDON, W.

Symons's Meteorological Magazine.

Edited by HUGH ROBERT MILL, D.Sc.

This Illustrated Magazine, founded in 1866, is devoted to the science 0.
Meteorology in all its branches.

The monthly Climatologies] Table of the British Empire and the monthly
Rainfall Map of the Thames Valley are uniqTie features. Special attention
is given to Correspondence from Meteorologists and Observers. The
meetings of Meteorological Societies are punctually reported. All important
Books bearing on Meteorology are reviewed. Original Articles and
descriptions of New Apparatus frequently appear. Exceptional Conditions
of Weather in the British Isles are discussed while still remembered.

Published on the 16th of each month. Price 4d.,
annum post free to any part of the world.

or 5s. per

A Specimen Number will be sent free on application to the
Editor at 62, Camden Square. London, jV. W.

Published by EDWARD STANFORD, Ltd., 12, 13, & 14, Long
Acre, London, VV.C.

POPULAR ASTRONOMY.

TWENTY=TWO VOLUMES COMPLETED.

A Journal for Reference on Current Astronomy.

Over 500 Pages of Reading Matter fully Illustrated in

each Volume.
Containing the Latest Astronomical News. Articles on
Astronomical Themes. Many Pine Lngravings. Spectro=
scopic, Planet and Comet Notes. Star Charts every Month.

A Valuable Journal in any General Library.

Subscription 10 the Twenty-third Volume(ten numbers) post free to any address
in the United States on receipt of 3 dollars 50 cents; Canada, 3 dollars 75 c<
and 16s. 6d. for all other countries. Preceding volumes al same price.

Editors: HERBERT C. WILSON, RALPH E. WILSON, and
CURVIN H. GINGRICH.

GOODSELL OBSERVATORY OF CARLETON COLLEGE,
NORTHFIELD, MINN., U.S.A.

WILLIAM WESLEY & SON, 28 Essex Street, Strand, London.

MAN

An illustrated monthly record of Anthropological
Science. II- per part. 10/- a year, post free anywhere.
CVXJ I \ I S OF 1/7,7/ rssi i
< irigin 11 \r... . , | ',„ Batm in1 ritl Deed n H Plot, D an IB) -
Were thi Pre I ><• n i tic Eg Lib] an 01 I thi piai \ I l ipam ;e

' and C like Objects used as A lets and in Charm Reviews Va/t'w

NorUiern Territoi i

.' Oerr. — The Hm

Variations de la colom
p< inl de ■ ue de I' Anthropologic Zo .'

London: The Royal Anthropological Institute, 50, Great Russell St.

General Asent FRANCIS EDWARDS, 81!. Hiab Street. Maryleboae. London W

n Si i.'iiiitn , Technii i] t ■ . I ■ , . . ,

Mi

ei ts, and Ibi al! Exams.
SECOND-HAND AT
HALF PRICES.
New, at 25 Discount.

Catalogues Free. State wants. Booksjesent on approval

HOOKS BOUGHT— BEST PRICKS GIVEN,
W. & G. FOYLE, 121-123, Charin&CrossRoad, London, W.C

Fourth Edition. Enlarged. Pp. xviii - 4'Jtl. with 113
Illustrations, including 5 Plates. Price 6s, net [postage 5d. .

CROSS «& COLE'S

MODERN MICROSCOPY

A Handbooh for Beginners and Students.

With Chapters on Special Subjects by

C. Andrews, F.R.M.S. ; F. J. Cheshire. F.R.M.S.

A. Earland, F.R.M.S. ; C. F. Rousselet, F.R.M.S.

T. H. Russell. F.L.S. ; C. D. Soar. F.L.S., F.R.M.S.

and W. Mark Webb. F.L.S.

<!

Mr J. /-.'. Barnard (Lecturer in Microscopy at Kin:'s I
i li Kn wiedgc," says: "It m i
confidence be recommended liie for those entering

on any ': the microscope.*'

BAILLIERE, TINDALL & COX, 8. Henrietta Street. Covent Garden, London.

The Leading Journal of Science.

SIXPENCE WEEKLY.

Attention is directed to a few of the topical
articles which have appeared in NATURE
since the outbreak of the war: "Science
and the State" [October 29); "The Manu-
facture of Dyestuffs in Britain: a Summary
and an Appeal" [January 21) "Synthetic
Drugs in Great Britain " [January
"The Manufacture of Dyestuffs " February
111, "Chemistry and Industry" February
18); "The Manufacture of Dyestuffs"
Feb "Duty-free Alcohol for

Scientific Purposes' [March i "Science
and Industry " [Ma "Periscopes'

[March 18) "Oil of Vitriol as an Agent of
'Culture [March 18) "Scientific Factors
of Industrial Success'' March "Supplies

of Laboratory and Optical Glass Apparatus "
[March 25) Any one number will be sent
by post on receipt of its published price,
plus postage.

Office: St. Martin's Street, London, W.C.

IV,

KNOW LI I ... I .

April. 1915.

National Relief Fund.

THE PRINCE TO THE PEOPLE.

Buckingham Palace.
'■ At such a moment wc all stand by one another,
and it is to the heart of the British people that I
confidently make this most earnest appeal."

EDWARD P.

To H.R.H. The Prim e of Wales,
Buckingham Palaci . L< indon.

7 beg to em' lose f : s. //

as a dona/ton to the National Reliej
Fund.

Name

. tddn ss i

The envelope containing this coupon need not be stamped.

PUSTLESS ROOMS

i i..i\. l.ii i..iv. Mm . ..in i and Linoleums

ysi FLORiGENE

i\ Regd. Name luggesied b) Floor-Hygiene).
VERY EARLY in EACH VACATION for Best Results.

It i IM I'l iK 1 AVI

Ti '

,-M|

th.it
irlnfl

. i 1

API'LICATION of

"HI ■■

accot i
iprli Icllnj of

\l 1 W.tl,

■

,itiv kind), i

which lisv

1 >1

only 'i

it J .
■<

DIR1

. i, i

foi ■-'

I.. 1 ' months,

id (without

it. i

■

■ ■

i- inter ' 1

1 '

These sanitary and labour-saving advantages are NOT attained by

sweeping-powders or any ottier method.

Strut /«< particula imi Ttitiuioniah to

The "DUST-ALLAYER" Co-
165, Queen Victoria Street, London, E.C.

Reprinted from "Knowledge" May, 1911, issue.

A BIRD'S-EYE VIEW

in tut:

HISTORY OF ASTRONOMY

(Wl TH FOLDING PLA TE).

By W. ALFRED PARR.

PRICE SIXPENCE.

London :
Knowledge Publishing Company, Limited,

Avenue Chambers, Bloomsbury Square, W.< .

Royal Naval Division

PUBLIC SCHOOL BATTALION.

"THE ADMIRALTY have given official
' permission for raising a Battalion
of 1,000 men, which will be strictly
limited to Public School or University
Men, and who will serve together as
a Unit.

Training is now going forward.

SERVICE

For the period of the

WAR.

Military Training.
Ages 18—35.

Applicants desiring to enrol should
apply at once to

ROYAL NAVAL DIVISION,

6, 7, 8 Old Bond Street, London, W.

Phone: Regen 6515.
GOD SAVE THE KING.

THE

English Mechanic

WORLD OF SCIENCE

Commences with Volume C I
its Second Century.

Foi m" years it has steadily and continuously broadened

the I infill s, an ' yearly added to the ranks

oi it ■ ;[■,. i, .11, l- . i ■■■ tun! irj hi ipers. We ask to-day, not
fori nscrip ion, bul Foi universal voluntai y servi< e in the task
,,i enli ting the young in the »ei \ ii e d 51 tern e it 1- no duty
0{ ours to discuss whether wi were read} as a nation for the
ei, ti itruggli in which the British I mpire is engaged; but

no 1 1 rel ih.it, after a gi n nation ol universal elementary
education, the majority ol our countrymen grow into man-

1 and womanhood ill equipped for the industrial struggle
with their competitors ol better-trained nations, and content
1, mi vicarious athletics and the unedifying,
lmt 1 .piil.tr " literature oi the time. ('i hundreds

oi th these it is the bare truth to say the fault

is not theirs, but that of their teachers. H youth were but
led judiciously, and without pedantry, to the realisation
ol the pleasures oi science, aptitude and inclination would
attrai 1 yearly increasing thousands to the profitable utilisation
thereol in manhood One proof that this is so is the eagerness
with which the English Mechanic is read in schools where
the teachers have familiarised the children with its contents,
Will more teachers make Tin- English Mechanic and World
of S< 11 hi 1 their school book ? If so, thousands of men and
women who will read its pages fifty years hence w:ll gratefully
remember them. ^^^^^^^^^^^_^

A Specimen Copy will be sent free to any address
on request.

ENGLISH MECHANIC,

5. EFFINGHAM HOUSE,
ARUNDEL STREET, STRAND, LONDON. W-C

CONTENTS.

Chapters in Spectrum Analysis. I (continued).

By W. Marshall Watts, D.Sc. 97

On the Formation of Hair Pigment.

By H. Onslow. 101

Dust. By William Swaine. ... ... ... ... 103

The Making of Gun-flints.

By Wilfred Mark Webb. F.L.S. 106

Solar Disturbances during February, 1915

Notes (continued) : —

Meteorology. By William Marriott. F.R. Met. Soc. 114
Microscopy. ... By J. E. Barnard. F.R.M.S. 115

Photography By Edgar Senior. 116

Physics. By J. H. Vincent. M.A.. D.Sc. A.R.C.Sc. 117
Radio-Activity. By Alexander Fleck, B.Sc. 118

Zoology.

By Professor J. Arthur Thomson. M.A.. LL.D. 119

By Frank C. Dennett. Ill Number of Spores in a Myxomvcete.
Notes — By W. B. Grove. M.A. 120

Astronomv. The Face of the Sky for May.

By A. C. D. Crommelin. B.A.. D.Sc. F.R.A.S. 112 By A. C. D. Crommelm. B.A.. D.Sc, F.R.A.S. 121

Botany. By Professor F. Cavers, D.Sc, F.L.S. 112 Pollards. ... ... ... ... ••• ■•• ••• 122

Chemistry. Stonyhurst College Observatory.

By C. Ainsworth Mitchell. B.A., F.I.C. 113 By Frank C. Dennett. 125

Geography By A. Scott, M. A.. B.Sc. 113 Reviews 125

Geology. By G. W. Tyrrell, A.R.C.Sc. F.G.S. 114 Notices 128

NOTICES.

CONTRIBUTIONS. — Every endeavour will be made to return unaccepted contributions which are accompanied by a stamped

addressed envelope, but the Editors will accept no responsibility for accidental loss.
ADVERTISEMENTS. — All matters relating to advertisements should be sent to the Advertisement Manager.
BUSINESS.— All other business letters should be addressed to the Secretary, and all remittance? made payable to the order of

" Knowledge " Publishing Company, Limited.
SUBSCRIPTIONS.—" Knowledge " will be sent post free; for a year, to any part of the world for 15/-. Singie copies mil be posted

for 1/3.
BOUND VOLUMES.— Recent Yearly Cloth-Bound Volumes may be obtained at 15/- net, post free within the United Kingdom.
BINDING CASES in Blue Cloth with gilt lettering, down to 1908,' 1/6 net each, by post 1/9: 1909 and after, 1/9 net each, by post 2/-
BACK NUMBERS.— 1885 to 1895, 2/- each ; 1896 to 1905. 1/6 each ; 1906 and after, 1/- each (except January to April, 1910. 2/-)

Issues prior to 1S85 are out of print.
LANTERN SLIDES of many of the illustrations may be obtained from Messrs. Newton & Co., 37, King Street, Covent Garden.

London, W.C.

Offices: AVENUE CHAMBERS, BLOOMSBURY SQUARE, LONDON, W.C.

Telephones .—(Office) 4060 City. "' ' (Editorials 042 Ealing

IONIUM

Permanent Alpha Ray Activity

RADIO-LEAD

MESO THORIUM

Glew's Scintillobcopes charged with IONIUM,

RADIUM, MESO-THORIUM, or ACTINIUM,

7 6 each.

Scintilloscopes showing Double Scintillations
Thorium "A," 15- each.

'The Naturalist's Companion.'

BROWNINGS PLATYSGOPIG LENS

With Larger Angles, Increased Field, and Improved Definition.

I

F. HARRISON GLEW,

156, CLAPHAM ROAD, LONDON, S.W.

Advertisement Rates.

Whole Page ...
Half Page ...
Quarter Page
One-Eighth Page -
One-Sixteenth Page
Per Inch, Narrow Column
Half ,, ,, ,,

6 6
3 S
115
O 18

o 10

O 7
O 4

d.
O

o
o

6
O
O
O

I

Discoi its for Series of Insertions and Rates for
Special Positions, when Vacant, on Application ro

THli ADVERTISEMENT MANAGER,

KNOWLEDGE OFFICE,

AVENUE CHAMBERS, BLOOMSBURY SQUARE, LONDON, W.C.

AN ACHROMATIC COMBINATION

Combining the Definition of a Microscope with the Portability ol
a Pocket l.ens.

.. |, ,.. . . p p Lens (which ever)

r^__ I Nature night to do)." Grant Ai.i.kn. in >

i^*^ ■• I I: ied one of the>e instruments and found it m\-.ilii.iblc."

(__joii\ I. Carrington, Editoi Gossip.

The Platyscopic Lens is invaluable for low lamination of

Pond Life, Botanical, Geological, Entomi . and other

objects, as il focusses about three times as far from the

Lens, and has a field unequalled for flatness, allowing
ipaque objei ts to be examined easily.

li is made in four degrees of power, magnifying respectively 10,
15, 20, ami 30 diams. : the lowest power, having the largest field,
is the best ad . ner.il use.

Mounted in Tort lagnifyittg ,0- '5- JO-

or 30 diailic, 15s. Od.

In .V 1 7s. 6d.

Combinations of any 2 powers, in 27s. 6d.

Ditto Ditto ' in X 32s. 6d.

ILLUSTRATED DESCRIPTION SENT FREE.

JOHN BROWNING, Manufacturing Optician,

146 STRAND, W.C, and (^

72 NEW OXFORD STREET. W.C. I

Estab. 1766. Tel, No.: 7804 Central.

LONDON.

KNOWLEDGE.

Aikii . 1915.

Index of Spectra

NEW SERIES.

Designed to complete and bring up to date
the Index of Spectra and previous Appendices.

Appendix V contains Air. Aldebaranium, Aluminium,
Alumina, Ammonia, Antimony, Argon. Arsenic,
Barium, Beryllium, Bismuth, Boron, Bromine,
Cadmium, Caesium, Call ium, Carbon, Cassiopeium,
Cerium. Chlorine, 12s. 6d.

Appendix W contains Chromium, Cobalt, Copper, Dys-
prosium, Erbium, Europium, Fluorine, and "Additions
and Corrections to Appendix V," 12s. 6d.

The Index of
Appendix B

Appendix C

Appendix D

Appendix E

Appendix F

Appendix G

Appendix H

Appendix I

Appendix J

Appendix K
Appendix L

Appendix M

Appendix N

Appendix 0

Appendix P

Appendix Q

Appendix R

Appendix S
Appendix T

Appendix U

Appendices B
Appendices J

The other parts of this work tire :

Spectra bound volume (including Appendix A), £1 5s.

(Tabic "t corrections to reduce to Rowland's standard, ultra-
h t spectra oj Co and \i, etc.), 3s. 6d.

rum ol [ron, telluric tines oi solar spectrum, spectrum oi
Hydrogi a), 7a. 6d.

I \i. jp ctraof i ..i. Li, Na, K, Rb, ( ;, Mg, i a, Zn, Sr, Cd, Ba,
Hg, absorption spectrum oj Bromine, Arc-spectrum of
Alumina), 5s. 6d.

[Spe< mi ■ >| Air, Cu, \-\ An, Al. In, II, t . CN, \. Si, ammonia,
and rable i >J reduction t ■ ► v, ai mini |, 4s. 6d.

| I In At -spa tra oi Cr, Sn, Pb, Sb, Bi, Same-spectra of K, Na,
L-. i.i, Sr, Ba, et( i, 3s. 6d.

[Rowland's Standard Wave-lengths, Spectra of Hg, He, Cd,
eb , and oxy-hydrogen spectra), 5s. 6d.

(The three spectra of Argon, the arc-spectrum of Ti, the spark-
spectra ol Cu, Ag, and An). 5s. 6d.

(The arc- and spark-spectra of Co and Ni, and " Index
Indicis "), 5s.

| 1 In spark-spectra of Fe and W, and the arc- and spark-
spectra oi Pt), 8s.

(Spectrum of Chl^nin , ;iii-l th< -park-spectrum of Mo) 5s.

[Spectra ol Bromine, Gallium and Radium, and the spark-
spectium of Uranium), 7s. 6d.

lii' an spectra of Mn and V, the spark-spectra of V, Au and
Si. and the spectrum of Argon), 6s.

(Flami spectrum of Radium, infra-red spectra of Alkalies,
ultra-violet spectrum •<{ Thorium), 4s.

[An spectrum of Mo, spark -spectra ol Ca, Sc, hi. Be Li, Tl,
K, Cs, Sb, As, Ra), 4s.

\n and spark-spectra of Ruthenium, Yttrium; Line- and
Band-spectra of Sulphur), 7s. 6d

■ l Neon, Xenon, and Krypti m, and a se< i*j I " Index
Indicis "), 4s. 6d.

(Spark -spectrin n of Cr ; ^rc- and spark-spectra of Pa and the
S) ■ ' ira of Polonium and Ex-radio), 5s. 6d.

(Arc- and spark-spectra ol h Os, and kin 10s. 6d.

(Arc- and spark-spectra of rantalum, Zirconium and Lan-
thanum), 8s.

(Table of th< Strong* r Lines ol the Eli ments, arrangi d ai i ord-
ing to wave-li ngth), 10s. 6d.

to I inclusive, bound in one volume, price £2 3s.

to Q , „ £2 8s.

From "Nature," December 11th, 1913: —

'Watts' Index of Spectra.' — Yet another
series of Appendices to this most valuable com-
pilation of wave-length data has been commenced
by the publication of Appendix Y."

Post free from t/ic Author:

Dp. W. MARSHALL WATTS,

"Shirley," Venner Road, Sydenham, London, S.E.

Direct Vision Spectroscope

Send for

Section J

of Catalogue

for smaller
Direct Vision
Spectro-
scopes,
suitable for
laboratory
work.

I Ins instrument lias a
fine micrometer strew with
divided drumhead and
scale, enabling one to pass
through the spectrum and
to obtain wave length de-
terminations with consider-
able accuracy. The prism
is of high dispersion, and
easily resolves the sodium
I > lines A pointer is also
fitted into a positive eye-
piece.

It

P... <-,.=;■ I Instrument - *9 10
Hiicts. | stand . .£2 2

DELIVERY FROM STOCK.

o
o

ADAM HILGER, Ltd.,
75a, CAMDEN ROAD, LONDON, N.W.

Telegrams: "Sphericity, Camroau, London." Telephone: North 1687.

fnl

ll!lllll]llll||l!l|lllllll!lllilllllllllllllllli|||'llllll!lillilllllll[

OHMS

Keep one of our Departments
always busy. We manufacture
them in the form of

RHEOSTATS

of all types, values, and carrying
capacities, from the SMALLEST
SLIDER to the LARGEST
LOAD or CALIBRATION Set

BRITISH MADE ONLY

ISENTHAL & Co.

(Department 2>

Denzil Works, Neasden, London, N.W.

Contractors to the Admiralty. War Office, India Office,
Colonial Office, and the Postmaster General.

m

m

Knowledge.

With which is incorporated Hardwicke's Science Gossip, and the Illustrated Scientific News.

A Monthly Record of Science.

Conducted by Wilfred Mark Webb, F.L.S., and E. S. Grew, M.A.

APRIL, 1915.

CHAPTERS IN SPECTRUM ANALYSIS.

By W. MARSHALL WATTS, D. Sc.

I. — Law and Order in Spectra.
A. Line Spectra.

(Continued from page 69.)

The absorption spectra of potassium, rubidium, and

caesium show long series of regularly arranged

pairs of lines similar to those seen in sodium.

These three metals are very closely allied in their

chemical and physical properties, and their spectra

show a most remarkable agreement. In the

diagram (see Figure 79) these three spectra are

mapped upon a scale of oscillation-frequency —

that of caesium at a "height" of 17638, that of

rubidium at the "height" of 7301, and that of

potassium at the "height " of 1 528, as shown by the

scale on the left-hand edge of the diagram, these

numbers being the squares of the atomic weights :

132-81 for caesium, 85-45 for rubidium, and 39-1

for potassium. The connecting -lines, marked

m = 2>, m=\, m=5, and so on, show the exact

correspondence of the spectra line for line. Further,

the lines joining corresponding points in caesium

and potassium pass almost exactly through the

corresponding points in rubidium.

The principal series in potassium is set forth' in

the following table, with the wave-lengths calculated

from the formulae

n it iconc u 109675

O.F. = 35005-56 — nA,QCAxa

'» + . 293076 -^?)

m

I

for the less refrangible component, and

109675

O.F. = 35005-56 —

m + -296228 - I^8)'

»i

1

for the more refrangible component of the pairs
of lines.

Table 18.
The Principal Series in Potassium.

ill.

Observed.

Calculated.

O— C.

O.

C.

f 7699-23

7699-10 \
7665-60 /

+ •13

2

I 7665

27

-•33

3

f 4047

38

4047-51 \
4044-13 J

-13

i. 4ii44

32

+ •19

4

r 3447

53

3447-59 \

-06

I 3446

53

3446-56 i

-03

_

f 3217

76

3217-83 \
3217-36/

-07

o

\ 3217

31

-05

6

/ 3102

37

3102 -27 i
3102 00/

+ 10

\ 3102

15

+ •15

7

3034

94

/ 3035 09 \
X 303500 /

-10

8

2992

47

2992-43

+ 03

9

2963

37

3-53

-•16

10

2942

8

2942-99

-19

11

292S

0

2927-86

+ 14

12

2916

6

2916-38

+ .22

13

2907

6

2907-45

+ •15

14

2900

4

2900-38

+ 02

15

2894

6

2894-67

-07

16

2889

7

2890-00

-•30

17

2885

9

288612

- -22

IS

28S2

9

2882 -87

+ •03

19

288d

3

2880-12

+ •18

20

2877

9

2877-77

+ •13

21

2875

8

2875-75

+ -05

22

2874

l

2873-99

+ •11

23

2872

5

2872-46

+ •04

24

2871

1

2871-12

-02

25

2870

0

2869-93

+ 07

N

97

OS

KNOWLEDGE.

April, 1915.

For rubidium the formulae
OF. = 33688-20 -

Kl«Mi75

(l.r.

O.F. = 33688-20 -

(„+.; ,,•_,;,.„ _±Z3542y line)
V m — \

109675

•l)738()»\" ,:

, (m-r-

(m + . 365934- '""""'"I Hno
\ wi — 1 /

give equally p""l results, as shown in the following
tabic:

Table 19.
The Principai Series in Rubidium.

III.

Observed.

Calculated.

O— C.

2

i 7949-04

7949-03 \
7803-13 /

+ ■01

03-17

+ •04

'1

I 4215-72

4215-72 1

4201-99 J

0

.>

1 1201 98

-•01

4

i 3591-74

3591-74 \

0

I 3587-23

3587-22 J

+ •01

_

I 3350-99
V 3348-86

3350-94 \
3348-93 J

+ •05

s

-•07

6

I 3229-26

I 3228- IS

3229-27 \
3228-10 J

-•01

+ •08

7

f 3158-47
I 3157-69

3158-39 \

3157-67 /

+ ■08

+ •02

8

3112-95

3112-95

0

9

3082 -39

3082-34

+ •05

10

3060-62

3060-56

+ •06

11

3044-33

3044-47

-•14

12

3032-20

3032 -25

- -05

13

3022-70

3022-74

- -04

14

3015-16

3015-20

-•04

15

3009-03

3009-11

-•08

16

3n()4-ll

3004-12

-■01

17

2999-96

2999-98

-•02

18

2996-51

2996-51

0

19

2993-52

2993-57

-•05

20

2991-12

2991-06

+ •06

21

2988-94

2988-89

+ ■05

22

2987-01

2987 -02

-•01

23

2985-45

2985 -38

+ •07

24

2984 -US

2983-94

+ •11

25

2982 -68

2982-67

+ •01

26

2981-51

2981-53

-•02

27

2980-52

29S0-53

-•01

28

2979-62

2979-62

0

29

2978-81

2978-81

0

30

2978-10

2978-08

+ •02

31

2977-39

2977-42

-•03

In caesium the formulae

O.F. = 31404-6

109675

O.F. = 31404-6 -

m + -418206-
109675

•09002 \a

m — 1

( m + . 449975 _l089294y
\ m — 1 /

give the following results :

Table 20.
Tin: Tkincipal Series in Caesium.

III.

Observed.

Calculated.

O— C.

2

I 8949-92

8949-92 \
8527-72 J

(I

\ 8527-72

ii

3

1 4593-34

4593-34 \

0

l 1555-44

4555-44 )

0

4

/ 3888-79

I 3876 -53

3888-75 \

+ •04

3876-36 /

+ •17

5

( 3617-56

3617-44 \

+ 13

\ 3611-67

36 1 1 -62 i

+ •05

6

I 3480-28
l 3477-03

3480-19 \
3477-13 /

+ •09

-10

7

f 3400-13

3400131

3398-14 /

0

I 3398-27

+ •13

8

/ 3348-84

3348-S 3 \
3347-68/

-•09

I 3347-56

-•12

9

r 3314-16

3314-25 i

-•09

l 3313-28

3313-33 /

-•05

10

f 3289-25

3289-50 \

3288-84 J

-■25

I 3288-68

-•16

11

3270-56

3270-72

-•16

12

3256-77

3256-92

-•15

13

3246-02

3246-18

-•16

14

3237-58

3237-65

-•07

15

3230-69

3230-78

-•09

16

322511

3225-11

0

17

3220-34

3220 -43

-•09

18

3216-45

3216-48

-•03

19

3213-02

3213-11

-09

20

3210-18

3210-26

-•08

21

3207-78

3207-80

-•02

22

3205-64

3205-66

-•02

23

3203-80

3203-79

+ •01

24

3202-13

3202-15

-•02

25

3200-71

3200-70

+ •01

26

3199-45

3199-42

+ ■03

27

3198-25

3198-26

-•01

28

3197-28

3197-23

+ •05

29

3196-20

3196-31

-11

30

3195-42

3195-47

-•05

31

3194-59

3194-72

-13

32

3193-94

3194-04

-■10

The remarkable similarity between the spectra
of the alkali metals was noticed by the early
observers. In 1869 Lecoq de Boisbaudran remarks
that the spectrum of caesium is, like that of
potassium, shifted bodily towards the red. Figure
78 is a photographic reproduction of some of the
beautiful drawings of spectra published by de
Boisbaudran. The caesium and rubidium lines
which he marks a, 6 are those of the principal series
marked m=3 in Figure 79 (the diagram does not
extend far enough to the right to allow of the red
lines of the three elements to be shown, i.e., those
for which m=2).

That there exists some relationship between the
atomic weights of allied elements and their spectra
is certain. If we knew the precise law of this
relationship, the measurement of the wave-lengths
of the lines in the spectrum of a new or rare ele-
ment, particularly of one difficult to obtain in a

April. 1915.

KNOWLEDGE.

99

I

a. Spectrum of the blue flame of illuminating gas.

b. Caesium chloride. Flame spectrum.

.?-'.< ■/>'.' '-<■ i >•> j/t'i' tyo //tf /!,,•

c. Rubidium chloride. Flame spectrum.

(I. Potassium chloride. Flame spectrum.

it>o ItO

!-■'■ I '■■ Jj,y

>■ Potas in::: ulphate (fused). Spark spectrum.

■

z.
f. Sodium sulphate (fused). Spark spectrum.

I I'.l Rl

100

KNOW I.I D

April, i<ns.

w

V.

a
o

April, 1915.

KNOWLEDGE.

101

state of purity, would afford much more exact
data for the determination of the atomic weight
than the chemical method. If we consider that
even in the case of an element whose atomic weight
has been determined repeatedly with the utmost
care — say silver or chlorine — the result is not
certain to one part in three thousand, whereas the
wave-length of a line can be measured with an
accuracy of one part in one hundred thousand,
we see how important the spectroscopic method
might become.

The diagram Figure 79 is drawn to exhibit a
relationship between oscillation-frequencies and
squares of atomic weights. It will be easily under-
stood that, if this relationship were exact, we could
calculate the atomic weight of one of the three
elements from those of the other two — say the
atomic weight of rubidium — from those of caesium
and potassium, 132-81 and 39-10 respectively.
Making the calculation for each set of homologous
lines m=3, m=\, ;« = 5, and so on, we obtain for
the atomic weight of rubidium numbers increasing
gradually (but slightly) up to the convergence-
frequency, of which a few examples are given.

4 gives the at. wt. of rubidium as 85-047

85-575
85-943
86-060
85-814
85-830
86-141
86-069
Mean 85-31.
The recognised atomic weight is 85-45.

It will further be remarked that in the diagram
the connecting-lines seem to intersect on the line
of zero atomic weight ; or, in other words, the
separations of the pairs of lines are proportional
to the squares of atomic weights. Thus for the

m =

4

give

m =

5

m =

6

m =

7

m=

8

m=

9

m=

10

m =

11

red pairs we have

Wave-lengths.
D . - f 7699-23

Potassium • ncc~ nn

[_ 766o-27
/ 7949-04
i 7803-17
I 8949-92
I. 8527-72
From the proportion Rb2 : C<

Rubidium

Caesium

Oscillation- Differ-
frequencies.

12984-81 ,

13042-35 .1

12576-74 i

12807-17 J

11170-26

11723-26
2=230-43 : 553-00 we

ence.

57-54

230-43

} 553-00

get for rubidium 85-73 when C?= 132-81.

(To be continued.)

ON THE FORMATION OF HAIR PIGMENT.

By H. ONSLOW.

The histological formation of the hairs of certain
animals and the condition in which the pigment
is present in them were described in an earlier
communication.* We must now inquire into the
processes involved in the production of this pigment.
The earliest investigators were of the opinion that
the melanins, or dark pigments of the skin and hair,
had their origin in the blood, as is the case with
the bile and certain other body pigments. There
was, however, little or no evidence on which to
base such a theory, except the fact that it was found
that the weight of iron contained in the ash of
negroes' skin was twice as great as that of the white
man's skin, and other equally inconclusive evidence.
It is now known that the keratin of the skin
and hair contains a certain quantity of iron,
which is not, however, a necessary component
of the melanin molecule, and has no connection
with the iron of haemoglobin. The theory that these
pigments were derived from the blood received its
death-blow with the discovery that the sap of the
Japanese lacquer-tree, described by Yoshida, con-
tained a ferment capable of oxidising a certain
phenolic substance or chromogen to the black
lustrous pigment which composes the surface of
Oriental lacquer. Shortly afterwards, the further

discovery that this oxidising ferment was widely
distributed throughout both the vegetable and
animal kingdoms served to form the foundation of
the modern oxydase theory of pigment formation.
Many of these ferments, called laccases, have the
power of oxidising some phenolic substances,
especially those containing several hydroxyl
groups, to products varying in colour from
yellow to black. Others, the so-called tyrosinases,
oxidise solutions of the amino-acid tyrosine,
as well as many polypeptides, containing tyrosine,
which are changed through red to violet, and
yield finally a black precipitate. A plausible
theorv for the production of many animal
pigments is suggested by the fact that phenols
{e.g., p-cresol) in the presence of amino com-
pounds may be made to show an almost infinite
variety of colours by suitably varying the phenol
and amino components.

In the vegetable kingdom these ferments are
found in a number of fungi, in potatoes, and in many
roots. Among animals they are found in the
body-filling of meal-worms, in the larvae of many
insects, and in the pigment sac of the cuttle-fish,
where they give rise to sepia. Among vertebrates,
also, both tyrosinase and tyrosine are found in

"Knowledge," Volume XXXVII, page 161 (May, 1914).

102

KNOWLEDGE

April, 1915.

melanotic tumours, and tyrosinase alone in tin-
skin of young "i t"' taJ rabbits.*

I he discovery of this wide distribution of tyro-
sinases resulted in the formulation of the now
commonly accepted theory thai the pigments of
the hair, skin, and scale: are in a greal many
produced by the action of an oxydase upon
some chromogenic substance. It is possible that
this chromogenic substance, which is of an aromatic
nature, musl be spUt off from the protein mole-
cule by a proteolytic enzyme before it can be
oxidised.

Further investigations have suggested that an
oxydase is of a dual nature, its two constituents
being a peroxide and a peroxydase. The peroxide
rnbines with the peroxydase (B) to form
an unstable compound (AJ'.O.,). This immediately
breaks down to yield :

(i) An atom of " active " oxygen, O.
(ii) The peroxydase, B.
(iii) The compound A.,0.

The chromogen is oxidised to the pigment by
the " active. " oxygen, whilst the compound A20
is reconverted by atmospheric oxygen to the
peroxide A20.,, so that the cycle can be repeated
indefinitely.

The isolation of the melanins and the determina-
tion of the constitution of the melanin molecule
has presented a problem of extraordinary difficulty
to the organic chemist, and even now a satisfactory
solution has not been obtained. The reasons for
this are chiefly the difficulty of obtaining sufficient
material, or of separating it from the keratin of the
skin and hair which usually surrounds it, and the
lack of strong enough reagents to dissolve the
keratin substance without altering the melanin
molecule. Attempts have been made to obtain
melanin from many sources, such as the skin of
negroes, human and horse hair, sarcomatous livers,
and the choroid coat of eyes ; but except in the last
two cases the melanin has been profoundly altered
in the process of extraction. Lately, however,
in America, a pigment has been obtained by the
long-continued action of very dilute alkalies upon
black wool in a form which evidently resembles more
closely the naturally occurring pigment than any
described hitherto. In this form it dissolves, not
only in alkali, but also in dilute acid, and behaves

in many other ways like a protein substance, or
a substance which is chemically combined with a
protein.

The investigation oi the natural pigments was
originated by the discovery of the black artificial
humins which occur as a cleavage residue during
the acid hydrolysis oi proteins. Recently another
humin has been studied, namely, the product
of the action of tyrosinase upon tyrosine, and
tyrosine itself has been oxidised by strong hydro-
chloric acid to a black substance. These artificial
products seem to bear a fairly close relationship
to the natural melanins, though it is difficult to
determine their constitution accurately. In spite
of the fact that tyrosine so easily yields black
products, it is not necessarily the mother-substance
of the natural pigments, as has so often been
suggested, for there is no reason why tryptophane,
or some other cyclic compound, should not function
equally well.

It may be seen from what has been said that the
black pigments have received the exclusive atten-
tion of investigators, and that the other hair
pigments, of which yellow would seem to promise
most opportunity for research, have been entirely
neglected, f It might be thought that this yellow
substance is connected with the well-known
urinary pigment, urochrome, or else with those
other body ^pigments called lipochromes, which
give to fat butter and blood serum their yellow
colour, and which have lately been shown to be
identical in many cases with the crystalline vege-
table pigments, carotin and xanthophyll. It does
not, however, seem to resemble either of these, and
indeed it is difficult to know whether a true yellow
pigment really exists, or whether the effect is
produced by the density with which the black
pigment has been deposited. For by suitably
diluting a solution of melanin, which is deep brown
by transmitted light and black by reflected light,
it is possible to obtain solutions of various shades
of brown, or even, on extreme dilution, a bright
yellow. The black, chocolate, and yellow pig-
ments show very similar solubilities in both acid
and alkali ; and, moreover, when equal weights
of these three pigments, dissolved in equal volumes
of dilute alkali, are compared by means of a colori-
meter the difference in the depths of the colours
is insignificant.

* It seems probable that only the peroxydase constituent of the tyrosinase can be extracted in this case, since the
addition of hydrogen-peroxide is necessary for the proper oxidation and development of the colour in vitro.

j The beautiful yellow pigment of our common brimstone butterfly has been shown to be a derivative of uric acid,
while the white pigment of cabbage butterflies is nothing else but uric acid itself. The uric-acid pigments are
confined to the Pieridae, and are not present in the wings of the Heliconiidae, which are mimicked so closely by the
Pieridae (genus Leptalis).

DUST.

By WILLIAM SWAINE.

In a certain sense we all know what dust is —
something very plentiful and often extremely
annoying. The housekeeper is plagued very much
with it. She sweeps it off the mantelpiece with
her cloth, but whither does it go ? In most cases
either back again to its old place or on to another
piece of furniture which very probably has only
just been swept clear of it. Since dust is so plentiful
one ought to become extremely familiar with what
it is, what it does, what are its advantages and
disadvantages, and the reason for its being where
it is. But it is very questionable whether we give
it very much thought.

Dust is found over land and sea, but it is obvious
that dust must be more plentiful over the land.
However, Dr. J. Aitken, of Glasgow, has devoted a
large part of his time to the study of its prevalence.
In 1891 he devised an instrument, called a " dust
counter," by means of which he has detected and
counted particles of dust. The following figures
are only very approximate : —

Number of Dust Parts
per c.c.

Place.

2000

600

500-200

Atlantic Ocean
Pacific Ocean
Indian Ocean

As much as
150,000

London, Edinburgh,
etc.

14,000-100 Ben Nevis

Measurements on Ben Nevis have revealed a
diurnal range, maximum in the afternoon (ascending
air currents), and minimum in the early morning.
Approximately for every three thousand feet
ascent the amount becomes four-fifths of the
number at the lower level.

How many dust particles must an inveterate
smoker puff out in a lifetime when with one puff
he expels 4,000,000,000, and what must be the
number from the exhaust of a petrol motor ?

The number of dust particles has lately increased
near country roads owing to the great increase in
motor traffic — as we all know to our cost. Tuber-
culosis has been noticed to have become more
prevalent amongst cattle grazing near a dusty
highway, and in fruit-growing districts the dust
clogs the pores of the leaves, causing thereby loss
to the gardener.

The causes of excessive dust formation on the

roads are chemical, physical, and mechanical, and
to-day methods of prevention are of two classes —
(a) sanitary removal by sprinkling with water or
some suitable hygroscopic solid, and (b) tar-spraying
the roads. The latter method is now largely adopted.
Tar-spraying, however, has its disadvantages.
Thus in a recent paper we read of the Carmarthen-
shire Main Roads Committee considering a claim
for damages from a bee-keeper whose stock, it was
maintained, had all died owing to the tar-spraying
of the adjacent road. Fish in streams have been
poisoned, thus causing an inquiry into the least
injurious tar for tar-spraying purposes. Authorities
appear to agree in their ideas of a future road.
Hubbard suggests " a bituminous concrete surface
with a cement concrete base," and this has been
tried in the United States with reasonable success.
Sir John Macdonald suggests a carpeted road, the
carpet to consist of bitumen and laid on a surface
of stone held together by some pitchy substance.

The main causes in the upraising of dust by
motors, and so on, are (a) cyclonic air currents
produced in the rear, (b) the great tractive force of
the hind wheels, together with (c) their uneven
turning motion.

Dusts are either harmless or harmful. The dust
which flies about the rooms in bakeries and wood
turneries is harmless and, according to some
people, fattening. Coal dust and that which
hangs about the mills of Lancashire and Yorkshire
are more or less harmful. According to certain
authorities the coal miner is least troubled with
lung diseases. Tin miners, quarrymen, potters,
stonemasons, and filemakers are, in decreasing
order of magnitude, subject to respiratory diseases.
Workers in most chemical works are considerably
affected by the corrosive action of the chemical
dusts. A visit to a soap works reveals the pre-
cautions taken by workers near caustic tanks.
Even people outside the works have uncomfortable
experiences with floating particles of caustic.
Then, again, it is only recently that we have had
legislation for the improvement of the conditions
for the phosphorus worker. Even now " phossy
jaw " is not extinct at these works.

In 1863 Tyndall wanted to have air freed from
dust as far as possible in order to carry on some
delicate experiments. This led him to investigate
the nature of dust. He found that if the air in a
chamber were kept still, the dust settled and could
be received as it settled by some suitable liquid,
e.g., glycerine. But it was not freed from dust.
Hence he adopted the plan of passing air over a red-
hot spiral of platinum wire contained in a tube.
This was the purest he obtained. Finding in 1878

103

MM

know LEDGE.

April, 1915.

that do fermentation took place in his dust-freed air,
knowing thai fermentation was caused by germs,
he arrived at the conclusion that there was some

connection between dust and germs. Nowadays
we know that what is usually called dusl is really
multitudes of microbes adherin to genuine dust.
It was to Pasteur's credit thai the " genu theory"
of disease was discovered, and with the intro-
duction of Listerism it has hern asserted that
" more human lives have been saved than the
wars of the last century have sacrificed." The core
of Listerism is the use of the carbolic spray with
which a wound and the neighbouring air are dosed,
thus killing any fatal microbes. Now microbes
cannot live in fresh air and sunlight, and thus
doctors advocate a combination of these two as a
preventive. Again, the number of microbes varies
directly as the number of dust particles ; the
smaller the amount of dust the less the number of
mil robes, and consequently the decrease in pulmo-
nary diseases. What a hotbed of disease must our
dustbins be where organic refuse and coal ashes are
thrown to decompose together ! As has been stated
previously, the higher we ascend the smaller the
number of dust particles, and consequently we see
why mountain air is so beneficial to persons suffer-
ing from consumption.

Physiographical Aspect.
Represented as a short genealogical tree : —
Atmospheric Dust.

Mineral Volcanic Products of Cosmic or

(Salts) (various) Combustion Meteoric

(carbon, sulphur) (chiefly iron)

Dr. J. Aitken was the first to show that when
water vapour condenses in the atmosphere it always
does so on some nucleus, e.g., dust particles. His
dust counter employs this principle. These are
not, however, the only agency. Mr. C. T. R. Wilson
has shown that air which is free from dust, but
ionised, is capable of having water vapour condensed
in it. Very probably phenomena such as fogs,
clouds, mist, or rain are due to both these influences,
dust being plentiful and ionisation caused by the
radio-active elements present in the atmosphere,
and by sunlight. More recently Dr. Aitken has
offered an explanation of fog. If sulphur dioxide
be exposed to a strong beam of white light it decom-
poses, slowly producing a yellow fog of sulphur.
Now sulphur dioxide issues forth with other
products of combustion from the mouths of
chimneys. With the action of sunlight, and a
little moisture in the form of water vapour being
present, a fog is produced. The characteristics of
the London fog are easily explained by this.

The magnificent sunsets which can be seen in
different parts of the Earth, and the reddish colour
at both dawn and twilight, are due directly to the
presence of dust particles and water vapour. In
the morning and evening the light from the Sun

has to travel through the greatest thickness of air
and dust, and since the blue rays are more easily
scattered than the red we have the familiar
gradation of spectral tints seen at these times.
Occasionally there is a second sunset, which is
a reflection in the clouds of a more brilliant primary
one. These primary and reflected sunsets were
much in evidence whilst the Krakatoadust (autumn,
1883) was spread in a layer about fifteen miles
above the surface of the Earth in a broad belt
about the Tropics, lasting an hour or two after the
real sunset. The " Bishop's Ring " was the name
given to the coronae which were formed by the Sun
shining through the dust. These coronae were an
outer edging to the Sun's disc, blue on the inside,
passing through the various colours of the spectrum,
the outermost being red. The sunsets at that time
were unusually vivid, and the story runs of an
American fire brigade setting out to put out an
alleged fire at a neighbouring village from which
the glow appeared to come. But the Krakatoa
eruption is not the only instance. After the Messina
disturbance a few years ago the sunsets attracted
people's attention, and it was noticed in meteoro-
logical circles that our climatal conditions suffered
a change. In 1783 volcanic dust (traced afterwards
from Skaptar Jokul, Iceland) descended on the
Orkneys and Shetlands and North Scotland,
ruining crops. In this way the dust was carried
a distance of over six hundred miles. Coseguina
(Nicaragua), a volcano, in 1835 threw out enough
dust to cause utter darkness for thirty-five miles
radius, and which, when it fell, was ten feet deep.
In four days an upper aerial current carried some
dust seven hundred miles. So-called " mud lavas "
are really the extremely fine volcanic dusts gathered
and mixed by the water, belching forth out of the
crater, and often doing more damage than a true
lava stream.

Cosmic dust is formed by the disintegration of
meteorites owing to friction (they travel from
twenty-five to forty miles per second) with our
atmosphere. The luminosity of shooting stars is
due to the rapid combustion of the meteoric dust
in the train of a meteorite.

The presence of sodium salts in the air is easily
demonstrated by brushing the dust from one's
clothes into a non-luminous flame. The character-
istic yellow of sodium is much in evidence. Very
probably the ocean spray accounts for its presence.
Salts of copper have been detected in city air,
and accounted for by the electric flashes of overhead
cables.

With the chemical we arrive at the most interest-
ing, and perhaps the most important, side of dust
phenomena. Until recently it was considered that
fire-damp was the sole cause of coal-mine explosions,
but experience has shown that within the last ten
years explosions have occurred more frequently in
well-ventilated mines. Thus causes have been traced
to coal dust which, in the presence of air, is very
explosive. Probably the reason is that oxygen

April, 1915.

KNOWLEDGE.

105

in a well-ventilated mine is continually absorbed
by the fine coal dust, whilst the neighbouring air
does not become stale. This combination is very
dangerous. Dr. Harger, at Liverpool, consequently
suggested " a small reduction in the percentage of
oxygen, and the addition of a little carbon dioxide
to such an extent as not to be harmful to respira-
tion, and to render coal-dust ignition impossible."
He further advised the introduction into the mine
atmosphere of flue gases, purified from harmful
gases and smoke. " It would," he said, " provide
immunity, not only from coal-dust explosion, but
from fire-damp explosions, and as regards respiration
would be as good as ordinary air, and for people
liable to consumption better." But the miner does
not relish the idea.

Possible dangers of firing fire-damp, or coal dust,
are : ( I ) Lamps of all descriptions ; (2) electric
leakage causing a spark ; (3) blasting explosives ;
whilst it is advisable that fire-damp should not
accumulate. Professor Thornton has investigated
the danger derived from electric sparking. Messrs.
Sellars and Campbell, at Manchester, have studied
explosions of coal gas and air in the laboratory ;
but perhaps the most practicable investigations
are those employing incombustible dusts as a
means of " quenching " any likelihood of the
spreading of fire by coal dust. Mr. William Gar-
forth, at. Altoft, and Professor Dixon (by Ryalo
Commission), at Eskmeals, are diligently pursuing
inquiries in this direction. Bicarbonate of soda
and stone dust have been found most efficient ;
but the fact still remains that these mineral
irritants, if inhaled, encourage pulmonary diseases.
It is possible, however, to minimise this, and
consequently this does not constitute a serious
objection. Owing to the continual accumulation
of coal dust the stone dust, and so on, must also
be replenished from time to time. The idea of
keeping the inflammable dust constantly wet in
order to render it safe is attended with the serious
objection that the miner would have to work under
very unhealthy conditions. It must be remembered
that the dust must be continually swamped to
prevent drying up ; a state of affairs much worse
than before, since spontaneous combustion is
rendered more likely, especially if any sulphide be
in close proximity.

Referring to dust which accumulates in flour mills
and oil-cake works, Dr. Harger said that ordinary
flour mills were on much the same plane as powder
magazines. To test this in a small way we only
need to enter a flour mill where the cleaner is
sweeping the floors, and to see the disturbed dust
ignite at some burning gas-jet and endeavour to
spread over the whole room. Measurements have
shown us that flour dust is much more explosive
than coal dust. Even bits of iron, when over-
heated by friction, are capable of inflaming this
highly explosive dust, and thus magnetic screens
are now employed to attract any stray bits of iron
which may be present.

Attempts are being made to utilise coal dust
owing to its high calorific value, and it is very
probable that it will some day be used to a larger
extent. Present-day methods of blowing the dust
into furnaces are unsuccessful.

The smoke nuisance dates as far back as Elizabeth,
whilst attempts at abatement have been made by
J. Watt (1785) and Cutler (1815). The causes are
traced to imperfect combustion, due to (a) inade-
quate supply of air, and (b) wrong combustion
temperature. Smoke in itself is not very harmful,
but the sulphuric acid produced from the sulphur
in the coal is very injurious, having a very corrosive
action, and unfortunately it cannot be eliminated by
the various methods adopted for smoke abatement.
The study of rain in different places suggests a
method of determining qualitatively and quantita-
tively the constitution of atmospheric pollution.
Tests with country and town rains show that town
rain is acid, whilst country rain is neutral. Anthra-
cite stoves are a successful attempt at decreasing the
smoke nuisance, whilst experiments are being made
with liquid fuel and electricity. Perhaps in the
future smoke will be a thing of the past, if Sir
William Ramsay's dream comes true, in which our
coal will be burned underground and electrical
energy stored up at the coalfields. At present,
however, the housekeeper can help by using gas-
stoves, although they are not very healthy.

The factory, especially so in copper smelting, is
very wasteful. Taking the case of copper smelting,
a large quantity of metal dust, together with arsenic,
is thrown out with the smelter smoke, having dis-
astrous effects on the countryside. Long flues
have been found to recover a large quantity of
metal, but electrical methods are now employed
to better advantage.

Sir Oliver Lodge in 1884 showed an experiment
at the British Association meeting in Montreal
in which smoke was caused to condense and fall in
fine particles by electrical means. By a similar
process he managed to clear from fog a space of
from fifty to sixty yards radius at Liverpool
University, the potential employed being one
hundred thousand volts, dense fogs being dissipated
quicker than light ones. This has been applied
recently to smelter smoke, and as much as ninety
per cent, of the metal dust can be recovered. The
commercial value "1 dust is only just beginning to
be realised. Wool dust, foi example, is now being
employed as a fertiliser. In the near future will
it be possible to collect road dust in order to extract
the rubber worn from motor tyres, and for it to be
profitable ?

To phenomena dependent on dust must be added
crystallisation and supersaturation — the former
needing its presence, and the latter needing its
absence.

And what would our world appear like if there

no dust ? Very probably the sky would

not have its delicate blue colour, but would be

black, with the Sun glaring down on the Earth

106

KNOWLEDGE.

April, 1915.

without any diffusion, whilst the stars would be
visible during both day and night ; and no gloriously
tinU'il sunrise or sunset for the poet or man of
science to contemplate. On the other hand, no
smoky towns, no dusty highways or furniture, and
no fog. Bui which dusts cause the aesthetic results ?
Chiefly the volcanic and cosmic — those winch we

cannot help. And which dust is it which causes
ns so much annoyance, and which is so familiar?
That which wc can help, by altering our roads, our
locomotion, our domestic fires, and our factories.
However, such is the progress of civilisation, and
truly " God made the country, and man made the
town."

THE MAKING OF GUN FLINTS.

By WILFRED MARK WEBB, F.L.S.

li is interesting at the present time, when the
manufacture of cartridges and shells is of the utmost
importance to the nation, to remember that the
production of gun-flints still goes quietly on.
Thousands arc exported every year, particularly
to tropical countries, where more primitive methods
linger, or are found to be more convenient ; or,
again, where the British Government sees to it
that modern firearms do not get into the hands of
the natives.

There -reins little doubt but that the maker of
gun-flints, or the flint-knapper, as he is called, is
carrying on an industry which has continued un-
broken from very early prehistoric times, when man
first began to fashion implements of stone. It
would appear, nevertheless, at first sight that
there is a fallacy somewhere, and that there must
have been a very long gap between the dying out
of the flint arrowhead and the invention of the
flint-lock musket.

This is true ; but it must be remembered that
the flint in the guns was put there to produce
sparks, and was only an adaptation of the strike-a-
lights which all through the ages, and even within
the memory of many persons still alive, have been
used for the purpose of obtaining fire.

There is, indeed, a considerable family likeness
between the flints made for the tinder-box and
the prehistoric flint implements which are known
as " scrapers " (see Figures 82 and 90).

The work of flint-knapping as it is carried on at
Brandon, in Suffolk, is briefly this. The flints are
taken out of pits, as surface material is refractory
and of little use. The picks used, though now made
of iron, show by their shape (see Figure 80) that
they have been modelled upon the primitive deer-
antler picks which have been found in prehistoric
workings. Figure 83 shows the breaking up of the
large flints with a heavy hammer into convenient
sizes, a process which is called " quartering" (see
Figure 8-1). From the lumps thus made flakes
are struck off with a lighter hammer, which are in
every way comparable to the flakes struck off by
prehistoric man from one stone with another.

It will be seen by looking at the core represented
in Figure 85 that it is possible to produce a flake
with one ridge running down the middle and two

sharp edges, or by removing the whole of one facet
and part of the two on either side a flat flake with
two sharp edges may be obtained. Several of the
latter arc shown in Figure 81. In the one of the
extreme left hand of the picture the under side of
the flake is seen, with the bulb of percussion at the
top. This is caused by the blow, and is familiar
enough in prehistoric flakes. The second specimen
shows the old facet, and the third is a flake which
has been cut up with the knapping hammer.

A knapper at work is shown in Figure 88, while
an enlarged illustration, to show details of this
important part of the work, is given in Figure 86.
The knapper holds the flake on the top of a wedge-
shaped piece of iron, driven into a block. In front
of the iron is a piece of leather, over which the
knapping hammer is held. This is a very light
tool, nowadays made, as a rule, from an old file,
and has thin, square ends. With this hammer it
is possible to cut the flake into pieces to form the
gun-flints, which are afterwards trimmed round
with a few dexterous blows.

To the student of flint implements, who is
astounded sometimes to see the minuteness of the
flakes which have been removed from the edges of
a flint knife or arrowhead, and wonders how the
work was done, it may be pointed out that one
blow of the knapping hammer may make dozens
of these ; and it is safe to surmise that the pre-
historic artificer was no less clever than his modern
representative, and much of the beauty of finish was
obtained by a few well-directed blows, and not by
much laborious chipping.

According to the sizes of the flakes, gun-flints
of various dimensions can be produced. The largest
are for cannon flints, and one of these is seen in
Figure 87, which also depicts gun, musket, carbine,
and pistol flints.

The photographs from which our illustrations
were made were obtained at the works of Mr. Fred
Snare at Brandon. Gun-flints are also made in
France, and these, as a rule, have one end rounded.
Mr. Snare also makes strike-a-lights, for flint and
steel are still used instead of matches in some parts
of the world, and it may be remembered that during
the Boer War many tinder-boxes were sent out to
our soldiers in South Africa.

April, 1915.

KNOWLEDGE.

107

Figure SO. The Pick used for getting Flint, and the various Hammers employed by Flint Knappers.

Figure 81. Flint Flakes entire, cut up. ami trimmed to form Gun Flints.

FiGUR] 32.

Prehistoric Scraper:

Modern Strike a I

108

KNOWLEDGE.

Al'RIL, 1915.

Figure 83. < fuartering

•

1 *

Figure 85. A ( ire.

E 8 1. Flaking.

Figure 86. Cutting up a Flake.

April, 1915.

KNOWLEDGE.

109

Figure 87. Cannon and Gun Flints.

Figure SS. Knapping.

Figure 89. Flint packed foi export.

FiGl Ri 90. Flint, steel, and fuse.

no

KNOWLEDG1

s

April, 1915.

w

N
FIGURE 91. 1915, February 25d. 12h. 14.5m.

W

FIGURE 92. 1915, February 26d. llh. 41m.

A ( iroup of Sun Spots.
From photographs kindly lent by the Astronomer Royal.

SOLAR DISTURBANCES DURING FEBRUARY. 1915.

By FRANK C. DENNETT.

Owing to cloud no observations were possible on five days,
February 2nd, 3rd, 7th, 13th, or 17th. On the remaining
days the disc never appeared free from spots. Spot dis-
turbances were more in number than in any month since
the autumn of 1910. The longitude of the central meridian
at noon on February 1st was 42: 52 '.

Xo. 10 of the January list remained visible until Februarv
6th, and therefore reappears upon our chart.

Xo. 11. — First seen on the 4th, as a somewhat distorted
elliptical outbreak, thirty-nine thousand miles in length,
increasing until on the 6th it was fifty-six thousand miles.
On the 8th only a small two-umbrae spot was visible, but
from the 9th until the 12th, when last seen, it was a long
group of about eight spotlets and pores.

Xo. 12. — On the 4th a solitary spotlet, but preceded next
day by pores, which on the 6th were arranged as on the
diagram. On the 8th and 9th a small leading spotlet with
a trail of tiny pores eighty-four thousand miles in length.
On the 10th and 11th two small spots were followed by a
group of pores. Last seen on the 12th.

Xo. 13. — Two pores only seen on the morning of the 4th.

No. 14. — A spot fifteen thousand miles in diameter,
just round the south-eastern limb on the 5th, having two
umbrae from the 8th until the 11th, and a line of three
pores on its northern side on the 15th and 16th. Last seen
on February ISth.

Xo. 15. — A fine spot first seen well round the north-
eastern limb on the 8th ; on the 10th its penumbra had
increased to a diameter of over thirty thousand miles,
and in the faculae following it two pores had appeared,
as shown on the chart. On the 11th part of the penumbra
had broken off. and three pores were closely east of it, the
more distant ones having disappeared. Only one or two
pores seen near it afterwards ; last seen at the limb on the
20th.

Xo. 16. — Three spotlets on the 9th, but on the 10th a
train of nine, as shown on the chart, sixty-three thousand
miles in length. The numbers were less on the 11th ; it
was seen until the 14th.

No. 17. — A small spot seen from the 10th till the 12th ;
there was a pore twenty-five thousand miles following it.

Xo. 18. — First seen as pores amid brilliant faculae
within the south-eastern limb on the 20th and 21st. A curved
group on the 23rd, fifty thousand miles in length. By the
25th the leader had grown to sixteen thousand miles in
diameter, and was a singular-looking object; the northern
trailer was also of peculiar formation ; the whole group was

altering its appearance rapidly. It was last seen on March
2nd. The Astronomer Royal has kindly supplied two photo-
graphs of this group, taken on February 25th and 26th,
which are reproduced in Figures 91 and 92. Unfortunately
the air was not in favourable condition for photographv on
the 25th.

Xo. 19. — Seen on the 21st as a close pair of spotlets. On
the 23rd a line of three pores close together, with a smaller
one following, the length of the disturbance being forty-
two thousand miles. Last seen next day as a solitary
pore in a faculic cloud.

Xo. 20. — When first seen on the 23rd a spot ten thousand
miles in diameter, with a pore to the south-east, making the
disturbance sixty-four thousand miles in length. This pore
was not seen after the 27th ; but on March 2nd there were
three pores west and south, and on the 3rd others showed
south-east as well, but too small to measure The spot last
seen on the 5th, faculae marking the position until the limb
was reached on the 8th.

No. 21. — A larger pore, followed by three much smaller
ones, seen on the 25th, subject to constant change. Last
seen on March 2nd.

Xo. 22. — Two spotlets, bright-lipped, only seen on the
26th, nearing the south-western limb.

No. 23. — A spot fifteen thousand miles in diameter,
just within the limb on the 26th, with fine faculae following
it on the 27th. On March 2nd the umbra was crossed by a
bright bridge. On the 7th the umbra was of the form of a
hook. When last seen, on the 10th it had a smaller com-
panion a little to the south.

No. 24. — Two spots and two pores between them had
broken out close to the central meridian on the 27th. The
leader some ten thousand miles in diameter, and the trailer
afterwards marked by pores until last seen on March 2nd
Its length was forty-three thousand miles.

No. 25. — A spot sixteen thousand miles in diameter
came round the limb on February 28th. seen to possess
two umbrae on March 6th, last seen on the 10th, only
faculae being seen in its place on the 1 1th.

Faculae were recorded near the west limb on Februarv
20th ; north-west on 1st, 6th, Sth, and 24th to 26th ;
north-east on Sth, 16th, 18th to 20th, 24th, 27th, and 28th :
south-west on 4th and 10th; and south-east on 18th to 20th,
25th, and 26th.

Our chart is constructed from the combined observations
of Messrs. John Mcll.irg. W. J. Waters, and the writer.

DAY OF FEBRUARY, 1915.

«.

3.

.

u

-

:»

■;

t.

21

•••

:

:a

'?

11

7

it

l

*

.1

.

1

1

&

2

i

s

20

ia

11

>»

,:-

b

1'

1 •

r

*

'

:

1

' 1

•w

,°

H

V

-

11

<

V

. N

I . ;■

1

21

19

ft,

'7

t

-i —

1

j

16

N

0 10 «) X) to so tt 10 • e iff » m w no m « wo «o no x x .1 30 v x > M ,tc t

B 111

NOTES.

ASTRONOMY.

I'.y A C. D. Crommelin, B.A., D.Sc, F.R.A.S.

llll DISTRIBU1 CON OF ALGOL-STARS IN SPACE.

'I Inn- is .hi article mi tins subject in The Astropk}
Journal, December, 1914, by II. N Russell and II. Shapley.
The s] " gives the masses, ami tin- type <>i spectrum

also gives the probable surface brilliancy. The absolute
magnitude can be deduced with some confidence: this
compared with the visual magnitude gives the distance
u is estimated that the uncertainty is not more than
twenty-five per rent.). The mean parallax of the ninety
stars discussed is .,,',-/'. implying a distance of 300 parsecs,
or 972 I..V. The mean of the distances, however, comes out
as 24001 Y ["he method gives 125 L.Y. for Algol, 109 L.Y.
for /j Aurigae. Din 1 1 measures of their parallaxes give
67 L.Y. and 95 L.Y. The agreement is tolerably good.
\V UrsaeMajoris(164 L.Y.) and R Canis Majoris (180 L.Y.)
also seem to lie within a measurable distance, but all the
others are very remote. They show a considerable con-
centration towards the galactic plane. Thus seventy-five
of the ninety stars lie within 30° of this plane — on uniform
distribution there would be only forty-five. The same result
holds for the linear distances from the galactic plane.
The average distance from this plane is about 450 L.Y.
The distances have been calculated on the assumption that
there is no absorption of light in space. Evidence is accumu-
lating that the absorption is sensible but small. Using
King's value of the absorption, the three greatest distances
of stars from the Sun, which before were given as 17200 L.Y.,
12400 L.Y., 7900 L.Y., are reduced to 4900, 4200, 3200
respectively. The average distance of all the stars dis-
cussed from the galactic plane is now reduced to 280 L.Y.

A similar investigation has been made for the Cepheid
variables : this was partly done by Hertzsprung, and has
been completed by Russell and Shapley. They prove to
be on the average one and a half times the distance of the
Algol variables. This is explained by their enormous
intrinsic brightness, so that they can be seen at a much
greater distance. Both classes of variables agree in in-
dicating that our stellar system is comparatively shallow
(perhaps not more than 1000 L.Y. in thickness) towards the
galactic poles. The median plane of the stellar system
appears to be somewhat to the south of the Sun, perhaps
some 50 L.Y. distant from it. This is probably the reason
of the greater richness of the southern hemisphere in bright
stars.

There are two other articles by H. Shapley in the same
magazine. One deals with additional variables in the cluster
Messier 3 (in Canes Venatici). S. Bailey had already found
at least one hundred and ten variables in it, their periods
being all under eighteen hours. He could not investigate
the centre of the cluster, as the star images coalesced there.
The great separating power of the sixty-inch mirror at
Mount Wilson, when used as a Cassegrain, has now permitted
the photographic scrutiny of the central region, and Mr.
Shapley now announces at least twenty-three new variables
within a minute of arc of the centre. The brightest maxi-
mum of these new variables is magnitude 14-3, the faintest
minimum is magnitude 17-4. In some cases the range of
variation is half a magnitude ; in others nearly two mag-
nitudes.

Mr. Shapley also discusses Cepheid variables, showing what
grave difficulties there are in the way of explaining these
by any hypothetical arrangement of pairs of stars. The
conclusion is that they are real pulsations in single stars of
ellipsoidal figure, either periodic rushes of heated gases
from the interior or periodic ebbs and flows of heat, causing
th( type of the surface to fluctuate.

Mr. II. Shapley also writes in No. 86 of The Contributions
of Mount Wilson Observatory on the effei I of the darkening
near the limb in Algol stars. It is well known that the disc
of our Sun is much less luminous at the edges than in the
centre. The effect is probably less in Sirian than in Solar
stars, but it would still be sensible. In the Algol system
neglect of this darkening makes the bright star the smaller,
but taking it into account the diameters may be equal. The
Supposed third star which causes a perturbation with period
of 1-9 years is also discussed. Its light may amount to
one-quarter of that of the whole system, but not more than
this.

MELLISH'S COMET— The orbit of this comet has been
deduced by Messrs. Andersen and Fischer, of Copenhagen.

Perihelion 1915, July, 25-109 Berlin M.T.

Arc from Node to Perihelion ...

239 13

Ascending

STode

75 28

Inclination

51 51

Log. perihelion distance

0-0747

Ephemeris

for Berlin midnight

—

R.A. S. Dec.

Log. r.

Log A.

Mag-

h. m. s. o

nitude.

April 10 ...

18 14 8 3 7

0-2952

01635

8-1

,, 26 ...

18 31 18 7 39

0-2555

0-0455

7-4

May 12 ...

18 47 50 16 39

0-2138

9-9013

6-4

,, 28 ...

19 6 25 35 39

01715

9-7428

5-4

June 13 ...

19 49 13 68 53

01314

9-6604

4-9

,, 29 ...

5 28 56 78 58

0 -0983

9-7365

5-0

July 15 ...

6 31 33 63 11

0-0782

9-8527

5-4

„ 31 ...

6 40 55 55 4

0-0763

9-9432

5-9

Aug. 16 ...

6 40 54 50 42

0-0930

O-0036

6-4

The comet will be visible in England till the middle of
May, by which time it will probably be faintly visible to
the naked eye. The brightness in June and July will prob-
ably be greater than that given above, which takes no
account of the physical brightening that usually takes place
on approach to perihelion. It is hoped that our readers
in the southern hemisphere will be able to obtain satis-
factory observations.

The recovery ot Metcalf's Periodic Comet, recently
announced in " Knowledge," proved to be an error. The
object observed was the asteroid Lampetia.

BOTANY.

By Professor F. Cavers, D.Sc, F.L.S.

INDIVIDUALITY OF THE CHROMOSOMES IN
PLANT NUCLEI. — A melancholy interest attaches to
a recently published paper by Sharp (La Cellule, Volume
XXIX), which represents one of the last pieces of biological
research done in the University of Louvain before the
destruction of that town by the Germans. It deals with
the much discussed question of the individuality of the
chromosomes of the nucleus, a subject which has during
recent years received a large amount of study at the
Louvain laboratory by Grdgoire and his pupils, who have
maintained that the chromosomes retain their individuality
throughout the nuclear divisions that occur in the life of
the organism, and are not fused together permanently
when the nucleus goes into the resting condition between
its divisions. Sharp claims that in many cases, in the cells
of the Broad Bean plant which he investigated, the chromo-
somes can be identified even in the resting nucleus, and
that some of the stages leading up to the splitting of the
chromosomes have been misinterpreted by previous investi-
gators, who have also overlooked important stages. Accord-
ing to Sharp, the actual splitting takes place at a later

112

April, 1915.

KNOWLEDGE.

113

stage than has been supposed ; and, if his observations are
correct, they strongly support the theory of the individuality
of the chromosome — a point of considerable importance in
connection with questions of heredity, since it is generally
agreed that hereditary qualities are carried by the chromo-
somes, while various questions in inheritance depend upon
the question whether the chromosomes do or do not retain
their individuality.

BIOLOGY OF FEGATELLA (CONOCEPHALUM).—

It has been shown by several writers that Marchantia,
Fegatella, and some other members of the Marchantia
family of Liverworts are capable of growing in water or in
saturated air and in extremely feeble light, and that
under these conditions the thallus structure is greatly
simplified. The characteristic air-chambers, containing
green assimilating filaments, become reduced in extent
and simplified in structure in the branches formed in such
wet and dark conditions, and the chambers may be absent
altogether, the whole thallus also becoming longer and
narrower, though chlorophyll is still formed. Miss May-
brook (Sew Phytologist, Volume XIII) has studied the
modifications in the thallus of plants of Fegatella (Conoce-
phalum) conica, a common Liverwort found chiefly beside
streams and in other moist places. Her plants were collected
from a small cavern in a hedge-bank, and she has worked
out, in a very interesting manner, the relation between the
structure of plants growing in different light intensities.
She concludes from her observations that the absence of
air-chambers from the plants found in the wettest and
darkest positions is due to the combined effects of darkness
and moisture, since in plants growing in decreased intensities
of light there is a gradual decrease in the number of chambers
per unit of thallus surface and in the size of these chambers.
The internal structure of the thallus shows interesting
deviations in structure ; for instance, diminished length of
the curious beak-like cells which normally terminate the
assimilating filaments. The final disappearance of the
chambers is apparently dependent upon the moisture
factor, for only in those plants showing marked adaptation
to a moist habitat were the chambers totally undeveloped,

CHEMISTRY.

By C. Ainsworth Mitchell, B.A.(Oxon), F.I.C.

FLUORINE IN MINERAL WATERS.— Recent in-
vestigations of MM. Gautier and Clausmann (Bull. Soc.
Chini. de France, 1914, No. 15) have shown that all mineral
waters contain fluorine, the proportion being greatest in
waters of volcanic origin. Thermal alkali bicarbonate
waters are particularly rich in the element, although the
proportion does not appear to depend upon the temperature.
Speaking generally, mineral waters of the same kind show
an increase of fluorine accompanying a rise in the total
salts. In the case of calcium sulphate waters, whatever
their origin, the amount of fluorine is about two milli-
grammes, while sea water contains about three milli-
grammes per litre, the proportion varying slightly in
different places and at different depths.

THE COLOUR OF METALS.— Various facts in support
of the theory that all metals are naturally of the colour ol
silver are given by Dr. L. Martiouchck in a Russian chemical
journal, and his communication is abstracted in the Bulletin,
Sociiti Chimique (1914, Volume XVI, page 751). The yellow
tint of certain metals, su< b ai i alcium, has been found to
be due to the presence of traces "I impurities, the pure
metal being silvery white. Heine has also shown that
when copper is spcciallv purified it becomes oi a paler
tint, the red colour being apparently the result oi oxidation
caused by the presence of lead oxide. Moreover, the metals
potassium, sodium, and rubidium are of a yellow colour
when obtained by reducing their chlorides with calcium
in the presence of air. In this case the yellow tint is due
to the nitrogen, and not to the oxygen, in the air.

POTASH FROM HEDGE CLIPPINGS— Mr. E. J.
Russell calls attention in the Journal, Board of Agriculture
(1914, Volume XXI, page 694) to the high proportion of
potash contained in the ash of bonfires of hedge clippings,
weeds, and the like. Samples contained about eleven per
cent, of potash (ICO), or nearly as much as kainite. which
contains about 12-5 per cent. Hence the ash obtained in
normal processes of the form would be worth about forty
shillings per ton in normal times, and much more under
the present conditions. It is pointed out, however, that
precautions must be taken to protect the ash from the rain.
since the potassium salts in the ash are readily soluble
in water. For example, the potash in a heap of ash was
reduced by fifty per cent, after a single night of moderate
rain. It is calculated that the hedges from a twenty-acre
field would yield an amount of ash equivalent to nearly
two hundredweight of kainite, and that the labour of
obtaining and burning the clippings would amount to
threepence to eightpence per pound of ash. Hence the
potash in this form would be expensive if the whole of the
operations were specially done for the purpose ; but where
the trimming and so on have to be done in any case, the
value of the ash would repay the cost of collecting the
clippings.

AN OXIDISABLE VARIETY OF NITROGEN.— It has
been found by Mr. T. M. Lowry(PM. Mag., 1914, XXVIII.
412) that air that has been subjected first to a silent and
then to a sparking electric discharge shows the spectrum
of nitrogen peroxide, apparentlv formed by the oxidation
of a variety of nitrogen produced under the influence of the
discharge. After a few seconds this oxidisable kind of
nitrogen reverts to a form which can no longer be oxidised
either by oxygen or by ozone, and it is suggested that this
momentary production of modified nitrogen may play an
important part in the technical processes of fixing atmo-
spheric nitrogen. The chemically active form of nitrogen
discovered by Mr. Strutt, and described at the time in
" Knowledge," cannot be oxidised by ozone under the
conditions described.

GEOGRAPHY.

By A. Scott, M.A., B.Sc.

LLASSIFICATION OF SE1 UMENTS.— Although the
chief characteristics of the various types of sediments are
fairly well known, a paper by A. C. Trowbridge (Jour.
Geol., May-June, 1914), in which these characteristics are
presented in a tabular form, should prove very useful in
the examination of the varii ius dep sits now being laid down
on the Earth's surface. Sediments arc divided into aeolian,
fluvial, pluvial, talus, glacial (including till and lluvio-
glacial), lacustrine, and marine deposits including shallow
and deep water). Instead of a division into littoral and non-
littoral, lacustrine deposits are divided into those of agitated
waters, and those of quiet waters. Similarly, shallow-water
marine deposits are classified into those >>t major agitation
and those of minor agitation, the former resembling the
near-shore lacustrine ami the latter the still-water
lacustrine, save in the nature of the tossils Emphasis in-
laid on the " lens and pocket structure " of fluvial di
and on the intermediate nature of Quvio glacial sediments,
which are similar texturally to the fluvial, and lithologically
to the glacial.

STREAM PIRACY -Three interesting case-, showing
oi development oi the " int type

.•I rivei capture, are described in the Publications of the
University oi Virginia N i 20, July. 19141 The first case
occurs m a rejuvenated river system, where the main stream
is entrenching itself, and at the same time approaching,

by lateral Cutting, a tributary, the junction with which is

at presenl "in- and .< quartei miles lower down. In the
second e.i";e, both the main and tributary streams are

Ill

KNOWLEDGE.

April, 1915.

meandering, and two meandei are laterally cutting towards
each other, thej have not yet joined on the surface,

the intervening rock, which is limestone, has been undercut

b .in i mi ut ili.it .1 tunnel has been formed from t ho

mi. mi to the other. In the third case, the junction

oi two stn n moved one and three-quarter

miles upstream 1>\ intercision, due to the cutting through

"( .1 ridge of chert winch formerly eparated two meanders.

SHAl'l I'l Mil \M\KtTIi i oXTINENT.— Prob-
ably the most discussed point in Antarctic physiography has
been the que tion as to whether there is one continent or
two; that is, whethei there is a continuous range from
Graham land to South \ ictoria Land, or whether, as sug-

I by Mawson, Graham Land is united to King Edward
\ II I and, and separated by a faulted trough or rift valley

\ ii toria Land. The evidence has been discussed by
i .i lllith . Taylor (Gcog. Join .. ( fctobei , November, December,
1914), who reviews both the geological and physiographic
data. The rocks of Prince Leopold Land arc like those of
South Victoria Land. Further, a comparison with the
Australian coastal type points to the conclusion that the
West Antarctic cordillera continues to King Edward VII
I ind, with an intermediate broad belt of lowland — the
ner— corresponding to the Tasman Sea between
Australia and New Zealand. Another point in favour of
tins idea is that the Victoria Land mountains belong to the
" Atlantic. " or " subsidence " type, whereas Graham Land
belongs to the " Pacific " type, which may be continued
from the Andes by the South Georgian loop. The Royal
Society Range is probably caused by a late Tertiary- fault,
while the foothills seem to be a typical " Scnkungsfeld "
area.

ANTARCTIC GLACIER TYPES.— In the same paper
an elaborate account is given oi the ice-fields of the Antarctic
continent. Several types of glacier occur in close juxta-
position. Of those with large alimentation the great ice-
i i p. which is between two thousand and three thousand
ei I thick, has been shown to have but little movement.
There are several piedmonts, the largest being the Wilson
and Putter Point glaciers, which are probably residual
from a former glaciation. There are also the large outlet
glaciers and numerous small col and dendritic or tributary
ones. All the forms of glacial action are well shown by one
or other of these types. Thus, the action of the ice-cap
and of the piedmont lobes is mainly protective. Glacial
erosion, as commonly understood, is evidenced by the
outlet glaciers, while " sapping " action, or cirque erosion,
generally occurs on the steep slopes of the Royal Society
range. An account is also given of the various stages of
cirque formation and of glacial deposition. One interesting
deduction is that the present conditions in South Antarctica
are very unfavourable for glacier erosion, as well as for
cirque erosion, which requires rapid alternations of freezing
and thawing.

THE GULF STREAM. — In the same journal, Commander
Hepworth discusses the origin and course of the Gulf Stream.
Most ocean currents have a close connection with atmo-
spheric currents, though the Earth's rotation is also a power-
ful factor. The north-east and south-east trade winds give
rise to a drift current, which develops into the north and
south equatorial currents. The Gulf Stream is primarily
due to components of those which find their way into the
Caribbean Sea; thence past Yucatan into the Gulf of
Mexico, and finally through the Gulf of Florida. The other
hypotheses as to its origin, based on temperature differences,
on the silt brought by the Mississippi, and so on, are shown
(o be untenable. One interesting fact is the daily and
monthly variation in the velocity, which has been correlated
with the variation in the heights of the tides. While it has
been maintained that the Gulf Stream disappears when it
comes into contact with the Labrador current, it is more

probable that it can be traced as far north-cast as Spitz-
bergen and the Barents Sea. This is borne out by the
evidence of the plankton and also by the occurrence, in
these regions, oi warm water oi high salinity, such as is
typically found in the Cull Stream. The results of a series
of investigations of the relations between sea temperature
and air temperature, extending over the last ten years,
indicate that no important temperature changes have
occurred in the North Atlantic within historical times.

GEOLOGY.

By G. W. Tyrrlll, A.R.C.Sc, F.G.S.

THE ORIGIN OF THE BRIGHT AND DULL
LAMINAE OF COAL.— In the December number of The
Journal of Geology Mr. T. E. Savage discusses the origin
of the bright and dull laminae which make up the mass of
an ordinary coal, with especial reference to the coals of
Illinois. Any theory of origin has to explain the extreme
regularity and wide horizontal extent of these laminae
(over several hundred square miles in Illinois) ; the alter-
nation of the bright and dull layers ; the predominance of
mineral charcoal and of plant spores in the dull laminae ;
and the numerous pinnae and pinnules of ferns in the midst
of mineral charcoal fragments. Mr. Savage's views on the
accumulation of coal-beds may be summarised as follows :
(1) The vegetable accumulation began in very shallow
swamps. (2) That, as the swamps deepened gradually, the
accumulation kept pace with the increasing depth. (3) In
oft-recurring cycles of drought, successive levels of the
vegetable mass were exposed to the air, and were so modified
by partial atmospheric decay as to result in the formation
of the dull laminae with their mineral charcoal. The bright
laminae would thus be formed by decomposition out of
contact with air. Quoting Mr. Savage in the above-
mentioned paper : " The dull laminae and mineral charcoal
partings of the coal-beds are the records of repeated inter-
ruptions of accumulation, during which the surface of the
vegetable material in the swamp was above water and
exposed to atmospheric decay, resulting in the destruction
of the softer parts of the plant tissues, leaving them in an
indurated and more or less skeletonised and fibrous con-
dition. On resubmergence these residual portions of the
vegetable materials were not so readily impregnated with
the fundamental matter of the bog as were those parts of
the mass that had not suffered partial atmospheric decay,
and hence are of dull appearance. Such periods of arrested
accumulation of the plant material, due to the exposure of
the surface of the vegetable matter of the bog, would be
favourable for the accumulation on such a surface of a
relatively larger proportion of spores than would be mingled
with the vegetable mass during periods of submergence and
of normal vegetable growth in the bog, and the resistant
nature of the spore cases would permit their better pre-
servation than the ordinary plant tissues during such times
of exposure. These conditions would explain the greater
abundance of spores in the dull than in the bright laminae
of the coal-beds. The variation in thickness of the dull
laminae would be due to the unevenness of the surface
of the exposed vegetable matter in the bog." These con-
ditions also explain the alternation of the bright and dull
layers, and their wide extent, since they were coterminous
with the boundaries of the swamp itself.

METEOROLOGY.

By William Marriott, F.R.Met.Soc.

THE WEATHER OF APRIL— Although April is the
mid-spring month, when some warm and genial weather
may reasonably be expected, yet there is perhaps no other
month in which we are exposed to such great and sudden
changes of temperature. The increasing power of the sun's
rays and drying north-easterly winds cause excessive
evaporation. Some days may be warm and genial, while.

April, 1915.

KNOWLEDGE.

115

on the other hand, days of wintry rigour are experienced,
with heavy showers of hail or snow. Hence the old saying
" Changeable as an April day."
April was a very cold month in the years 1860, 1S79,
1SS1, 1884, 1SSS, and 1908 ; and it was' very mild in the
years 1844, 1865, 1869, 1874, 1893, and 1894.

The average mean temperature at Greenwich for April
is 47°-3 ; in 1865 it was as high as 52:-9; while in 1860 it
was as low as 43-3. The average maximum temperature
is 57-2; the highest mean was 66"-3, in 1865, and the
lowest 51°-7, in 1908. The average minimum temperature
is 39° -0 ; the highest mean was 42-5, in 1850, and the
lowest 34°-2, in 1852. The absolute highest temperature
recorded was 81°-5, in 1865, on the 27th, and the absolute
lowest 23° -0, in 1847, on the 17th. The average number of
da}"s on which the temperature falls to or below the freezing-
point is three.

The average rainfall for the month of April is 1 -61 -in. .'
the greatest amount was 4-35-in., in 1829, and the leasl
006-in. in 1817. The heaviest fall in one day was 1 50-in..
in 1910, on the 16th. The average number of " rain days "
[i.e., on which 01-in. fell) is 12-0 ; the greatest number of
days was twenty-one. in 1848, and the least two, in 1852.

The average amount of bright sunshine at the Kew
Observatory, Richmond, is one hundred and fifty-two
hours, or about five hours per day.

The average barometric pressure in London for April
is 29-933-in. ; the highest mean was 30-308-in., in 1817,
and the lowest mean was 29-590-in., in 1829.

" April showers bring forth May flowers."

THE RAINFALL OF 19 T4— Dr. 11 R. Mill, the Director
of the British Rainfall Organisation, in his account of the
principal features in last year's rainfall, says that the note-
worthy features of the monthly rainfall were the prevailing
wetness of the four months February, March, November,
and December. Of these February was wettest in Ireland,
and December in Great Britain. The rainfall of December
was exceptional in all parts of the Kingdom, but especially
so in the South of England, where it was probably unpre-
cedented in this respect. Of the remaining months, January
was everywhere dry. and, following an unusually dry De-
cember, gave a character to the midwinter season of 1913-
14 greatly in contrast with that exhibited in the same period
of 1914-15. From April to October the rainfall was in
general well below the average, though local thunderstorms
in England brought the general fall of July slightly above
the average, whilst that of August was above the average in
Ireland for a similar reason. The persistent dryness of the
seven months, and in particular the small rainfall of ( ►ctober,
which was the driest month of the year, was probably as
abnormal as was the great rainfall ol December. Taking
the British Isles as a whole, it appears that the rainfall for
the year was six per cent, above the average, and so 1914
must be classed as a moderately wet year.

AUSTRALIAN WEATHER, 1911 —The following are
the results of some of the observations t"i the year 1911
at several of the principal towns in Australia as given in
The Monthly Weather Report recently issued by the Common-
wealth Bureau of Meteorology : —

Mean Sunshine

Temperature Rainfall Evaporation. Hours.

in. in.

Perth 63-2 ... 23-38 ... 66-34 ... 2961

Alice Springs 70-0 ... 7 09 ... 97 10 ... —

Adelaide 62-9 ... 15-99 ... 48-14 ... 2415

Brisbane 69-3 ... 35-20 ... 4l>34 ... 2510

Sydney 63-4 ... 50-24 ... 37-45 ... 1996

Melbourne 58-6 ... 36-61 ... 38-87 ... 1755

Hobart 54-6 ... 26-78 ... 31-98 ... 195(1

MICROSCOPY.

By J. E. Barnard, F.R.M.S.

LIGHT-FILTERS.— The wave-length of the light used
for illuminating purposes has a very definite influence on
the resulting microscopic image. A filter may be selected
for one of three reasons : to improve the correction of the
optical system — and this applies to both the substage
condenser and the objective — to increase or decrease con-
trast in the image, or to increase resolving power. It is
possible to combine, at least in part, all three qualities
n one filter, although it is obvious that to obtain the best
result each factor must be dealt with independently. In
these days, objectives are so well corrected that the visual
image is almost free from any very definite colour aberration
but under certain exacting conditions it may become evi-
dent. A filter which will cut out the particular colours for
which the objective is not corrected can easily be made.
It may be assumed that objectives are corrected for that
part of the spectrum which has the highest visual luminosity,
the region of the green, yellow, and blue-green. It follows
that if the colours at the extreme ends of the spectrum
are eliminated — the red and violet, for instance —
the resulting image will be free from any outstanding
colour. There is no better filter for this purpose than that
known as Gifford's F-line screen. It is made by dissolving
malachite or methyl-green in hot glycerine, the strength
of solution depending on the thickness of screen used. In
addition, a thin piece of signal-green glass must be immersed
in the cell, to cut out the outstanding red which otherwise
passes. Alternatively, the cell may be made up with one of
its sides of signal-green glass, that is, if the cell is of the type
which can be taken apart for cleaning purposes. The only
objections to the Gilford screen are that the dyes mentioned
are not very stable in solution, and that the luminosity
of the screen is not high, as its maximum transmission is
in the blue-green. A screen that is quite permanent, and
that has higher luminosity, is Zetnow's filter. This is
perhaps the most useful of any, either for visual or photo-
micrographs purposes. It allows light of wave-lengths
between five hundred and seventy and five hundred and
fifty micro-millimetres to pass. It is made by dissolving
ten grammes of pure dry cupric nitrate and cue gramme of
chromic acid in fifty cubic centimetres of distilled water.
The thickness of liquid should be one centimetre. If it is
not convenient to have so thick a cell, the solutions may.
of course, be more concentrated, the relative quantities of
each substance being maintained. Another method is to
keep read}' saturated solutions of copper sulphate and
bichromate of potash, and to mix them as required A
precipitate is thrown down, which dissolves in glacial
acetic acid. The screen may thus be varied from yellow-
green to blue-green to suit the objects under examination.
The influence of a suitable screen on resolution is well
known, although it is perhaps not so thoroughly realised
in practice as it might be. Resolution is dependent on the
wave-length of the light used in the medium between the
object and the front lens of the objective, and on numerical
aperture. The latter factor is a constant, that is. assuming
that the full aperture of the objective is utilised The former
is a variable, and. in the ca>r • •! white light. i> the
mean wave-length of the light emitted by the radiant.
Reduction of the mean wave-length therefore, by cutting
out the red. for instance, increases possible resolution.
By using a screen which effectively cuts out the red and
yellow, improvement may be effected The method i-
tairlv obvious, but further reference to the matter will
be made in this column in succeeding numb

THE QUEKETT MICROSCOPICAL CLUB.— The five
hundred and fifth ordinary, which was also the forty-ninth
annual, meeting of the Quekett Microscopical Club was
held on Tuesday, February 23rd. at 20, Hanover Square,
W., the President, Professor Arthur Dendy. D.Sc, F. R.S.,

116

KNOWLKDGK.

April. 1915.

invited Prt Minchin to occupy the chair, and

gave in- annual address. The title wai "The Biological
ption "i Individuality. " Professor Dendy observed
that probably most ol us think that we can recognise
and define an individual, but that, though this is
true >>t an individual man or dog, or an individual
oak tree 01 cabbage, ii we cans- our investigations below
the mii (ace, we find many cases thai are not a little puzzling,
and the purpose ol the address "as to enquire whether it
i- really possible to frame a definition oi individuality,
from a biological point of view, that will be of general
applicability throughout the animal and vegetable king-
doms. There appeared to be two main paths by which the
problem could be approached : the morphological and the

physiological, On the one hand, it was possible to enquire
what eonsitntes a perfect individual from the point ol view
of structure; and. on the other, as to what constitutes
,tn individual as regards function. In the case of the higher

animals the question might also be approached in a third
way, namely, from the psychological standpoint. The
-I i in ture of various unicellular and colonial organisms, and
of many of a higher development, was discussed, and diffi-
( nines which arise in deciding their claim to individuality
commented upon. Two examples from the higher class
may be given. Taking a colonial organism — say an obelia
or sertularia — the fertilised egg develops into a single
individual, but that individual does not stop developing
when it has attained its full growth : it branches out and
produces other individuals by a process of budding, and in
the colony thus formed it is impossible to say where one
individual ends and another begins, though it may be quite
possible to say how many individuals there are altogether
by simply counting heads. Perhaps the most interesting
case was one which well sums up difficulties occurring,
especially from the physiological point of view. It may be
given in Professor Dendy 's own words : " Many of the
higher animals, though they do not form colonies in the
morphological sense, have the habit of living together in
social communities, which we may regard as colonies of
completely separated individuals. The Honey Bee is a
familiar example. In a hive of Bees we find individuals
of three kinds, easily distinguished from one another both by
habits and by structural peculiarities. The Queen is a per-
fect female, and is alone capable of laying eggs. The
ordinary workers are imperfect females, which have sacri-
ficed the power of reproduction, and concentrated their
energies upon the collection of food and other important
services necessary for the welfare of the community as a
whole. The Drones are males : they do no ordinary work ;
their sole function is to fertilise the Queen. None of these
different kinds of individuals could live a really independent
life : they are all mutually dependent upon one another.
The morphologist, however, could not refuse to regard
them as separate individuals, and probably the physiologist
would agree with him. But, if we are to be strictly logical,
from the physiological point of view the complete individual
can be nothing less than the entire community." . . .
" It appears, then, to be hopeless to seek for any
biological definition of individuality that can be applied
to more than a very limited number of cases : we have
constantly to modify our ideas on the subject as we
. pass from one group of organisms to another, and every-
thing depends upon the point of view." ..." Individu-
ality, though a very real, is a very elusive, phenomenon,
and one which perhaps lies outside the legitimate domain
of the biologist. We can do little more than collect the
remarkable facts that confront us so frequently in the
course of our investigations, and hand them over to the
philosophers to deal with as best they can."

PHOTOGRAPHY.

By Edgar Senior.

PAPIER MINERAL.— One of the most useful of photo-
graphic materials is a form of tissue paper, known as

" papier mineral," readily obtainable at most photographii

dealers. A sheet attached to the glass side ol a negative

affords great facilities for alterations and improvements
m negatives generally, as it may be worked upon in various
ways to modify the effect produced in printing. In land-
i ape work, the appearance of distance may be made more
real by its means ; and it is also one oi the greatest aids 1 < •

successful vignetting. The opening in the vignetting mask,
if covered with a pine- oi "papier mineral," will enable
a much softer and a more easily controlled vignette to be
obtained, and at the same time allow also advantage to be
taken of direct sunlight in printing, should it be necessary ;
and in a variety of ways it will assist the photographer
to improve his work. In almost all cases where ground glass
is useful this semi-transparent paper can be made to take
its place ; thus a piece stretched over plain glass can be
used as a focusing screen, should the latter get broken when
travelling. Then, again, in portraiture " papier mineral "
is useful for covering light movable screens or pasting
direct on to a skylight, and sunlight may be filtered through
it, and effects produced, which are in every way satisfactory ;
and on dull clays it does not obstruct the light sufficiently
to appreciably lengthen the time of exposure. When using
" papier mineral " as a means of obtaining the effect of
atmosphere in the print from a landscape negative by-
causing the more distant objects to appear more or less grey —
" the greater the distance the greyer the objects should
appear " — it must not be forgotten that the lights of distant
objects are grey compared with those in the foreground,
and care must be taken that these distant lights do not
appear too strong in the print. To obviate this, resort is
sometimes made to strengthening those in the foreground
and middle distance, but this requires to be done very care-
fully. Thus, by means of tissue paper, it is possible to
produce in the photographic print an effect more nearly
in accord with nature than the negative alone would be
able to render, owing to its imperfect gradations. If the
photographic process gave a true rendering of all objects
depicted, then resort to any such means would not be neces-
sary ; but as it usually falls short of doing so, any means
may be considered legitimate that will enable the desired
end to be obtained, and produce the effect that a perfect
process would do. In all cases, however, care must be taken
not to overdo it.

DEVELOPMENT WITH EIKONOGEN.— The develop-
ing properties of this substance were first pointed out in
1881 by Professor R. Meldola, who prepared the acid
from which the sodium salt was afterwards obtained,
and introduced under the name of "eikonogen," a name
derived from the Greek, and signifying "image-producer."
In its pure state eikonogen is a white substance. It is
the sodium salt of amido-^-naphtholsulphonic acid, its
constitution being expressed graphically as follows : —

CH

CNH„

HC <^\ C /\ COH

NaS'O.C

CH

^CH
CH

or doH.OHNHjSOsNa.SHX)

The substance is somewhat sparingly soluble in water,
but dissolves more readily in the presence of alkalies
Sodium sulphite is the best preservative, and acids added
to the solution cause the free acid to be precipitated in the
form of white needles. It can be recrystallised from
solution in sodium sulphite. Eikonogen as a developer
was patented in 1889 by Dr. Andresen, of Berlin. It is
very quick in its action, and produces soft negatives of
a very fine colour, and on this account it is invaluable
in portraiture. It is also specially suited for instantaneous
work, and it has been claimed that it will give more detail

April, 1915.

KNOWLEDGE.

117

with a short exposure than many of the alkaline developers.
This, however, appears doubtful, as it is believed that the
detail brought out is similar, whatever be the developer
employed. The advantage of eikonogen is that it prevents
that excessive contrast that is likely to be obtained at times
with "pyro" and still further with hydroquinone ; and the
great difficulty often experienced by those who have been
used to either pyro- or hydroquinone as a developer has
been that of not getting sufficient density in the image
with eikonogen. But the entire absence of fog allows of
the image being afterwards intensified to the required
extent without difficulty. Then eikonogen may be mixed
with either " pyro " or hydroquinone, or may be used after
these at any stage of development, so long as the alkali
employed as the accelerator is a carbonate. Thus, suppose
that, with pyro as the developer, there is the appearance
that the high lights are becoming too dense before the details
in the less illuminated portions of the subject are well out;
then these may be developed without any further perceptible
increase of density by washing off the "pyro" solution,
and applying one of eikonogen and carbonate of soda, the
quantities being regulated according to the stage that the
negative has reached. It should also be mentioned that
the solution of eikonogen should be kept as near as possible
at a temperature of 65° F., as it is very insoluble in cold
water, and will crystallise out, and therefore lose nearly
all its developing power. With this developer the quantity
of sulphite required appears to vary with the nature of the
subject and the plate used ; it must, however, be at least
equal to that of the eikonogen, and may often with advantage
be increased to twice, or even three times, that. Except
for very quick exposures, a small quantity of bromide-
should be used in the developer, as it appears to have the
effect of producing greater density in the negative. As,
however, restrainers act much more powerfully than with
pyro, only three or four drops of a ten-per-cent solution
should be added to each ounce of developer ; and the bro-
mide must be potassium, and not ammonium. Develop-
ment with eikonogen may also be conducted tentatively
by adding the alkali in small quantities at a time. A
saturated solution of potassium carbonate should be made,
which may be added in drops as development proceeds.
The developer may also be allowed to remain stationary
upon the plate without markings of any kind appearing,
provided that the solution is quite free from any deposit ;
and, if required, further development can be instantly
checked by immersion of the plate in a one-per-cent.
solution of either acetic or citric acid. Over-exposure
can, to an extent, be corrected by increasing the quantity
of sulphite in the developer, although eikonogen cannot be
said to allow of much latitude in this direction. Oi the
many formulae that have been given from time to time the
following will be found useful for portrail oi" landscape
work generally : —

Portraits and I. ami'-' mi

rains

Eikonogen... ... ... ... ,5

Soda sulphite 22

Soda carbonate ... ... ... 16-5

Water (distilled) ... ... 1 ounce

For very quick exposures the following formula is to be
recommended : —

For Very Short Exposures.

Eikonogen 14 grains

Soda sulphite ... ... ... 75

Potassium carbonate ... ... 30

Water (distilled) ... ... ... 1 ounce

Then, again, eikonogen is especially suitable for use with
isochromatic plates, and, when mixed with hydroquinone,
yields results on these plates that arc excellent in ever]
way. The following formulae, which were originally
published by Carbutt, are for a developer of this nature
which the writer has used repeatedly with great success : —

Carbutt's Formula.

For Snapshots on Isochromatic Plates.

Eikonogen... ... ... ... 2 grains

Hydroquinone ... ... ... 1 grain

Soda sulphite ... ... ... 12 grains

Potassium carbonate ... ... 6 ,,

Water (distilled) ... ... 1 ounce

For Portraits on Isochromatic Platks.
Eikonogen... ... ... ... 1-6 grains

Hydroquinone ... ... ... 0-8 grain

Soda sulphite ... ... ... 10 grains

Potassium carbonate ... ... 5

Water (distilled) ... ... 1 ounce

For Landscapes ox Isochromatic Plates.
Eikonogen... ... ... ... 1-9 grains

Hydroquinone ... ... ... 0-95 grain

Soda sulphite ... ... ... 11 grains

Potassium carbonate ... ... 3-6

Water (distilled) ... ... ... 1 ounce

Care should be taken not to over-expose the plates,
when these mixed developers will be found to do everv-
thing required, if the development is carried far enough.
Sufficient has now been said as to the value of eikonogen
alone, as well as when mixed with hydroquinone ; and,
as the substance can be obtained at a cost less than that of
pyro at the present time in many cases, it is worth while
giving it a trial.

PHYSICS.

By J. H. Vincent, M.A., D.Sc, A.R.C.Sc.

THE COOLIDGE AT-RAY TUBE.— This tube diners
very much from the usual form of .t-ray bulb, both in con-
struction and in the principles underlying its operation.
It is manufactured by the British Thomson-Houston
Company, which has communicated a detailed account of
Dr. Coolidge's invention to The Electrician (Januarv 15th,
1915). The usual concave cathode is replaced in the new
tube by a spiral of thin tungsten wire, which is heated to
incandescence by a small battery. This wire gives out the
necessarv stream oi corpuscles, which, when they strike
the anti-cathode, givi- rise to the i-ravs. Tin- anti-cathode
also serves as the anode, and is made of wrought tungsten.
When the tungsten wile is cold the tube is capable of with-
standing an electrical pressure oi one hundred thousand
volts without the insulation of the vacuum breaking down,
so perfect is the exhaustion. When, however, the wire is
hot, the tube becomes conducting in one direction, namely,
through the space from the tungsten plate to the spiral,
the current being carried entirely by the stream of corpuscles
issuing from the hot wire. It is claimed for the new tube
that its action is more easily controlled than that of the old
tube, anil in particular that the conditions ,,f working are
more readily reprodu

VICKY SHORT-WAVED ULTRA-VIOLET LIGHT.—

The wave-length oi the light in the middle of the visible

i 'i ■> brum is about six thousand tenth metres, a tenth metre

being 10 -,° metres. Stokes fust studied the ultra-violet

region Ol the spectrum, and carried his work as far as

length 1800 oi so The region lying between 4000
and 2000 may be called the ordinary ultra-violet region
Tins radiation is remarkable for us photographic and
fluorescent effects. Schumann many years ago earned the
knowledge ol the ultra-violet up to the estimated wave-
length 1000 The whole work had to be executed in a
rOSCOpe which could be evacuated, as air is opaque

to these shorl wavi Special photographic plates had
to be used, and the prisms and lenses construct)
fluorite. By the use oi a concave grating in a vacuum,
Lyman has recently pushed the limit ol the spectrum up
to nine hundred tenth metres, and has hopes oi still further
invading the unexplored region lying between the shortest
known ultra-violet waves and the longest waves oi the
X-rayS. These have a wave-length ot the order of one
tenth metre, while shorter still are the y-waves given out

by radio-active bodies.

118

KNOWLEDGE

April. 1915.

A M \\ Ml I HOD OF COUNTING TI1K MOLECULES
OF A GAS In ihe Astrophysicai Journal for December.
h»l4, Fowle describes a new method i>>i determining the
number of molecules v0 in a cubic centimetre of a gas at
norma] temperature and pressure. The method consists in
determining the transmissibility oi light of various wave-
lengths through the dry air vertically above Mount Wilson,
and computing the results by a formula due to Rayleigh,
This formula gives the coefficient of transmission in terms of
the refraction and oi the number of the particles in unit
volume Rayleigh was the first to regard the molecules of
.in .!•- capable ol acting as scattering particles, and considers
that, while as seen from the Earth's surface, much of the
light from the sky is tine to comparatively gross suspended
matter, yet an appreciable proportion is attributable to the
ulesol the air themselves, and that at high elevations
where the blue is purer the latter part may become pre-
dominant Fowle's result is w„ = (2-70± -02) x 1019, which
is in close ai < ord with the best determinations of this con-
stant by other methods.

FRICTIONAL ELECTRICITY.— Very little is known
about electrification by friction, so that a paper on this
subject by Morris Jones is very welcome (Phil. Mag.,
February, 1915). Measurements were made of the charge
produced on a surface by friction and of the frictional
work spent in generating it. The specimens were insulated,
and pressed against a rotating wheel covered with various
materials. The charge generated was measured by a
quadrant electrometer, and the work done could also be
determined. It was found necessary to give the insulators
a rest alter each rub, lor, if an insulator was rubbed a number
of times in succession, the deflexions rose to the maximum,
though the work done was the same for each rub, and less
than that required to give the maximum for a first rub.
When the normal pressure between the specimen and the
rubber was maintained constant, it was found that for each
pair of materials the charge reached a maximum as the quan-
tity of work was increased. The sign of the charge was plus
on quartz, glass, fluor-spar, Iceland spar, and heavy spar
when rubbed on flannel, silk, and chamois leather, but
negative on ebonite, amber, and sealing-wax when rubbed
on the same materials. When specimens of various metals
were rubbed against silk, the results were more complicated,
the charge varying both in magnitude and sign with the
state of the surface ; the maximum charge proved to be
independent of the pressure and velocity. A tentative
mathematical theory of the effects is given based on the
assumption that the friction removes electrons from either
the rubber or the specimen at a speed proportional to the
rate of working.

QUARTZ GLASS. — This material is surpassed only by
invar in respect to its invariability of size with temperature.
It was discovered by Professor C. V. Boys, who used threads
of this material to support the deflected masses in his
classical research on the Newtonian constant of gravitation.
Boys showed how to prepare these threads by the bow and
arrow and other methods, and also prepared small pieces
of rods and tubes before the oxy-hydrogen blowpipe.
When once quartz has been fused it is very easy to work,
as it does not crack with sudden change of temperature.
This is partly owing to its low coefficient of expansion, but
also probably to its great mechanical strength. Shenstone
still further unproved the methods of making fused silica,
and the material is now a commercial article, being obtain-
able in two grades : one perfectly clear and colourless, the
other being silky and translucent in appearance. The
methods of manufacture have been so far perfected that
complicated apparatus of quartz glass can now be easily
made, and a preliminary difficulty as regards sealing the
leading in wires for electrical purposes has been overcome
completely. This wonderful and beautiful product has
already been applied to some commercial purposes, such as
for making electric lamps, and the extension of its uses
to various other fields is certain.

RADIO-ACTIVITY.
By Alexander Elf.ck, B.Sc.

ANNUAL REPORT— The report issued annually by
tin Chemical Society always devotes a section to the
progress made in radio-activity during the past year.
Most of the questions raised in the section of the report
which has ]ust been issued have been mentioned from time
to time in these columns The three following subjects,
dealt with more fully in the report are, however, of some
importance, and may briefly be referred to now.

NEW WORK ON THE DISINTEGRATION SERIES.
— Fajans and Towara have announced, in the Natiowissen-
schaflen (1914, page 685), that they have discovered a
radio-active substance which they have not been able to
separate from bismuth, and which gives a-rays. The activity
of the bismuth which has thus been obtained is five times
as active as an equal quantity of uranium ; and, deducing
its period from the range of its a-rays, the period of average
life of this " radium-H " is between one hundred thousand
and one million years.

THORIUM ACTIVE DEPOSIT.— It has been generally
accepted that when a radio-active element underwent dual
disintegration we had a homogeneous collection of atoms
which had the faculty of choosing in which of two ways
they could disintegrate. If the experiments of Wood
(Proceedings Physical Society, Volume XXVI, page 248)
are confirmed, a large modification either of our views on
dual disintegration or on the evolution of the radio-elements
through the Periodic Table will be required. The
experiments in question dealt with the volatilisation of
thorium active deposit, and seemed to show that the
substance hitherto referred to as thorium-C is composed
of two elements, one of which commences to volatilise about
200° C. below the other.

ATOMIC- WEIGHT DETERMINATIONS OF RADIUM
AND URANIUM. — Despite the most careful atomic-weight
determinations, there is still a greater discrepancy between
the values obtained for these elements than there should
be if the three o - particles emitted between uranium-I
and radium had the same atomic weight as helium derived
from the atmosphere, namely, 3-99. The writer of the
report — Professor Soddy — therefore suggests that it is
an open question whether the law of the conservation of
mass accurately holds in radio-active change. To the
present writer it seems that a more probable explanation
would be that radio-active helium is an " isotope " of
atmospheric helium, but of a slightly higher atomic weight,
just in the same way as Ashton's meta-neon had an atomic
weight of 22 compared to that of 20 for atmospheric neon.

ACQUIRED RADIO-ACTIVITY.— Sir W. Crookes has
recently published a paper (Philosophical Transactions of
the Royal Society, Volume CCXIV, page 433) describing the
behaviour of diamonds when buried in a radiferous salt or
exposed to radium emanation. As is to be expected, the
gems, just like any other material similarly placed, are coated
with the active deposit, and so possess the " acquired
activity." The author, however, finds this difference, that
the material producing the activity so obtained can easily
be dissolved from glass ; while, when it is obtained on dia
mond, it can withstand the most vigorous chemical agents.
The activity is, so far as can be ascertained, constant over
a period of years.

In the paper referred to Sir W. Crookes does not attempt
to explain the phenomena observed, although it would be
easy to suggest a number of explanations capable of expert
mental verification.

April, 1915.

KNOWLEDGE.

119

CONDENSATION OF THORIUM AND RADIUM
EMANATIONS.— In The Philosophical Magazine for March
the present writer also contributes a paper on the condensa-
tion of these two emanations. The object of the research
was to find out whether isotopes had or had not the same
temperature of condensation. It was found that in a
mixture of the two emanations at atmospheric pressure,
thorium emanation appeared to be condensed before radium
emanation ; while, if the experiment was made in a vacuum,
the reverse was the case. From theoretical considerations
it was shown that results of this nature are to be ex-
pected, even if individual atoms of each emanation had
identical condensation points. The difference in behaviour
is in all probability due to the different periods of
average life. Indirect evidence was obtained in one ex-
periment that the two emanations behaved identically in
respect to their condensation and volatilisation.

By altering the external conditions the condensation
point of either emanation can be varied between — 150° C.
and - 185° C.

RELATION BETWEEN X-RAY WAVE-LENGTHS
AND ABSORPTION.— A paper on this subject, by Pro-
fessor W. H. Bragg, appears in The Philosophical Magazine
for March. It deals with the absorption of rays emitted by
substances when these are bombarded with cathode or
.r-rays. It is well known that secondary rays are of two
types, and are characteristic of individual elements. The
main conclusion reached is that it is probable that " the
characteristic rays of a substance form a system which
can only be excited as a whole." In the meantime this
result has been proved to be correct for some six or so
elements ; if, however, further work enables it to be
stated in a generalised form applicable to all the elements,
an important step will have been made in our knowledge,
not only of the material, using the word in its widest sense,
inside an atom, but also of how that material is held
together.

ZOOLOGY.

By Professor J. Arthur Thomson, M.A., LL.D.

RELATIVE LENGTHS OF OUR TOES.— Onera A.
Merritt Hawkes finds that there are three types of feet, of
which two are common. The first or great toe may project
beyond all the others (L type). The second toe may pro-
trude, not only beyond the third, fourth, and fifth, but also
beyond the first (S type). This is much less common than
L. The first and second toes are of the same length, and
longer than the others (E type). This is very unusual.
There is some limitation in regard to sex, the S type occur-
ring more commonly in females than in males. As the
S type is commonest in the foetus, it may be said that
in this, as in some other features, woman is a more youth-
ful type than man. In inheritance the L type is irregularly
dominant over the S type of foot.

PHEASANTS AND MUTATION.— Mr. C. William
Beebe, the Curator of Birds to the New York Zoological
Society, has been studying pheasants for some years, and
his opinion on the factors of evolution is well worth having.
He says that he began with some prejudice against the
" mutation theory " (of brusque, discontinuous, or saltatory
variations), but that the more he observed such species as
the golden and Amherst pheasants (Chrysolophus piclus
and amhersiiae), the colour relations in both sexes, and the
results of hybridism, the more necessary some such phe-
nomena as saltations appeared to be in these particular
instances. The genus Phasianus seems to afford good
illustrations of continuous variation, and the genus
Euplocomus of saltatory variations. Both forms have been
operative in nature.

CROCODILE'S NEST.— Mr. \V. Schultze, of the Bio-
logical Laboratory at Manila, describes the nest of a

crocodile (Crocodilus paluslris) near Taytay, Palawan. A
peculiar mound of grass on the shore of a lake attracted
attention, and it was found to be a crocodile's nest. A
space about eight metres long and five metres wide had
been cleared of the coarse, wiry grass {Ischaemum) which
grew there, and a mound had been made 2-5 metres in
diameter at the base and 1-5 metres in height. The grass
was mixed with sand, and was moist. About the centre
of the mound there were thirty eggs in several layers. The
egg is oblong ellipsoidal, with a very hard porous shell,
a high porcelain lustre, and a strongly marked opaque
white band around the middle (girth). It was found that
the time of incubation in the Philippines is between seven-
teen and eighteen weeks.

HOW A STING -RAY PROTECTS ITS EYE.— It is
well known that the eyes of fishes are lidless, and cannot be
closed like those of most higher vertebrates. Sometimes,
however, they are well protected from injury, and B. Sun-
dara Raj gives a good example in Trygon kuhlii, one of the
sting-rays. It lies buried in the sand with the eyes, the
spiracles, and a portion of the formidable spined tail pro-
jecting. If sand or other particles be dropped down, the
upper margin of the spiracle nearest the eye forms a pro-
jecting fold which serves both to protect the eye and to
exclude foreign objects from the spiracle.

SIZES OF RED BLOOD CORPUSCLES.— An interest-
ing suggestion has been made by Dr. J. Burton Cleland
that specialisation is attended with a reduction of the size
of the red blood cells. Thus, among fishes, those of Ceratodus
are 39 x 23 to 25/i, which is " cumbersome " ; those of
Elasmobranchs vary from 18 x 12-5 to 23 x 13 -5m : those
of Teleosteans range from 9x7 to 13-5 x 10-3m- In
Therapion unicolor they are almost spherical, 6 to 8^-
Similarly in birds the Emu has 15-5 to 16-5x8-5 to 9-S^i ;
the Grebes, Penguins, Herons, Pelicans, and the like have
approximately 1 4 x 8/i ; in Passerine birds (except Cor-
vidae) there is a definite tendency to smaller cells, 10 to
12x5 to7M.

STINGS OF JELL YFISHES— The stinging threads of
the common jellyfish (Aurelia aurita) are not strong enough
to pierce the ordinary human skin, but bathers on British
coasts have sometimes painful experience of the virulence
of the orange or the blue species of Cyanea. In other waters
there are much more formidable jellyfishes. Thus Mr.
S. F. Light, in describing Philippine medusae, notes of
Chiropsaimus qiiadrigatus that the sting of the tentacles
is very dangerous. Swelling and inflammation begin almost
immediately, blisters form, the heart action is impaired,
respiratory spasms and nervous twitchings of the muscles
ensue, and there is intense general pain. The natives of
Palawan reported that the sting may be fatal. Another
dangerous form is Daciylometra quinquecirrha, which causes
severe poisoning. The native remedy is sugar solution
taken internally and applications of vinegar externally.

NESTS OF FALSE SCORPIONS— A very fine piece of
observational work has been done by Mr. II. Wallis Kew, who
has for the first time described the whole process of nest-
making in the little creatures known as false scorpions, or
pseudoscorpions, which are moderately well represented in
Britain. Nests are made by all individuals of both
for moulting, for brood purposes, and sometimes for
hibernation, The interior is lined with dense spun tissue,
almost like silk paper, which takes days or even weeks to
make. There may be an external covering of earthy or
ible m.itt rials attached by silk. The silk is formed by
glands in the cephalothorax, and is conveyed by dm
the tips of the chelii erae, or first pair of appendages. The
silk is drawn out in separate viscid threads, which may
coalesce or remain separate. There are five or six from each
chelicera, but these may form one. The spinning is asso-
ciated with continuous forward and backward movements
of the body, and with lateral movements of the cheliccrae.

120

KNOWLEDGE.

April, 1915.

HYBRID COCKATOOS— Dr. Ernest Warren, of the

Natal Museum, describes a very interesting case oi hybridism.

The male bird was the common Sulphur-crested Cockatoo

itua galsrita), the female the so-called Slender-billed

Ltoo {Licmetis nasiea). The hybrid seemed to be a

thorough Mind. Out of ten characters it was nearer

Cacatua in five, nearer Licmetis in one. and almost exactly

intermediate in four. In even,' character examined, with

the possible exception of the coloured and non-coloured

lores, there is very obvious blending of the male and female

tics. There was no evidence of Mcndelian

inheritance.

HABITS OF TESTACELLA.— The Testacellid Slugs
widely from the other British Slugs: Limacidae and
Aiionidae. They retain a small external shell, visible on
the surface, near the posterior end, whereas in the others
the shell is either a hidden vestige or quite absent. Again,
while most British Slugs are omnivorous, the Testacellids
are essentially carnivorous, and feed largely on Earthworms
caught by night. Mr. Charles Oldham writes : " The
Earthworm is seized by a sudden, rapid extrusion of the
Slug's odontophore or lingual ribbon, a structure provided
with close-set rows of long, slender, barbed teeth, which
afford an excellent hold on the Worm's soft body, and the
whole of this stupendous meal, in bulk perhaps three times
that of the Slug, is gradually ingested." In its early
struggles the Earthworm often dashes the Slug about,
but the bull-dog grip is not relaxed. In hot, dry weather
and in the cold of winter Testacella lies inactive in a cocoon-
like cell made of earth and mucus. The elliptical eggs,
about five millimetres in longer axis, are deposited under-
ground. There are three British species.

STRENGTH OF SPONGE-CURRENTS.— Ever since
Robert Grant discovered the currents produced in water
by living sponges the hidden activity of these often very
vegetable-like animals has excited interest. The last con-
tribution to the subject is Professor G. H. Parker's estimate
of the strength and volume of the currents. In Stylotella
the pressure is equal to a column of water 3-5-4 millimetres
in height. In seven others it was less, usually a little over
two millimetres. In Spitwsella sororia, the common Ber-
muda finger-sponge, a tube put into an exhalent aperture,
or osculum, showed that the rate of flow is about four
millimetres per second, and the rate of discharge about
seventy-eight litres per day from each osculum — over
four hundred and fifteen gallons for the whole sponge.
As the experiments were made in the laboratory, the esti-
mate is probably under the mark. An undisturbed specimen
of Spirastrella at low water was found capable of over-
coming a pressure of four millimetres of sea water. Big
sponges often produce deformations of the surface of the

sea above them, as a vigorous spring does ; but Professor
Parker's interesting investigations indicate that the cur-
rents flow at low pressure.

COMPANIONS OF J 1 l.l.YFISHES.— It is well known
that some medusae swim about with horse-mackerels
(Carangidae) in the shelter of their Sowing lips. Mr. S. F.
Light describes this in a Philippine jellyfish, Rhopilema
visayana, with which a species of Caranx has established a
companionship. " The fish would be seen playing about
among the mouth, arms, and appendages, and on being
alarmed would disappear under the edge of the bell,
between the arms or in the subgenital porticus." A similar
condition was found in the case of Lobonema mayeri. Inside
the Rhopilema there was usually a crab (Char ibdis crucij era) ,
considerably paler than is typical for the species, which
suggests a prolonged residence within the medusa. It is
interesting to notice Light's observation that the companion
fishes were seen eating dead specimens of Rhopilema visayana,
though their relation with the living forms seemed to be
quite friendly. " I am told," Mr. Light adds, " that
R. visayana, which is closely related to the common edible
medusa of Japan (R. esculenta), is used for food by the
inhabitants of the east coast of Leyte, where it is preserved
in vinegar."

COLOUR CHANGE OF NEWTS.— The colour changes
of the Palmated Newt (Molge palmata) are well described by
Mr. Charles Oldham. " Individuals living in a pond with
a dark, muddy bottom are dark green in colour, and in
consequence when at rest are almost invisible from above ;
similarly those in a pond with a bottom of yellow clay
are yellowish in colour and alike inconspicuous. If, how-
ever, one of the dark green Newts be placed in a glass
vessel upon a white surface, it will, in the course of a few
hours, become yellowish-drab in colour, but often paler in
tint than the Newts which rested on the yellow clay;
whilst, if one of the yellow-skinned Newts be taken from
the pond with the bottom of yellow clay and placed into a
glass vessel, it will be seen presently to exhibit greenish
spots and marblings over the whole of the upper surface,
and ultimately, by the expansion of these green areas, to
acquire an almost uniform dark-green tint over the whole
of the surface exposed to view from above. The green
will, indeed, be darker in tint, provided the glass vessel
stands upon some dead-black surface, than in the Newt
which was taken from the pond with the bed of dark mud."
(Trans. Hertfordshire Nat. Hist. Soc, Volume XV, 1915,
page 207.) The colour-change depends on the contraction
and expansion of the living matter of the pigment cells,
which are under the control of peripheral nerves. The
stimulus from the coloured environment first affects the
eye, for blind animals do not change.

NUMBER OF SPORES IN A MYXOMYCETE.
By W. B. GROVE, M.A.

In November, following the directions of Mr. S. P. Bolton,
I found on a tree-stump a huge mass ot aethalia of the
Myxomycete (Brefeldia maxima). The crowded aethalia
covered a space of about six square feet, and were just
ripening their spores. As the number of spores was evi-
dently enormous, it was thought it would be interesting to
make an estimate. For this purpose a gramme of spores
and capillitium was taken and shaken up in two hundred
cubic centimetres of water, with a little ether to loosen the
spores from one another. After thorough shaking, the number
of spores was counted, in the ordinary way, by a blood-
corpuscle-counting apparatus of Zeiss. Allowing about
six per cent, for capillitium, the number worked out at
10s in a cubic centimetre. Thus, in the whole mass
covering the stump, roughly estimated at about five hundred

cubic centimetres, there were half a million million spores.

This result can be checked by geometrical considerations.
The aethalium contains nothing but spores and capillitium ;
the size of the spores varies from 9 to 12^. Taking 10/i
as an average, the volume of a spherical spore is
approximately \ • (j^)6 cubic millimetres.

If equal spheres are packed as tightly as possible in a
given space, geometry teaches us that about twenty-six per
cent, must be allowed for the spaces between the spheres ;
if, then, we allow six per cent., as before, for capillitium,
and a further eighteen per cent, for the obvious loose packing
and occasional larger spores (this last amount is, of course,
a mere guess), we get a total allowance of fifty per cent.

Therefore the number of spores in one cubic centimetre
= 50% of 2xl0°xl0s = 109.

THE FACE OF THE SKY FOR MAY.

By A. C. D. CROMMELIN, B.A., D.Sc, F.R.A.S.

Table 21.

Date.

Greenwich
Noon.

May ,

„ 6

ii ii

,, 16 ....

, 21

,. 26

.. 31

Su
R.A.

Dec.

h. m.

2 30-5
249-6

3 9'°
328-7
348-6

4 87
4 29-0

N.i4-8
16-3
■7"7
18 g

2D"0
2I'0

N.2I-8

Moon.
R.A. Dec.

h. m. o

16 i8"o S. 26*3
21 23-3 S. 15-7
1 9-8 N.I2'0
5 15-8 N.27-s
9 33-6 N.14'5
13 44-7 S. 15-9
19 9-6 S. 25-4

Mercury.
R.A. Dec

2 29-6 N.14-5

3 "'6 >8'5

3 54-4 21-8

4 35'4 *4'i

5 "2'5 25'3

5 44 '3 25'°

6 9-6 N.25'2

Venus.
R.A. Dec.

h. m. o

O 22"! N. 0"6

0 44-2 2-9

1 64 5-1
1 28-7 7'4

1 5i'3 9'6

2 14*2 1 1 '7
2 37'5 N-"3'7

Jupiter.
R.A. Dec.

h. m.

23 24"2

23 277
23 31-1
23 34 '4

23 37'4
23 40-3

23 43'°

5"o
46
4'3
3 '9
36
3 '3
3'1

Saturn.
R.A. Dec.

in.

h

5 SS'3

5 57'5

5 59-8

6 2*2

6 4-8

6 7-3

6 10 'o

N.22'7

22"7
22*7
22*7
22*7
22 7

N.22'7

Uranus.
R.A. Dec

21 12*7 S.i6'8

21 13*0 16*8

21 132 168

21 i3'3 i6"3

2i 13*4 i6'8

ai 13*3 i6'8

21 13*2 S.i6*8

Neptune.
R.A. Dec

h. m 0

759*2 N.20*3

7 59"5

7 59'8

8 0*2
8 0*7
8 i*i
8 i*7

20*3
20 *3

20"2

20 "2

20 '2

N.20*2

Table 22.

Date.

Greenwich Noon.

Greenwich Midnight.

Sun.
P B L

Moon.
P

Jupiter.

P B L L T T,
121 2

O 0 o

- 24'4 -4'I 309-3
*3'4 3'6 243-3
22-3 3-0 177-1
ao'g a'5 iii'o
I9'S 1 '9 44"9
'7'8 l'3 338-7

— 16*1 -o*7 272*6

+ 7-3

— i8-o

— 20 '9

- 2-6

+18-5

+ i9'"

- 8-4

a 0 a oh. ni. h. m.
— 253 +i*s 129-6 267-7 8 27 e 4 36 e
23'3 16 1540 238-7 7 47' S 24 '
25-4 1-7 178-6 209*8 7 te 6 i:f
25-4 1-7 203-2 iSi'o 6 26 e 7 oe
25-4 i-8 228-0 152-4 5 45' 7 47'

6

„ 8

„ 16

P Is the position angle of the North end of the body's axis
measured eastward from the North point of the disc. B, L
are the helio-(planeto-)graphical latitude and longitude of the
centre of the disc. In the case of Jupiter System I refers to
the rapidly rotating equatorial zone, System II to the tem-
perate zones, which rotate more slowly. To find intermediate
passages of the zero meridian of either system across the
centre of the disc, apply to Ti T2 multiples of 9h 50m-6,
9h 55m-7 respectively.

The data for the Moon and Planets in the Second Table

are now given for Greenwich Midnight, i.e., the Midnight at

the end of the given day.

The letters m, e stand for morning, evening. The day is
taken as beginning at midnight

The Sun is moving Northwards at a slackening pace.
Its semi-diameter diminishes from 15' 54" to 15' 48". Sunrise
changes from 4" 36m to 3n 52m ; sunset from 7" la™ to 8h 4m.
The Sun's surface is likely to repay careful scrutiny, owing
to the recrudescence of activity.

Mercury is in superior conjunction with the Sun on 1st;
then it is an evening star, well placed for observation. East
Elongation, 23° from Sun on 31st. Semi-diameter increases
from 2k" to 4". Illumination diminishes from Full to g.

VENUS is a morning star. Illumination increases from
| to ?. Semi-diameter diminishes from 6\" to 6".

The Moon.— Last quarter 6d 5h 23m m. New 14d 3h 5\m tn.
First quarter 22d 4" 50m m. Full 28" 9b 55™ c. Apogee

14

respectively. Maximum librations 6" 7° W., 14" 7° S„ 22" 8" E.,
27 7° N. The letters indicate the region of the Moon's
limb brought into view by libration. E., W. are with
reference to our sky, not as they would appear to an
observer on the Moon (see Table 24).

Mars is still badly placed, near Venus on 14th.

Jupiter was in conjunction with the Sun on Feb. 24th,
and is still difficult to observe. Equatorial diameter 36",
Polar 34".

Configurations of satellites at 3h 30™ a.m.
Jupiter's Satellites.

Day.

West.

East. I

)ay.

West.

East.

May I

2

O

134 M

»y 17

Oi

243

„ 2

I

0

234

, 18

21

0

34

» .i

0

1234

. >9

23

0

14

. 4

21

0

34

, 20

3'

0

24

. S

3

c

14 '•

, 21

0

214

, 6

3'

0

24

. 22

23'

0

4

. 7

32

0

1

• 23

Oi

2 34

, s

ii

0

I*

. 24

4

0

2>

>•

. 9

41

u

23

. 25

421

0

3

, io

4

0

123

. ZQ

42

0

1

i II

421

u

3

■ 27

43'

0

2

. 12

432

0

1

, 2S

43

0

21

• '3

431

V1

2

. 29

423'

0

. 14

43

y

1

, ;o

4

0

'3

-'•

. «5

343>

u

• 51

4

0

2?

•

, lb

0

243

The following satellite phenomena are visible at

Greenwich, all in the morning hours : — ld 3h 30m I. Oc. R ■

14d 3h 59™ 51* I. Fc. D. ; 16d 2b 30m I. Tr. I.. 3h 36™ I. Sh.

I.; 21d 3h 44™ II. Tr. I.; 23d 3h llm I. SIi. I. ; 24d 3h 55m

d 9h e. Perigee 28 6 e, semi-diameter 14 43 , 16 46" |, Qc. K. ; 2S'1 3b 47m II. Sh. I.; 31d 2b 16*° 35' 1 Ec P

The Northward motion of Jupiter will make this year's
opposition (which ocean on September 17th* mote favourable
for European observers than those of the last four years, in
which it has been verv low down.

121

122

KNOWLEDGE.

April, 1915.

Saturn is an evening star in Gemini. Is now approaching
conjunction with the Sun. 2i° South of Mercury on 31st.
Polar semi-diameter 8". Major axis of ring 38", minor 17".
Angle P-6°-2.

The Satellite positions are not given, owing to the planet's
proximity to the Sun.

Uranus is a morning star, but badly placed. In
quadrature with Sun on Sth. Near Moon on 6th, 7h m.

Neptune is an evening star in Cancer; diameter 2".

Double Stars and Clusters. — The tables of these,
given three years ago, are again available, and readers are
referred to the corresponding month of three years ago.

Variable Stars. — Stars reaching their maxima in or near
May, 1915, are included. The lists in recent months may
also be consulted (see Table 23).

Meteor Showers (from Mr. Denning's List) :

Date.

Radian!.

Remarks.

K.A.

1

Dec.

Mar. — M. iv

263

+

6°2

Ralher swift.

A pi. 19 May 9

201

+

8

Slow.

Apl.— Mav ...

■93

+

5S

Slow, yellow.

Apl. — May ...

296

0

Swift, streaks.

.May 16

338

—

2

Aquaria's, swift, streaks.

„ 7

246

+

3

Slow, bright.

,, II-lS ...

231

+

27

Slow, small.

,, 3010 Aug

3.33

+

28

Swift, streaks.

May — lune ...

2S0

+

32

Swift.

May July ...

252

-

21

Slow, trains.

„ 181031...

245

+

29

Swift, white.

The May Aquarids are of special interest from their asso-
ciation with Halley's Comet. Accurate observations of their
paths are desirable.

Table 23. Long-period Variable Stars.

Star.

Right Ascension.

Declination.

Magnitudes.

Period.

Date of Maximum.

T Camelop. ...
R Auri^ae
K Comae

R Serpentis

RU Herculis

li. m. s.

4 3' 48

5 10 25
11 59 54

15 46 47

16 6 41

+65 59
+ 53 3°
+ 19 16
+ 15 23
+25 17

7'0 to 13- 5
6-510 13-3
7'3 <° i4'6
5'8to 135
70 to 142

d.
370
448
362
357
483

1915— Apr. 19
„ Apr. 4
„ June 1
,, May 2
„ May 16

Night Minima of Algol ld 0h-4m, 3d 9m-2e, 18d 5h-3m, 21d 2h • 1 111, 23d llh-9e, 26d 8h -7 c. Period 2d 20h 48m-9.
Principal Minima of /3 Lyrae 5d 9hm, 18d 7h m, 31d 5h m. Period 12d 21h 47m-5.

Table 24. Occultations of Stars by the Moon visible at Greenwich.

Disappearance.

Reappearance.

Dale.

Star's Name.

Magnitude.

Time.

Angle from

Time.

Angle from

N. to E.

N. to E.

I9I5-

h. m.

h. m.

*

May 1

4 Scorpii . .

5 6

1 45 '"

57

2 35 '"

329

,, 2

WZC 1098

67

—

3 28 m

247

, 3

BAC6I27

47

0 30 111

108

1 38 m

252

, 7

WZC 1466

7'l

—

—

3 11 "'

182

, 9

13 Piscium

6-5

2 53"'

354

3 '6 m

309

, 16

BACI754

57

7 5°' 97

8 46 <

278

, 16

BD + 26-884

6-8

9 6 e

179

—

. 24

WZC 802...

71

9 34 «

100

, 26

WZC 849

7-0

0 52 m

94

—

, 27

WZC 96s

7-2

11 15 «

41

—

, 31

Lacaille 7849

7-0

1 36 '"

222

From New to Full disappearances occur at the Dark Limb, from Full to New reappearances.

POLLARDS.

The making of pollards ensures a supply from time to
time of long poles suitable for fencing and other purposes,
in much the same way as they are obtained in the under-
wood of copses. There is this advantage, however, about
the former method, that pollards can be grown in odd cor-
ners, along the sides of streams (as in the case of willows),
or in hedgerows. Where we find pollards in woods or
scattered about common land, it seems likely that
they were produced in connection with common rights,
and that they were cut legitimately or otherwise by
cottagers who were not supposed to touch the forest trees.

There is no doubt but that old pollards which have been
left alone for many years, such as those at Burnham
Beeches, become very picturesque, but their conservation
is a matter of difficulty. The old trunk becomes hollow,
and often a mere shell has to support a large number
of solid branches (see Figure 93), each of wh'ch may
weigh several tons. Our illustrations (see Figures 93
to 97) show how, in the slightest wind or in the
still air, the pollards may break up, and many of them
have to be cut somewhat drastically in order to save
them at all.

April. 1915.

KNOWLEDGE.

123

FlGL'KE y3.

A Beech Pollard, showing the large mass of heavy

branches, which if not removed will destroy the

hollow trunk.

Figure y-t.

A Pollard that has lost one side, and to pn
which the limbs must be lopped.

Win and prop i" prevent the Pollard from breaking up.

124

KNOWLEDGE.

April, 1915.

F 1GURE 96.

Limb of a Pollard that has been broken off by the wind.

Figure 97.
A Pollard cut back to preserve it from utter ruin.

STONYHURST COLLEGE OBSERVATORY.

By FRANK C. DENNETT.

The Annual Report of this institution for 1914 has just
been issued by its able Director, the Rev. Walter
Sidgreaves, S. J., F.R.A.S. The year has proved remarkably
mild and cloudy. The mean barometric pressure was 0-041
inch below the average, and the mean temperature l°-5
above the average. The rainfall proved to be 3-113 inches
in excess of the mean quantity. Only one " record "
seems to have occurred : January 8th had the heaviest fall
of rain — 2-074 inches — for a January day that has occurred

Y£Afl

IS H 13 It 1/ 10 0 S 7 6 S t 3 2 1

isie

^

v

iSOQ

V.

-T

1900

\

1901

)

1902

ri

1903

^**

190*

1105

<

-.-,-"

1906

/

»

*

1907

<

<

100?

s

^

x%

1909

>

v^

IQ'O-

<

•«._

191/

••

10^

»

10/.?

r

>

|9/»

PCD

.

4

Figure 98.

Magnetic Mean Declination Range. Mean Daily
Spot Area.

during the previous sixty-seven years. May was the only
month with a mean temperature below the average, and
cloudiness is shown by the fact that the total hours of sun-
shine registered are three hundred and twenty-eight less
than the average of the past thirty-four years. September
gave a record of thirty sunny days, with 176-5 bright hours.
The wind record is below the annual average to the extent
of two thousand three hundred and eighty-six miles. The
strongest gale reached only forty-four miles in the hour
on February 22nd. The rainfall of the year shows an excess
of three inches above the usual record. January. March,
May, July, September, November, and December each
yielded a rainfall above the average, especially the last two,
which together had a rainfall of 14-46 inches, or 5-392
inches in excess of the mean. In August and October

little over half the usual amount fell. Magnetic records
appear to be missing on five days — January 5th to 8th and
June 29th. Of the remainder, one hundred and twenty-two
are marked as calm, two hundred and ten as small, and
twenty-five as moderate ; three days only are marked as
greater, April 5th and 6th — when the fine sun-spot group
No. 5 was crossing the central meridian — and September
27th ; but no very great disturbances occurred. The
magnetic conditions during the year have been remarkably
quiet. Solar observations were made on two hundred and
seventeen days, and drawings made on one hundred and
thirty-three : only nineteen of these showed faculae, and
one hundred and fourteen spots and faculae. The mean
disc area of spots (in units of one five-thousandth of the
visible surface) appears at 0-82, and the mean daily range
of the magnetic declination (in minutes of arc) at 10 '-2.
These are included in the diagram constructed by the
writer (see Figure 98), showing the variations since 1898,
as given in the Stonyhurst reports, and are worth studv.

The present report is additionally interesting in that it
gives a record of the expedition organised by the Joint
Permanent Eclipse Committee of the Royal and Royal
Astronomical Societies to Hernosand, in Sweden, to observe
the total eclipse of the Sun, August 21st, 1914. Originally
it was arranged for Professor A. Fowler and Father Cortie,
accompanied by Major Hills and Father O'Connor, with
Dr. Fowler's assistant, to go to Kiev, in Russia. The Rus-
sian Government, however, would not at first grant the
necessary permission to the Jesuit Fathers. This objection,
however, was withdrawn later at the intervention of Dr.
Backlund, the Imperial Astronomer at Pulkova, but by
good fortune the news did not reach the party. The out-
break of War would have stopped the party at Riga, as,
indeed, was the case with Professor Fowler. Had they
reached Kiev the clouds would have prevented observations.
As it was, they, through the good offices of Professor B.
Hasselberg, found a capital site, with exceptional con-
veniences, at Hernosand, in a field at the rear of the Technical
School. Moreover, on the day of the eclipse they were
favoured with fine skies. The equipment was good, and the
observations successful. One photograph of the corona,
taken with the twenty-foot objective — four inches aperture
— is given in the report. A study of the rays in the corona
makes it apparent that some of them are due to the great
sun-spot (No. 24 in the " Knowledge" List). The corona
was generally of the minimum type, the beautiful short
radiations around the poles, the arc extending for 75° about
the North and 65' about the South Pole. A long " fish-tail "
extended away from the western limb, and spreading rays
of the " intermediate " type from the eastern. Eight pro-
minences appear on the plates, some being fine ones. Like
other observers, they found what is usually known as the
" characteristic coronal radiation " at wave-length 5303 to
be barely traceable on the photographic plates. This appv
to be weak at the times of sun-spot minimum, as it was faint
in 1900. For more minute details the reader is referred to the
report itself, which is well worthy of study.

REVIEWS.

BIOGRAPHY.

Life of Sir John Lubbock {Lord Avebury) I [y HoRACl
G. Hutchinson. 2 volumes. 338 and 334 pages. 2 illus-
trations in each volume 8J-in. -,5.1-in.
(Macmillan & Co. Price 30/- nel |
It Mr. Hutchinson is not concerned with apportii
to Lord Avebury his precise niche in Fame's temple, tin-
volumes be lore us bring home to the reader the (act that
the niche, wherever it may be situated, must be a very
import. nit one.

Mr. Hutchinson mentions more than once the comment
th.it bankers considered l ord Avebury to be a good scientific

man. while men i 't science looked upon him .is ,i i;o(xl banker ,
and. though we agree that the biography " dispos
ever ol that ill-considered criticism, it may lx- well to look
Eoj a moment at the reasons which may have led to it. It
is not recorded, apparently, who is responsible for the
epigram, but we should imagine that it was not made by
a banker.

Scientific men who specialise are prone to the very human

125

126

KNOWLEDGE.

April, 1915.

ailment known as " gutting into a groove," and look askance
upon versatility which Lord Avebury possessed to a very
remarkable degree. They seem to forget the necessity of
broadmindedness, and fail to appreciate that he who makes
known to the World what is being done in science is doing
a very important work, with the help most probably of
talents winch they do not themselves possess. Science is
ignored far too greatly by the powers that be and by the
commercial classes in this country ; and the mere fact that
a man who has distinguished himself as a financier, a
politician, and an administrator has also made a mark in
science is of very great value to science.

At one time there was a tendency to belittle Lord Ave-
bury's scientific work because some of the observations
which he used were earned out by others. Nobody objects
to the fact that an architect does not with his own hands
build the houses which lie plans, or that a modern sculptor
puts only the finishing touches to the marble. Many
scientific men have become famous through using the
observations of others which they did not originate, and
many a zoological professor has added his name to that of
a demonstrator on the title pages of a paper written by the
latter to the mutual advantage of both.

Lord Avebury, who wasted very little of his time, planned
out the work which he wanted done, and it was by delegating
part of this that he was able to do so much.

Mr. Hutchinson's book recalls that, besides being a
banker, Lord Avebury was a member of Parliament, where
he played no small part ; was Chairman of the London
County Council, president of nearly all the scientific societies
at one time or another. Warden of Birmingham University,
and Rector of St. Andrews ; but even the two volumes
before us are not sufficient to record a very great deal of
the useful work which Lord Avebury did. We are reminded
of his support of Darwin, and that we owe the terms
" palaeolithic " and " neolithic " — now household words in
science — to Lord Avebury. Educational movements in this
country have profited by the help of Lord Avebury, which
he was ever ready to give, and not the least of his endeavours
was that to preserve something of the beauties and anti-
quities of our land.

The biography of Lord Avebury strengthens one's feeling
gained from the lives of other famous men, whose career
at school was cut short, that our system of education is not
calculated to encourage individuality, and that those who
go through the ordinary school course, and make their way
in the world, succeed in spite of it. In conclusion, we may
say that every thinking person would be the better for
carefully reading Sir John Lubbock, Lord Avebury's
life. W. M. W.

CHEMISTRY.
Photo-Chemistry.- — By S. E. Sheppard, D.Sc. 461 pages.
47 illustrations. 7£-in. x 5-in.
(Longmans, Green & Co. Price 12/6.)
This is the latest addition to the series of text-books
of physical chemistry edited by Sir William Ramsay, and
it fills a distinct gap in chemical literature. Most of the
previous treatises on the subject have dealt, in the main,
with the reactions of light in its special adaptation of
photography, and there was no convenient handbook
discussing the other aspects of photo-chemistry. The
boundaries of this division of chemistry are not well-defined,
for some of the radio-active phenomena also fall within its
scope, and are therefore briefly touched upon in this book.
It has been the author's aim, not to describe all the known
photo-chemical changes, but rather to discuss typical
instances at sufficient length to illustrate the theory. The
book thus fulfils the true function of a practical handbook,
of throwing sidelights upon the meaning of new phenomena
met with by the student, and full references to original
papeis are given on every page. The branches of the subject
discussed include the measurement of quantities of light,
the absorption of light, dynamics of photo-chemical change,
special photo-chemistry, genesis of light in chemical change,

and organic photo-synthesis (including the chemistry of
chlorophyll). It is a book that should find a warm welcome
from the chemist, the photographer, and the botanist
with a knowledge of chemistry.

C. A. M.

GEOGRAPHY.

A Little Book on Map-Projection. — By M. Adams. 108 pages.

41 figures. 8J-in. x 5J-in.

(George Philip & Son. Price 2/- net.)

To the non-mathematical student of geography no part
of the subject presents so many difficulties as the study of
map-projection. Although several excellent books on
the latter subject have been written, the treatment in these
is, without exception, mathematical, and hence incompre-
hensible to many. For this reason alone this book by Miss
Adams should be found exceedingly useful. The subject
is treated in a strictly non-mathematical fashion, and even
the simple trigonometric ratios only appear in some non-
essential paragraphs. As is to be expected, the arrangement
of the subject-matter is not strictly logical, but this does not
in any way diminish the lucidity of the explanations.

The first part of the book treats of the principles of
map-projection, and of the various geometrical concepts
connected therewith ; while in the second part is given a
description of the types commonly in use. Sundry mathe-
matical notes on certain of the latter are given in an appen-
dix. A number of diagrams illustrative of the different
projections are of much assistance in the comprehension
of the descriptive parts (the diagram of the gnomonic
projection is a trifle confusing, however.) In view of the
great development of modern geographical teaching,
this book should prove valuable, both to teachers and
students, and it can be recommended as an attractive pre-
sentation of a subject usually considered somewhat " dry."

A. S.

FORESTRY.

Elements of Forestry. — By F. F. Moon, Professor of Forest

Engineering, and N. C. Brown, Professor of Forest

Utilisation, New York State College of Forestry,

Syracuse, N.Y. 392 pages. 8J-in. x6J-in.

(New York : John Wiley & Sons. London :
Chapman & Hall. Price 8/6 net.)

We have watched with interest the growth of State
forestry in the United States from its beginning under Dr.
F. B. Hough, in 1876, to the present day. In 1882 Dr.
Hough published a work with the same title as that now
before us — an excellent work, but based necessarily on the
experience of European countries. Not till 1891 was Presi-
dent Harrison empowered to reserve national forest land ;
but the thirteen million acres that he set aside, to which
President Cleveland added twenty-two million, rose under
President Roosevelt to one hundred and ninety-four and
a half million acres, " under the control of an efficient,
non-political, technically trained " Forest Service.
Deservedly, therefore, is this book dedicated to the last-
named ex-President as the man who " aroused the American
people to the importance of forestry as a national issue."
This importance is categorically demonstrated by the authors
under the following four reasons : —

" First. — We are cutting our timber about three times
as fast as it is growing.

" Second. — Our per capita consumption is unnecessarily
high, being two hundred and sixty cubic feet against
forty cubic feet in Germany and twelve cubic feet in
Great Britain.

" Third. — Our per-acre production has sunk so low
under the poor forest management until it is only about
one-fourth of the possible yield.

" Fourth. — Already the end is in sight for some species
of timber, and the virgin supply of forest material in the

April, 1915.

KNOWLEDGE.

127

United States will be practically exhausted by the year
1950."

This being so, it was clearly opportune that an up-to-date
textbook on the general subject should appear ; and the
present work is in marked contrast to Dr. Hough's book of
1882, in that it is the exposition of a complete system of
forestry of purely national growth and character. Al-
though, of course, the general principles of the physiology
of the tree, of what the authors term " silvics," and even of
sylvicultural management, forest protection, mensuration,
and technology, are the same everywhere, the application of
these principles to American species and American con-
ditions gives a thoroughly local colour to the entire work.
These principles, including also those of wood utilisation,
wood preservation, and forest finance, are so clearly set
forth as to render the book useful to anyone concerned with
timber or forestry in any land ; while the map and the
second half of the text give a more succinct and intelligible
account of the forest regions of the United States than we
remember to have met with anywhere else. A tolerably
full glossary of technical terms is given ; but the English
reader might be glad of an explanation of a good many
words, such as " burlap," " duff," " excelsior," " kerf,"
" ross," and " tierce," which find no place in it. As, how-
ever, the title-page bears the (to us) unusual inscription,
" First Edition First Thousand," we r.iay well look forward
to seeing all such terms explained in some future reissue.
A bibliography — mainly of United States Government
publications — is added to each chapter ; and the apparent
ambiguity of such names as Yellow, Hard or Norway Pine,
Red Cedar, and so on, is obviated by an appendix in which
the scientific names are given.

G. S. BOULGER.

LOGIC.

Logic : Deductive and Inductwe. — By Carveth Read, M.A.
417 pages. 7£-in. x 5-in.

(Alexander Moring. Price 6 /-)

This, the fourth edition of Mr. Read's " Logic," has been
completely revised, and some new sections have been added.
In the main, the author follows Mill, though not without
occasionally criticising his position. The first part of the
book, dealing with deductive logic, seems very satisfactory
on the whole, the author's presentation being straightforward
and clear, though the determination of the nineteen moods
of the syllogism and their reduction to the first figure
are treated rather briefly.

The latter part of the book, dealing with inductive logic
and allied topics, is of more questionable value, the writer,
it seems to me, lacking something of Mill's precision. Some
of the sections are, indeed, excellent, such as those on " The
Canons of Direct Induction " and " Definition of Common
Terms." But the defects in the chapters on " Transition
to Induction " and " Causation," and elsewhere, are so
serious that one hesitates to recommend the book to
students. In metaphysics, " causation," and consequently
" explanation," has an entirely different connotation from
that with which it is used in logic and the natural sciences.
It is very necessary, therefore, in a treatise on logic to make
this difference quite plain, especially as the common use
of these words has a vague idea of their metaphysical
meanings behind it. Now, Mr. Read not only fails to
do this, but habitually writes of " physical " causes as
though they were " efficient " cm i a well. Great stress,
moreover, is laid upon the principles of conservation of
matter and conservation of energy. But to base logic on
the principles of physical science, which themselves must
seek their justification in logic, is surely to argue in a circle ;
and the danger of this particular circle is the more evident
now that the principle of the conservation of mattei has
been called in question. Moreover, such a fallacious
statement as "... all Times and all Spaces are com-
mensurable, although in certain relations of space (as «•)

the unit of measurement must be infinitely small," is surely
remarkable in a book on logic, ^"hat, in fact, does the
necessity for an infinitely small unit imply but that the
things so needing to be measured are incommensurable ?

In the chapter on " Hypotheses " the author appears to
be straining after an unattainable ideal. As Poincare has
pointed out, every phenomenon permits of infinite hypo-
theses valid in the scientific sense of the term. The
pragmatic criterion is the only one that offers us any escape
from this burden of infinity ; and using that criterion we
should adopt that hypothesis which is simplest, and there-
fore most useful. There is no hint, however, of anything
of this in Mr. Read's treatment of the subject. These
defects are the more regrettable because of the commend-
able quality of much else in the book. There are thirteen
pages of examination questions at the end, but no index.

H. S. REDGROVE.

PHYSICS.

The Principle of Relativity. — By E. Cunningham, M.A.
221 pages. 8§-in. x5i-in.

(Cambridge University Press. Price 9/- net.)

The subject of this treatise has received a large degree
of attention since Einstein, ten years ago, brought the theory
of Relativity into prominence. The doctrine itself may be
regarded as teaching the futility of all experimentation with
a view to determining the motion of matter with respect
to the ether, if one is assumed to exist. If one does not
postulate any ether, then the principle resolves itself into
a denial of the possibility of determining absolute velocity
in a physical sense. Although beginning with a negative
hypothesis, the results are by no means limited to negations.
As the author unfolds the results of the theory, one is
reminded of the consequences flowing from the denial of
a perpetual motion, or of the statement that heat will not
of itself move from a place of lower to a place of higher
temperature.

The author is a well-known mathematician, a fellow and
lecturer of St. John's College, Cambridge, and it is therefore
natural to expect a highly mathematical treatment of the
subject ; but the mathematical part has been compressed
so as to leave room for very clear accounts of the optical
and electrical experiments bearing on the subject. In fact,
a large portion of the work will be read with ease and pleasure
by the non-mathematical reader. The usual table of con-
tents is reinforced by a very lucid and well-written summary
of each chapter, which will be especially useful to serious
students. The references given to the chief original papers
will form a vers- welcome guide to the voluminous literature

of the subject.

J. H. V.

Introduction to Physical Metallurgy. — By Walter Rosen-
hain, B.A., D.Sc, F.R.S. 368 pages, 53 figures in the
text. 88 figures on 32 plates. 8J-in. x5i-in.

(Constable & Co. Price 10/6 net.)

The arts of winning metals from their ores, and of fashion-
ing these mi't.ils into weapons and implements, have been
practised from prehistoric times, but the systematic study

0l the internal constitution and physical properties of

metals and alloys- the science oi Physical Metallurgy —
can l>r said to date only from 1864, when Sorby first noted
the striking similarity in the nature oi the microstructures
of steel and minerals in fact, nearly all the names uso-
ciated with tins branch oi science are those oi men suii
alive, and actively conducting investigations at the present
day.

This state of things naturally implies a large output of
original work which only .i fortunate few have tune to
follow closely. It implies, moreover. special methods of
investigation, and even .i special nomenclature, which make
it difficult, or even impossible, for those not familiar with

128

KNOWLEDGE.

April, 1915.

the science to understand the papers in which the results of
investigations are described.

The value of a book, therefore, which, while not over-
burdened with detail, yet gives a clear survey of the methods
of investigation and of the results so far achieved, cannot
easily be overrated ; and Dr. Rosenhain is to be congratu-
lated on having given us in the present volume just such
a book. The microscopic examination of metals, from the
selection and preparation of the specimen to the interpreta-
tion of the structures revealed, is discussed with the sure
touch of one with considerable experience, whilst the
lucidity with which the construction of constitutional
diagrams is described, and several typical alloy systems —
and notably the iron-carbon system — are discussed,
reveals the born teacher. The second half of the book
is devoted to " the properties of metals as related to
their structure and constitution." In this part are dis-
cussed the mechanical testing of metals, the effect of
strain, and the thermal and mechanical treatments of
metal. The final chapter deals with " Defects and Failures
in Metals and Alloys." The book is illustrated with numer-
ous excellent reproductions of photomicrographs, but the
omission of all details as to subject and magnification on
the plates themselves, and in most cases of the page number
of a given plate in the text, is a constant source of annoy-
ance to the reader, necessitating repeated references to the
list of plates at the beginning of the book. It is unfortunate
also that the chapter on " The Thermal Study of Metals
and Alloys " should be marred by several typographical

errors. With these exceptions, however, we have nothing
but praise for a book which can be unreservedly recom-
mended to all who are beginning the study of physical
mi'tallnrgy, and to those who, as manufacturers or users,
are chiefly interested in the properties of metals from the
" practical " side

T. S.
POND LIFE.

/'"/.<</ Life. — By E. C. Ash. 92 pages. Numerous figures
in the text. 6 j-in. x 4£-in.

(T. C. & E. C. Jack. Price 6/- net.)
Ponds and puddles have a fascination for the young ;
and, if some knowledge of the many interesting creatures
which live their life in small volumes of water is acquired,
the interest remains or increases in after-life. Mr. Ash's
little work, which is one of the series produced at the cost
of sixpence by Messrs. Jack, under the title of " The People's
Books," gives an account of the inhabitants of our ponds.
It is written in a light, not to say even jocular, vein, and
gives a good idea of what the enthusiast may expect to
find. Microscopic plants, infusoria, insects, spiders, mites,
aquatic worms, and amphibians are among the subjects
which are considered. We do not like to see Latin names
printed in ordinary Roman type, and zoologists do not use
capital letters for specific names ; still these are matters
which will not affect the general reader, who will find much
that is attractive in " Pond Life."

W. M. W.

NOTICES.

THE FLEMISH SYSTEM OF POULTRY-KEEPING.
- — Country Life asks us to announce a series of articles
which will shortly appear in its columns by Madame Albert
Jasper on " The Flemish System of Poultry-keeping."

THE " LONDON " MICROSCOPE.— We have received
from Messrs. R. & J. Beck a leaflet showing three models of
their " London " microscope, with the various objectives
and condensers suggested for use with them, the whole
being set out in such a way, with each item priced separately,
that anyone can tell at a glance what any particular outfit
would cost.

COCKROACHES AT THE ZOOLOGICAL GARDENS.
— On February 23rd, at the meeting of the Zoological
Society of London, Dr. P. Chalmers Mitchell, F.R.S., F.Z.S.,
Secretary to the Society, exhibited mounted examples of
three species of Cockroach — Periplaneta americana, P.
orientalis, and Phyllodromia germanica — all of which had
established themselves in different houses in the Society's
Gardens, and stated his wish that some naturalist would
endeavour to work out the causes of the selective distribution
of these insects.

PHOTO-MICROGRAPHY.— At the end of the course of
lectures on Photography which Mr. E. Senior is delivering
at the South Western Polytechnic Institute he will give
six practical demonstrations on Photo-micrography on
Monday evenings, from 7.30 to 9.30, beginning on
May 3rd. At these demonstrations special attention will
be given to the photographing of etched surfaces of metals
and alloys (metallography), but the course will also be
arranged to suit the requirements of students of geology,
botany, and so on, and of those wishing to use their own
microscopes to obtain photographic records of objects.
It is advisable that students joining this course should
possess an elementary knowledge of photographic manipu-
lation. The fee for the course is 2 /6.

A NEW PHOTOGRAPHIC PLATE.— A new plate has
been introduced by Ilford, Limited, for the use of those
engaged in Press - photography : it combines extreme
rapidity with quick development, quick fixation, and quick

drying, and should prove valuable to those photographers
who practise this class of work. It is supplied at popular
prices, and a sample for testing purposes will be forwarded
post free upon receipt of a professional card. The plate is
known as the " Ilford Press plate."

BOXWOOD FROM SOUTH AFRICA.— Our chief
supplies of boxwood for many years have been drawn from
the countries bordering on the Black and Caspian Seas.
These supplies have now been cut off, so that boxwood is
difficult to obtain and expensive to buy. The Imperial
Institute has recently examined the wood of Buxus
Macowani from South Africa. Several firms using box-
wood have also tested it, and the general opinion being
favourable, the Imperial Institute has suggested to the
Government of the Union of South Africa that it would
be well to place a trial shipment of this South African
boxwood on the London market.

GLASS APPARATUS FOR EDUCATIONAL PUR-
POSES.— Sir Alexander Pedler has sent us, on behalf of the
British Science Guild, a joint report of the Education and the
Technical Education Committees on the provision of glass
apparatus for educational purposes. The Joint Committee
has been endeavouring to obtain assurances of support for
British makers of educational glassware after the war as
well as now, and has also collected information respecting
the principal types and size of glass apparatus which is
in greatest demand. Seventy-one per cent, of the head
masters of the schools represented on the Head Masters'
Conference have authorised their science staffs to purchase,
as far as possible, only British-made glass apparatus during,
and for a period of three years after the conclusion of, the
war. In other directions fewer definite replies have been
received, owing to the fact that committees and boards have
to be consulted before an answer can be given. Another
report deals with the manufacture of optical instruments,
and we most heartily endorse the suggestion that the
Government should undertake the necessary research that
must be carried out before optical glass suitable for micro-
scope and photographic lenses, equal to that made at
Jena, can be produced in England.

April. 1915.

KNOWLEDGE.

PRUDENTIAL ASSURANCE COMPANY, LIMITED.

Chief Office: HOLBORN BARS, LONDON.

Summary of the Report presented at the Sixty-sixth Annual Meeting

held on 4th March, 1915.

ORDINARY BRANCH.— The Dumbei ar was

65,751. assuring the sum of £6.318,843, an annual premiui

of £424,353. The premiums received during the year were £5,035,625, ■ i a

i £115.107 over the year 1913. In addition, £10,315 premiums

under the Sickness Insurance Tables. The claims £4.014.658.

The number of deaths was 9,351. matured

was 24,986, the premium income of which was £136,735.

The number of policies in force at the end of the year v 922.505.

IXDrSTRIAL BRANCH. — The pn m ring I ar were

£8.176,202, being an increase of £301.746. I!
£3,373.850, including £393.360 bonui
including 6,731 endowment assurances matured, was 392,883. ["he nuinl i

- granted during the year to the*
upwards, who desired to discontinue their payments, was 103.514, the number in
force being 1,947,556. The number of free policies wh during th

year was 46,364.

The total number of policies in force in this Branch .it the end of the yi
20.085.010 : their average duration exceeds thirteen

The assets of the Companv. in bnth branches, as shown in tl
£91,202,344, being an increase ot £4.209.341 i ver th. < : 1913.

The outbreak of hostilities in August last placed u[*<n th
I llity of deciding what charg
active service. After careful consideration it was premium

in respect of existing policu s on I

■ spect o! existing p lii ies a the In if other members ol tin- regul
it was decided that £250 of assurance on any life should I e exempted from the pay-
ment of extra premium.

In the Ordinary B £110.

■
1876.
In the Industrial Bi
■

-
inclush

5\
10'
15

50
55

60

Premu

.til 10 ve

15 .

20 ,

25 .

30 ,

35 .

40 ,

50 ,

55 ,

60 ,

£2 10s. ;

£5

£5

i: 10s.

£10

£12 lCs.

£15

£20

£30

£40

£50

£60

■
1911 ha\
-
g £3.000 000 '

Balance Sheet of the Prudential Assurance Company, Limited,

being the Summary of both Branches, on the 31st December, 1914.

LIABILITIES.

Shareholders' capital ...
i ranee fund —
Ordinary Branch
Sickness insurance fund
irance fund —
Industrial Branch

1.000.000 0 0

£47.024.190
13.562

40.649.318 9 8

Investments reserve funds

Courts (Emergency Powers A>:l Reserve

Claims under life policies intimated and in course "I ;

Annuities duo and unpaid ...

Balance of bonus under life policies reserved tor distril

87.687.071 4 1

1.750.000 0 0

300.000 0 0

233.518 0 7

3.171 13 4

228.582 15 10

£91.202.343 13 10

ASSETS.

Mortgages on property within the United Kingdom 8,882,496 5 4

Mortgage- on property out of the L'nit. .1 Kn .^ 1- ni 336.449 2 9

Loans on parochial and other puUi' in. - ... ... ... 13.412,347 14 8

Loans on Life interests 1,193.287 0 11

Loans on Reversions 96,502 18 3

Loans on stocks and shares ... ... ... ... ... 76,385 2 0

Loans on Company's policies within their surrender values ... 3,221,385 7 9

Pel ional security ... ...

Loans to Educational institutions sc 43.969 19 1
Investments : —

it with the High Court (£24,400 2}% C olidati 17,568 0 0

Carried forward

£27.280.391 10 9

ASSETS
Invcsti

■
K.ulu.i

-

Life inl
Agents' balaw

:.230.391 10 9

1.41 3. 36S

143.117

4.621.551

•

5.411.862 IS 11

I S 10 11

4.115.S13 0 6

1 5

2 10
10 7
12 10
IS 11

5

21.S47.943
3.193.674

4,783.46!

9.143
4.200.467

:. 8.4 1

115.010

52^.743

14 S

4 I

6 6

11 7

19 11

10 7
16 0

11 S

1 0

The values of the Stoi kl
middle mark -

than provided ter by the Investments Ri
We certify that in our bclicl the Ass. I
therein less thi I
business to which it is ap]

A. C. THOMPSON, Cm, " '

20.000
1.241. 167

0 0
17 5

£91.202.34;

13 10

port th.it with the assistant e ol the t hai
explanati ins that wc haw n quired, an I in our opinion such m
of the state ol the Company's affairs according to tht

i!v for any purp »c otha tl

1*1111.1 *

l

We have « • I mil paymcnl

we find the sai VYc have al

out in tl lUDti ' ■ " ■

. 1915. ~ M I on il , n ;

KNOWLEDGE.

April, 1915.

CLARKSON'S

SECOND-HAND

OPTICAL MART.

TELESCOPES.

4$>in, W'rny.ni

r i : i massif c oak

lath siaml with

hers, liori-

7oni.il and vertical

moi ;n t s by

I [i ioke's joint,
slow mi i

in dei . .1 astro, ami
i .i.i\ ' \ epiei es £-40
4-in..full,Nejpretti
& Zumbra.ili.i/..
finder, 1 day, ;

. ase
:.'..in. Baker, altaz., hoi izontal and vertical

motions, findei . da} ami .■ astros,
1 -in. Casella, altaz., 1 daj . ■ astros.

Steward, on altaz. with equatoi ial

rcles), 1 day, 2 astros.
Wood, 1 astro, and 1 day eyepie* es

Mans ■''

Also Eyepieces, Finders, Diagonals, etc.

MICROSCOPES.

Ituctil ,

1(1

15 is

14 14 o

I.! 15 0

IS

MICROSCOPY. SECOND-HAND DEPARTMENT.

Watson

eyepieces, 1 -in., 1/6,
oil immersion

oltjccm 1 triple 1

piece, universal con-
denser . -
\\ ;it<on ' ' Edinburgh

M," , t/6, i/j o.i.,

piei es, triple

ei '■, and AMie

Kcck Large "London,"

; eyepii ■

and 1 i.j ■■!' immei sii >n

. tives, triple nosepiece, spiral Abbe

and iris, me< hanical stage, as new
Baker "D.P.H." No. 1, 2 eyepieces,

Leii/ ; ami 7 objectives, triple

n -■ piece, Vbbe condenser
Watson "Fram," eyepiece, spiral,

\ i- ; .' mble nosepiei e 1 \

and 10 . .

Leitz Mb, eyepiece, 3 and 7 objectives,

d< mbli piral A h and ins

Heck Small "London," spiral, \Ki"

and iris, double nosepiece, 2/3 and 1/6
Sw ift " Discovery," eyepiece, 2/3,

1 6, double nosepiece ..
Beck ".Star," sliding coarse and micro-

meter line adjustments. 1 eyepiece. 2/3

and 1/6 objectives, di mble n use piece.

spiral Abbe and in-, no case 3 5 o

Many others. Also Objectives (a large stock by all the
ending makers), Kyepieces. Double and Triple- Nose-
,■ . 1 ■■ . ( Condensers, Lamps, Spectroscopes, Miootoines,

PRISM BINOCULARS

BY
ROSS. ZEISS,
GOERZ. etc.,

FOR SALE

AND
WANTED.

338 HIGH HOLBORN

(I Ipp site Gray's l"n Road),

LONDON.

SPECIALLY ATTRACTIVE SLIDES
FOR POPULAR EXHIBITION V STUDY.

Zoology, Marine and Freshwater.

Unique preparations, wit/tout pressure^ in their natural
form and beauty foi Dark Ground (■>■ transparent),

1 ,v\, M,-<it4s<r, Polyzoa, with their glorious .uia\

■ >i tentacles; ffofothurians with wheel plates, etc.; ■>
■ in of th< curious Salfa and other Tunicata ; youn

developing in their eggs ; the celebrated
(W ; also the Radiolarian Spheerozoum^ the "Volvox of
the sea," etc., etc.

Insects and Parts. I.arvaof /7«;>/(-,/<,'/i«/
(also for polariscope). Superb tongues of the rare
Sylvan Wasp and Hornet, also piercing organs of the
Gaafly, etc.) etc.

Special Cements, Forceps. - 1 etc, etc., for

Mounting and Dissecting.

SECOND-HAND
INSTRUMENTS,
OBJECTIVES, &c.

NEW LIST

NOW READY.

Post free on request.

To Beginners."— Expert advice freely given

on ^election of suitable equipment; much time and
needless expense can thereby be saved. Write 01 call.
WuNTFD Microscopes, Objectives, etc., or whole

Outfits purchased for Cash.

EXCHANGES M*

CLARKE & PAGE,

25, Thavies Inn, Holborn Circus, LONDON.

LIVING SPECIMENS

FOR THE

MICROSCOPE.

Vol vox globator, Desinids, Diatoms, Spirogyra,
Amceba, Actinophrys, Spongilla, Vorticella, Stentor,
Hydra Cordylopohra, Stephanoceros, Melicerta,
Polyzoa, and other forms of Pond Life, 1s. per tube,
with printed drawing, post free. Thomas Hoi. ton,
Naturalist, 25, lialsall Heath Road, Birmingham.

MINERALOGY AND
GEOLOGY.

JAMES R. GREGORY & Co.,

Mineralogists, &c.

Are in .1 better position than ever for supplying

Collections of Minerals, Fossils & Rocks,

A* they hav

ateriaj.

LISTS AS USUAL.

139, Fulham Road, South Kensington, S.W.

Tele
Telegri

Western '2X41.

1 Meteorite:.. Londo

Microscopes, Telescopes, Spectroscopes,
Binoculars, Surveying Instruments, 4c,

BY THE BEST MAKERS AT MODERATE PRICES.

Lists sent post free on request.

Scientific Instruments Sought, Exchanged and Sold

on Commission.

JOHN BROWNING,

146 STRAND, and 72 New Oxford St..

LONDON.

Telegrams :

'AUKS," LONDON.

Telephone
884 GERRARD.

Established

Stevens' Auction Rooms,

38, KING ST., COVENT GARDEN, LONDON, W.C.

Every FRIDAY at 12.30, Sales are held at the
Rooms of Microscopes and Slides, Telescopes,
Si rveving Instruments, Electrical and Scien-
riFic Apparatus, Cameras and Lenses, Lanterns
and Slides, Cinematographs and Films, in great
variety, Lathes and Tools, Etc.

Goods may be sent for inclusion in early Sales.

Settlements made one week after disposal.

Catalogues and all Particulars Post Free.

Valuations for Probate or Transfer, and Sales con-
ducted in any part of the Country.

FOR ALL KINDS OF EDUCATIONAL

Mineral Material,

COMMON ORES, and SELECT CRYSTALLIZED
SPECIMENS, at ALL PRICES.

G. H. RICHARDS & Co.,

Dealers 'n all kinds of British and Foreign Mineral
Specimens.

PRICE LISTS FREE.
4£ Sydney Street Fulham Road, South Kensington
London, S.W.

F. WIGGINS & SONS,

102, 103, 104, Minories, LONDON, E

Contractors to H.M.
Government.

FOR

LAMPS.

STOVES.

VENTILATORS,

ELECTRICAL WORK

AND ALL PURPOSES.

Largest Stock in the World. Tel. No. 2248 Avenue.

Printer of
' Knowledge.

JOHN KING,

Uxbridge, Southall, and Ealing,

T s favourably equipped for the PRI NTI NG of

*■ Scientific Hooks, Brochures, Catalogues, &c, ami
will be pleased to submit estimates.

Address all Communications to

213, UXBRIDGE ROAD, EALING, LONDON, W.
"Phone: 1144 Ealing.

Binding Cases for Knowledge Volume, 1914.

IN BLUE CLOTH, WITH GILT DESIGN AND LETTERING.

9d. net each : by post,

Knowledge Office: AVENUE CHAMBERS, BL00MSBURY SQUARE, LONDON, W.C.

A most acceptable Girt at any time.

KNOWLEDGE VOLUME FOR 19 14.

Container; 440 Pages m'Ii 425 Illustrations, many being Full Page Plate'..
... .i in Blue Cloth. <dlt Design and Lettering, 15.- net. post free within the United kingdom.

Publishing Office: AVENUE CHAMBERS, BLOOMSBURY SQUARE, LONDON, W.C, or through any Bookseller.

April, 1915.

KNOWLEDGE.

WATSON'S
MICROSCOPES

The best obtainable. British-made throughout.

F.FFIflTF.NT • Enable the worker to get the best out of his
*■"■ »v>AAjn x . jnstruinellt-

CONVENIENT '. Eiery necessary movement is embodied.

STABLE " With either tripod or horseshoe foot.

PRACTICAL : Intended fur hard work.

LAST A LIFETIME.

The "RESEARCH" Microscope.

Specification : —

Mechanical Stage — Giving move-
ments 2" X If. Both milled
heads on same axis.

Fine Adjustment — Side limb,
vertical lever type.

Coarse Adjustment — Diagonal
rack, long range, enables
3" objective to be focussed when
on nosepiece.

Compound Substage — Rack and
pinion focussing with centering
screws for condenser.

Movements are slotted and sprung
throughout, and wear can be at
once compensated.

Tripod foot giving stability in
any position.

Guaranteed for 5 years.

Fop the Amateur op Professional this
instrument embodies every desirable movement, and
,is at once the cheapest and the best
obtainable.

Prices: — ,

Research Microscope ...

£12 10 0

00. 00. with eyepieces
No. 2 and No. 4, objectives 1" and
.11 mm. working distance for pond
life or blood counts), aplanatised
Abbe illuminator with iris diaphragm.
In mahogany case 17 17 6

Full details of the above, and also of 32 Different
Models at all prices, will be found in Watson's Micro-
scope Catalogue, No, 2 k, which will be forwarded
gratis on application.

APPARATUS FOR:—

PHOTOMICROGRAPHY. POND LIFE.

METALLURGY. PETROLOGY.

BACTERIOLOGY. PROJECTION.

HEMATOLOGY, &c, &c.

W. WATSON & SONS, LTD.,

Contractors to fx/ny eovetnments,
313 HIGH HOLBORN, LONDON, W.C.

Branches :

16 Forrest Road, Edinburgh; I96 Great Portland Strew, London, W.

Dki-6ts :

2 Easy Row, llirminiiham; 78 Swanston Street, Melbourne, Australia:

2I2 Notre Dame Street West, Montreal, Canada.

Optical Works— HIGH BARNET, HERTS. ESTABLISHED 1837.

The BECK BINOCULAR

BECK BINOCULAR MICROSCOPE.
No. 1081 P.S.

(Patent applied for)

Not only an advance on
previous Binoculars, but
better tban a Monocular
with all powers.

1. Resolution equal to that

of a Monocular.

2. Equal illumination in

both eyes.

3. Short tube length, mak-

ing Microscope com-
pact.

4. No special object-

glasses or eyepieces

required.

5. Standard angle of con-

vergence.

6. Stereoscopic vision.

7. Binocular vision, saving

eyestrain and giving
better results than
Monocular vision.

8. Converted into a Mon-

ocular by a touch.

Full descriptive Booklet and Price List on application.

R. & J. BECK, Ltd- 68 Cornhill, London, E.C.

DENTS CLOCKS

WATCHES AND CHRONOMETERS

FOR SCIENTIFIC USE.

Sidereal op Mean Time Clocks for

Observatories, £21 and upwards.

THREE GRAND PRIZES
and ONE GOLD MEDAL

ill! FRANCO-BRITISH EXHIBITION.

The only Grand Prize awarded
to a British Firm for Watches,
Clocks and Chronometers.

The only Grand Prize awarded
for Astronomical Regulators.
Chronographs, and Ship's
Compasses.

TRADE MARK

61, STRAND, and 4, ROYAL EXCHANGE, LONDON.

Telephone So. 61 City.

UXB
PR

Address

JOH

RIDGE

If

NTING

and wi

N KING Printer of

•' r%ir»\J» "Knowledge,"

, SOUTHALL, AND EALING,

favourably equipped for the

OF SCIENTIFIC BOOKS, BROCHURES, Ac,
1 be pleased to submit Estimates.

Road, Ealing, London, W.

Tn.l«NOal . 114* |UI

CAUTION.

The Proprietors of SCHWEITZER'S
"COCOATINA, "FAIRY COCOA," &c,
beg to inform their clients that XOXE of their
products are manufactured in Germany ; that
they are a private E\GLISH COMPANY man-
aged by a Board of EXGLISH DIRECTORS; and
that all shares are held by relatives and con-
nections by marriage of the late sole proprietor.
Captain Thomas Edward Symons, R.N.

KNOWLEDGE.

April, 1915.

FOR

Zoology & Botany Classes & Forestry Work.

Adopted by Agricultural!} and other Colleges
under various Government Departments.

[Jauscfi [omf>

DISSECTING MICROSCOPE.

The best Instrument of its kind.

Has hinged base provided with suitable receptacles for imuj
instruments used in the work.

and dissecting

Complete with two Coddlngton
lenses, 38mm. and 19mm.,

Inland parcel post, Cd. ^^^_^_^_-______

ITS. 6d.

Foreign, Is. Ctl.

MICROSCOPES FOR AIL REQUIREMENTS UP TO THE MOSTADVANCED RESEARCH.

OVER 100,000 SOLD, WHICH ARE IN USE THROUGHOUT THE WORLD.

Call and Inspect at our New Showrooms, or ask for List "A 2" (Microscopes) post free.

Also particulars of MICROTOMES, PHOTO-MICROGRAPHIC and DRAWING APPARATUS, PROJECTION APPARATUS,
CENTRIFUGES, GANONG'S APPARATUS lor PLANT PHYSIOLOGY, VISCOSIMETEUS, Sc, on application.

N.B.— ALL OUR INSTRUMENTS BEING MADE AT OUR OWN
FACTORY IN ROCHESTER, N.Y., THERE WILL BE NO DELAY IN
DELIVERY, AND WE HAVE JUST RECEIVED LARGE STOCKS.

Trade Mark.

BAUSCH & LOMB OPTICAL CO.

Contractors to British and Foreign Governments,

37-38, HATTON GARDEN, LONDON, E.G.

[Telephone: Holborn 2640.] OR THROUGH ALL DEALERS. [Telegrams: "Optibalof, London:

Trade Ma

Dr. A. HUTCHINSON'S
NEW

UNIVERSAL GONIOMETER

For the Examination 0! Small Crystals and
Mineral Grains.

This instrument can be used lor any of the following purposes : —
As an Ordinary Goniometer for the Measurement of Angles.
As an Axial-angle Apparatus.
As a Kohlrausch Tolal-rerlectometer.

For Determining Refractive Indices by the Prism Method.
For Experimental U'oik in Mineralogy.

Descriptive PatrplUct on Application.

JAMES SWIFT & SON,

UNIVERSITY OPTICAL WORKS,

81, TOTTENHAM COURT ROAD, LONDON.

Pastorelu & Rapkin,

(Estab. 1750.) Ltd.

46, HATTON GARDEN,

LONDON E.C.

GLASS-TOP BOXES,

BOTH CARD &. WOOD, FOR COLLECTORS. MUSEUMS. &c,
for STORING SHELLS. EGGS, COINS OR OTHER OBJECTS.

In all sizes,

both pound

and

rectangular.

FLATTERS & GARNETT, Ltd.,

MAKERS OF LANTERN AND MICROSCOPE SLIDES,

309, OXFORD ROAD (%££'). MANCHESTER.

ACTUAL MANUFACTURERS of all kinds
of Meteorological Instruments.

STANDARD

INSTRUMENTS.

(With Kern Certificates, if dr.

id.)

Fort in's Barometers.

Maximum Thermometers.

Minimum Thermometers.

Hygrometers.

Earth Thermometers.

Sunshine Recorders.

Rain Gauges.

Anemometers.

Self-registering Rain Gauges.

, Barometers.

_ .. Thermometers.

Self-recording Rajn Gauges

1 Anemometers.

Etc.

Illustrated Price List Post Free.

ContractOPS to H.M. Government.

Telephone: 1981 Holborn. Telegrams: Rapkin, London.

\* We pay carriage and guarantee safe delivery
within U.K. on all our Instruments.

Printed for the Proprietors (Knowledge Publishing Company, Limited), by John King, Ealing and Uxbridge. — April, 1915.