iV'. MEMOIRS OF TIIK NATIONAL ACADEMY OF SCIENCES. ^^OLXJME II. 1883. WASHINGTON: GOVERNMENT PKINTINa OFFICE. 1884. m: E IM O I R s 1. Report of the Eclipse Expedition to Cakoline Island, May 1883. 2. Experimental Detei:mix\tion of Wave-Lengths in the nvisible Prismatic Spectrum; nv Prof. S. P. Lang LEV. 3. On the Subsidence of Particles in Liquids ; by Prof. W. H. Brewer. 4. On the Formation of a Deaf Variety of the Human Race ; by A. Graham Bell. :i NATIONAL ACADEMY OF SCIENCES. FIRST MEMOIR, REPORT ECLIPSE EXPEDITION TO CAROLINE ISLAND MAY, 1883. LETTER OF TRANSMITTAL. Princeton College, Princeton, N. J., December 22, 18S3. SiE : I biive tbe honor to transmit to you, tbrongh tbe bands of Professor Cofflu, the report of tbe committee of tbe Academy, to wliicb was intrusted tbe arrangements for securing obser- vations of tlie eclipse of May, 1883. It contains tbe reports and observations of Professor Holden and bis associates in tbe expedition, and 1 Jiave, in compliance witb a request of tbe comnnttee. prefixed a brief introduction, giving an account of tbe proceedings of tbe committee and of the organization of tbe party. Very truly yours, C. A. YOUNG, Chairman. Prof. O. C. Marsh, President of the National Academy of Sciences. T^BLE OF CO]sr TENTS Pag©. I. — Prefatory note by Prof. C. A. Young, chairmaa of the Eclipse Committee of tbe National Academy of Sciences - ----- ..-.--- n II. — Organization of the American Eclipse Expedition ..--..------------- 16 III. — Narrative of the journey from New York to Caroline Island and return, by Prof. E. S. Holden - - - 16 IV. — Caroline Island ..-......--..,...----- 20 i 1. Its history, by Prof. E. S. Holdek - ^io 5 2. Description of the island, by Prof. E. S. Holden and Lieut. E. F. Qualtrough, U. S. N. - - 22 ^ 3. Longitude of Caroline Island, by Mr. AVinslow Upton - - 26 § 4. Meteorology of Caroline Island, by Mr. WiNSl-OW Upton _... 41 (a). Description of instruments and station 41 (6.) General weather conditions ....- 42 (c). Meteorological observations between April 25 and May 9, 1833 - 44 (;?). Meteorological observations during the eclipse - --........ 53 (e). Diurnal periodicity of the southeast trade wind - -- 59 (/). Observations of solar radiation during the stay on Caroline Island - -------- 61 (3). Radiation observations during the eclipse - 85 (h). Curves of pressure, temperature, etc. ------..----.------- 86 5 5. Botany of Caroline Island: collections by I>r. AV. S. Di.xoN, U. S. N., and identifications by Prof. W. Trelease - 87 ^ 0. Notes on the zoology of Caroline Island, by Dr. W. S. DisoN, U. S. N. - - - 90 Memorandum on the butterflies, etc., of Caroline Island. Collections by Dr. J. Paxi.s.v ; iden- tifications by Dr. Authur Butler and Mr. Hermann Strecker ------ 92 § 7. Chemical constituents of the sea-waterof the lagoon of Caroline Island, determined by Messrs. Stillwell and Gladding - -- 96 V. — Observations of twenty-three new double stars, by Prof. E. S. Holden and Prof C. S. Hastings - 97 VI. — Plans for work on the day of the ecliitse, by Prof. E. S. Holden ---..-..--.--- 98 VII.— Reports on the eclipse of May 6, 1883 --------------- - 100 («). Report of Prof. Edward S. Holden - ------ 100 (b). Report of Prof. C. S. Hastings ------- - 102 (c). Report of Mr. Charles H. Rockwell ------- --.. 126 (d). Report of Mr. Erasmus D. Preston ...----.------------ 126 (f). Report of Mr. WiNSLOW Upton - --.....-.----- 1.33 (/). Repor(?of Ensign S. J. Brown, U. S. N. ------ - 136 (17). Report of Lieut. E. F. Qualtrough, U. S. N. - 139 (A). Report of Dr. W. S.Dixon, U. S. N. ------ - . 143 (i.) Report of Midshipman W. B. Fletcher, U. S. N. --------------- 144 (./.) Report of Midshipman J. G. Doyle, U. S. N. - 144 (k.) Memorandum in regard to the photographic observations of the eclipse by Mr. H. A. Law- rence ---------- - 144 S. Mis. 110 2 9 Fig. 2. GENERAL CHART OF CAROLINE ISLANDS. SOLAR ECLIPSE, MAY 6, 1883 INTRODUCTION By ri;or. ('. A. Youxo. The unusual duration of the total eclipse of May, 1883, early attracted the attention of astron- omers; but an examination of its track showed that it would not be visible at any well-known or easily accessible stations, and no preparations were therefore made to secure observations. In May, 1882, Mr. Ohaeles H. Eockwell, of Tarrytown, N. Y., while in the Sandwich Islands for the purpose of observing the trausit of Mercury, learned that there are two small islands lying almost exactly on the central line of the eclipse, and he determined to endeavor to have an eclipse expe- dition organized from the United States. He presented the matter before the Montreal meeting of the A. A. A. S. in August, but various circumstances prevented any definite action of that body. In November, 1882, the writer, at Mr. Rockwell's suggestion, brought the subject before the National Academy of Sciences at their New York meeting, and a committee was appointed, con- sisting of Messrs. Coffin, H. Drapeu, A. Hall, Hilgard, Newcomb, and H. A. Neavton, with the writer as chairman, to commend the project of an eclipse expedition to some suitably situated island in the Pacific, " to persons interested in the advancement of science, and^ to the Navy De- partment of the United States for such aid and facilities as can be best afforded." Subsequently, on the death of Dr. Draper, Professor Langley was appointed in his place, and Mr. C. S. Peirce was added to the committee. Mr. Kockavell also, though not a member of the Academy, was invited to join the committee, as having been the real originator of the project. Mr. Coffin was chosen secretary, and to his energy and wise and skillful management our success in organizing and sending out the expedition is due. It was at first proposed to raise the necessary funds for tlie expt^ditiou by private subscription, and Mr. Eockwell was put in charge of the matter. His own illness, the lamented death of Dr. Draper, and other untoward circumstances combined, however, to prevent his success, and on January 24 he reported that this plan must be abandoned. It was at once decided to apply to tlie Government. Early in February the committee presented the matter to the honorable Secretary ot the Navy, representing that the Department could greatly aid tlie undertaking by detailing a ship of the Pacific squadron for the transportation of the party, and by giving the use of certain astro- nomical instruments under its control. The application met with a prompt and favorable response. A meeting of the committee was lield in Washington on February 15, at which plans for the expedition were discussed and settled, and the chairman and secretary were directed to address further communications to the Secretary of the Navy to arrange plans of operation to secure the .services of suitable observers, to prepare necessary instructions, and, in short, to do wliatever was 11 12 MEMOIKS OF THE NATIONAL ACADEMY OF SCIENCES. needful and in tlieir power to secure the object desired. Prof. E. S. Holden, director of the Washburn Observatory, Madison, Wisconsin, was selected as chief of the party and its scientific director, and Mr. Kockwell as the disbursing and business agent. A memorial was presented to Congress asking for an appropriation of $5,000 to defray the neces- sary e.\i)enses of the party. This api)lication was heartily indorsed and supported by *he honorable Secretary of the Navy and by all the members of Congress who are interested in scientific matters; and the grant was obtained without any serious oppo.«ition. This appropriation, however, though practically secured, was not available in season for the departure of the expedition, and, to meet the diflSculty, the trustees of the Bache fund of the National Academy advanced $3,500, to be re- paid from the Congressional appropriation. Subsequently the Academy itself, on the recommendation of the trustees, authorized an appro- priation of $500 from the income of the Watson fund for observations of this eclipse. The party left New York on March 2, in the Pacific Mail steamer bound for Callao via Panama. At Callao they found the U. S. S. Hartford in readiness, and sailed at once for Caroline Island, arriving there on April 21. At Panama, in accordance with certain arrangements which had been made by cable between the Solar Physics Committee of the British Eoyal Society and our own committee, they were joined by Messrs. Lawrance and Woods, who were especially charged by the British committee with photogiaphic observations. A French expedition, under Mr. Janssen, also came to Caroline Island a few days after the arrival of our own party. The history of the expedition and an account of the work accomplished are fully given in the following reports of Professor Holden and his associates. We are under great obligations to all these gentlemen, Professor Holden, Professor Hastings, of Baltimore, Mr. Eockwell (who, in addition to scientific work, had charge of the disbursements and business matters of the expedition). Ensign (now Professor) S. J. Brown, U .S. N., Mr. E. D. Preston, of the United States Coast and Geodetic Survey, and Mr. W. Upton, of the Signal Serv ice. United States Army, for the zeal and intelligence with which each accomplished the work assigned him ; also to the institutions with which they were severally connected for granting to these observers prolonged leave of absence, and, except in the case of Mr. Upton, continuing their salaries without diminution. Our acknowledgments are specially due to Hon. W. E. Chandler, Secretary of the Navy, foi' continual interest and effective aid, without which we should have been unable to accomplish any- thing; also to the Superintendent of the United States Naval Observatory for the loan of instru- ments ; to the Superintendent of the United States Coast and Geodetic Survey, and to Commodore J. G. Walker, Chief of the Bureau of Navigation. Applications to the Secretaries of State and of the Treasury for certain assistance from their Departments were cordially and promptly granted, and we take the opportunity to express our thanks. The tribute paid by Professor Holden, in his report, to Captain C. C. Carpenter, command- ing the Hartford, and to his officers and crew, is cordially indorsed, as well as his api^reciatiou of the services of those ofiBcers who took part in the observations of the eclipse. The committee held a final meeting in Washington on October 23. The reports of Professor Holden and his associates (excepting .Professor Hastings) were presented, discussed, and put in proper form for presentation to the Academy at its November meeting in New Haven. The chairman was requested to prepare ati introduction to the reports, and it is in obedience to this request that the preceding pages have been prepai-ed. It would be improper to tiiil to state that the writer is indebted to the secretary, Mr. Coffin, for nearly all the substance and niuch of the form of what he has written. INTKODUOTION. 1 3 The reports of Professor Holden and his associates speak for themselves, aud will certainly be fouud valuable aud interesting. The question of an intra-Mercurial planet would appear to be definitely settled in the negative by Professor Holden's work. Professor Hastings's observa- tions, and his discussion of them, unquestionably open (if they do not also close) an important and interesting inquiry as to the correctness of certain generally received views as to the nature of the corona. The observations of Mr. Upton are extremely valuable, and the same is true of nearly all the others, throwing new light, as they do, not only upon the strictly astronomical problems of the eclipse, but upon the meteorology and natural history of a comparatively unknown region. Peinceton, December, 1883. OF tHE OPERATIONS OF AMERICAN EXPEDITION TO OBSERVE THE TOTAL ECLIPSE, 188;i, MAY 6, AT CAROLINE ISLAND, SOUTH PACIFIC OCEAN. To Prof. C. A. Young, Chairman of the Eclipse Committee of the National Academy of Sciences : My Dear Professor Young : It gives me great pleasure to address to you my report of the Total Solar Eclipse of May 6, 1883, together with the reports of the other members of the Ameri- can expedition and with a memorandum from the chief of the English photographic party which accompanied us. We had all hoped and expected to have you for our director in this expedition, and you will allow me to express my regret that unforeseen circumstauces prevented this. My first official connection with the expedition dates from my reception of the following letter of instructions, under which I acted: Washington, D. C, February 28, 1883. Prof. E. S. HOLDEN : Dear Sir : The Committee of the National Academy of Sciences on the Solar Eclipse of May 6, 1883, has selected you as the Chief and Scientific Director of the party organized under its direc- tion for observations of the various ijuenomena on that occasion ; to prescribe and arrange the work of each member, except so far as it may have been laid down by the committee in special instructions to any one, or may have been assigned to the representative of the United States Coast and Geodetic Survey. The names of the party and the letter of instructions to each have been communicated to you. This leaves the eclipse work iu your hands, but the committee desires that every facility which can be obtained, be afforded Mr. Preston for his gravity determinations. As for your own special work, the search for intra-mercurial jjlanets, the programme sketched ERRATA. Page Hi, line 11. — The stateiiieut in liuo 11 is derived fruiii a letter of Mr. Arundell, and is uudoubtedly correct. The fifty or cue hundred people spoken of on pajje il, line 25, were probably imported workmen. Page "24, Pig. 6. — By an error, which was discovered too late to be corrected, the shadow.s of the foliage in Fig. 6 are those of a northern forest. They should be fir less marked and regnlar, and the trunks of the trees should all be brilliantly lighted. With thi.s exception, the cut shows the character of the growth admirably. Page :U, line '> fw)m bottom. — For "27 AS read 'iTSit. Page 33, line 10 from bottom. — For di.scordancies raiil discordances. Page 43, title of cut. — For Fig. 15 read Fig. 13. Page .50, title of cut.— For Fig. 16 read Fig. 14. Page .57, title of cut. — For Fig. 17 read Fig. 15. Page 58, title of cut.— For Fig. 1« read Fig. Ifi. Page 67, title of cut.— for Fig. 10 rend Fig. 17. Page 80, title of cut.— For Fig. 13 read Fig. 18. Page 86, title of cut.— For Fig. 14 read Fig. 19. Page 113, line 11. — For Jasskx read Jansskn. OF THE OPERATIOiXS OF AMERICAN EXPEDITION TO OBSERVE THE TOTAL ECLIPSE, 1883, MAY G, AT CAROLINE ISLAND, SOUTH PACIFIC OCEAN. To Prof. C. A. YotTNft, Chairman of the Eclipse Committee of the National Academy of Sciences : My Dear Professor Yoxjnct: It gives me great pleasure to address to you my report of the Total Solar Eclipse of May 6, 1883, together with the reports of the other members of the Ameri- can expedition and with a memorandum from the chief of the English photographic party which accompanied us. We had all hoped and expected to have you for our director in this expedition, and you will allow me to express my regret that unforeseen circumstances prevented this. My first official connection with the expedition dates from my reception of the following letter of instructions, under which I acted: Washington, D. C, February 28, 1883. Prof. E. S. HOLDEN : Dear Sir : The Committee of the National Academy of Sciences on the Solar Eclipse of May 6, 1883, has selected you as the Chief and Scientific Director of the partj' organized under its direc- tion for observations of the various phenomena on that occasion; to prescribe and arrange the work of each member, except so far as it may have been laid down by the committee in special instructions to any one, or may have been assigned to the representative of the United States Coast and Geodetic Survey. The names ot the party and the letter of instructions to each have been communicated to you. This leaves the eclipse work in your hands, but the committee desires that every facility which can be obtained, be afforded Mr. Preston for his gravity determinations. As for your own special work, the search for intra-mercurial planets, the programme sketched in your letter to me of February 6, marks out distinctly what you should aim at accomplishing. I send you letters to Admiral Hughes, commanding United States naval forces, Callao, and to Captains Carpenter and Ftffe, commanding U. S. S. Hartford and Fensacola, one of which will be detailed to convey the party to their destination. They are communicated for your information. Mr. Rockwell will act under your direction as to the expenditure of funds, and it is desirable to have your certificate to his vouchers after your leaving New York. It is expected that you leave New York in the Pacific Mail steamer of March 2, for Panama and Callao. On arrival at the latter place please report to Admiral Hughes for conveyance to Caroline Island, as indicated in directions given him by the Navy Department. I wish you a pleasant voyage and full success in the enterprise intrusted l;o you. I am, very truly, yours, J. H. C. COFFIN, Secretary of Committee of the National Academy of Sciences. 15 16 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. As our voyage and our subsequent stay on Caroline Island were something out of the run of common experience, you will allow me to give some details concerning them, which usually do not form a part of a scientific report. II.— ORGANIZATION OF THE EXPEDITION. The American party consisted of Edward S. Holden, director of the Washburn Observatory, Madison, Wis.; Charles S. Hastings, professor of physics in the Johns Hopkins University, Bal- timore, Md.; Charles H. Rockwell, Tarry town, N. Y.; E. D. Preston, aid United States Coast and Geodetic Survey, Washington, D. C; Winslow Upton, United States Signal Office, Wash- ington, D. C; Ensign S. J. Brown, U. S. N., United States Naval Observatory, Washington, D. C. The original six members of the party were joined on April 20 by four volunteer observers, all officers of the U. S. S. Hartford. These were, Lieut. E. F. Qualtrough, U. S. N.; Passed Assistant Surgeon W. S. Dixon, U. S. N.; Midshipman W. B. Fletcher, U. S. N. ; Midshipman J. G. Doyle, U. S. N. On March 11, the party was strengthened by the ioining (at Colon) of the two English gen- tlemen who were sent out by the Royal Society of Loudon to make photographic observations of the eclipse, under instructions from J. Norman Lockter, Esq., F. R. S., and Cajitaiu W. de W. Abney, Royal Engineers, of the Science and Art Departmeut of the South Kensington Museum. These were 0. A. Lawrence, London, England; C. Ray Woods, London, England. During our stay on Caroline Island (April 21 to May 9), the following petty officers and men of the Hartford remained with ns and rendered very intelligent assistance : Horace Yewell, seaman-gunner; Charles Emms, carpenter's mate; Peter Murphy, cariienter; John Smith seaman; J. C. Harold, seaman ; C. A. Perkins, ordinary seaman (apprentice); James McKenna, ordinary seaman (apprentice) ; Peter Burns, steward ; Thomas G. Brooks, assistant steward ; Mortimer C. Spence, landsman. Our party on the island consisted of twenty-two persons in all. III.— JOURNEY FROM NEW YORK TO CAROLINE ISLAND AND RETURN. (New York to Colmi, 1,989 miles; Colon to Callao, l,7i!2 miles ; Callao to Caroline Island, 4,324 miles; Caroline Island to Honolulu, 2,100 miles; and from Honolulu to San Francisco, 2,092 miles.) By Prof. E. S. Holden. The six members of the American party sailed from New York March 2, 1883, on the Pacific Mail steamship Acapulco (Capt. W. Shackford), and arrived at Colon March 11, after touching at Castle Island, March 7, to send off a mail. At Colon the exijedition was joined by the English photographic party. As the steamer on the west coast of South America did not leave until the evening of March 12, the American party remained in Colon till the morning of that day, and went from thence to Panama. Both in Colon and in Panama we were indebted to the courtesy of Capt. J. M. Dow, of Panama, for expediting our movements and for personal favors. At Panama I telegraphed to the United States and also to the admiral commanding the Pacific squadron. Through the kindness of my ftiend Clarence Gary, Esq., of New York, I found that all our telegrams over the lines along the west coast of South America and through to the United States were sent free of charge. Early in the morning of March 13 we sailed on the P. S. Navigation Company's steamer Bolivia (Captain Ferguson), for Callao, stopping at Buenaventura (March 14), Tuniaco (March 15), Guayaquil (March 17), Payta (March 18), and arrived SOLAR ECLIPSE, MAY (i, 1S83. 17 at Gallao, Miircli 20. I at once (sailed on Capt. C G. (Jakpenter, coiimiandiiig the Hart/ord, from whom I learned that he would be ready to sail on March 22. March 21 was spent in Lima, and on March 22 the Hartford left Oallao for Caroline Island, a distance of 4,324 miles. On the twenty-third day out from Callao we sighted one of the islands of the Marquesas group. and at 8 a. m. of April 20 Caroline Island was seeu as a low green streak on the Innizon. We had come 4,324 miles in twenty-nine days, mostly under sail (an av^erage of 149 miles per day), without seeing a single sail or any land, except Magdalena Island of the Marquesas, which we had gone out of our course to sight. I cannot refrain from quoting here Darwin's entry in his Jour- nal of a Voyage in the Beagle, under date of December 19, 1835 : " We may now consider that we have nearly crossed the Pacific. It is necessary to sail over this great ocean to comprehend its immensity. Moving quickly onwards for weeks together, we meet with nothing but the same blue, profoundly deep ocean. Even within the archipelagoes the islands are mere specks and far distant one from the other. Accustomed to look at maps drawn on a small scale, where dots, shading, and names are crowded together, we do not rightly judge how infinitely small the proportion of dry land is to the water of this vast expanse." STAY ON CAROLINE ISLAND. (From April 21 to Miiy 9.) It must be remembered that we knew absolutely nothing of Caroline Island, except that it had been inhabited in 1874 by at least one white man and some thirty natives. The boat landing was known to be somewhere on the southwestern side, and iiu •' entrance to the lagoon" was spoken of on the eastern side. The Hartford approached the island from this side, and from end to end there was nothing to be seen but a line of heavy breakers, then a strip of white beach, and above this a growth of trees, the highest of which were cocoa palms. Finally, in among these, was seen the gable roof of a European house, but no inhabitants. Coasting round the island, everywhere sur- rounded by high surf, the Hartford came opposite the place where the boat landing was reported, and the whale-boat was lowered aud Lieutenant Qualtrough sent in her to land if possible. It seems all very simple now, after Caroline Island, its reefs, its lagoon, and its landing are as famil- iar to us as the beaches of New England ; but at the time it was all quite strange and new. The advent of a man and a dog on the reef was an event. It seemed to settle one thing, at least, and that was that we should find some assistance in lauding. But the native disappeared and Lien- tenant Qualtrough was left to find his own way among the breakers, which he did in a capital manner. The ocean reef forms a solid wall all round the islands, except at one narrow and crooked en- trance, just wide enough for a boat and oars, aud through this entrance each boat must come or be broken into bits against the steep face of the coral wall. The whale-boat returned shortly with the news that there were four native men, one woman, and two children on the islands, that two frame houses were standing, and that we could land at once. Un the 2()th of A]>ril the first of our boxes were sent ashore. The boats were loaded alongsule and rowed to the entrajice of the naiTow pas- sage. This was entered on the top of a wave aud the boat was skillfully steered by the cockswain through its windings. As soon as the bow came over the flat surface of the reef the crew jumped out and hauled it up into the shallow'water covering the whole surface of the reef. At high water this ocean reef was covered to a depth of about 30 inches and at low water to about 10 inches. The boxes were then lifted from the boat and transported by carrying parties to the high-water mark — a distance of 1,400 feet. This transport had to be made over the rugged surfixce of the S. Mis. 110 3 18 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. ocean reef and through water varying in depth from 1 to 3 feet, as I have said. From high-water mark other carrying parties transported tlie boxes along the beach of the lagoon and across the island to the site of onr observatories (some 1,.'300 feet farther), which had been selected by Dr. Hastings and myself. On board the Hartford I had prepared a plan of the proposed camp; the position of each observatory was fixed on the ground by a stake, and to this stake all the boxes of each instrument were brought. In this way all proceeded in an orderly manner. By the evening of the 21st all the boxes and baggage of the expedition were landed, as well as bricks, cement, lum- ber, etc., for the observatories. The entire party slept on shore also, and I shall never forget the quiet rest of that cool night after the intensely hot day of active work. Our hammocks were slung on the wide veranda of one of the houses close to the beach of the mirror-like lagoon. The wind was cool and fresh as it blew through a break between two of the islands and directly from the open sea, the monotonous roar of whose surf was incessantly heard. The nearly full moon was overhead and the long fronds of the cocoa palms made grotesque shad- ows on the level ground. Occasionally there would be heard the shrill cry of some sea-bird flying over, and other than this and the roar of the breakers there was nothing to disturb the quiet and rest which came as a fitting conclusion to our restless month at sea. During the 22d of April the Hartford remained by the island, and a force of carpenters and bricklayers proceeded rapidly with the construction of our observatories. By night time the observatories belonging to myself, Dr. Hastings, and Mr. Preston were up, and piers of brick or wood completed. The brick piers of the English party were well under way and were com- pleted on the 23d by Mr. Woods, who tlius added a new profession to his former acquirements. The Hartford sailed at (i p. m. of the 22d for Tahiti and some of us went to the ocean reef to see her oft". Besides her lights, we saw those of VEclaireur, the man ofwar which was bring, ing the French eclipse expedition. Early on the morning of the 23d I met the maitre d'equipage of the Eclaireur on the reef and gave him such information as to the landing, etc., as I was sure would be of use. Shortly after this the French party came on shore for the day, and the morning was spent in aiding them to select a site for their observatories, etc. This party consisted of M. Janssen, director of the Observatory of Astronomical Physics of Mendon ; M. Tkouvelot, assistant at the Mendon Observatory ; M. Pasteur, photographer of the Meudon Observatory. These gentlemen were accompanied by M. Tacchini, director of the Observatory of the Eoman College and M. Palisa, astronomer of the Imperial Observatory of Vienna. Besides these astronomers there were seventeen of the crew of IJEclaireur left on shore, making the French party twenty-two in number. Thus the total population of the island was fifty -one in all, including natives. Our relations with the gentlemen of the French expedition were throughout of the most cordial cliiiracter, and so far as our researches lay in the same direction, we worked together to a common end. It was a pleasure to us to be able to extend to them what aid was possible, and to receive the same in return. During the remaining days of April everything was making progress towards complete readi- iness for observations of tlie eclipse. The observatoi-y of Dr. Hastings and my own were com- pleted by April 27, and each of us used a six-inch equatorial for some hours each night in an examination of the southern sky. During the course of this we detected some new doubles and red stars, a list of which is given later. The vision was not excei^tionally good, and compara- tively few hours were given to telescopic work, owing to tlie impossibility of obtaining a (piiet SOLAR ECLIPSE, MAY G, 1883, 19 sleep during the diiy. Still tvventy-tliree double stars were found. This shows that if a suitable telescfope were to be used iu a favorable place iu the southern hemisphere, as (^uito or Santiago for example, a great number of new objects could be catalogued in a comparatively short time. It appears to me that this expedition is worth mailing. Every day during May a reliearsal for the eclipse observations was gone througli with, and two days before May G everything was in complete readiness. On the morning of May 6 there were three rain showers and (several persistent banks of clouds. The sky was clear at first contact (about 10'' 3"' local mean time), cloudy at intervals till near totality; clear during totality, except slight haze during the first minute of totality; cloudy a few minutes after third contact, and finally clear at fourth contract. The observations of the various parties may be considered to have been successful; but the success was owing to the apparent accident of the dissipation of a local cloud. I am more than ever convinced that my conclusion to go to Flint Island, had I found the French party occupying Caroline Island, was a sound one. Immediately after the eclipse we commenced prejiarations for departure. These occupied May r 7 and May 8. Captain Carpenter had promised to return from Tahiti with the Hartford by the morning of May 9, but we were pleased to see his arrival at 4 p. m. of the 8th. By hard work all was packed and delivered on the Eart/ord by 4 p. m. of May 9, and at 5 p. in. the Hartford with the expedition on board took her departure for the Sandwich Islands. We left Caroline Island with mingled feelings of pleasure and regret. Each one of us had at least some one thing left to do or to see, and yet it was a pleasure to leave the place where our mission had been accomplished and to meet our friends in the ship who were endeared to us by that intimacj' which sea-life induces. This is the place to say one word in regard to the outfit of stores and provisions which was lirovided iu New York and Callao by Mr. Eockwell and myself. All the advice we received in the United States from various persons who might have.been supposed to know, was to the effect that we had better not encumber ourselves with stores, etc., from New York ; that the markets of Callao and the resources of a man-of-war would am^jly supply our needs. Acting contrary to this advice we took a large quantity of provisions from New York, together with the canvas, tents, etc. which we were told could be obtained from the man-of-war. At Callao an additional supply of pro- visions was purchased, together with the bricks, cement, and lumber which were found to be nec- essary for the English expedition and our own. The stock of provisions and stores proved to be exactly what we wanted, and we were enabled to support the twelve men of the party on Caroline Island without trouble and to provide a sufficient though primitive cuisine. Our only mistake was in not purchasing all our provisions and tools in New York, and I have given a brief account of our preparations in this direction, iu order to say to other expeditions similar to our own that they will do well to buy all their outfit in New York and pay the freight to the point of destina- tion cheerfully, I have to express the thanks of the expedition to the honorable Secretary of War, and to my friend Col. H. C. Hodges, Quartermaster's Dei)artment, for the loan of three tents, which were of great service to us. JOUKNEY FROM CAROLINE ISLAND TO THE UNITED STATES. From Caroline Island the Hartford proceeded directly to the Hawaiian Islands under sail, and on May 24 we were anchored in the beautiful bay of Hilo. From Hilo a party from the ship visited the volcano of Kilauea, which v were fortunate enough to find in a very active state. Leaving 20 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. Hilo ou May 29, we arrived at Honolulu tbe next day. Here Mr. Preston and Mr. Beown left the party in order to undertake pendulum observations on tlie island of Maui. On the evening of June 3 the rest of the party embarked on Pacific Mail steamship Zealandin (Captain Webber) and after a disagreeable passage arrived at San Francisco on June 11. We had been absent from the United States for one hundred and one days, during which we had traveled some 1,500 miles; seventy days had been i)assed at sea. We had undertaken the exi)edition with a willingness to undergo any hardships or discomforts for the sake of the astro- nomical opportunity, but the difficulties vanished as we saw them nearer. Not a mishap of any kind occurred to interfere with the success of our work, and the entire voyage and the stay on the island was a beautiful snrprise to us. Fifty days of our journey were spent on the U. S. S. Hartford, and it is a pleasure for me to return the thanks of the expedition to the officers and men of this vessel for their constant and thoughtful kindness and willingness. We have especially to thank Captain Carpenter and Lieut. Commander Edwin White for their promptness in landing our bulky cases under rather exceptional difficulties. Four of the officers of the Hartford volunteered to aid us in our observa- tions on Caroline Island, and l>y the courtesy of Captain Carpenter they were detailed for the service. Their reports follow in order, and they will show how intelligent and valuable assistance was given. To these gentlemen. Lieutenant Qualtrough, Dr. Dixon, Midshipmen Fletcher and Doyle, we desire to make this formal tender of our sincere thanks. It should appear that while Congress and the National Academy appropriated an adequate sum for our current expenses, we still owe to the Navy an aid at least equal. We had the intelli- gent assistance of four trained observers ou the island and the willing aid of the officers and crew of a large war vessel, and without these our difficulties and expenses would have been greatly and seriously increased. IV.— CAROLINE ISLAND. ^ 1. HISTORY.— By Prof. E. S. Holden. The sum of our knowledge of Caroline Island, before the arrival of the Eclipse Expedition, was given in the following extract from Findlay's South Pacific Directory (1877, page 742) : '• Caroline or Thornton Island, is 7 to 8 miles long, N.NE. and S.SW., and from 2 to 3 miles wide, well covered with cocoanut and other trees, of tolerable height, which render it visible at a distance of 16 to 20 miles. It consists of many islets of various sizes, encircling a lagoon. The reef on the windward side breaks, except at the NE. point, to the distance of a mile from the south point of the island. This reef sends out two branches to a distance of 1^ miles — one toward the SE., the other toward the S W. and is consequently dangerous to appi'oach at night. The reef is close to the islets on the west side, and no breakers were seen on the NW. point. There is no an- chorage, but a landing (not always safe) may be effected on the north side of the SW. bifurca- tion, described above and uear the spot where the English flag is hoisted on a mast. There are about thirty inhabitants and the resident European is Mr. Brown. It was taken possession of by Captain Nares, H. M. S. Reindeer, for the English, and its latest assigned position is lat. 9° 5i' S., long. 150° 6' W." From various hydrographic notices we also learned that Caroline Island was first seen by Cap- tain Boughton in 1795. He assigned the position long. 150° 25' W., and lat. 9° 57' S., and he gave it the name it now bears. At one time it was called Thornton Island. It was visited in 1870 by Lieutenant ChauviniJire, of the French transport Somme, and in 1868 by Captain Nares, R. N., who took possession of it for the British. The chief occupation of the inhabitants, who numbered Fig. 3. MARiE, OR NATIVE BURIAL PLACE. W^y] ^ SOLAR ECLIPSE, MAY a, 1883. 21 27 iu 1868, was raising stock, pigs, poultry, and collecting fish for salting, and also planting cocoa- nut trees for oil. About 1878 guano was exported from the island. The foregoing comprises the entire history of the island. I have api)lied by letter to every persou who might be supposed to know anything of the early history of the island, even to the secretaries of the missionary societies in Loudon and New York, without obtaining any informa- tion of value. 1 addressed letters to various gentlemen who were familiar with the islands in the South Pacific, asking for such information as they had on the history, the aboriginal popula- tion, &c., of Caroline Island. Among the replies I have received is one from a gentleman resident on Earoonga, which is given below : "Raeotonga, September 21, 1883. " Sir : Your note to the Bishop of Tahiti has been forwarded to me by the Eeverend William Wyatt Gill, of the London Missionary Society. I will give you with pleasure what I have heard concerning Caroline Island, from good authorities — the Messrs. Brown Brothers, the former own- ers of the island. Some years ago, I had a conversation with these gentlemen, and they told me that in seeking for guano, they came upon a grave, which made them interested. They sought farther and found others, numbering altogether fifty. In the graves they found stone axes, and highly polished green stones, such as are used by the Maoris of New Zealand,, and spears of the same description. The graves had a few stones placed around them. " Messrs. Brown & Brothers planted the cocoanut trees on the island. It must have been ten or fifteen years afterward that the island was leased to Mr. Arundell of the firm of Houlder Bros. & Co. Although I have been several months on Flint Island in the said company's employ, I have never seen Caroline Island, but Mr. Arundell told me he had found axes, fancy stones, etc., on the island. " Messrs. Brown & Brothers told me they thought the number of the inhabitants at the time they took possession* could not have been over fifty or a hundred people. It seemed as if there had been a storm or hurricane at some short period previous, which had desolated the place. The occupation of the natives, if they had any, would be fishing or fighting, or anythiug they could possibly do in such a small island. • « « • * • # "J. MORTIMER SALMON." In a note from the Rev. W. Wyatt Gill, he says that he does not believe the island had an aboriginal population, which is in all likelihood the case. In a letter dated Auckland, New Zealand, August 6, 1883, Mr. Arundell, the present lessee of the island, says: "I regret that I have not many facts in the history of the island to communicate to you. It was taken possession of by Her Britannic Majesty on July 9, 1868, and the English flag hoisted by Commodore (now Sir George) Nares in H. M. S. Reindeer. We became Crown tenants in 1872, and have remained in possession ever since, carrying on guano operations there; and in 1881 I took the affair up individually and apart from my firm, and commenced the planting of cocoanuts there, as also on the neighboring Flint Island. I presume you took iihotographs of the island, but if not, and they should be of any use or interest, I could send you some of the houses, scenery, etc., which we took with our own camera a few years back. " There are some curious old marais, i. c, burying or sacrificial places. Probably my natives did not show them to you. Of these I have phofeograijhs and plans, and should you care about them, I would forward them also." • ••**♦ • * * This must have been between the years 1865-1872. — E. S. H. 22 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. Tbe drawing from which Figure 3 is engraved was made by George W. Robertson, Esq., of Liverpool, and is accurate. Mr. Arundell describes it very briefly in a letter of January 1st, 1884. The plan gives the disposition of the various masses about the central space. The figures in the margins are the elevations of the ten smaller blocks shown in the plan on the borders of the inclosure. The two walls at the ends are not represented in plan, but are revolved 90° so as to appear in elevation. With this explanation the figure can be understood. The material of the blocks and walls is coral and coral conglomerate. Mr. Arundell opened cairn C without finding any trace of bones, ashes, or of any human remains. They are situated on the western side of the most northern islet, and there are a few smaller ones on the south point of the longest islet on the eastern side. They must have been built by a native population, but no natives were known to inhabit the island at its first occupation by the whites. 52. DESCRIPTION OF THE ISLAND. By Prof. E. S. Holden; and Lieut. E. F. Qualtrough, U. S. N. Our own observations and the careful survey of the island which was made by Lieutenant Qualtrough and Midshipmen Fletcher and Doyle, enable me to give a tolerably accurate description of Caroline Island. I desire, however, before giving the results of our own work to quote from Professor Dana's Corals and Coral Islands, and from Darwin's Votjatje of the Beagle, their accounts of typical coral atolls which they visited. The only changes necessary in their descriptions, to make these apply exactly to our station, are changes in the dimensions of the ocean reefs, the beaches, etc. The general features of a coral atoll are most perfectly and graphic- ally described by them. To understand their accounts, I may say that the general shape of Caro- line Island is that of a pear-shaped ring of islets, encircling a lagoon. The islets are based on the ocean reef which Dana calls the shore platform. Between the islets are portions of this platform, which are nearly bare at low water. Inside the ocean reef is the lagoon, which is itself filled with reefs of corals. Professor Dana says : "The shore platform is from one to three hundred feet in width, and has the general features of a half- s«bmerged outer reef. Its peculiarities arise solely from the accumulations which have changed the reef into an island. Much of it is commonly bare at low tide, though there are places where it is always covered with a few inches or a foot of water; and the elevated [outer] edge, the only l)art exposed, often seems like an embankment preventing the water from running off. The tides, as they rise, cover it with water throughout and bear over it coral fragments and sand, commin- uted shells, and other animal remains, t6 add them to the beach. "The heavier seas transport larger fragments; and at the foot of the beach there is often a deposit of blocks of coral, or coral rock, which low tide commonly leaves standing in a few inches of water. On moving these masses, which generally rest on their projecting angles, and have an oi)en space beneath, the waters at once become alive with fish, shrimps and crabs, escaping from their disturbed shelter; and beneath appear various actinise or living flowers, the spiny echini and sluggish heche de mer, while swarms of shells, having a soldier crab for their tenant, walk off' with unusual life and stateliness. Moreover, delicate corallines, ascidia-, and sponges, tint with lively shades of red, green, and pink the under surface of the block of coral which had formed the roof of the little grotto. The beach consists of coral pebbles or sand, with some worn shells, and occasionally the exuviie of crabs and bones of fishes. Owing to its whiteness, and the contrast it attords to the massy verdure above, it is a remarkable feature in the distant view of these islands. _,<' '';-, "•' ^1 ^v:*^ >5 ... .*?*»* CSV J\^ ^ I)' « i»«'^^-5^® ^ --^ .S(' «',e> a** .© ■'. i- *>■.,« ft & -SB, ^'^Z^'j^"^^^\^^%ff^--^'0 • ■■■-■•'- -~ r., ^ . .. . ■&«^ 4' '^ .-^^-r-'-V-.s-.-sS r^^S^^ a (-3 H O r H o > o t— t I— I f > o 03 filil ■?! !' 1 i|||fi-:|* feiiff iiwiiiji; l!l«^:i;'l|^'f'i SOLAR ECLIPSE, MAY 0, 1883. 23 "The emerged land beyond the beach in its last stage stands G to 10 feet ont of water. The surface consists of coral sand, more or less discolored by vegetable or animal decomposition. Scat- tered among the trees stand, still uncovered, many of the larger blocks of coral, with their usual rough angular features and blackened surface. There is but little dejith of coral soil, although the land may appear buried in the richest foliage. In fact, the soil is scarcely anything but coral sand. It is seldom discolored beyond 4 or 5 inches, and but little of it to this extent. There is no proper vegetable mold, but only a mixture of darker particles with the wliite grains of coral sand. It is often rather a coral gravel, and below a foot or two it is usually cemented together into a more or less compact coral sand-rock. " The shore of the lagoon is generally low and gently inclined, yet in the larger islands [as at Caroline Island] there is usually a beach resembling that on the seaward side, though of less extent. A platform of reef-rock, at the same elevation as the shore-platform, sometimes extends out into the lagoon ; but it is more common to liud it a little submerged, and covered for the most part with growing corals; and, in either case, the bank terminates outward in an abrupt descent, of a few yards or fathoms, to a lower area of growing corals or to a bottom of sand. Still more commonly we meet with a sandy bottom, gradually deepening from the shores, without growing coral. These three varieties of condition are generally found in the same lagoon, char- acterizing its diflerent parts. The lower area of growing corals slopes outward and ceases when the depth is 10 to 12 fathoms or sooner. "There are usually currents flowing to leeward through the lagoon, and out, over, or through the leeward reef, the waves with the rising tide dashing over the windward side, and keeping up a large supply, which is greatly increased in times of storms ; and this action tends to keep open a leeward channel for the passage of the water." The various illustrations scattered through this section (which are engraved from photographic prints kindly furnished by the gentlemen of the English expedition) will make this description more clear to those who have not aetually seen a coral atoll. They have been redrawn from the prints by Mr. R. N. Brooke, of Washington, to whom our thanks are due for the care which he brought to his difficult task. From Darwin's Journal the following extracf;s are taken : "The ring-formed reef of the lagoon island is surmounted in the greater part of its length by linear islets. On entering the lagoon the scene was very curious and rather pretty. Its beauty, however, entirely depended on the brilliancy of the surrounding colors. The shallow, clear and still water of the lagoon, resting in its greater part on white sand, is, when illumined by a vertical sun, of the most vivid green. This brilliant expanse, several miles in width, is on all sides divided, either by a line of snow-white breakers from the dark heaving waters of the ocean, or from the blue vault of heaven by the strips of land, crowned by the level tops of the cocoauut trees. As a white cloud here and there affords a pleasing contrast with the azure sky, so in the lagoon, bands of living coral darken the emerald-green water." "The next morning after anchoring I went on shore. The strip of dry land is only a few hun- dred yards in width. On the lagoon side there is a white calcareous beach, the radiation from which under this sultry climate was very oppressive; and on the outer coast, a solid broad plat of coral rock served to break the violence of the open sea. Excepting near the lagoon, where there is some sand, the land is entirely composed of rounded fragments of coral. In such a loose, dry, stony soil, the climate of the intertropical regions alone could produce a vigorous vegetation. On some of the smaller islets nothing could be more elegant than the manner in which the young an^ 24 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. full-grown cocoanut trees, without destroying each other's symmetry, were mingled into one wood. A beach of glittering white sand formed a border to these fairy spots." " The long strips of land forming the linear islets have been raised only to that height to which the surf can throw fragments of coral, and the wind heap up calcareous sand. The solid plat of coral rock on the outside, by its breadth, breaks the first violence of the waves, which otherwise in a day would sweep away these islets and all their productions. The ocean and the land seem here struggling for mastery. Although terra Jirma has obtained a footing the denizens of the water think their claim at least equally good. lu every part one meets hermit crabs of more than one species carrying on their backs the shells which they have stolen from the neighboring beach. Overhead numerous gaijnets, frigate-birds, and terns rest on the trees ; and the wood, from the many nests and from the smell of the atmosphere, might be called a sea-rookery. The gannets, sitting on their rude nests, gaze at one with a stupid yet angry air. The noddies, as their name expresses, are silly little creatures. But there is one charming bird ; it is a small snow-white tern, which smoothly hovers at the distance of a few feet above one's head, its large black eye scanning, with quiet curiosity, your expression. Little imagination is required to fancy that so light and delicate a body must be tenanted by some wandering fairy spirit." " The next day I employed myself in examining the very interesting yet simple structure and origin of these islands. The water being unusually smooth, I waded over the outer plat of dead rock as far as the living mounds of coral, on which the swell of the open sea breaks. In some of the gullies and hollows there were beautiful green and other colored fishes, and the form and tints of many of the zoophytes were admirable. It is excusable to grow enthusiastic over the infinite numbers of organic beings with which the sea of the tropics, so prodigal of life, teems, yet I must confess I think those naturalists who have described, in well-known words, the submarine grottoes decked with a thousand beauties have indulged in rather exuberant language." " Every single atom, from the least particle to the largest fragment of rock, in this great pile, which, however, is small compared with very many other lagoon islands, bears the stamp of having been subjected to organic arrangement. We feel surprised when travelers tell us of the vast dimensions of the pyramids and other great ruins, but how utterly insignificant are the greatest of these when compared to these mountains of stone accumulated by the agency of various minute and tender animals ! This is a wonder which does not at first strike the eye of the body, but, after reflection, the eye of reason." The foregoing extracts give a complete picture of the typical coral atoll, and, as I have said, we require simply to make a few changes in the dimensions to make them exactly apply to Caroline Island. The frontispiece, which is derived from the survey made at my request, will give the necessary changes at a glance. To this I add a brief description furnished by Lieutenant Qualtrough. "Caroline Island, or chain of islands, is of coral formation of the lagoon type, and in shape is an irregular elongated oval ; it is 5f miles long from NNE. to SSW. and its circumference, meas- ured on the outer or inclosing reef, is approximately 13 miles. The greatest breadth is at the south- ern end, where it measures Ij^ miles, and the average width may be placed at three quarters of a mile. "The atoll consists of a chain of twenty-five little islets, well covered with trees and shrubbery, the whole forming a quiet scene of grove and lake, charmingly set off by the contrasting ocean. Between the patches of verdure there is a flat, water-covered table of coral rock, which is covered Kin. 6. — Group of Pandanus Trees. i.lG. -J. BkACH Ol' l.AGlniN (Luulvl.NG NUK.1 H). Fig. S. — Beach of Lagoon (looking south). SOLAR ECLIPSE, MAY G, 1883. 25 with little conil heads which show at low water. On some of the islands there are spaces void of vegetation, extending from lagoou to sea-beacb, which indicate the existence at a former time of a water separation. "The inclosing platform reef fringes the shore, forming a wide extension, elevated at; its outer edge, around the greater portion of which the surf breaks with considerable violence. There is a passage through, or over, this bordering reef near the southern end, which is deep enough to permit small ships' boats to penetrate to the lagoon at high water. "The surface of the Islands is covered with a growth of trees and other vegetation, much of which has been planted by the hand of man, especially large numbers of cocoa palm.s, which are being raised for the production of cocoanut-oil. The water in the lagoon is extremely salt, and evidently of greater density than the water of the outer sea. " The climate of the island, though warm, is delightful, for, surrounded as it is by sea, the tem- perature is equable. The weather, though mostly fine, is somewhat changeable, with occasional sudden showers, which occur generally at night or during the early morning. The prevailing winds in April and May were from the ^N". and E. " The following inscription exists, posted on a blackboard on the lower island : "'Caroline Island, latitude 9° 56' S., longitude loOo OC W. Lea.sed from Her Most Gra- cious Majesty Victoria, Queen of Great Britain and Ireland, by Messrs. Hoxjlder, Bros. & Co., i!^o. 140 Leadenhall st., London, England, and Fanniiig's Island, North Pacific Ocean. Agents : Mdme. T. Salmon, veuve Brander, Tahiti; Thomas H. Dayies, II. B. M. vice-consul, Honolulu; Macondray & Co., San Francisco." " There are some traces of former iubabltauts, among which may be mentioned three houses and two sheds, in good repair, on the lower island, and two others on the northern island of the group. About one-third the distance up the lagoon a canvas hut exists on one of the smaller islets on the eastern side of the lagoon, and two wooden huts stand on one of the western islets, some distance further up the lagoon. At various places around the beach, anchors, chains, spars, and i)ieces of the woodwork of vessels may be seen, some of them, perhaps, being the remains of wrecks on the reef in years gone by. The island is Inhabited at the present time by seven persons, four men, one woman, and two children, who are engaged in the planting and care of the young cocoanut trees now about 3 feet high. " Some varieties of phosphatic guano are found on the islets, but at the present time there seems to be no effort to export any. The source of fresh water on Caroline, as on many coral islands, is the rains, which percolate through the sands and collect upon the coral rock, which forms the basis of the island. There are two shallow wells on the lower island, and another on the upper or north- ern island. "Tidal observations made in the lagoon show no relation between the rise and fall in the lagoon and that outside. The lagoon is open to windward, and the wind evidentlj- exercises great influence over the height of the water." The brick piers which we constructed for the support of our instruments, and the frames of our observatories, which we left standing, will serve to signalize our occupation of the island. In particular I placed upon the upper surface of the pier of the transit instrument a marble slab bearing the inscription, "U. S. Eclipse Party, 1883, May G." This marks the point to which our latitude and longitude are referred. It may be added that a series of tidal observations was made by Lieutenant Quaxtrough and Messrs. Fletcher and Doyle. These show the lunar tidal interval on the day of full and chonge S. Mis. 110 4 26 MEMOIRS OP THE NATIONAL ACADEMY OF SCIENCES. to be i*" ; that is, the time of high water water is 4'' later than the moon's trausit. The greatest daily range was 1' 7" ; the least daily range was 0' 5". i 3. LONGITUDE OF CAROLINE ISLAND.— By Mr. Winslow Upton. The longitude of Caroline Island was determined by means of chronometers and from obser- vations of moon culminations. The care of the chronometers was in the hands of Ensign Brown from the time of leaving New York until March 24, after leaving Callao in the Hartford, and in my hands for the rest of the voyage. The observations for time with the transit on Caroline Island were maarisons were made with the chronometers of the ship as follows: Bond, 233, mean time; Negus, 1288, mean time; Negus, 1065, mean time; Wood, 425, mean time. For the greater part of tlie expedition nine chronometers therefore were in use. On the Zealnndia, from Honolulu to San Francisco, comparisons were made with the two chronometers of that ship, but were not used in the reductions. Throughout the journey ft'om New York to San Francisco daily comparisons were made of the several chronometers. At New York observations of the time-ball checked the running of 1340 and 1536 from Washington. At Aspinwall the local time was obtained by sextant observa- tions, and by comparison with the chronometer of the Royal Mail steamer Medway, Fletcher., 1608. At Callao no observations were made, the local time adopted depending upon comparisons with the Hartford and^values deduced from the rates of the chronometers. At Caroline Island sextant observations were made until the mounting of the transit. At Honolulu sextant observa- tions were made, and at San Francisco comparisons at the observatory of the United States Coast and Geodetic Survey with the chronometer of the transit of Venus party under the charge of Mr. Edwin Smith, the correction of which was determined by transit observations made by Prof. H. S. Pritchett. At Honolulu chronometers 202 and 1589 were left behind, and for the voyage from Honolulu to San Francisco but three chronometers in consequence were avaiLable. The following table contains the adopted chronometer corrections at the various places enumerated above. The chronometers are designated by their numbers, and the corrections are in Greenwich mean or sidereal time. Nos. 202 and 1589 were regulated to Washington time, but were set by Mr. Preston at Caroline Island to local sidereal time, which explains the change in the corrections. Nos. 1536 and 2786 were regulated to Caroline sidereal time. The others were running on Greenwich mean time. Fii:;. 9. — One of the small Islets borderinc the Lagoon. tlG. 10. — SuLlll blluRL Lil llil, Lai.uON. SOLAK ECLIPSE, MAY 6, 1883. Table I. — Chronometer corrections in Greenwich mean or sidereal time. 27 Date. {If'ashiiiglon time.) Feb. -JS-OOO ■ - - - . 2.U54 - - - - 3.170 . - - - 11.000 .... 'J'2.140 - - - - Place. Mar. Mar. Mar. Mar. Mar. June Washiugtoii At sea - - At sea - - Aspiuwall - Callao - - ii3.968 , At sea - 1.07G Houolulu I Jmio 12.3S5 ----- Sail Francisco • 1340. m. 8. -6 .'■>;!. 78 -7 3.8 -7 10.3 203. /(. m. 8. 1589. h. m. s. 2786. A. m. 8. + .■■> 7 29. 7 I + ,5 (i 35. -3 j -flO 1 23.8 + 57 27.3 !+.'■, 7 10.3 ' +ld 0 57.3 -f 5 7 30.9 + 5 7 49.7 i +10 0 21.5 -8 3.5 -8 14.20 +10 1 30. 7 +10 2 44. I + 9 55 .51.0 + 9 55 3.73 Date. ( Washington time.) Feb. 28.000 - - - - Mar. 2.054 - - - - Mar. 3.170 - - - - Mar. 11.000 - - - - Mar. 2i.l40 - . - - Mar. 23.968 - - - - June 1.07() - - - - Place. 1536. +10 m. 8. 1 22.06 233. Wasbington - At sea - - - At sea - - - Aspiuwall - - +10 1 39.3 Callao - - - - : 1-10 1 .55. 1 ; - - - - At sea - - - - ( +17 24. 0 Honolulu- - - +10 3 34.3 +20 0.9 1988. June 12.385 i San Francisco - +10 3 47.78 —5 34. 1 —5 28. 5 1065. 425. -4 26.4 -4 41.9 +1 57.3 +2 39. 1 With regard to the corrections given in the preceding table some explanations are necessary. The corrections on February 28.000 were determined at the United States Naval Observatory, those on March 2 and 3 by comparisons with 1340. The sextant ob.servations at Aspinwall consist of three double altitudes of the sun, giving the correction to 1340 — 7'" 2^9. The comparison with the chronometer of the Medtcay gave — 7'" 4:'.3. Giving the latter double weight, as it was said to depend on equal altitude observations made the day previous, the correction — 7'" 3^8 results. Cor- rections to the other chronometers were obtained by comparisons. They were used only in deter- mining the chronometer rates from New York for obtaining the con-ections at Callao. The- corrections to be adopted at Callao received especial attention, as it was intended to make this point one of the terminal points of the campaign. Unfortunately but two days were spent at this port, and no observations were made. The corrections therefore depend upon comparisons with the Hartford chronometers, and ujwu corrections deduced by using the rates from New Y'ork. Comparisons with the chronometer 1288 of the Hartford were made on March 21, using 202 as a hack and 1340 as the standard for the expedition chronometers. These gave: 1340 — 1288 = 1"' 34^55; 1288 corr. —5"' 34».26 (given by the navigator of the Hartford) ; 1340 corr. —7'" 8'.8. The correction to 1288 depends upon sextant observations made March 4, on shore, by the method of single altitudes brought forward by a rate determined for an interval of ninety-six days, and checked by a deck observation March 18. The correction was furnished through the kindness of the navigator of the Hartford. The computation of the chronometer corrections, by using the rates from New York, was thus made : From the preceding table of corrections the mean rates were obtained New York to Aspinwall, and from the chronometer comparisons March 10, 11, 14, 15, the mean values of the relative rates between 1340 and each of the other chronometers. The temperatures changed greatl.y between New York and Aspinwall, but were more constant between Aspinwall and Callao. A rate deter- mined at Aspinwall is therefore better for carrying forward the corrections from Aspinwall to Cal- lao. The comparisons March 10, 11, were the last made on the Acapxdco, and those March 14, 15, the first on the Bolivia ; their mean was adopted for the relative rates at Aspinwall. The follow- 28 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. ing table contains the mean rates of each chronometer New York to Aspinwall, the mean relative rates from these figures, then the relative rates at Aspinwall, obtained as above. The diflerences are large, and in the absence of any evidence as to the superiority of any one chronometer it is assumed that the differences should be distributed equally between 1340 and the chronometer compared with it in each case. The corrected rates of 1340 are therefore obtained as given in the sixth column, and the mean taken, rejecting the comiiarison with 202, as it was the hack chronom- eter and ran irregularly. The rates in the last column ai-e the values adopted for the rates at Aspinwall. Table II. — Rates of each chronometer at Aspinwall. Chronome- ter. Mean rate, New York to Aspin- wall. Rel a t i V 6 rate 1340 m i n u 8 each. Rel a t i V e rate at Aspin- wall. Difference. Rate of 1340 from each chronome- ter. Adopted rate at Aspin- wall. 1340 202 1589 27S6 1536 8. + 0.91 + 0.27 — 3.92 + 3.38 — 1.57 8. 8. 8. 8. 8. -f 0.72 — 0.20 — 3.66 -f 3.50 — 1.40 + 0.64 + 4.83 — 2. 47 + 2.48 + 0.92 + 4.38 — 2. 78 + 2. 12 -1- 0.28 — 0.45 — 0.31 -- 0.36 [+ 1.0.5] + 0.69 -f 0.75 -f 0.73 The chronometer comparisons between Aspinwall and Callao showed departures from the above values. These comparisons were treated in a manner similar to that above given for determining a correction to the rate of 1340, and hence to that of each chronometer. The following- table gives the results : Table III. — Mean rates adopted, Aspinwall to Callao. Chronome- ter. Ad 0 p t e d rate a t Asp in- wall. Relative rate 1340 m in u, a each. Rel alive rate from chronom- eter com- parisons. DLfFerence. Rateofl340 from each chronome- ter. Ad o p t e d rate, As- pinwall to Cal- lao. 1340 202 1589 2786 1536 8. + 0.72 — 0.20 — 3.66 + 3.50 — 1. 40 8. 8. 8. 8. + 6.71 — 0.41 — 3.45 + 3.32 — 1.37 -f 0.92 + 4.38 — 2.78 + 2. 12 + 1. 12 -f 4.16 — 2. 61 -f 2.08 + 0.20 — 0.22 + 0.17 — 0.04 [+ 0.82] + 0.61 -f 0.81 -f 0.70 By means of the rates given in the last column of Table III, the correction of each chronometer was obtained for the time of the first comparison of chronometers in Callao Harbor after their removal to the Hartford. The resulting corrections of 1340 from each chronometer (rejecting 202) are: Corr. to 1340, March 22.140. m. s. By rate -7 11.7 From 1580 11.3 2786 11.5 1.53G 10.8 Mean -7 11.3 = I. > c c SOLAR ECLIPSE, MAY 6, 1883. 29 The correction given by comparison with the Hartford chronometer 1288 rednced to the above time by the rate of 1340 is — 7"' 9».3. Adopting tlie mean — 7'" 10'.3, and deducing the corrections to the other chronometers, we have the corrections already given in Table I. Comparisons with all tlie chronometers of the Hartford were first made on March 24. Carrying forward the correction of 1340 by its assumed rate +0».71, we have the corrections given in Table I on that date. It will be seen that the corrections adoi)ted at Callao are uncertain by an amount wliich may reach several seconds. The uncertainties arise from the necessary assumptions made in bringing forward the chronometer corrections, the unreliability of the observation at Aspinwall, and the possible errors in the corrections given for the Hartford chronometer 1288 due to the length of time since observations had been made and to the uncertainty in the longitude of Callao given on chart No. 784, United States Hydrographic Office. In the absence of direct observations at Callao, the corrections adopted are. the best attainable. At Honolulu observations with the sextant were attempted both morning and evening for several days after the arrival of t\iQ Hartford. Clouds, however, prevented observations by equal altitudes, but good observations by single altitudes were obtained on three occasions, giving the following corrections to 1340 : m. «. May 30.392 -8 2.4 June 1.037 3.0 June 2.034 4.4 Mean, May 31.821 -8 3.3 Reducing to June 1.07G, the time of the nearest chronometer comparisons, we have the correc- tions given in Table I. At San Francisco advantage was taken of a time determination made at the observatory of the United States Coast and Geodetic Survey, on the evening after the arrival of the expedition, by Messrs. Edwin Smith and H. S. Pritchett, of the United States Transit of Venus Expedition, through whose courtesy a comparison was made between the chronometers. The resulting correc- tions are given in Table I. Determinations of the local time at Caroline Island were made by Mr. Preston with the transit instrument. Previous to the mounting of the instrument, observations with the sextant were made every morning and evening, which were reduced by the method of equal altitudes. The correc- tions in local time to 1340 by these observations were as follows, not including the sextant deter- minations on April 23, a. m., which it was considered unnecessary to use : h. h. m. Si. April 20, 12 -10 8 33.1 21, 0 34.0 21, 12 34.4 22, 0 34.6 On April 24, 7'', the transit determination of time gave the coiTcction — lO*" 8™ 35'.C7. From these determinations the correction for April 20, 23'', the time of the last comparisons on the Hart- ford before the removal of the chronometers to the shore, was deduced by using the sea rate 30 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 4-0^835 II]) to the removal, and +0^4:7 after removal, the former being obtained in the coraiiutation later exi)hiined, and the latter the shore rate on Caroline Island. The following are the results : Sextant observations : April L'O, 2.5 h. m. s. ~ 10 8 3;',.48 3;5.98 34.15 34.12 Mean - 10 8 33.93 Transit mounted 140 feet west of site of sextant observations : h. m. s. Reduction to transit instrument - - - _ - - .09 Resulting corr. (from sextant obser- vations) - 10 8 34.02 Resulting corr. (I'rom transit obser- vations) -10 8 34.00 Mean - 10 8 34.04 Upon leaving Caroline Island, the last time determination with the transit Instruraentby Mr. Preston was carried forward by the rate +0^47 to the time of the first comparisons after the return of the chronometers to the Hartford. The computation was as follows : 7(. VI. It. m. s. May 8, 7 49, local time corr. to 1340= -10 8 42.33 Red. - .42 9, 5 local tinu> - 10 8 42.75 The following table gives the corrections on local mean or sidereal time for each of the nine chronometers before lauding at Caroline Island and immediately upon leaving the island, derived from the chronometer comparisons and using the above corrections for 1340. The times are ex- pressed in Washington mean time to correspond with those in Table I. Table IV. — Chronometer corrections at Caroline Island, escpressed in local mean or sidereal time. April 21.161. May 9.408. Difference. li. m. s. h. m. s. A. m. 8. 1340 — 10 8 34. 04 - 10 8 42. 75 — 0 0, 8.71 202 — 4 53 5. 82 + 14.75 + 4 53 20. 57 1589 — 4 51 24. 56 + 40. 85 - 4 52 ,5.41 2786 - 2 19.09 — 3 35. 35 — 1 16.26 1536 + 1 34.59 + 2 4. 95 + 30. 36 233 — 9 42 35. 41 — 9 41 48.66 + 46. 75 1288 - 10 6 33. 10 — 10 6 28. 69 -f- 4.41 1065 — 10 5 33. 45 — 10 5 36.20 — 2. 75 425 — 9 58 44. 50 — 9 58 28. 27 + 16. 23 Chronometers 202 and 1589 were altered to local sidereal time for convenience in observations, and were frequently carried about on the island, the latter being used by Mr. Preston in connection with the chronograph. No. 1536 was moved occasionally, and 1340 only once, on the day of the SOLAR E(3LIPSE, MAY C, 1S83. 31 eclipse, the latter being kept carefully as the staudard of reference. The observations with the transit showed that on shore it had a gaining rate of 0'.47. a much smaller value than its sea rate. No. 2786 was not removed from the vessel. We are now ready to determine the longitude from the chronometers, making use of the Green- wich corrections given in Table I, and the Caroline Island corrections given in Table IV. Two chronometers, 1340 and 1536, are available for the journey, New York to San Francisco, and the whole nine between Callao and Honolulu. The following table contains the mean rates of each chronometer and the resulting longitude. In obtaining the former the ditterences between the chronometer corrections at New York, Callao, Honolulu, aiul San Francisco (Table I) were taken and diminished by the changes which took place during the stay at Caroline Island (Table IV, last column). Dividing these by the resjiective intervals of time, diminished by that from April 21 to Maj' 9, we have the mean sea rates of the chronometers. This assumes that the rates of those chronometers, viz, 1340, 202, 1589, and 1530, which were removed to the island, and were observed to have difl'erent rates on shore, returned to their former traveling rates after the resumj)tion of the voyage. The daily chronometer comparisons show the same relative rates after leaving Caro- line Island as before arrival, and hence justify the assumption, except in the case of 1589, which had been used in the transit observations on shore and also had had its hands moved. A correc- tion to the longitude was therefore obtained for this chronometer by summing up the departures of the observed relative rates between 1340 and 1580 from their mean values, the resulting longi- tude being given in the sixth column. By means of the rates given in columns two and tliree the Greenwich corrections were obtained for the times April 21.101, and May 9.408, and the local corrections from Table IV at those dates subtracted from them. Both of the computations give the same longitude, and are simply a numerical check on each other. Table V. — Chronometer rafcs and longitude. Mean daily rate. Longitude. Cliroiiom- eter. I.— New York II.— Callao to to I. II. II.— A(l()]ited. Sau Francisco Honolulu. «. 8. Ii. m. s. 7l. Ml. s. ». 1340 + 0.833 + 0.845 10 0 56. 83 10 0 .W. 4 58.4 202 — 0.744 59.0 1.589 — 3. 207 .50. 6 58.7 2786 + 3.686 50.0 1536 — 1.33U — 1. 306 10 0 :u. 33 .59. 7 59.7 233 — 2. 165 (iO. 4 60.4 1288 — 0. 024 .59. 7 59. 7 1065 + 0.2i-.0 60.0 60.0 425 Mean — 0. 503 56 0 .56. 0 10 0 57. 1 10 0 ,59. 0 The last column contains the seconds of the longitude used in deriving the mean result. Nos. 202 and 2788 were both excluded, the former because of its daily use as a hack, and its poor run- ning, shown by the daily comparisons; the latter also for its poor ruiniing. (See Table of rates.) It remains to inquire if any corrections can be obtained to the resulting longitude from the daily comparisons. This is unnecessary in the case of 1340 and 1536 between New York and San Francisco, as but two chronometers were used, and the corrections, if obtained, would .simply reduce 32 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. eacli to the moan of the two. The comparisons between Callao and Honolulu show a tine agree- ment from day to day, probably due in part to the almost constant temperatures to which they were exposed. A correction to 1.^89 was obtained, as above explained, and applied in the last column, but for the other chronometers it was found that the corrections would change the result by only 0.2 second, a quantity within the errors of the computation. The adopted values of the longitude are therefore: h. m. s. 10 0 .59.0, Callao to Honolulu (7 chronometers). 10 0 57.1, New York to San Francisco (2 chronometers). During the stay upon Caroline Island the Eartford visited Tahiti, where time determinations were made by the navigator of the vessel, which have kindly been furnished, as follows : m. s. April 30. 233 slow 18 40.22 1288 fast 5 37.75 1065 fast - 1 41.70 425 slow 2 10.65 The observations were made by equal altitudes with the sextant and I assume for Muta Uta Island, lat, -17° 31' 39" ; long., 149° 34' 21". Eeducing these values to April 21 and May 9, by rates determined from the comparisons at Caroline Island on those dates, and comparing with the local corrections (Table lY), we have the following values of the longitude : //. in. S. L>33 10 0 52.47 1288 53.17 1065 53.05 425 53.11 Mean 10 0 .53.0 The assumed position of Muta Uta Island is taken from the revised edition of Bowditch Navigator, but its authority and reliability could not be obtained. LONGITUDK FROM MOON CULMINATIONS. Observations of moon culminations were obtained by Mr. Pkeston on April 25, and 27, and 28. The last, however, cannot be used, as clouds prevented the determination of the posi- tion of the instrument. Three moon-culminating stars were obtained on the tirst night, but clouds interfered with the observations on the second, necessitating the determination of the constants of the instrument by the other stars observed. The computed right ascensions of the moon are as follows : /». m. s. April 25 17 22 20.09, from m Ophiuchi. 20.10, from i Ophiuchi. 20.11, from 58 Ophiuchi. 17 22 20.10, mean. April 27 19 12 41.,34. The resulting longitudes were obtained with the aid of the lunar ephenieris of the American ephemeris and are given below. Through the courtesy of the Superintendent of the United States SOLAE ECLIPSE, MAY 6, 1883. 33 Naval Observatory, the observation of moon culminations made at Wasbington have been reduced, and their results communicated, as follows : Date. Moon's R. A. Corr. to Eph. April 24 26 27 29 h. VI. 8. 16 17 22. 47 18 6 6.14 19 1 25. 49 20 52 6.25 a. — 0.12 0.00 — 0.11 — 0. 91 The observation on April 27 can therefore be reduced by diiect comparison with the observa- tion at Washington, and that of April 25 by applying to the ephemeris place the correction — OMl, which increases the longitude by 3M. The following are the resulting longitudes : Date. Eph. uncorrected. Corrected. April 25 27 h. m. 8. 10 0 51.9 10 0 52. 9 h. m. 8. 10 0 .55. 0 10 0 55. 6 Mean - 10 0 55. 3 Resulting longititje. From the preceding sections we have the following values' of the longitude : h. m. s. 10 0 .59.0. Seven chronometers, Callao to Honolulu. 10 0 57.1. Two chronometers, New York to San Francisco. 10 0 53.0. Four chronometers from Tahiti. 10 0 55.3. Two moon culminations. On account of the uncertainty in the assumed position of Tahiti it was decided not to use the third value given above, but to take the mean of the other three, giving the first double weight. The resulting longitude is — 150° 14' W"' 1 ^^^^ ^™™ Greenwich. ADDENDUM. TABLE OP CHRONOMETER RATES, AND OBSERVATIONS WITH THE SEXTANT FOR TIME AND LATITUDE. Relative Chronometer rates. The following table contains the relative daily rate of each chronometer referred to 1340, deduced from the chronometer comparisons, and designed to check the running of the chronometers. The rates between New York and Callao were also used, as previously explained, in determining the corrections at Callao. The discordancies in the first part of the voyage are doubtless due to the rapid change of temperature after leaving New York. Between Callao and Honolulu a maxi- mum and minimum thermometer, placed near the chronometers, was daily read. The tempera- tures increased gradually from 12° to 86°, reaching the maximum ofi" Caroline I.sland, and decreas- ing to 74° on the journey to Honolulu. The daily range was only 2° or 3°, and could not always be determined, because the motion of the vessel disturbed the indices of the thermometers. The rates in this part of the voyage were very constant, as will be seen from the table. Chronometer 202 was used as a hack. Chronometer 2786 ran poorly, and also its second hand was a little out of posi- tion, so that some confusion arose among the different obser\ers as to which half-second to adopt in reading. The latter circumstance accounts for part of the discrepancies at Honolulu. The com- S. Mis. 110 5 34 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. parisons were in general made at 11 a. m., local tinie. The expedition chronometers were secured to the floor in the admiral's cabin ; the ship's chronometers were in the navigator's room, with the exception of 425, which was in the admiial's cabin. Relative rates of chronometers from daily comparisons. [1340 — Each cbrouometer. Rate given is for twenty-four houra preceding the corresponding date.] NEW YORK TO ASPINWALL. Date. 202. 1589. 1 2786. 1536. Observer. 3. 8. 8. s. March 4 + 0. 69 + 5. 00 — 0.60 •+ 3.19 S.J.Brown. 5 + .28 4.08 2.49 2.23 Do. 6 — .13 4.66 1.84 2.56 Do. 7 + .47 5.06 2.14 2.52 Do. 8 .11 4.64 i 3.18 2.16 Do. 9 .35 4. 68 3.41 2.32 Do. 10 .86 4.68 3.36 2.10 Do. 11 + .50 + 4.35 — 2.16 + 2. 13 Do. 'Probably an error of 1' in the comparison. ASPINWALL TO CALLAO. March 14 + 0.84 + 4.21 — 2.28 + 2. 13 S. J. Brown. 15 1.49 4.27 3.31 2.13 Do. 16 1.10 4.23 3.33 2.09 Do. 17 1.22 4. 22 3.20 1.87 Do. 18 1.45 4.13 2.29 2.15 Do. 19 L18 4.12 2.00 2.09 Do. 20 1.22 4.12 2.37 2.17 Do. 21 + 0.48 + 3.98 2.12 L98 Do. Note. — Between New York and Aspinwall, the air temperatures changed from 48" to 77° ; between Panama and Callao, from 77° to 63°. CALLAO TO CAROLINE ISLAND. Date. 202. 1589. 2786. 1536. 233. 1283. 1065. 425. Observer. 8. s. 8. s. ». 8. «. s. March 22 23 + 0.73 — .57 + 4.00 4 07 — 2.47 2 04 + 1.89 . S .T Rrowv 1 88 ; Do. Do. W. Upton. 24 + .59 + 1.21 4. 18 1 56 1 80 25 4.24 2. .56 1.96 + 2. 76 + 0.75 + 0.43 + 0.87 26 1.77 4.33 2.41 1.98 2.92 .81 .48 1.24 Do. 27 1.90 4.37 1.91 1.97 2.93 .87 .49 LIO Do. 28 2.32 4.22 2.20 1.98 2.97 .81 .41 1.21 Do. 29 2.32 4.20 2.24 2.03 2.88 1.04 .38 1.29 Do. 30 1.85 4.28 1.63 1.98 2.95 1.02 .50 1.32 Do. 31 1.94 4.43 2.06 2.09 2.97 1.09 .68 1.27 Do. April 1 2.07 4.47 1.81 2.17 2.92 0.83 .57 1.32 Do. 2 2.45 4.45 2.07 2.10 2.98 .94 .77 1.48 Do. 3 2.20 4.42 2.38 2.10 2.92 .72 .64 1.35 Do. 4 2.57 4.30 2.03 2.14 3.02 .89 .65 1.35 Do. 5 2.08 4.30 2.62 2.23 2.97 .77 .57 1.27 Do. 6 2.73 4.51 2.57 2. 22 3.03 .84 .68 1.25 Do. 7 2.82 4.44 2. .52 2.30 2.92 .83 .57 1.10 Do. 8 2.29 4.45 2.25 2.23 3.05 .88 .67 1.30 Do. 9 2.45 4.46 2.60 2.27 3.07 .90 .69 1.58 Do. 10 1.97 4.50 2.30 2.15 3.04 .97 .63 1.55 Do. 11 1.09 4.37 2.86 2.17 2.94 .68 .53 1.55 Do. 12 0.74 4.27 2.97 2.25 2.93 .79 .58 1.71 Do. 13 1.06 4.20 3.00 2.13 2.89 .74 .53 1.55 Do. 14 1.50 4.16 2.81 2.14 2.93 .79 .47 1.65 Do. 15 1.28 8.20 3.18 2.17 3.00 .76 .57 1.70 Do. 16 1.19 4.24 3.32 2.08 2.86 .72 ..52 1.64 Do. 17 1.04 4.32 3.31 2.11 2.90 .74 .47 L66 Do. 18 0.51 4.17 3.14 2.25 3.03 .77 ..54 L87 Do. 19 0.12 4.16 3.41 2.18 2.95 0.87 0.51 1.83 Do. 20 0.87 4.19 3.28 2.15 2.99 0.79 0.52 1.63 Do. 21 + 0.39 •+ 4.75 — 3.40 + 2.24 + 2.76 + 0.66 t+ 0. 16 + 1.71 Do. * Chronometer carried to and from shore. + Checked by a second comparison. Note.— The comparisons on March 22 were made in Callao Harbor ; those on April 20 and 21 while the Hartford was lying oflF Caroline Island. SOLAR ECLIPSE, MAY 6, 1883. CAEOLINE ISLAND TO HONOLULU, 35 Date. 202. 1589. 2786. 1536. 233. 1288. 1U65. 425. Observer. 8. «. s. 8. 8. 8. 8. s. May 10 + 2.17 + 3.91 — 3.31 + 2. 20 + 3.16 + 0.86 + 0.51 + 1.49 W. Upton. 11 2.41 3.87 3.64 2.29 3.10 .80 .50 1.49 Do. 12 2.25 3.81 3.61 2.33 3. 26 .85 ..■sa 1.49 Do. 13 1.70 3.84 3.28 2.26 3.07 .79 .43 1.43 Do. 14 1.85 4.06 3.41 2.29 3. 16 .74 .49 1.45 Do. 15 1.95 3.62 3.70 2.24 3.09 .81 .52 1.49 Do. 16 1.76 3.70 3.64 2.23 3.12 .88 .55 1.41 Do. 17 1.68 3.70 3.79 2.21 3.02 .79 .48 1.35 Do. 18 1.71 3.60 3.79 2.22 3.14 .90 .59 1.38 Do. 19 1.69 3.69 3.87 2.18 3.14 .87 .54 1.39 Do. 20 1.65 3.61 3.78 2.04 2.89 .90 .51 1.27 Do. 21 1. f.5 3.55 3.40 2.02 2.33 .83 .46 1.05 Do. 22 1.50 3.58 3.24 1.95 3.17 .73 .40 0.99 Do. 23 1.53 3.55 2.88 2.03 2.86 .89 .61 1.02 Do. 24 1.47 3.65 2.66 2.12 3.03 1.04 .86 1.09 Do. 25 1.64 3.74 2.49 2.27 3.23 1.09 .90 1.13 Do. 27 1.05 3.81 2.29 2.28 3.26 1.13 0.95 1.27 S. J. Browu. 28 1.23 3.36 .3.28 2.32 3.22 1.18 1.04 1.08 Do. 29 1.27 3.68 2.55 2.32 3.16 1.04 0.99 1.02 W. Upton. 30 1.50 3.56 2. 20 2.23 3.06 1.04 0.82 0.89 Do. 31 1.09 3.70 4.04 2.83 - . - - - . - _ _ 0.98 E. S. HOLDEN. June 1 1.54 3.61 3.00 2.28 3.28 0.94 0.80 1.18 W. Upton. 2 1.81 3.80 2.96 2.25 3.25 1.11 0.66 1.42 E. S. HOLDEN. *3 1.20 3. 70 2 87 2. 12 1.02 + 0. 63 t3 + 0.68 + 3! 26 - 2] 89 + l!75 + 2.83 + 0.48 + 0.39 W. Upton. *A. M. tP. M. Note. — Ou May 24 the Bariford anchored in Hilo Harbor, remaining until the 29th, and arriving at Honolulu on the 30th. The comparisons on .June 3, which were made before the chronometers were moved from the Hartford, indi- cate quite plainly that 1340 lost half a second between the morning and afternoon comparison. The winding was done before the former comparison, and there is nothing to explain the discrepancy. HONOLULU TO SAN FRANCISCO. Date. 2786. 1.536. Observer. June 4 *— 3. 67 *+ 1.62 W. Upton. 5 3.04 2.28 Do. 6 3.12 2.30 Do. 7 3.16 2.38 Do. 8 3.47 2.36 Do. 9 3.19 2.31 Do. 10 3.06 2.31 Do. 11 3.18 2.23 Do. A. M. 12 3.05 2.03 Do. p. M. 12 2.99 2.02 Do. 13 2.98 tl.77 Do. 14 — 3.12 + 2.00 Do. * These are derived from June 2, and confirm the change of 0».5 in 1340 previously noted. t Chronometer carried to and from observatory of United States Co.ast and Geodetic Survey in San Francisco. Note. — The chronometers were secured in the pilot-house on the Zealandia. No. 2786 was used as a hack, and was carried daily into the captain's cabin to compare with the ship's chronometers. As these were not used in the reduc- tions they have been omitted from the table. The Zealandia arrived in San Francisco in theevening of June 11. The temperatures in the pilot-house decreased between Honolulu and San Francisco from 80° to 60°. 36 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. OBSERVATIONS FOR TIME. [Aspiuwall, March 11, 9.45 a. m. Double altitndes of suu. S. J. Brown, observer. Chronometer, Hutton, 202. E. D. Preston, recorder.] Time. 2 alt.© Remarks. Index corrections. Chronometer comparison. Off arc. On arc. 1340. 202. h. m, 8. 9 5 33. 5 11 11.0 14 39. 0 0 / // 100 7 20 I 101 40 40 i 103 18 10 Mercury tremulous ou ac- ( count of wind and surf ( Good sight. / // / // 38 10 26 20 0 20 10 40 Correction, +5' 50" h. m. 8, 2 10 17.0 = 2 13 22. 0 = 4 12 28. 0 = 4 15 30. 0 = h. m. 8. 8 11 19.5 8 14 25.0 = 10 13 50. 5 = 10 16 53. 0 1340 fast, 7"' 2>.9. S. J. Brown, computer. [Caroline Island, April 20, p. m Double altitudes of sun. W. Upton, observer. Chronometer, Negus, 1589. C. S. Hastings, recorder.] INDEX COKRECTION. Before observation. After observation. Off arc. On arc. Off arc. On arc. O / II / // O ' II / // 359 21 40 25 40 359 22 0 25 40 50 40 0 50 50 30 10 40 30 40 20 40 Corr. + 6 20". Corr. + 6' 5". Mean -| - 6' 12". Time. 2 alt. 0 Time. 2 alt. 0 A. m. 8. 10 16 1.5 16 48. 5 17 50. 5 18 34. 0 o ' 67 10 66 50 66 20 66 0 h. m. 8. 10 21 19.0 21 42.0 22 5.5 22 27.5 o ' 63 40 63 30 63 20 63 10 Above readings were through clouds. W. Upton, observer. W. B. Fletcher, recorder. II. Time. 2 alt. © Time. 2 alt. O h. m. 8. 10 32 22 32 42. 5 33 4.5 33 26. 5 o ' 59 40 59 30 59 20 59 10 h. m. 8. 10 34 46 35 6.5 35 29 35 50.5 o 57 30 57 20 57 10 57 0 Sky clear f conditions favorable. SOLAR EOLIPSE, MAY 6, 1883. 37 CHRONOMETER COMPARISONS. 1340. 1589. h. m. 8. h. m. n. 11 56 8. 5 = 8 33 55 2 37 52.5 = 11 16 5 REDUCTION BY METHOD OF SINGLE ALTITUDES. [W. Upton, computer.] h. m. 8. 1589 fast— 4 51 27. 93 1340 fast— 10 8 33.52 [Caroline Islaiul, April 21, a. m. Double altitudes of suu. Clironometer, Negus, 1589. W. Upton, observer and recorder.] INDEX CORRECTIONS. Before observation. After observation. Time. 2 alt. o Time. 2 alt. 0 Oflf arc. On arc. Off arc. On arc. o / /' / // O ' " / // .'(. m. 8. o / h. m. 8. 0 ' 359 21 50 26 0 359 22 0 26 30 2 56 37.5 57 30 3 5 24. 0 60 30 50 25 40 0 0 57 21. 5 57 50 6 10 60 50 60 26 20 Corr. + 5' 52".5 56 4 58 10 6 53.5 61 10 50 26 10 58 48. 5 58 30 7 37 61 30 33.1". Corr. + 6' 2".5 (2 wt). Adopted + 5' 59".2. CHRONOMETER COMPARISONS. 1340. 1589. h.m. «. h.m. 8. 5 16 36 = 1 57 10 8 4 29 = 4 45 30 REDUCTION BY METHOD OF SINGLE ALTITUDES. h. m. s. 1.589 fast 4 51 23.70 1340 fast 10 8 32. 60 Combining with observation April 20, p. m., made at nearly corresponding time. April 20, 12'', 1340, fast 10'' 8" [". Also combined witb observation April 21, p. m., by method of equal altitudes. W. Upton, computer. [Caroline Island, April 21, p. m. Double altitudes of sun. Chronometer, Negus, 1589. W. Upton, observer and recorder. ] INDEX CORRECTION. Before observation. After observation. Time. 2 alt. o Time. 2 alt. 0 Off arc. On arc. Off arc. On arc. o / // / // o / // / // It. m. 8. 0 ' h. m. a. 0 359 22 0 26 0 359 21 50 25 40 10 31 3.'^.5 61 30 10 35 47. 5 58 30 0 10 22 10 50 32 17.5 61 10 36 30.5 58 10 10 10 21 50 50 33 2. 0 60 50 37 14.5 57 50 10 0 22 0 40 33 44. 5 60 30 37 57. 5 57 30 Corr. + 5 '55" Mean Corr. + 6' 9" -1- 6' 2" 38 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. CHRONOMETER COMPARISONS. 1340. h. m. 8. h. 111. 8. 1 20 56 = 10 4 30 chron. 202. 23 22. 5 = 10 5 15 chron. 1589. 24 36 =5 13 30 chrou. 1536. CHRONOMETERS REMOVED FROM SHIP TO THE SHORE. h, m. a. h. m. s. 2 9 53 = 10 53 35 chron. 202. 10 5 = 52 5 chron. 1589. 10 38.5 = 5 59 40 chron. 1536. Reduction by method of equal altitudes, combiuiDg with observations April 21, a. m., and April 22, a. m. W. Upton, computer. [Caroline Island, April 22, a. m. Double altitudes of sun. Chronometer, Negu.s, 1589. W. Upton, observer and recorder. ] I. INDEX CORRECTION. Time. 2 alt.e Time. 2 alt.0 h. m. 8. 2 40 16.5 41 1.0 42 25. 5 4S 7.5 o ' 48 0 48 20 49 0 49 20 h. m. 8. 2 45 47 46 30 47 13 47 56. 5 o ' 49 30 49 50 50 10 50 30 II. 3 0 46. 5 57 30 3 9 37 60 30 1 30.5 57 50 10 21 60 50 2 13.5 58 10 11 4.5 61 10 2 56.5 58 30 11 47.5 61 30 Before observation. After observation. Off arc. On arc. Oft' arc. On arc. O ' " / // O 1 II / // 359 22 10 25 50 359 22 10 25 50 21 50 40 22 10 40 22 0 50 21 50 40 22 0 40 21 50 40 Corr. + 6' 9'' Corr. + 6' 7" 1 Mean + 6' 8" CHRONOMETER COMPARISONS. 1340. 1589. h. m. «. h. m. s. 5 31 41.5 = 2 16 10 6 40 0. 5 = 3 24 40 Reduction by method of equal altitudes, combining with observations April 21, p. m., and April 22, p. m. W. Upton, computer. [Caroline Island, April 22, p. m. Double altitudes of the sun. Chronometer, Negus, 1589. W. Upton, observer and recorder.] I. INDEX CORRECTION. Time. 2 alt.© Time. 2 alt. G h. m. 8. 10 34 45. 5 35 28 36 12.5 36 55. 5 O ' 61 30 61 10 60 50 60 30 h. m. s. 10 38 58. 5 39 42 40 25.5 41 9 o ' 58 30 58 10 57 50 57 30 II. 10 56 17.5 57 0 57 43 58 26. 5 50 30 50 10 49 50 49 30 11 1 4.5 1 47.5 3 12.5 3 56.0 49 20 49 0 48 20 48 0 Before observation. " After observation. Off arc. On arc. Oflf arc. On arc. O ' " o ' o / " / // 359 22 5 0 0 26 0 0 5 359 21 40 21 40 21 50 21 50 26 0 25 40 25 40 26 0 Corr. + 5' 59" Mean - Corr. + f 6' 6" 6' 12" CHRONOMETER COMPARISONS. 1340. 1589. h. m. 8. h. m. ». 1 29 49. 5 = 10 15 35 2 28 40 = 11 14 35 Reduction by method of equal altitudes, combiniug with obsorvatious April 22, a. ra. W. Upton, computer. (Observations were also made April 23, a.m., but were not used in the reductions.) SOLAK ECLIPSE, MAY G, 1883. 39 OBSEKVATIONS FOR LATITUDE. [Caroline Island, April 23. Double altitudes of the sun. Pocl£et watch No. 3649. W. Upton, observer aud recorder.] INDEX CORRECTION. Time. 2 alt. o Resultiuglatitude. h. m. 8. O t II O f " 0 18 43 133 58 20 — 9 59 30 20 30 133 45 10 54 21 30 133 38 0 48 23 43 133 20 0 2 alt. O 0 / // 57 . 25 10 132 4 50 45 26 15 131 .55 0 .57 27 2 131 48 20 45 28 45 131 32 30 Mean — 9 59 48 Off arc. On arc. O / II / // 359 22 0 25 50 Corr. 4 6' 5" y^ATCH COI UPARISON 1340. 3649. h. HI. «. h. VI. a. 10 48 30= 0 39 24 - Reduction by method of circummeridian altitudes. W. Uptox, computer. [Caroline Island, April 24. Double altitudes of the sun. Pocket watch No. 3649. W. Upton, observer and recorder.] INDEX CORRECTION. Time. 2 alt.o Resulting latitude. h. m. s. o / " o ' " 11 49 43 134 17 20 — 9 59 37 50 57 20 30 41 52 8 23 10 42 53 15 25 40 2 alt.0 31 57 43 133 26 30 31 58 45 26 20 40 59 40 26 10 40 12 0 40 25 40 2 alt.e 40 3 22 134 26 0 55 4 25 24 20 51 5 18 22 40 48 6 23 20 10 48 Mean — 9 59 42 Before observation. After observation. Off arc. On arc. Off arc. On arc. o / // ;»9 22 30 30 30 30 Corr. + 5' 46 / // 25 50 26 0 0 0 "adopted. o ' // 329 22 30 Corr. + / // 26 0 5' 45" WATCH COMPARISONS. 1340. 3649. h. m. >. h. m. 8. 9 45 0 = 11 37 1 10 22 10 = 0 14 13 Reduction by method of circummeridian altitudes. W. Upton, comiiuter. APPROXIMATE LATITUDE BY SEXTANT OBSERVATIONS. April 23—9 .59 48 24 42 Mean — 9 59 45 40 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. OBSERVATIONS FOR TIME. fHouohihi, May :!0, p. m. Double altitudes of the sun. W. Upton, observer. Cbroiionieter, Hutton, 202. S.J. Brown, recorder.] I. INDEX CORRECTION. Time. 2 alt. 0 Time. 2 alt. 0 h. m. s. C ' h. VI. 8. o ' 8 47 14. 25 74 30 8 49 31 74 30 35 20 54 20 58.75 10 50 15.75 10 48 19.75 74 0 38.5 0 II. 9 5 58 66 0 9 8 17.75 66 0 G 19.75 65 50 40 65 50 42.5 40 9 2.5 40 7 4 65 30 23 65 30 Before observation. After observation. Off arc. Ou arc. I Off arc. On arc. o ' /. ! / // 359 22 0 I 25 30 10 I .SO 5 i 20 Corr. + 6' 14". Mean + 6' 19". 359 22 0 I 25 10 10 0 - - - - I 15 Corr. + 6' 23". CHRONOMETER COMPARISONS. 1340. 202. h. m. s. h. m. s. 1 45 30 = 8 8 50 3 35 40 = 9 59 18 REDUCTION BY METHOD OF SINGLE ALTITUDES. [W. LTpTON, computer.] h. m. 8. 202 slow 10 1 29.5 Greenwich sidereal time. 1340 fast 8 2. 4 Greenwich mean time. [Honolulu, June 1, a. ra. Double altitudes of the sun. W. Upton, observer. Chronometer, Hutton, 202. Mrs. W. Upton, recorder.] I. Time. 2 alt.0 Time. 2 alt.O A. m. 8. O ' h. m. 8. O ' 0 48 8. 5 61 10 0 50 29 61 10 31.5 20 52 20 52 30 51 12.5 30 49 15.5 61 40 35 61 40 II. 0 55 55 64 40 1 3 1.5 1 66 50 56 16.5 50 23.5 67 0 39.5 65 0 45.5 10 57 2 65 10 4 7.5 67 20 INDEX CORRECTION. Off arc. On arc. o / " / // 359 22 10 25 30 5 30 0 30 0 20 Corr. -f - 6' 14". CHRONOMETER COM- PARISONS. 1340. 202. h. m. 8. h. m. s. 5 14 15 = 23 44 2 7 5 10 = 1 35 15 Somewhat disturbed by clouds and jarring of the mercury from passing carriages. SOLAR ECLIPSE, MAY fi, 188,3. 41 REDUCTION BY METHOD OF SINGLE ALTITUDES. [W. Upton, comimter. ] h. m. 8. 202 slow 10 1 31.1 Greenwich sidereal time. 13-10 fast 8 3.0 Greenwich mean time. [Honolulu, Juno 2, a. m. Double altitudes of the sun. W. Upton, ob.server. Chronometer, HirnoN, 202. Mrs. W. Upton, recorder.] INDEX CORRECTION. Time. 2alt.0 Time. 2 alt.O h. m. s. o / h. m. 8. o / 1 1 22.5 65 20 1 3 40. 5 65 20 43. 5 :!0 4 3. 5 30 2 .5.5 40 21). 5 40 29 50 4 47.5 50 Off arc. ! On arc. 0"" / /' / // 359 22 0 25 20 21 50 15 ' 22 0 10 22 0 0 . Corr. + 6' 26" CHRONOMETER COM- PARISONS. 1340. 202. Ii. VI. «. h. m. 8. 5 18 48 =23 52 30.5 6 51 22. 5 = 1 25 20 REDUCTION BY METHOD OF SINGLE ALTITUDES. [W. Upton, computer.] h. m. s. 202 slow 10 1 31.2 Greenwich sidereal time. 1340 fast b 4.4 Greenwich mean time. ^■i. THE METEOROLOGY OF CAROLINE ISLAND. By Mit. ^YIN.sLOW Upton. DESCRIPTION OF INSTRUMENTS AND STATION. The meteorological record kept at Caroline Island covers the period of two weeks extending from April 25 to May 1». During this time frequent observations were made with the ordinary meteorological instruments, and with special radiation apparatus furnished through the courtesy of the Chief Signal OfHcer. The following was the meteorological outfit : 1 small instrument shelter (window pattern). 1 aneroid barometer (IIottinger, 3241). 1 maximum thermometer. 2 minimum thermometers. 6 ordinary thermometers. 1 Browning's rain-band sfiectroscope. 2 pair conjugate thermometers. 2 pair VioLLE's conjugate bulbs. 1 Eobinson's anemometer (belonging to the U. S. S. Hart/ord). The proper exposure of the 7iieteorologicaI instruments received special attention. The shelter was erected, with the open side facing the south, upon a wooden support about 4 feet high, under S. Mis. 110 6 42 MEMOIRS OF THE NATIONAL ACADEMY OP SCIENCES. the shade of a high cocoanut tree, there being several other trees in the immediate vicinity. The roof sloped towards the north, and after April 29 was surmounted by an additional roof raised about 4 inches above the first. The north side of the shelter contained a door, which was fre- quently open. This arrangement of the shelter proved very satisfactory. The whole shelter was shielded from the direct rays of the sun, except for a short time soon after sunrise, by the branches of the trees, and the rays which came through these branches during the heated portion of the day fell upon the upper roof. The important condition of a free circulation of air about the instruments was also secured, since the branches of the trees were from 10 to 20 feet above the shelter, allow- ing the wind to blow beneath them. Three sides of the shelter were made of open louvre work, Mhile the fourth was wholly open. In order to test, by actual observation, the success of the above method of ex^iosure, a series of readings was made of the dry-bulb thermometer, and of a thermom- eter whirled rapidly in the open air. The readings were made under various conditions during sev- eral days, and are given at the end of this report. They show that the readings of the dry-bulb thermometer may be accepted without correction as giving closely the temperature of the air. Within this shelter were placed the maximum, minimum, dry-bulb, and wetbulb thermometers, and beneath it, one foot above the grass, a thermometer adapted for measuring the minimum tem- perature at night close to the ground. The bulbs within the shelter were elevated 5 feet above the ground. The aneroid barometer was of the Goldschmid pattern, and proved to be a good instrument. It was generally kept in the house, but during the frequent observations on April 29 and May 6, was for convenience placed in the shade in the open air or in the instrument shelter. Comparisons between the readings of this barometer and the mercurial barometer furnished Mr. Preston by the United States Coast and Geodetic Survey were frequently made, and are given at the end of this report. From them a constant correction of + 0.104 inch to the aneroid baro- meter was derived, and has been used in the reduction of the readings. The elevation of the in- strument was about 10 feet above the level of the sea. The anemometer was mounted on an iron rod, 9 feet 7 inches above the ground, in a large open space to which the wind had good access, especially from the north and east, the only direc- tion in which the wind was observed to blow during the period of observation. The rain-band spectroscope was read occasionally only. Its readings at the different observa- tions were nearly the same, as will be seen from the record given at the end of this report. In damp insular positions in the tropics the instrument seems to give about the same indications from time to time, and therefore is of less value as a hygrometer than in the temperate zone. The instruments were read daily at frequent intervals between 6 a. m. and 9 \>. m. As the principal object of the observations was to furnish a basis of comparison for those made in connec- tion with the eclipse, the record is especially full between the hours of 10 a. m. and 2 ]>. m. The observations are given in detail at the end of this report. From them may be gleaned the follow- ing facts bearing upon the meteorology of the island. GENERAL WEATHER CONDITIONS. With the exception of one day, May 4, the conditions were uniform, and characterized by lair weather with cumulus clouds passing rapidly over the sky, giving rise to frequent but slight showers. Upwards of twenty of tliese showers were noted during the two weeks, the rainfall at each being small. The sky was sometimes clear for several hours, especially in the middle of the day and in the early evening. The clouds observed were almost wholly of the cumulus class, cirro-stratus being also seen occasionally. The only weather disturbance occurred on May 4, Fig. 15. MEAN BAROMETRIC CURVE, APRIL 25-MAY 6. Pressures reduced, to Sea Level. Time. tfu -^0.00 . pjm:. A.M. ;■ a S lO 11 12 1 2 3 4 s e 7 8 a -e9.9S ^ \ - -29.ao \ / ^ - -29.85 y - — -29.80 1 1 1 1 1 \ 1 1 1 1 1 1 1 1 1 — SOLAR ECLIPSE, MAY 6, 1883. 43 wlien it rained steadily from about inidnigbt to 9.50 a. in.; it remained cloudy until afternoon, when the sky gradually cleared. Following tlii.s day, the clouds were more frequent than they had been for several preceding days, the wind stronger, the humidity .somewhat greater, and showers more frequent. BAROMETRIC PRESSURE. The barometric pressure was markedly uniform from day to day, the diurnal movement being clearly ajjparent. The following table contains the hourly barometric readings between April 25 and May C, reduced for temperature and elevation. Values in brackets are interpolated for the purpose of obtainiug the mean values. Reduced barometric readings. uo to t-' ad s o > ^i ^ g. >i >. CS o Pn p< a. Qi p< 1=4 £ cd C8 a C8 i^ O W <1 < < < ■< < IS s s S S S S A. M. 7.00 29.95 29. 99 29.96 29.93 29. 91 29. 89 29.92 29. 94 29. 97 [30. 03] 29. 99 29. 98 29. 955 8.00 .97 .98 .97 .95 .93 .90 .93 .94 .98 30. 03 30. to .98 . 963 9.00 .97 .99 .98 .95 .92 [ .90] .93 .95 .97 .06 29.99 .99 . 9(i7 10.00 .97 .99 .97 .93 .90 .89 .92 .94 .97 .03 .99 .98 .957 11.00 .92 .9(5 .95 .91 .86 .87 .90 .92 .93 .01 .96 .94 .928 12.00 .93 .93 .92 .87 .84 .84 .87 .87 .89 30.00 .94 .94 .903 p. M. 1.00 .90 .91 .88 .85 .75 .83 .85 .85 .85 29.96 .90 .89 .868 2.00 .87 .88 .85 .82 .75 .80 .82 .83 [ .83] .92 .89 .87 .844 3.00 .86 .87 .83 .80 .76 .79 .81 .83 : .83] .90 .88 .87 .836 4.00 .87 .SS .84 .80 [ -78] .79 r .83] .84 : .84][ .90] [ .89] .88 .845 5.00 .89 .90 .85 .83 " .80] .81 [ .H5] .87 " .85] .90 [ .90] .90 .862 6.00 .89 .91 .85 .84 [ .82] .83 [ .87] [ .89] .86 .92 .91 .91 .875 .7.00 . - .95 .89 - . - . .91 . - - - - 8.00 - . .98 .90 - - - - - - - - . - .93 - - - . - - - 9.00 .96 .98 .90 .91 .87 .90 .93 .94 .97 .96 .94 .96 .938 It will be seen from this table that a barometric maximum occurred on each day at about 9 a. m., and a minimum at about 3 p. m. No regular barometric ob.servations wei'e made at uight after 9 p. m., but Messrs. Preston and Brown, in conuectiou with their observations, read a mer- curial barometer occasionally during the night. From these observations it is learned that a sec- ond maximum occurred at about 9 p. m., and a secoiul minimum at about 3 a. m. The table also shows indications of a barometric period covering several days, a minimum occurring April -9, and a maximum May 4. The latter was accompanied by the heavy rain-storm elsewhere mentioned. AIR TEMPERATURE. The thermometric readings show a similarity from day to day, and also, as would be ex])ected from an insular station, a small daily range averaging 9o.3. The highest reading noted was 89o.3 on April 28; the lowest 72°. 4 during the rain-storm on the morning of May 4. The minimum ther- mometer placed on the ground gave readings nearly identical with those of the minimum thermom- eter in the instrument shelter. The daily maximum temperature occurred at very nearly noon, and the minimum at about 6 a. m. HUMIDITY. The relative humidity was always great, ranging from an average of 70 per cent, in the middle of the day to 84 per cent, in the early morning. The lowest value observed was CI ]>er cent, at 11.30 a. m.. May 2. 44 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. RAINFALL. In order to measure approximately the rainfall a gauge was impi'ovised with the aid of a tin can of uniform diameter. The frequent showers gave in general an inajjpreciable amount of rain, though some of them gave small amounts, one-tenth of an inch or over. The meteorological summary gives the record of the rainfall, from which it will be seen that the total amount during the two weeks was about 8 inches. More than half of this fell in the rain-storm of May 4, when it rained hard and steadily from midnight to 9.50 a. m. WIND. The observations of the direction and velocity of the wind give some interesting results. The former was almost always noted as east or northeast, and was at no time observed to be from any other quarter than between north and east. The island is situated in the region of the southeast trades, which makes it noteworthy that not a single record gives a direction south of east. The table of wind velocities on page — gives in detail the results of the anemometrical obser- vations. From this it will be seen that there is no indication sufficiently marked of any diurnal change in the wind's velocity. It is, however, apparent that there was a decrease of velocity from the beginning of the series to May 2, and an increase to May 7. These dates follow the dates of mininnim and maximum pressure mentioned above by an interval of about two dajs, but the series is for too short a period of time to warrant the drawing of any inferences as to their relation. Indeed, it may be said that the indications of periodicity in both these cases may be only acci- dental, and not real indications of a progressive movement. It would take a longer continued series of observations to decide the question, and therefore the above are in Mitioned as only possibilities which these observations suggest. The average hourly velocity of the wind was G.05 miles ; the largest total movement in twenty- four hours was 212.3 miles, from 7 a. m. May 7 to 7 a. m. May 8 ; the least 59.2, between the same hours May 4 and 5. The highest velocity observed was on April 30, during the passage of a squall which was characterized by wind without rain. At 12.35 p. m. the anemometer registered 1 mile in 3'" 40", the equivaleut of 10 miles an hour. The wind usually increased during the pas- sage of the heavier showers. METEOROLOGICAL OBSERVATIONS BETWEEN APRIL 25 AND MAY % 1883. The observations given below were made with the following instruments: Aneroid barometer, Hottinger, 3241. Dry-bulb thermometer. Green, 799, stem graduated. Wet-bulb thermometer. Green, 797, stem graduated. Maximum thermometer, Green, 725, stem graduated. Minimum thermometer, Green, 710, stem graduated. Minimum thermometer for use at ground. Hicks, 5521, stem graduated. Robinson's anemometer. Green, 111. Tlie readings of these instruments are given exactly as recorded, with the following exceptions : The readings of the maximum thermometer have been corrected by the amount — 0°.5, deter- mined by thirty-seven comparisons with the dry bulb made April 27-30. The readings of the minimum thermometer. Green, 710, have been corrected by the value. -f 0O.4, determined by sixty-two similar comparisons; those of the minimum thermometer. Hicks, 5.521, by + 2O.0, determined by forty similar comparisons. The large correction to the latter was due to a bubble in the instrument, which was several times removed, but as often formed again. SOLAR ECLIPSE, MAY 6, 1883. 45 The readings of the aneroid barometer have been reduced by appl^'iiig the corrections for instrumental error, temperature, and elevation. These have been obtained as follows: REDUCTION OF OBSERVATIONS MADE WITH ANEROID I5AR0MKTKR, HOTTINGER, 3241. Comparisons between aneroid barometer, Hottinger, 3241, and mercurial barometer, Green, lit.'JG. 3241. 1936. Readings for tcni} corrected e rat lire. Correc- Diite. Hour. tion to 3241. t. Reading. t. Reading. 3241. 1936. c in. o in. in. in. in. Aiiril 25 10.40 a. m. 85 29.927 91.4 30. 123 29. 84 29. 96 + 0. 12 27 7.00 a. III. 83 .927 81.7 .031 .85 .89 .04 27 2.00 p. 111. 85 .827 92.6 .037 .74 .86 .12 27 9.00 p. 111. 84 .673 81.2 .032 .79 .89 .10 28 2.30 J). III. 86 .778 98. 7 .002 .69 .82 .13 28 9.00 p. lu. 83 .876 82.4 .030 .80 .89 ■ .09 30 9.00 p. m. 84 .873 81.7 .038 .79 .90 .11 May 1 11.00 a. 111. 85 .875 95.6 .080 .79 .90 .11 6 H.OO a. 111. 83 .949 86.1 .120 .87 .97 .10 6 9.00 p. 111. 82 . 922 81.7 .081 .84 .94 .10 7 Ci.OO p. 111. 84 . 813 81.7 .020 .73 .88 .15 7 9.00 p. 111. 83 .887 81.2 .046 .81 .90 .09 8 7.00 a. 111. 81 .870 80.8 . 025 .80 .89 .09 Mea + 0.104 1 " - - - Temperature corrections to bai-omrtcr, Hottinger, 3241. I Kurni.slu'd by maker. I t. o 7G 80 84 Corr. in. — 0. 00 — 0. 07 — 0. 085 88 — 0. 10 92 — 0. U Elevation of instrument above sealevel, 10 feet. Reduction to .sea-level, + 0.01 inch. Combining these reductions we have the following table by which the barometer readings in the column "Reduced reading" are obtained from the observed readings : t. Reduction o in. 76 + 0.054 SO .044 84 .029 88 .014 92 + 0.004 46 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. Comparisons between dry bulb thermometers, Green, 7d9,p}aced in the instrument shelter, and Green, 811, read afttr being swung rapidly through the air. [These comparisons were made on dift'ercnt days betweeu April 25 aud May 2. The swinging of Grekx, 811, was repeated seTiral limes until it seemed certain that it had assumed its true reading. The dirterencesonly between the readings are given. The instrumental corrections to both of these thermometers are O.O.] 811—799. I. Before extra roof was i)laced upon shelter. II. After extra roof was placed upon shelter. III. During a period of calm, May 2. + - O 0 0. 6 0. 3 .3 .3 .2 .1 .0 1.0 .0 .8 .4 .3 .0 .6 .2 .4 1.7 .9 .3 1.2 + - o o 0. 0 0. 4 .6 .1 .2 .3 .0 .2 .2 .1 .0 .0 .3 .2 .1 .4 .0 + 2. 0 — 1. 1 + 0°.9 + O^M + - o o 0. 5 0. 7 .3 _ s '. 1 +0.5 — 1.9 Sum — 1^.4 Mean — 0^.3 + 1.5 — H. 1 Sum —6°. 6. Mean — O^.S. If we assume, as is usual, that the whirled thermometer gives a close approximation to the true air temperature, the above comparison shows what correction should be applied to the ther. mometer in the instrument shelter. It will be seen that the effect of placing a double roof upon the shelter was to diminish this correction, the correction becoming almost inappreciable except in the extreme case on May 2, when there was no wind and the air was accordingly stagnant in the shelter. As a result of these comparisons, it was decided to adopt the readings of the dry -bulb thermometer within the shelter without any correction for the air temperature. APRIL 25, 1883. u 3 O w Barometer. Thermometer. .3 1 u S) +^ 2!». 99 82.8 77.8 80 331.9 NE. Fair. 3 cum. 8.00 83 . 94.". .9-' H5. 0 79. rt 80 339. 0 NE. Clear. 2 cum. 9.00 84 . 91 ;i) . 99 K!. 0 77.7 77 347. 4 NE. Clear. 2 cum. 1 10. 00 84 .90" . 99 80. 0 79.7 74 352. 6 NE. Fair. 4 cum. 11. 00 84 .932 . 90 h7.2 79.7 70 360. 3 NE. Fair. 3 cum. 12. 00 84 . 902 .93 87.2 79.8 70 367.2 NE. Fair. 3 cum. p. M. 1.00 84 .877 .91 86. 2 78.7 70 374.8 NE. Clear. 1 cum. 2.00 85 .858 .88 85. 8 78.6 73 382. 4 NE. Fair. 3 cum. 3.00 85 .848 .87 8.5.8 78.8 73 389. 3 NE. Fair. 3 cum. 4.00 85 .855 .88 84.9 79.0 74 393. 6 NE. Fair. 4 cum. 5.00 84 .872 .90 83.9 711.3 77 396. 3 NE. Fa i r. 3 cuui. 6.00 84 .883 .91 82. 2 77.2 79 402. 2 NE. Fair. 5 cum. 7.00 84 .925 . 95 75.5 73.5 89 408.1 NE. Rai n . 10 nim. 8.00 82 . 945 .98 78.0 77.8 100 410. 3 NE. Clondv- 9 cum. 9.00 82 .944 .98 79.2 76.3 88 418.1 NE. Cloud'y. 10 8tr. _ Miscellaneoits. — Minimum, 80,8 at 7.00 a. m. ; 75.1 at 9. CO p. m. Minimum at ground, 81.1. Maximum, 87.8. Light showers.at 10.05 a. m., 2.15, 4.05 ji. m. Heavy showers in the evening after 6.30 j). m. Rainfall, 0.3. APRIL 27, 1883. Barometer. I'hermometer. i a a o Clouds. o o K t. Observed reading. Reduced reading. Dry. Wet. i a Wind Weat A. M. 6.00 81 29.913 29. 95 81.0 76.8 82 476.0 NE. Fair. 2 cum.,2cir. str. andcir cum. 7.00 83 .927 .96 82.0 77.2 80 484.4 NE. Fair. 2 cum., 2 cir.str. aud cir. cum. 8.00 83 .940 .97 78.8 75.9 89 494. 5 E. Rain. 9 cum. 9.00 83 .947 .98 84.6 79.2 78 502.1 NE. Fair. 3 cum., heavy nim. in north. [ 10.00 83 . 935 .97 84.5 79.2 81 511.8 NE. Fair. 4 cnm. 11.00 83 .914 .95 a5.2 79.4 74 519. 4 NE. Fair. 3 cum. and cir. str. 12.00 84 .887 .92 87.2 80.9 74 525.8 E. Fair. 3 cum. and cir. str. 1.00 84 .850 .88 86.2 79.2 72 532.7 E. Fair. 3 cum. and cir. str. 2.00 85 .827 .85 86.7 79.7 71 539.0 E. Clear. 2 cum. and cir. «tr. 3.00 85 .810 .83 85.0 78.2 72 .544. 7 E. Fair. 3 cum. aiul cir. str. 4.00 85 .812 .84 84.3 78.2 73 549. 9 NE. Fair. 3 cum. aiul cir. str. 5.00 85 . 822 .85 82. 9 77.7 77 555. 0 NE. Fair. 3 cum. and cir. str. 6.00 85 .829 .85 82.0 77.6 82 559.6 NE. F'air. 4 cum. and cir. str. 7.00 84 .861 .89 81.8 77.4 81 564. 3 NE. Clear. 1 cum. in horizon. 8.00 84 .869 .90 81.8 76.6 80 568.9 NE. Clear. 1 cum. 9.00 84 .873 .90 81.6 77.0 80 575.3 NE. Clear. 1 cum. Miscellaneous. — Miuimura, 78.1. Maximum, 88..3. Shower, 7.40-8.00 a. ra. ; inappreciable. 7.30 p. m., zodiacal light seen — an arch in west, 2.5'' high and 40' broad, with limits poorly defined. 48 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. AI 'KIL 28, 1883. Barometer. Thermometer. 3 s s Eh Clouds. O K t. Observed reading. Reduced reading. Dry. Wet. Rel.h a s ■< a 1 A.M. 6.00 82 29. 879 29.91 80.8 76.7 83 627.1 E. Clear. 2 cum. and cir. str. 7.00 82 .895 .93 79.9 76.3 85 632. 1 E. Fair. 4 cum. 8.00 82 . 912 .95 83.0 78.5 80 636.6 E. Fair. 3 cum. 9.00 82 .913 .95 85.0 78.8 e2 643.8 E. Clear. 2 cum. iunorlh. 10.00 83 . 902 .93 S5.0 80.0 80 650. 9 NE. Clear. 1 cum. and cir. str. 10. 35 83 .887 .98 85.9 79.0 72 - - _ E. Clear. 1 cir. str. 11.00 84 .877 .91 86.5 78.7 67 654.9 NE. Clear. 1 cir. str. 11. .30 84 .862 .89 86.8 79.7 69 656.8 NE. Clear. 1 cum. in horizon. 12.00 P.M. 12.30 84 .8.39 .87 87.2 80.2 72 658, 5 NE. Clear. 1 cum. in horizon. [ 84 .832 .86 87.8 61.0 73 660.2 E. Clear. 2 cum. 1 1.00 84 .820 .85 87.0 80.1 72 661.4 E. Clear. 2 cum. 1. 30 85 .805 .83 87.0 30.7 75 663.1 NE. Clear. 2 cum. 2.00 8.S .798 .82 87.3 80.3 71 664.2 NE. Fair. 4 cum. 2.30 86 .778 .80 86.0 79.0 72 666.7 E. B'air. 4 cum. 3.00 86 .777 .80 87.0 80.1 72 669.9 E. Fair. 4 cum. 3.30 86 .775 .80 «5.2 78.0 72 672.2 E. Clear. 2 cum. 4.00 86 .779 .80 8.5.5 78.0 71 675.4 E. Clear. 1 cum. 4.30 86 . .788 .81 84.0 77.8 74 678.2 E. Clear. 1 cum. 5.00 85 .800 .83 83.2 77.2 74 681.6 E. Clear. 2 cum. 6.00 85 . 815 .84 82.4 77.2 79 687.4 E. Fair. 3 cum. 9.00 83 .876 .91 82.0 77.3 80 708.9 E. Clear. 1 cum. Mkcellaneons. — Minimum, 79. 2. Minimum at ground, 79. 5. Maximum, 89. 3. Shower about 10 p. m., giving 0. 02 inch of rain by estimation. 6.30 a. m., fine alternate dark and light streaks extending completely across the sky through the zenith ; sun behind heavy cumuli. APRIL 29, 1883. c a o W Barometer. Thermometer. a s 1 o a a a .a 1 Clouds. t. Observed reading. Reduced reading. Dry. Wet. A. M. 6.30 7.00 8.00 8.30 9.00 9.30 10. 00 10. 30 11.00 11.30 12.00 p. M. 12. 30 1.00 . 1.30 2.00 2.30 3.00 3.30 9.00 83 82 82 83 83 83 84 86 86 86 86 92 89 89 88 88 S7 83 29. 862 .872 .898 .885 .882 .872 .865 .841 .819 . 815 .791 .743 748 .740 .741 .745 .748 .838 29.89 .91 93 .92 .91 .90 .89 .86 .84 .84 .81 .75 .76 .75 .76 .76 .77 .87 81.4 82.2 84.3 8.5.5 8.5.9 86.1 87.1 86.1 87.1 87.1 87.9 88.0 87.0 87.7 87.7 87.5 87.0 86.1 82.3 76.6 77.2 78.3 79.0 79.0 79.7 80.2 79.1 79.5 80.5 80.0 80.2 80.0 80.5 80.3 80.0 79.9 79.2 76.8 78 79 73 73 72 75 72 72 68 73 70 70 72 73 73 71 72 72 76 767.4 770.9 777.3 780. 3 783.0 785 (i 788.6 791. 3 794.3 797.2 800.2 802.9 805. 9 817.6 810.9 812. 3 814.5 816.8 855.7 NE. NE. NE. NE: NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. E. Fair. Fair. Clear. Clear. Clear. Clear. Clt-ar. Fair. Clear. Clear. Clear. Clear. Fair. Clear. Clear. Clear. Clear. Fair. Clear. 3 cum. and cir. str. 3 cum. and cir. str. 2 cum. 2 cum. 2 cum. 2 cum. 2 cum. 3 cum. 2 cum. 1 cum. 1 cum. 1 cum. 4 cum. 2 cum. 2 cum. 2 cum. 2 cum. 3 cum. 1 cum. MisceUaneom.—Minimum, 77. 7. Minimum at ground, 77. 8. Maximum, 88. 4. SOLAK ECLIPSK, MAY «, 1883. 49 APRIL 30, 1883. o w Barometer. Thermometer. a 3 ,=1 s i o a ■< Is a/ Clouds. t. Observed reading. Ked need reading. Dry. Wet. A.M. 6.00 7.00 7.30 8.00 9.00 9. 30 10.00 10. 30 11.00 11.30 12. 00 P. M. 1.00 2.00 3.00 3.30 4.00 4.30 .5.00 6.00 9.00 83 82 83 83 29. 835 .858 .8711 . 869 29. 87 .89 .90 .90 81.0 82.8 84.0 84.1 8.5.9 86. 2 85. 0 76.8 79.0 79. 5 78.8 79.2 79. () 79.2 82 83 82 80 72 72 75 921.4 925. 3 927.5 929. 5 935. 4 938. 0 939. (i NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. Clear. Clear. Clear. Clear. Clear. P'air. Fair. Clear. Clear. Clear. Clear. Fair. Clear. Clear. Clear. Clear. Clear. Clear. Clear. Clear. 2 cum. and cir. str. 2 cum. 1 cum. 2 cum. 2 cum. 4 cum. 5 cniH. 2 cum. 1 cum. 1 cum. 2 cum. 3 cum. 1 cum. 1 cum. in horizon. 1 cum. in horizon. 1 cum. in horizon. 1 cum. in horizon. 1 cum. in horizon. 1 cum. in horizon. 1 cum. in horizon. 84 85 85 86 86 86 86 86- 88 87 86 86 85 86 84 .883 .868 .864 .848 . 832 . 823 . 805 .783 . 775 .764 .770 .785 .790 .806 .873 .91 .89 .89 .87 .85 .84 .83 .80 .79 .78 .79 .81 .81 .83 .90 86.7 86.9 86.8 83.5 84.8 84.8 84.6 83.8 8.3.2 82.9 82.0 82.0 80.0 -9.9 80.0 78.8 79.1 7H. 3 78.0 77.8 77.2 77.0 77.9 77.6 73 72 73 78 75 75 73 75 75 75 82 82 944. 0 945.7 947. 9 9.58. 5 968. 3 978. 2 981.5 984. 8 987. 2 0.1 0.7 20.8 Miscellaneous. — Minimum, 79.5. Minimum at ground, 78.8. Maximum, 88.2. Slight .showers at 5.00, 8.00, 10.00 a. m., and 8.00 p. ni.; inappreciable. 12.30 — 1.00 p. m., a wind squall passed over. At 12.35 the aueuiometor registered 1 mile iu 3 minutes 40 seconds, which equals 16 miles an hour. Solar shiidow bauds socu iu the oast just after sunset. MAY 1, 1883. s o X Barometer. Thermonioter. a S g o a £ Si •6 a 1 Clouds. t. Observed reading. Reduced reading. Dry. Wet. A. M. 6.30 7.00 7.30 8.00 8. .30 9.00 9.30 10. 00 10.30 11.00 12.00 P. M. 1.00 2.00 3.00 9.00 81.9 82.8 ' 83. 5 84.3 85.5 a5.6 85.7 86.0 86.6 85.8 86.5 86.8 86.0 85.1 81.5 76.0 76.7 77.0 77.8 77.6 78.4 78.0 77.7 77.9 77.1 78.0 78.1 77.2 77.2 76.1 74 75 71 71 69 73 71 68 67 66 67 66 66 67 78 86.8 90.2 94.0 97.9 101.4 105. 0 109.1 113.0 117.3 121.5 129.2 135. 6 142. 7 149.4 187.0 NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. ■NE. NE. Clear. Cleaj-. Clear. Clear. Clear. Clear. Clear. Clear. Clear. Clear. Clear. Clear. Clear. Clear. Clear. 1 cum. and cir. str. in horizon. 1 cum. and cir. .str. in horizou. 1 cum. iu horizou. 2 cnm. 2 cnin. 1 cnm. ;ind cir. str. 1 cnm. and cir. str. 1 cum. in horizon. 1 cum. i:i horizou. 1 cum. iu horizon. 0 haze iu horizon. 1 cum. and cir. str. 1 cir. str. in south. 1 cir. str. in south and west. 1 cum. 82 82 82 83 83 84 84 85 85 85 86 86 83 29. 887 .891 .899 .907 .897 .900 .888 .875 .847 .820 .802 .789 .»95 29. 92 .93 .93 .94 . 93 .93 .92 .90 .87 .85 .82 .81 .93 Miscellaneous. — Minimum, 80.2. Minimum at ground, 80.8. S. Mis. 110 7 Maximum, 87.6. 50 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. MAY 2, 1883. o o A. M. 6.30 7.00 8.00 9.00 10.00 10.30 11.00 11.30 12.00 p. M. 12.30 1.00 2.00 2.30 3.00 3.30 4.00 4.30 5.00 9.00 Barometer. Observed reading. 29. 902 .909 .915 .910 .900 .887 .870 .850 .8.32 .825 .807 .802 .805 .808 .817 .827 .845 .913 Reduced readiue. 29. 94 .94 .95 .94 .93 .92 .89 .87 .85 .85 .83 .82 .83 .83 .84 .85 .87 .94 Thermometer. Dry. 81.6 82.0 84.0 84.8 86.0 87.3 87.0 87.8 87.8 87.4 87.0 87.1 86.7 84.5 84.5 84.0 83.1 82.7 81.0 Wet. 76.0 75.5 76.2 76.7 76.8 78.4 78.0 77.5 78.9 78.0 77.9 78.0 78.0 76.2 76.6 76.0 75.7 75.6 75.0 a a « 78 72 67 68 66 65 66 61 66 62 66 66 67 67 67 68 68 73 74 a a <1 246.8 250. 3 258.1 265.2 270.7 272.4 273. 6 274.8 276. 6 277.9 278.9 279.7 280.0 280. 5 281.4 282. 1 283.5 284.7 292.7 •a a NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. NE. Calm Calm NE. NE. NE. NE. NE. NE. Fair. Clear. Clpar. Clear. Clear. Clear. CK'ar. Clear. Clear. Clear. Clear. Clear. Clear. Clear. Clear. Clear. Clear. Clear. Clear. 3 cum. 2 cum. 1 iiim. 2 cum. 1 cmii. 1 cnni. 1 Ctlltl. 1 cum. 0. 0. 0- 0. 0. 0. 0. 0. 0. 0. 1 CUU'. Clouds. Miscellanemts. — Minimum, 80.2. Minimum at ground, 80.8. Maximum, 88.7. MAY 3, 1883. Barometer. Thermometer. a s o Clouds. 5 W t. Observed reading. Reduced reading. Dry. Wet. a < Wind A. M. 7.00 80 29. 930 29.97 81. 5 76.0 78 311.0 NE. Clear. 2 cum. 7.30 81 .9.37 .98 82.8 75.2 70 312.3 NE. Clear. 2 cuui. 8.00 81 .942 .98 83.5 76.2 71 313.8 NE. Clear. 2 cum. 8.30 82 .940 .98 85.0 77.4 67 315. 6 NE. Clear. 1 cuiu. 9.00 82 *.837 .97 85.3 77.9 69 317.5 NE. Clear. 1 cum. 9.30 83 .942 .97 86.0 78.2 68 320.2 NE. Clear. 1 cum. 10.00 84 .938 .97 85.6 77.6 67 323. 2 NE. Fair. 3 cum. 10. 30 84 .923 .95 86.8 78.0 66 326.2 E. Clear. 2 cum. 11.00 85 .908 .93 87.5 79.0 67 329.2 NE. Clear. 2 cum. 11.30 85 .877 .90 86.2 77.2 65 332. 5 NE. Clear. 1 cum. 12.00 85 .862 .89 86.9 78.0 66 335.7 NE. Clear. 1 cum. in horizon. p. M. 12. 30 85 .836 .86 86.0 77.5 68 338.0 NE. Clear. 1 cum. iu liorizou. 1.00 86 .825 .65 86.8 78.0 66 340.2 E. Clear. 1 cum. in horizon. 1.30 86 .821 .84 86.7 78.7 69 342.0 E. Clear. 1 cum. in horizon. 2.00 2. 30 86 5 78 5 69 70 344 2 E 86 .807 .83 86.0 78.6 346.1 E. Fair. 3 cum. 6.00 86 .838 .86 82.9 77.7 80 363.2 NE. Cloudy. 9 cum. and nini. 7.00 84 .885 .91 77.2 7,n.O 90 374.1 NE. Cloudy. 9 cum. and nim. 8.00 84 .902 .93 77.5 75.5 90 382.3 NE. Rain. 10 cum. 9.00 84 .9.37 .97 78.0 75.3 88 386.8 Calm. Rain. 10 cum. « Probably should be 29.937. Miscellaneous. — Minimum, 76.2. Minimum at ground, 75.5. Maximum, 88.1. R.ain began at 6.00 p. m. Light showers in the evening, with occasional thunder and lightuinf; ured on the 4 th. Rainfall meas- SOLAR ECLIPSE, MAY 6, 1883. MAY 4, 1883. 51 Barometer. Tliermoraeter. ^ c S o § ^ Clouds. a o t. Observed readiug. Reduced reading. Dry. Wot. 1 a < ■a s A. M. 7.00 7.30 8.00 74.2 74 0 99 403.8 NE Raiu 78 79 29. 9 SO 29. 988 30 03 10 nim. .03 7.^.. 8 74.2 95 409.2 NE. Rain. 9.00 79 30. 010 .06 76.2 75.2 96 414.5 NE. Rain. 10 nini. 10.00 79 29. 966 .03 76.2 74.5 93 423.6 NE. Cloudy. 10 8tr. 11.00 79 .908 .01 80.0 76.1 82 429.2 NE. Cloudy. 10 8tr. 12. OU 80 .960 30.00 81.8 75.8 75 435.6 N. Cloudy. 10 str. 1.00 80 .917 29. 96 81.0 75.8 79 442. 6 N-. Cloudv. 10 str. 2.00 80 . 8H0 .92 82.0 75.6 74 443.3 N. Cloudy. 9 str. 3.00 80 .860 .90 83.4 77.0 73 443.7 NE. Cloudy. 9 str. 5.00 82 .867 .90 81.0 76.2 79 443. 8 Calm. Clear. 2 cir., cir. str., and str. horizon. about 6.00 81 .883 .92 77.5 74.8 86 443.8 Calm. Clear. 1 cir., cir. str., and str. liorizou. about 9.00 80 .938 .98 76.0 74.3 94 444.9 Calm. Clear. 0. MisceHaneous. — Minimum, 72.4. Minimum at ground, 73.0. Maximum, 84.5. Rained hard and steadily after 1.00 a. m. until d.M a. ni. Rainfall to 7.00 a. ni., 4.2 inches ; after 7.00 a. m., 0.5 inch ; tot.il, 4.7 inches. MAY 5, 1883. Barometer. Thermometer. 5 1 e Clouds. u 3 t. Obserred reading. Reduced reading. Dry. Wet. a < % ^ <3 A. M. 7.00 79 29. 945 29. 99 80.9 77.8 88 463.0 NE. Clear. 2 cum. and .'*tr. 8.00 81 .957 30.00 82.2 77.7 82 469.7 NE. Clear. 1 cum. and str. 8.30 82 .952 29.99 82.5 78.0 81 472.7 NE. Clear. 2 cum. and str. 9.00 82 .950 .99 83.0 77.7 80 476.4 NE. Clear. 2 cum. and str. 9.30 83 .955 .99 83.0 78.2 80 4n0.0 E. Clear. 2 cum. 10. 00 83 .955 .99 83.2 78.1 79 484.0 E. Fair. 3 cum. 10.30 84 .945 .97 83.3 78.0 79 488.4 E. Clear. 2 cum. 11.00 84 . 932 .96 83.7 77.8 75 492.0 E. Clear. 2 cum. 11.30 84 .918 .95 83.7 78.5 81 496.5 E. Clear. 2 cum. 12. 00 84 .912 .94 84.0 78.5 77 501.2 E. Fair. 4 cum., cir. str., and str. 1'. M. V. \m 1.00 85 .877 .90 79.0 78.0 97 507.4 Calm. Fair. 7 cum., nim. in east horizon. ( 2.00 85 .870 .89 80.0 77.5 88 513.9 E. Rain. 10 cum. and nim. 3.00 84 .852 .88 82.5 76.7 76 519.4 E. Fair. 6 cum. and str. 6.00 84 .d76 .91 81.8 78.1 83 532. 1 E. Fair. 4 cum. and str. 9.00 83 .910 .94 81.7 77:9 83 550.9 NE. Clear. 1 cum. in horizon. Miscellaneovs. — Minimum, 75.4. Minimum at ground, 74.4. Maximum, 84.3. R.ain, 5.30-6.00 a.m., giving 0.4 inch; 12.45-12..55 p.m., giving 0.15 inch; and 1.50 to 2.10 p.m., inap- preciable ; total 0.55 inch. 2.45 p.m., top of a rainbow seen in eastern horizon. 5.45 p. m., one heavy dark band extended from clouds in the west to the eastern horizon, evidently the shadow of the clouds. 52 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. MAY 6 1883. Barometer. Thermometer. Rel. hum a o ^ ^ Clouds. t. Observed reading. Reduced reading. Dry. Wet. Anetn a ^ 1 A. M. 7.00 •82 29. 940 29.98 81.5 78.1 86 622.2 E. Fair. 3 cum. 8.00 83 .949 .98 83.3 79.4 81 631.3 E. Fair. 2 cum. and haze. 8.30 83 .953 .99 84.9 78.9 74 636.0 E. Fair. 3 cum. and baze. 9.00 83 .953 .99 83.0 79.0 82 640.1 E. Fair. 4 cum. and haze. 9.30 83 .960 .99 79.6 78.6 98 645. 3 E. Cloudy. 9 cum. 9.45 86 .958 .98 82.7 79.8 89 647.2 E. Fair. 3 cnm. 9. r>7 83 .952 .98 83. 6 80.0 83 049. 3 E. Fair. 3 cum. For obs jrvations in this interva 1 see " Special Observat ons ill couuection witli tl le Solar Eclipse." ' p. M. 1.15 87 29. 843 29.86 85.0 78.9 74 676. 0 E. Clear. 2 cum. 1.30 88 .845 .86 85.0 78.6 74 678. 3^ E. Clear. 2 cum. 2.00 86 .848 .87 85.0 79.0 74 682. 6 E. Clear. 1 cuiu. 2.30 85 .847 .87 84.4 78.7 76 686. 2 E. Fair. 3 cum. 3.00 85 .848 .87 84.2 78.8 76 690.3 E. Clear. 2 cuin. 3.30 85 .848 .87 84.2 79.9 76 693. 7 E. Fai r. 4 cum. 4.00 84 .850 .88 83.8 78.3 78 697. 0 E. Fair. 3 cuui. 4.30 84 .856 .89 83.1 - 78.4 80 700.4 E. Clear. 2 cum. 5.00 83 .865 .90 82.8 78.0 80 703.7 E. Clear. 2 cum. 6.00 83 .875 .91 82.1 77.9 82 710.3 E. Fair. 3 cum. and haze. 9.00 82 .922 .96 82.0 77.9 82 738.2 E. Clear. 2 cum. Miscellaneous. — Minimum, 79.2. Minimum at ground, 78.9. Maximum, 85.5 (moditied by the eclipse). Showers 8.00-9.00 and 9.15-9.25 a. m., giving 0.10 inch. MAY 7, 1883. Barometer. Thermometer. a 3 1 Clouds. s w t. Observed reading. Reduced reading. Dry. Wet. .a "3 a a Weat A. M. 7.00 82 29. 927 29. 96 79.6 76.8 89 810.7 E. Rain. 10 str. 9.00 82 .955 .99 85.0 79.8 80 828.0 E. Fair. 4 ciuu. 12.00 83 .888 .92 86.0 79.8 74 . - - E. Fair. 4 cum. p. M. 6.00 84 .813 .84 81.9 76. 3 74 914.3 E. Fair. 3 cum. 9.00 1 83 .887 .92 81.8 76.4 78 941.9 E. Clear. 1 cum. Miscellaneous. — Minimum, 77.7. Maximum, 87.0. Rained [i. m., five minutes before last contact. The temperature remained ahnost stationary until after 2.00 p. m. 11.10 a. m., color of sky bluish, but greenish about the horizon. 54 MEMOIRS OP THE NATIONAL ACADEMY OP SCIENCES. Condensed meteorological summary. Temperature. 7 a. m. 12 m. 9 p. m. Date. Rain- fall. Min. Max. Meau. Red'd Air Rel. Red'd Air Rel. Red'd Air Rel. • bar. temp. hunj. bar. temp. hum. bar. temp. hum. 1883. Inches. April 25 78.2 88.2 83.2 29. 95 81.9 82 29.93 86.0 74 29.96 82.2 82 'f 26 80.8 87.8 84.3 .99 82.8 80 .93 87.2 70 .98 79.2 88 0.3 27 78.1 88.3 83.8 .96 82.0 80 .92 87.2 74 .90 81.6 80 (+) 28 79.2 89.3 84.2 .93 79.9 85 .87 87.2 72 .91 82.0 80 *0.2 29 77.7 88.4 83.0 .91 82.2 79 .84 87 9 70 .87 82.3 76 0 30 79.5 88.2 83.8 .89 82.8 83 .84 86.8 73 .90 82.0 82 (t) May 1 80.2 87.6 83.9 .92 62.8 75 .87 86.5 67 .93 81.5 78 0 •2 80.2 88.7 84.4 .94 82.0 72 .87 87.8 66 .94 81.0 74 0 3 76.2 88.1 82.2 29.97 81.5 78 29. 89 86.9 66 .97 78.0 88 (t) 4 72.4 84.5 78.4 30.03 74.2 99 30.00 81.8 75 .98 76.0 94 4.7 5 75.4 84.3 79.8 29. 99 80.9 88 29.94 84.0 77 .94 81.7 83 0.6 6 79.2 a85. 5 082.4 .98 81.5 86 .94 082.2 81 .96 82.0 82 0.1 7 77.7 87.0 82.4 .96 79.6 89 .92 86.0 74 .92 81.8 78 0.3 8 79.9 86.4 83.2 .91 81.7 80 .86 83.6 81 .90 81.8 83 (t) 9 Tot 78.0 al rain fall - - - .91 79.0 91 - - - - - - - - - - - - - - - - "ll*" 7.5 Estimated. oEclipse caused lower reading than it would have re.iched. t Inappieeialile. t Eutered under 4th. I Estimated on April 23. Wind velocities. HOURLY MOVEMENTS IN MILES. CO (^ otj ai o (N at « 5< ^ ei in Hour. •"g 77^ rTn t>> ^ >. >> >i P< Pi -J! ^ c4 S tS a A. M. 6.00 to 7.00 . - 8.4 5.0 - - 3.9 - - - - - ■ - - - _ _ 7.00 to 8.00 7.1 10.1 4.5 6.4 4.2 7.7 7.8 2.8 5.4 6.7 8.00 to 9.00 8.4 7.6 7.2 .'S.7 5.9 7.1 7.1 3.7 5.3 6.7 9.00 to 10.00 .5.2 9.7 7.1 5.6 4.2 8.0 5.5 5.7 9.1 7.6 10. 00 to 11. 00 7.7 7.6 4.0 5.7 4.4 8.5 2.9 6.0 5.6 8.0 11.00 to 12.00 6.9 6.4 3.6 5.9 3.9 7.7 3.0 6.5 6.4 9.2 p. M. 12. 00 to 1. 00 7.6 6.9 2.9 5.7 10.6 6.4 2.3 4.5 7.0 6.2 1.00 to 2.00 7.6 6.3 2.8 5.0 9.8 7.1 0.8 4.0 0.7 6.5 2.00 to 3.00 6.9 5.7 5.7 3.6 9.9 6.7 0.8 - - 0 4 5.5 3. 00 to 4. 00 4.3 5.2 5.5 - - 6.6 - - 1.6 - - 0.1 - - 4. 00 to 5. 00 2.7 5.1 6.2 - - 5.3 - - 2.6 - - 0.0 - - 5.00 to 6.00 ■ 5.9 4.6 5.8 6.6 - 0.0 Observations made on May 6 are given in connection with the report upon the eclipse observations. SOLAK ECLIPSE, MAY C, 1883. TOTAL MOVEMENTS AND HOURLY AVERAGES. 55 Date. 7 a. m. to 9 p. m. 9 p. m. to 7 a. in. fol- lowing day. 7 a. ni. to 7 a. m. fol- lowing (lay. Total movement. Hourly average. Total movement. Hourly average. Total movement. Hourly average. April 26 27 28 29 30 May 1 3 4 5 6 7 8 86.2 90.9 76.8 84.8 85.5 96.8 42.4 75.8 41.1 87.9 116.0 131.2 137.4 6.16 6.49 .5.49 6.06 6.11 6. 91 3. 03 5.41 2.94 6.28 8. 29 9.37 9.81 66.3 56.8 62.0 69.6 69.4 63. 3 18.3 17.0 18.1 71.3 72.5 81.1 70.1 6. 63 5. ()8 6.20 6. 96 (!. 94 6. 33 1.83 1.70 l.f^l 7.13 7. 25 8.11 7.01 1.52'. 5 147.7 138. 8 154.4 154. 9 160. 1 60.7 ^ m. 8 .59. 2 1.59. 2 188.5 212.3 207. 5- 6. 35 6.15 5.78 6.43 6. 45 6.67 2.53 3.87 2.47 6.63 7.85 8.85 8. 65 Averag 6.05 OBSERVATIONS OF TUE RAIN-BAND. The instrument used in these ob.servatious was a Browning rain-band spectroscope. Two pointings were made at each observation, tlio first towards the horizon, the second to an altitnde of about 45°, and the intensity of the band estimated on a scale of 5. Alt. Date Hour. Sum. Remarkti. 0° 45° A. M. April 27 8.00 4 3 7 Rain-lincB very (li.stinct. 28 7.00 4 3 7 On rain eloudsin north; rain-lines ilistinct. 28 7.00 5 4 9 On clear sky in south ; raiii-liues indistiuct. 29 8.30 3 2 5 May 1 6. 45 4 3 7 Rain-lines distinct. 1 7.30 4 3 7 Do. 1 10.00 4 3 7 Do. 2 8.00 4 3 7 Do. 2 11.30 4 3 7 Do. 3 7.00 4 3 7 Do. 3 9.00 3 2 5 Rain-liues indistinct. 4 8.00 4 4 8 On clouds ; lines indistinct. 5 9.00 5 3 8 6 10.30 4 3 / Lines indistinct. 6 11.10 3 2 5 Do. ilETEOUOLOGIOAL OBSERVATIONS DUEING THE ECLIPSE. The meteorological observations made during the stay at Caroline Island have been discussed in what precedes. It remains to speak of the special observations made at the time of the eclipse, and to show what conclusioas may be derived from them. Observations of the barometer, dry and wet bulb thermometers, maximum and minimum thermometers were made by myself as opportunity offered during the progress of the eclipse. Observations of the conjugate thermome- ters, Violle's conjugate bulbs, black and white bulbs in the sun, and of the direction and velocity of the wind, were made by Seaman J. C. Harold every five minutes between 10.00 a. m. and 1.15 p. m. 56 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. GENERAL WEATHER CONDITIONS. Tlie sky during the early portion of the 6th of May was partly cloudy, and the clouds threatened rain. Slight showers occurred between 8.00 and 9.00 a. in., and a heavy shower at 9.15 a. m., after which the sky cleared. But at no time during the day was the atmosphere free from a haze, which was apparent to the eye and also showed itself in the readings of the instru- ments. The relative humidity was above the average, being 81 per cent, at noon and 74 per cent. at 2.00 p. m., and the radiation instruments gave lower readings than on other days, especially in the morning. Passing clouds prevailed during the day, but interfered only a little with the observations of the eclipse. At the first and fourth contacts there were no clouds in the vicinity of the sun. Itnniediately after the second contact a light clou, 1 Mean tenipcratuni. April 2.'.- May (J ((imittiiij; May 4.) - 1 1 1 1 1 1 1 1 1 1 1 1 ' 1 SOLAli EOLIPSE, MAY 0, 1SS,3. 57 The foUowiiif; tabic coiitaitis the reduced readiiij;s for May (I, and a coiiii)aii.soii w itli values iiitcr|)olatcd IVoiii tlu' iiicau values above given. BAROMETKIC PKESSUKE Hour. May fi. Mean of six (lays. Dim Diir. uiinus mean (lilF. A. M. 9.57 2!). 0P5 29. 938 0.047 — 0. 001 10. l.'l . 9S7 . 932 . 0,55 + . 007 lO.iiO . 971 . 92(; . 045 — . 003 10. -|(» . 9(;5 . 920 .045 — . (103 11.00 . 944 . 908 . 036 — .012 11.10 . 945 . 901 .044 — . 004 11. ir. . 937 .898 . 039 — . 009 11.90 . 927 .895 .032 — .016 11. a.5 .928 .891 .037 — .011 11.43 . 935 .N'-i2 .053 + . 005 11. r>o . 940 .879 .061 + .013 12. 00 . 939 .875 .064 H- .016 r. M. 12. 10 . 935 .868 .067 + . 019 12.20 .9I(; . 862 .0.54 4- . 006 12. 30 . 903 . 8.55 .048 . OUO 12.50 . 889 ' . 848 .041 — .007 1.00 Moa . 8S8 11 (lilV. .844 0. 044 — .004 0.048 The above tables show tbat on all days but May 6 there was a steady fall iu pressure, and therefore the observed rise on that (biy \vas peculiar to the day. The last column of the second table indicates a more rapid fall than the average during the fust partial phase, and also tliat the time of the maximum difference from the average course occurred at about 12.10 p. m., or thirty- three minutes after the close of the total i>hase. The highest reading was recorded at 11.50 a. ni., or tliirtcen minutes after the end of totality. While the rise in pressure was small, being at its maximum only 0.019 above the average value, it is yet greater than the errors of observation. The instrument used can be read accu- rately within 0.005, and as it was kept at nearly uniform temperature during the period of obser- vation, the possible uncertainty from failuie of the attached thermometer to record the tempera- ture of the instrument can scarcely amount to 0.005. On the supposition that the errors have the same sign, there still remains 0.01 inch which is not accounted for, and the observed progression depends upon six or more observations. It is not difUcult to imagine also that the inflow of air towards the path of the shadow might be snIUcient to cause an increased pressure suscei)tible of measurement l\y a sensitive barometer. TEMPERATURE. The eft'ect of the eclipse in reducing the temperature of the air may be shown by comparing the thermometric readings with tliose of other days. The mean values of the observed tempera- ture, April 25 througli INIay 5, omitting the rainy day, May 4, arc as follows : Hour. Degrees. Hour. Degrees. A. M. A. M. 7.00 81.9 11.00 86.3 8. 00 8.3.4 12.00 p. M. 86.7 9.00 84.9 1.00 85. 7 10.00 85.5 2.00 85. 9 The following table contains a comparison between the observed readings on Jlay G and values interpolated from the above averages. It will be seen from the column of ditferences that at 9.57 a. m., before the beginning of the eclipse, the observed reading was 1^.9 below the aver- S. Mis. 110 8 58 MEMOIRS or THE NATIONAL ACADEMY OF SCIENCES. age, ami tliat nt l.oO p. in., after its close, it was O.S below. Interpolating from these values the diftcrences which would probably have existed at the time of the eclipse had there been no unusual phenomenon, we have the values of the effect of the eclipse given in tlie last column under the heading " Depression." AIR TEMPERATURE. Hour. May (i. Average. Diff. o Regular de- crease for tlie clay. Depres- sion. A. M. o o o o 9. 57 63.0 85. 5 1.9 1.9 0.0 10.15 84.4 85.7 1.3 1.8 -0.5 10.30 84.5 85.9 1.4 1.7 —0.3 Maxiiiuiin, 84'-'.(!. 10.40 84.0 m.o 2.0 1.6 0.4 11.00 83.5 86.3 2.8 1.5 1.3 11.10 83.0 86.4 3.4 1.5 1.9 11.20 82.7 86.4 3.7 1.4 2.3 11.43 82.0 86. 6 4.6 1.3 3.3 ) Miniiniiiii, 81*^.4 ; maxi- 11. 50 82.2 e6.6 4.4 1.3 3.1 i nimii (lepre.i.sion , 3'^.9. I'J. 00 82. 2 86. 7 4.5 1.2 3.3 r. M. 12. 10 83.0 86. 5 3. 5 1.2 2.3 12. 20 82.8 86.4 3.6 1.1 2.5 12.30 83.7 86.2 2. 5 1.1 1.4 12.35 84.0 86. 1 2.1 1.1 1.0 12. 50 84.4 8.5.9 1.5 1.0 0.5 1.00 84.8 85. 7 0.9 0.9 0.0 1.15 85.0 85.8 0.8 0.8 0.0 Maximum, 85^^.2. 1.30 85.0 85.8 0.8 0.8 0.0 Tlie maximum depression of temperature was therefore only about 4°, but this was sufficient to reduce the temperature to a value 0^.1 lower than it had been at 7.00 a. m. on the same day; and Qo.G lower than it was at 9.00 p. m. HUMIDITY. The effect of the eclipse upon the humidity may be found by comparing the psychrometric readings taken during the progress of the eclipse with tliose of other days. The following table gives the result of this comparison, the values iu the column lieaded "average" being deduced from the mean values from April 25 through May 5, omittiug May 4. Tlie " regular decrease for the day " is interpolated from the observed differences at 9.57 a. m. and 2.00 p. m. : RELATIVE HUMIDITY. Regular de- Hour. May 6. Average. Diff. crease for the day. Diff'. A. M. 9.57 83 74 9 9 0 10.15 81 74 7 8 -1 10. 30 81 73 8 8 0 10.40 82 73 9 d 2 11.00 78 72 6 7 -1 11. 10 80 72 8 7 1 11.20 83 71 12 4 5 11.43 82 71 11 6 5 11. 50 81 70 11 6 5 12. 00 81 70 11 6 5 p. M. 12. 10 79 70 9 (> 3 12. 20 80 70 10 6 4 12. 30 78 70 8 6 2 12. 35 77 70 7 5 2 12.50 76 70 6 5 1 1.00 78 70 8 5 3 1.15 74 70 4 5 -1 1.30 74 71 3 4 -1 2.0U 74 71 3 3 0 The above table indicates an increase iu the relative humidity during the eclip.se, reaching ^'w jjer cent. Fig. 18. CURVE OF RELATIVE HUMIDITY DURING ECLIPSE. A.M. Tinie. P.\M. Relative Humidity 10.00 lO.lS 10.30 W.41 11.00 11.15 11.30 11.45 12.00 12.15 12.30 12.45 1.00 1.15 - S5 - SO I— ^5 Obser\e(l n-lative humidity, May G. Me.in liuiiiiility. April 2j-May fa (omitting M.ay 4.) - J I \ I l_ L J I L SOLAli ECLIPSE, MAY 0, 1SS;5. 513 WIND. TIio pieseut eclipse funiisljcd au unu.sually favorable opportunity for determining any ductua- tions that might occur in the direction and velocity of the wind caused by the eclipse. The regularity of the wind from day to day, both in direction and velocity, made it possible to obtain a reliable basis of comjjarison. Observations were made every live minutes from 10.00 a. m. to 1.15 p. m., with the result that no appreciable change was detected cither in direction or force. The wind blew with almost the same velocity from the eastward during the period of time occupied by the eclipse. The following table gives the ob.served velocity in miles for every ten miimtcs from 10.00 a. m. to 1.30 p. m. : Time. Velocity. Time. Velocity. Time. Velocity. 10. 00 to 10. 10 10. 10 to 10. 20 10. 20 to 10. 30 10. 30 to 10. 40 10. 40 to 10.50 10. .'.(Mo 11.00 11. 00 to 11. 10 11. 10 to 11. 20 1.9 1.4 1.3 1.0 1.7 1.4 1.5 1.4 11. 20 to 11. 30 11. 30 to 11. 40 11. 40 to 11. 50 11. 50 to 12. 00 12. 00 to 12. 10 12. 10 to 12. 20 12. 20 to U. 30 12. 30 to 12. 40 1.4 1.3 1.3 1.3 1.2 1.5 1.3 1.3 12. 40 to 12. 50 12. 50 to 1.00 1. 00 to 1. 10 1.10 to 1.20 1.20 to 1.30 Meau - - 1.3 1.3 1.1 1.5 1.5 1.38 The mean ten-minute velocity from 7.00 a. m to 9.00 p. m. is exactly the same, viz, 1.38 miles. The observations on other days show the following relation between the velocities from 10.00 a. m. to 2.00 p. m., and those from 7.00 a. m. to 9.00 p. m.: Mean wind velocity for each ten minutes. Date. 10 a. m. to 7 a. m. to Dittereuce. 2 p. m. 9 !>. m. April 26 1.24 1.03 + 0.21 « 27 1.13 1.08 + .05 28 0.55 0.98 — .43 |29 0.93 1.01 — .08 1.20 1.02 + .18 Mav* 1 1.24 1.15 + .09 2 0.38 0.50 — .12 S 0.88 0.90 — .02 4 0.»2 0.49 + .33 5 Moa 1.25 1.05 + .20 + 0.04 Meau of April 20, 27, 29, 30, May 1, 5, when the bourly velocity was greater than 6 miles is +0.11. Judging from these comparisons it might have been expected that the wind would blow somewhat stronger between the hours of 10.00 a. m. and 2.00 p. m. than during the rest of the day. On the contrary, the observed velocity was the same. Con.sequently, if the passage of the moon's shadow had any effect at all on the velocity of the wind, it was to slightly diminish it. DIUKNAL VARIATION IN THE VELOCITY OF THE SOUTHEAST TRADE-WIND. The series of observations with the anemometer on Caroline I-sland is not snfBciently exten- sive to indicate any diurnal periodicity in the wind velocity. During the voyage from Callao, however, the Hartford sailed day after day in the region of the southeast trades upon almost the same parallel of latitude, and with but few changes in the positions of the sails, no steam being used. The conditions were so constant during the interval of twenty-two days from March 23 to April 13, in which the vessel sailed in latitude — lio.o from longitude 79° to 137°, that it was 60 MEMOIKS OF THE NATIONAL ACADEMY OF SCIENCES. tbougUt ii tabiilatiou of the hourly .speed of the vessel might give some imlicatioii of the diurnal course of the wiud velocity. The following table was therefore made, which gives the hourly speed, taken from the ship's log, through the courtesy of Cajitaiu Carpenter. It will be seen that the mean values show a distinct increase in the evening and a corresponding decrease in the morning, with the maximum at 11.00 p. m. and the minimum at 11.00 a. m. It seems fair to attribute this to the diurnal variation in the wiud velocity. There is (juite an unexpected regularity in the progression when we consider the approximate nature of the method. If not attributable to diurnal change in the wind itself, it yet indicates a diurnal change in the eli'ect of the wind upon the sails, and is therefore of interest. Hourly speed of the U. 8. 8. Hartford, March 23-April 13. Date. 1 a. m. 2 a. m. 3 ii. ni. 4 a. 111. 5 a. in. 0 a. m. 7 a. m. 8 a. 111. 9 a. 111. 10 a.m. 11 a. ui. 12 in. m. m. m. VI. ?H. m. VI. »«. VI. m. m. m. March 23 3.3 3.0 3.4 4.4 5.4 5.8 5.0 4.4 4.4 4.0 4.6 5.0 24 6.5 6.0 6.0 .5.6 4.7 4.1 3.8 3.8 4.4 5.0 5.0 4.2 25 .5.0 .5.0 5.8 0.2 5.5 ,5.8 0.2 6.5 0. 5 5.9 6.6 6.0 20 7.2 7.0 8.0 8.0 8.0 7.0 0.8 0.4 0.5 5.5 7.6 7.8 27 7.5 7.5 8.2 7.8 7.2 6.8 6.4 0.0 5.8 6.0 4.5 4.0 28 5.6 5.6 .5.6 5.0 0.0 6.0 5.8 0.2 6.0 0.0 .5.9 5.8 29 7.0 7.6 7.0 7.0 7.0 7.0 7.0 6.8 7.2 7.8 8.5 9.0 30 8.0 8.0 8.0 8.0 7.5 7.6 8.0 7.6 7.3 7.6 7.7 8.0 31 8.0 8.0 7.8 8.0 8.0 H.O 8.0 7.8 7.8 8.0 7.5 8.0 Ai>iil 1 8.0 7.4 6.8 0.0 7.2 7.6 7.2 6.4 7.0 7.3 0.0 5.9 2 8.4 8.2 7.6 7.8 7.4 7.0 7.0 6.0 0.4 6.8 7.1 6.8 3 6.0 6.4 .5.4 .5.4 .5.5 5.6 0.2 6.2 .5.6 .5.5 5.9 6.0 4 7.4 7.0 7.2 7.2 7.8 7.2 0.8 0. 6 0.5 5.8 0.0 6.2 5 7.2 6.8 7.0 8.0 7.0 5.6 0.5 0.6 0.2 .5.0 5.6 6.0 0 7.1 6.8 5.4 5. 0 5.6 5.0 4.6 .5.0 r>.o 4.8 4.8 4.6 7 7.2 7.4 7.0 7.0 6.5 0.0 0.1 .5.6 0.5 6.4 0.5 6.2 8 6.fJ 7.0 0.8 7.0 7.4 7.2 0.5 6.0 6.0 0.0. 5.6 6.2 y 5.8 5.4 ,5.2 4.6 4.8 4.4 4.4 4.8 ,5.0 4.8 4.7 5.2 10 4.5 4.5 4.4 4.4 4.8 4.0 2.2 2.8 2.7 3.3 4.0 3.9 11 6.2 6.5 0.8 6.8 6.8 6.9 7.2 7.1 6.8 6.4 6.4 0. 2 12 6.4 f). 2 6.0 6.0 0.0 7.0 6.8 0.4 0.6 0. 3 6. 2 0.4 13 Sums - 6.8 6.2 6.4 5.4 4.9 5.0 5.6 6.0 .5.8 5.4 5.2 5.0 145.9 143. 5 141.8 141.8 141.6 136.0 134.1 131.6 132.0 130.2 1.32. 5 133.6 Means - 6.6 6.5 6.4 0.4 0.4 6.2 0.1 6.0 6.0 5.9 6.0 0.1 Date. Ip. m. 2 p.m. 3 p. ni. 4 p. m. 5 p. in. 6 p. in. 7 p. m. 8 p. m. 9 p. ni. 10 p.m. 11 p. 111. 12 p.m. m. m. «i. m. m. VI. VI. j«. VI. vt. »i. VI. March 23 6.0 6.0 7.0 6.9 7.0 6.8 7.0 7.2 0.8 6.4 0.4 6.8 24 5.0 .5.4 4.3 4.3 4.0 4.4 4.0 4.4 4.4 4.4 5.0 .5.0 25 5; 8 6.0 6.0 6.0 0.4 0.0 7.0 7.0 7.2 8.0 7.0 7.0 26 7.0 8.0 8.0 7.2 7.2 7.2 8.0 8.2 8.2 7.6 7.2 0.8 27 4.3 4.4 4.5 5.2 5.0 6.1 6.3 5.8 5.0 5.4 5.4 5.4 28 6.0 0.2 5.8 6.4 7.0 6.4 6.4 6.2 8.0 8.0 7.4 7.0 29 8.8 8.6 8.3 8.3 8.5 8.0 9.2 9.3 9.2 8.8 8.4 8.0 30 8.0 8.0 8.0 8.0 8.5 8.8 8.8 8.4 8.0 8.8 8.6 8.8 31 7.4 0.8 6.6 0.0 6.0 0.8 7.0 7.6 8.2 8.4 8.4 8.4 April 1 6.8 7.6 7.8 7.9 7.9 7.8 7.7 7.2 7.8 8.0 8.6 8.0 2 6.8 0.9 6.7 0.0 7.0 7.0 7.0 7.3 7.2 6.8 7.2 6.4 3 0.0 0.2 0.0 6.0 6.3 6.6 6.4 7.2 7.2 7.0 7.0 7.7 4 5.8 5.0 5.8 ■5.3 6.0 6.5 7.2 7.6 7.4 7.5 7.4 7.5 5 5.7 0.1 0. 2 6.2 6.0 6.8 7.0 6.8 7.2 7.5 7.4 7.2 6 4.8 5.4 5.7 6.1 0.1 5.8 0.0 6.2 0.6 0.8 7.2 7.0 7 0.4 6.1 0.0 6.0 6.0 6.2 0.4 6.8 7.0 7.0 7.2 6.8 8 6.0 5.5 5.0 5.8 6.0 5.6 5.2 0.2 6.3 5.9 6.0 6.0 9 4.7 4.2 3.9 4.0 3.8 3.7 3:4 3.4 3.6 3.8 4.0 4.0 10 4.0 4.0 4.4 .5.0 5.2 4.9 4.0 4.6 5.6 .5.2 6.0 6.0 11 6.0 x;.4 6.0 6.0 5.8 6.6 7.0 7.0 7.2 7.0 0.2 0.4 12 0.1 5.5 4.9 5.2 5.3 5.4 5.0 r>.7 6.2 7.0 7.0 7.0 13 Sums - 5.4 .5.4 5.0 5.0 5.0 5.0 4.5 4.2 4.0 4.4 4.8 4.4 133.4 134.9 132. 5 133. 4 137.2 139.0 142. 3 144.3 148.3 149.7 150.4 148.2 Means - 0.1 6.1 0.0 0.1 6.2 6.3 0.5 6.6 6.7 6.8 6.8 0.7 SOLAR ECLirSE, MAY «, 188;}. 61 OBSERVATIONS OF SOLAR RADIATION. Ill Milditioii to tlic. oidiimry metcoroloyiciil observations, ;i scries of obsorvatious of solar liuliatioii was planned. Their objeet was primarily to furnish a basis of comparison for the obscr- \ations made with the same instruments durinj;; the eclipse, but they also furnish a means of diiter- iiiinint;' the intensity of the solar heat on the days upon which the readinj;s were made. They arc of es])ccial interest on account of the position of the observing station. Two kinds of instruments were employed, furuisbed through the kintbicss of the Chief Signal Officer. 1. Conjugate thermometers of the MAuii:,-L>KYY pattern. — These were made especially for the expe- dition bj' Messrs. J. & H. J. Grbkn, New York, and consisted of a l)lack and bright bulb ther- mometer, each inclosed iu a vacuum,* the iuclosure being spherical in shape where it surrounded the bulb of the thermometer. The diameter of the iuclosure was 2.15 inches, the bulb being cen- trally situaterass supports 7 inches high, and each pair of supports was screwed to a board i)aiutcd black. The boards were placed upon the ground iu an open grassy si>ot selected with especial care for these observations. The thermometers w ere nearly horizontal, but sufficiently inclined, bulb downward, to secure an unbroken column of nier- cury. The inclosures of the thermometers constituting a pair faced each other at a distance of several inches, the white bulb toward the east. The board containing the instruments was turned at frequent intervals during the day iu order that they might have approximately the same posi- tion with regard to the sun. The Violle bulbs were mounted each upon a wooden stand 10 inches above the ground, with the stems of the thermometers projecting horizontally toward the south or opposite the sun. The ordinary thermometers were exposed horizontally, each attached by a brass sujjport to the corresponding thermometer of the conjugate pair, and situated a couple inches above it. The instruments thus placed were in a fa\'orable position for the desired observations, which were made hourly or oftener upon every clear day during the stay upon Caroline Island, beginning with April 27. *Thc instruments devised by Marid-Davy are described iu tlio Bulletiu Mensuel do I'Obs. Phys. Ceutral de Mout-' souris, 1873, ]). 80, and 1874, jip. 131 aud 189. *A full description of these iiistrumeuts, with the formula for reducinj; the readings, is'giveu iu " Sur la Kadiation Sola ire," by M. J. Viullu, Paris, 187'J. (32 MEMOlliS OF Tlil<] NATIONAL ACADEMY OF SCIENCES. The following table contains the observatious iu detail : FKIDAY, APRIL, 27. Tiuio. Coijj I gate tliL-riiioiiietera. Violle' s bulbs. Ordiuary tbcrmoiuctcrs. Keuiaiks. Black. Bright. Black. No. 742. Gilt. No. 751. Black. No. 1137. Bi-i-lit. No. 1136. No. 4. No. 3. No. 2. No. 1. A. M. 7. 00 94.3 85.7 Sun just ciitcriuf; cloud. 8.00 81.2 . . . 78.6 _ _ - _ _ - _ - - _ - - . . S](iinkliug ; bulbs wet. i).00 130.0 - . _ 105.1 . - - - - - 95. 0 88.2 Suu clear. 10. 00 110.1 . - - 96.1 . . . _ _ _ 89.2 86.0 Sun boliind clouds. 11.00 134.0 _ _ - 108. 7 . . . . . . - - 95.7 90.0 Suu behind thin cir. str. clouds. 12.00 144.6 - - • 115.7 - - - 42. 4 34.8 98. 0 93. 0 Do. 12. 10 142. 9 144.9 114.9 112.8 40.8 34. 8 101.7 95. 3 Suu clear. 12.12 144.7 146.3 11.5.7 113. 8 41.3 34.9 103.5 96.2 Do. 12. 15 144.9 146.9 116.0 114. 2 41.2 35.1 102. 0 96. 5 Do. 1.00 141.7 144.5 114.5 112. 3 42. 5 37.8 102.0 95.0 Sun behind thin cir. str. clouds. 2.00 138. 7 139. 8 113. 4 111.6 42.7 38.1 100. H 94.8 Do. :i. 00 133. 0 132. 4 110.1 lOH. 3 42. 5 37. 7 100. 3 93. 5 Do. 4.00 126. 9 126. y 10.5.7 104. 3 41.2 36.4 9.5.0 89. 5 Do. 5.00 80.2 86.8 83.4 83.6 28.4 28.8 83.2 82.7 Suu behind clouds. Summurij. — Poor day. Suu clear at 9.00 a. ui. and 12.10 to 12.15 ji. m. ouly. SATURDAY, APRIL 28. Time. Conjugate thermometers. Violle' 5 bulbs. Ordinary therniometers. Remarks. Black. Bright. Black. No. 742. Gilt. No. 751. Black. No. 1137. Bright. No. 1136. No. 4. No. 3. No. 2. No. 1. A. M. 7.40 123. 8 99.7 38.8 3.5.1 95. 3 87.0 Sun in thin haze. 8.00 114.0 11.5.3 94.9 95. 6 34.8 32. 1 97. 2 89.0 Sun cuu'rjfing from cloud. 9. 00 137.0 139. 3 108.1 108. 0 40.8 30.4 97.4 90. 3 Suu clear. 9. 30 136.5 139. 2 108.9 108. 5 41.1 36.6 100.5 92. 0 Do. 9. 35 137. 6 140.3 109.8 109. 4 41.8 37.2 100. 0 92. 0 Do. 10. 00 137. 3 140.0 109. 9 109. 2 41.0 36.3 100.7 91.4 Do. 10. 30 136. 4 140.2 , 110.1 110.2 42.9 37.9 102. 0 93.8 Do. 10. 35 138. 0 141.8 ' 111.1 111.1 43.0 38.2 102. 3 94.2 Do. 11.00 140.6 144.1 114.0 1 113.7 43.8 38.7 102. 5 94.3 Do. 11.30 140.1 143.2 i 113.9 1 114.3 43.4 38.6 101. 0 94.0 Do. 12. 00 143.2 146.2 115.0 114.9 44.4 39.2 105. 0 96. 2 Do. 12. 30 147.0 149.2 118.2 118.2 46.3 40.4 106.5 97.5 Do. 1.00 143. 2 143.9 116. 5 116. 5 45.2 39. 7 104.0 96.8 Do. 1. 30 141.0 141.5 1 116.2 11.5.5 45.1 39. 6 103. 2 96. 0 Do. 2. 00 143.1 146. 5 lis. 3 118. 0 47.6 42. 0 105. 5 99. 0 Sun behind thin clouds. 2.08 145.0 148.3 120.1 118.8 48.5 42. 0 107.0 99.8 Sun clear ; clouds immediately afterward. 2.15 145.9 148.5 118.0 117.8 46. 0 40. 4 106. 2 97.7 Sun clear. 2.22 148.5 150.2 118.8 117.0 45.1 39. 8 105. 2 96.8 Sun clear just before entering cloud. 2.30 133.6 135.8 109.8 109. 0 40. 9 3(!. 7 103. 2 95.5 Sun clear, but in clouds just be- fore and afti'r. 3.00 137. 8 139. 9 111.6 110.6 43.1 37.8 102.3 94.8 Sun behind thin clouds. 3. 30 134. 6 137. 8 109. 0 108.8 41.5 36.8 99.5 92. 2 Do. 4.00 127. 7 130.4 113. e- 104. 5 39.7 35.7 96.8 90.0 Sun clear. 4.30 5. 00 121.0 105.0 98.0 92.0 37.6 32. 8 34.2 32.0 Do 107. 2 91.6 86.0 83.8 Sun just entering cloud. * Should he 103.6. Summary. — Sun clear 9.00 a. m.to 2.00 p. ul indicated, at about 12.30 and 2.30 j). m. The i>. m. observations affected by i)assing clouds. Two maxima SOLAR ECLIPSE, MAY 0, 1883. 63 SUNDAY, APRIL 29. Tiino. Coiij igate tlicrmometer.s. Viollk' s bulbs. Ordinary tb Miiiometers. Remarks. Bhack. Bright. Black. No. 742. Gilt. No. 751. Blaitk. No. 1137. Itriolit,. No. 1136. No. 4. No. 3. No. 2. No. 1. A. M. 6.40 89.8 89.9 83.8 83.6 28.4 28.1 8.5.3 81.4 Siin in thin olonils. G.50 90.0 91. 2 84.0 84.2 28.7 28.4 85. 5 82.7 Sun in cIoikIs. 0. .'■)5 101.8 102.7 88.7 88.5 31.0 29. 5 89. 5 84. 5 Snn ahiiost clr;u': clumis i'l lllow. 7.48 124. 5 125. 1 100. 5 99. 2 36.7 33.5 . . Snn in tliiii liazc. 7. .''>4 120. 0 125. 9 100. 9 100. 5 37.9 .34.3 _ - Do. 8.00 128.1 127. 0 100. 7 101.3 38.8 35. 1 _ - - _ Do. 8.30 131.7 130. 3 103. 3 103.0 38.8 35.4 . - - - Sun just cnliTiiin cIoihI. 8.40 131.7 130. 5 103. 5 104.2 38.8 35. 4 . . Sum clear. 9.00 135. 0 133.5 10.5.4 106. 6 39.7 .36.0 97. 5 90. 5 Do. 9.20 138. 5 130. 3 107. 2 108.7 40.5 36. 6 100. 3 92.4 Do. 9.30 139. 7 137. 5 108. 1 109. 6 41.0 37.0 100. 3 92.3 Snn clear, but jnsl outof f ondK. 9. 35 140.8 138.7 108. 9 110.2 41.4 37.4 101. 2 93.3 Sun clear or in lia/.c 10. 00 144.2 142.7 111.9 112.8 43.1 38. 9 104. 0 95. 0 Do. 10. 30 1.50. 5 149.9 116.2 116.5 4.5. 5 40. 5 Ids. s 97. s Snn just ont(win!i ''louil. 11.00 142.0 142. 5 112.4 112.1 45. 6 38. 2 101.0 94. 0 Sun clear. 11.15 143. 5 145.1 114.0 113.8 4.5.6 38. 7 105. 2 96. 7 Do. 11.30 144.0 146.0 115.7 114.4 45.6 39.9 105. 5 97.5 Do. 11.45 144. 0 147.3 116. 0 114.8 45. 6 39. 5 107.0 97. 8 Do. 12.00 143.2 146.2 115.8 11.5.0 45.5 39. 9 106. 8 98. 0 Do. 12. 15 143. 7 147.0 116.2 11.5.3 45. 5 39.8 107.7 98.0 Do. 12. .30 144.0 147. 0 110.9 116.0 45. 5 40. 2 106. 5 98. 0 Do. 1.03 147.7 149.2 119. 1 118.7 46. 5 41.1 108.2 100. 0 Snn clear. Max. readiuj^s clonils. nflcr 1.30 141.0 140.7 115.6 114.9 46.0 39. 5 105. 7 98.0 Sun clear. 2.10 138.0 139. 8 115. 1 114.2 46.0 39.7 101.0 96.0 Do. 2. 30 135. 5 140. 5 114.4 113.5 46.0 39.7 101.8 9(i. 5 Do. 3.00 139.0 137. 9 112.2 112.0 46.0 39.2 102. 0 95. 5 Do. .3.30 135.0 133.0 109.8 109.0 45.9 38.3 99.2 94.0 Do. SiimmtDii. — Troubled by passing clouds thronghont the day, though generally clear when readings were nia Black. No. 742. Gilt. No. 7,51. Black. No. 1137. I'.iight. No. 1130. No. 4. No. 3. No. 2. No.l. A. M. a 30 , 91. 3 91.7 84.0 84.0 38.8 38.3 83.8 82.0 .Smi clear ; iicrliaiis in 1 .TZP. fi. 35 9(i. 7 97.8 85.9 86.2 30.3 39.1 S.'j. 3 82.5 Do. <).40 100. 1 101.0 80.9 87.7 31.2 39.7 SO. 5 83.0 Do. 0. 4.'-. 103. 9 104. 3 86.9 89.0 31.9 30.2 80.7 83.5 Do. f>. .50 105. 3 100.9 88.6 90.0 32. 2 30.5 87.2 83.5 Do. (;. 55 107. 5 109.3 90.8 91. 2 32.6 30.7 88. 5 83.8 Do. 7.00 109. 8 111.0 93.3 93.3 33.5 31.3 89.2 84.5 Sun clear. 7. 15 114.5 117.0 95.5 95. 0 34.4 33. 0 90. 5 85.3 Do. 7. 30 131. 8 133. 8 99. 5 99. 0 37. 5 34.1 93.2 87.0 Do. 8.30 129.2 130. 5 104. 8 105. 0 40.8 30. 5 98. 0 92.0 Do. 8.45 133.3 137. 0 107. 5 107. 5 41.8 37.5 98.2 91.2 Do. 9.00 '126.0 135.0 108. 3 107. 8 43.0 ,38.4 99. 5 92.5 Do. 9.30 138. 0 138.8 109. 8 110.0 44.0 39. 0 101.3 94.0 Do. 10. 00 140. 9 141.3 111.5 113.0 44.0 40.0 103. 0 95.0 Do. 10. 30 143. 5 143. 9 113.5 115.0 44.8 39.9 103. 5 90.0 Do. 11.00 140. 0 147.0 114.0 110.8 40. 9 41 8 100. 5 99.2 Do. 13. 00 147. 9 149.3 114.0 117. 5 47.3 41.0 100. 5 99. 3 Do. 1.00 140.3 tl50. 2 114.5 117. 3 46.7 41.3 107. 5 99.2 Do. 2. 00 144.2 145.0 113.2 115. 5 46.2 40.7 100. 3 97.0 Do. 3. 00 139. 2 130. 5 108. 5 111.5 45.4 40.3 102. 0 95.0 Sun bchiuil thin cir. st •. 3.40 133. 5 139.8 103. 2 107.7 43.0 38.7 99.5 92.5 Do. "Reservoir partly in shadoof the stem. tProhahly the maxiuinni reading hel'oro 1.00 p.m., .as the column w.is foniud liroken at 2.00 p. ni. Summary. — Observations in e.arly a. m. were made f'lcqnently. Up to 3.00 p. ni. all readings an^ nnu.-sually good. WEDNESDAY, MAY 2. Time. Coi ij iigatc thermometers. Voille'.s bulbs. Ordinary thermometers. IvelllMlks. Bl.ack. Bright. Black. No. 743. Gilt. No. 751. Black. No. 1137. Bright. No. 1136. No. 4. No. 3. No. 2. No. 1. A. M. 0.30 90.2 91.0 83. 5 84.0 28.0 28. 2 83.3 83.0 Sun bi'hind thin clouds. 7.00 110.8 111.2 9,3.8 93.0 33. 9 30.8 87.3 84.0 Sun clear. 7.40 133. 0 121. 0 98. 2 99.0 38.0 34.9 91.3 87.0 Do. 8.00 131.2 137.5 103. 8 102.7 40. 3 36. 5 94. 5 89.0 Do. 8.30 137. 9 124. 9 103. 8 102. 8 39.8 36. 5 98.2 91. 0 Sun clear, but just emerged from clouds. 9.00 137.8 135.0 107.9 108.4 42.0 38.0 101. 0 93.5 .Sun clear, but euierged from clouds live minutes iH'fore. 10.00 145. 0 143.0 113. 5 114.3 45. 6 40. 5 104.7 96.0 Sun dear. 10.30 140. 9 144.8 11.5.1 115. 3 4.5. 5 40.8 103. 0 95. 8 Do. 10. 45 147.5 145.5 11.5.2 115.3 45. 9 41.0 105. 4 96.5 Do. 11.00 148.3 147.0 110. 0 116.3 4(5. 3 41.3 106. 0 97.0 Do. 11.15 149. 0 148.5 110.4 117.0 47.0 41.7 107. 7 98. 5 Do. 11.30 148.9 149. 3 110.5 116.8 40. 9 41.7 109. 2 98. 5 Do. 12. 00 148.0 148.9 11.5.8 116.5 46. 3 41.1 100. 0 97.7 Do. 12.30 148.0 149.2 11,5. 8 117.2 46.0 41.0 107.2 98.5 Do. 1.00 147.4 149.2 110.2 117.8 47.9 42.6 109.0 98.5 Do. 2.00 144. 5 145. 5 115.5 117.0 49.1 43.6 107.2 98.8 Do. 2.30 141.7 141.0 114.0 114.8 47.8 42.7 104. 5 97. 5 Do. 3.00 *138.7 143. 7 110. 0 113.3 47.5 42.4 104. 3 95.5 Do. 3. 30 135. 0 1.39. (i 107.2 109. 4 44.8 40.4 103.8 94. 0 Do. 4.00 131.5 135.0 tll5.5 106. 0 43.9 39. (i 101. 0 93.5 Do. 4.30 124. 5 137. 0 102. 5 100. 8 40.0 30.8 97.4 88. 5 Do. 4. 45 120.0 120. 7 100.0 98.0 37.0 34.1 93. 0 87.0 Do. 5.00 110.0 116. 0 97.7 95.8 35. 9 33. 3 91. 5 80. 5 Do. * Bulb close to grass blade. t Should bo 105.5. Summm-y. — Sky almcst wholly clear after 9.00 a. m. Tho p. m. observations are especially good. BOLAE ECLIPSE, MAY G, 1883. THURSDAY, MAY '.5. G5 Tlino. Conjugate tbermonioters. VlOLLlS s bulbs. Ordinary tbernioiueters. RcmarkH. Black. Bright. Black. No. 742. Gilt. No. 751. Black. No. 1137. Brigbt. No. 1136. No. 4. No. 3. No. 2. No. 1. a A. M. 7.00 100. 8 106.6 91.0 90. 4 33.2 30.8 89. 5 84.5 Suu clear. 7.30 114.2 114.1 96.0 95. 0 35.1 33.2 88.5 85.0 Sun partly clear; iii clouils jii.st before. 8.30 131.2 130.9 104.4 )04.2 40.6 37.0 96. 2 89.8 Sun clear; in clouds at 8.00 a. in. •J. 00 I3G. 2 136.0 107.5 108. 0 41.6 37. 5 99. 5 92.0 Snii jii.st entering cloud. 10. 30 143. () 142.2 112. 0 113.3 43. 6 38.7 104.0 96. 0 Suu clear. 11.00 147.5 148.0 114.9 116.2 44.2 39.2 104.0 96.3 ])0. 11.30 14(j. 7 147.9 ' 114.5 115.6 44.5 39. 5 105. 5 97.0 Do. 12.00 14G.S) 148.7 i 115.1 116. 0 44.9 39. 8 105. 5 97.5 • Do. 12. 30 140. a 148.2 115.1 116. 6 45.2 40.0 106.0 98.0 Do. 1.00 140. 0 148. 1 115. 5 117.0 45.9 40.5 107.3 98.0 Do. 1.30 147.5 147.1 ; 116.0 116.9 46.2 41.0 106.5 98.7 Do. 2. 00 144.7 145.0 ; 114.0 11.5.2 44.8 39.8 100. 0 97.2 Do. 2.30 140. 8 141.0 111.0 112.6 43.9 39.1 103. 0 96.0 Sun just entering cloud. Summari/. — Sky not wholly clear. Observations before 10.30 a. ui. and after 2.00 p. lu. were interfered with by passing clouds. Between these times readings are reliable. No radiation observations were made May 4 on account of clouds. SATURDAY, MAY 5. Time. Conjugate thcrmometora. ViOLLE .s bulbs. Ordinary th erniomoters. Remarks. Black. Bright. Black. No. 742. Gilt. No. 751. Black. No. 1137. Bright. No. 1136. No. 4. No. 3. No. 2. No. 1. A. M. 8.30 129.2 126. 8 103. 5 101.2 36.4 33.4 92.2 88.0 Sun in haze. 10.00 137.5 137.2 109. 5 109.2 39.7 35.7 98.0 91.8 Sun clear. 10.30 142. 6 142. 5 112. 5 112. 3 41.7 37.2 99. 8 93. 2 Do. 11.00 142. 0 142. 5 111.7 111.9 40.8 36.3 100.8 93.7 Do. 11.30 143.0 141.5 112. 0 112.5 41.4 36.7 101. 3 95.0 Do. 12. 00 143.0 144.6 112. 0 113.0 41.1 36.5 10-2. 5 95.0 Suu just out of cir. btr. clouds. Summani. — Sky cloudy nearly all day, but the few readiug.s made are reliable. ' S. Mis. 110 1) 66 MEMOIKS OF THE NATIONAL ACADEMY OF SCIENCES. SUNDAY, MAY 6. Coiij ugate tbcruiometers. Violle' s bulbs. Ordinary tliermoiuetera. Time. Eem.nrks. Black. Bright. Blaclc. Gilt. Black. Briglit. No. 3. No. 1. No. 742. No. 751. No. 1137. No. 1136. A. M. 9.45 125.2 98.6 35.1 31.8 94.0 87. 5 Sun clear, but ju.st cuicrgcil fidui clouds. 9.57 137.0 105. 1 38.3 34.8 95. 2 89.2 Sun clear. 10. 35 p. M. 12.35 131. 0 104.3 37.1 34.4 94.0 88.8 Sun clear, in partial eclipse. 121. 0 99.7 35.8 33.3 94.2 90.0 Do. 12.50 130. 4 105. 0 37.7 34. 5 97. 0 90.8 Do. 1.02 13(5. 3 108. 5 39.2 35. 5 98.3 91.7 Do. 1.15 139.0 110.3 39.7 36.0 9S.2 91. 5 Sun clear. . 1.30 139. 0 110.9 39.8 36.1 98.8 91.8 Do. 2.00 135. 6 110. 2 39.7 36.0 98.3 91.5 Do. 2.30 133. (i 109.3 40.5 36.5 97.2 91. 3 Sun just out of clouds. 2.32 134. 9 109.6 40.5 36.5 99. 2 91.3 Sun clear. Max. values before ag scured . .lin ob- 2.45 138.2 108.9 40.1 36.3 96.8 90.7 Suu clear. 3.00 13(;. 7 107. 3 39.5 35.8 97.2 91.2 Do. 3.15 134. 5 105.7 38.6 35.3 95. 7 90. 0 Do. 3.45 129.5 102.7 37.7 34.4 95.3 89.5 Sun behind thin clouds. Cloudy at 3.00 3.50 132.9 103.8 38.5 34.9 96.5 89. 2 Sun clear. 4.00 126.2 101.0 36.8 33.8 93.5 88.2 Sun in haze. 4.15 122. 3 101.0 36.1 33.4 92.3 87.4 Sun clear, but whole sky is hazy. 4.30 117.2 98.5 34.8 32.6 91.2 86.7 Suu in haze. 4.50 110.2 94.6 32.9 31.4 88.7 a5. 3 Do. 5.00 109.2 93.8 32.8. 31.2 87.6 85.0 Do. Summiirii. — Cloudy until 9.45 a. ni., aud at iutervals throughout the day. [Special observations made from 10.00 a. in. to 1.15 p. ni. are given below.] Special observations in connection tcifh solar eclipse. J. C. Harold, observer. SUNDAY, MAY 6. Time. Conjugate thermometei'S. Violle .s bulbs. Ordiuiiry thermometers. Remarks. Black. Bright. Black. Gilt. Black. Bright. No. 3. No. 1. No. 742. No. 751. No. 1137. No. 1136. A. M. 10. 00 137.5 106.0 38.5 35.0 97.0 90. 0 Suu clear. 10.05 138.5 106.5 39.5 35.5 98.0 90.5 Do. 10.10 139. 0 107.0 39.5 35.5 97.0 89.0 Do. 10. 15 138.0 107.0 39. 0 35. 5 97.0 89.0 Do. 10.20 137.0 107. 0 39.0 35. 5 97.0 90.0 Do. 10.25 136.0 106. 0 38. 5 35. 5 96.0 90.0 Do. 10. 30 133.5 105. 5 38. 0 35. 0 95. 0 89.0 Do. 10.35 131.0 104. 5 37.0 34. 5 94. 0 88.5 Do. 10.40 124. 0 101.0 36.0 34.0 87.0 88.5 Sun iu cloud. 10. 45 113.5 96.0 33.0 32.0 90.0 86.0 Sun clear. 10. 50 115.5 97.0 33.5 32. 0 91.5 87.0 Do. 10. .55 115. 0 97.0 34.0 32.0 90.5 86.0 Do. • 11.00 113.0 96.0 33.5 32.0 89.0 86.0 Do. 11.05 109. 0 94.0 32.5 31.5 88.0 85.0 Sun in cloud. 11.10 104. 5 92.0 31.5 30. 5 86.5 84.0 Do. 11.15 100.0 90.0 30.5 30.0 85.5 84.0 Do. 11.20 99.5 87.0 28.5 28.5 84.0 82. 0 Do. 11.25 90.0 85.0 28.5 28. 5 83.0 82.0 Sun clear. 11.30 86.0 83.0 27.5 28. 0 82.0 81.0 Do. 11.32 85.0 82.0 26.5 28.0 81.5 81.0-1 11. 34 84.9 82.0 27.0 28.0 81.5 81.0 11.36 82.0 82.0 27.0 28.0 82.0 81. Of Total phase of eclipse. Lantern used. 11.38 82.0 82.0 27.0 28.0 82.0 81.0 J Pig. 19. CURVES OF BLACK AND BRIGHT BULB THERMOMETERS DURING ECLIPSE. Temp A. M. Tine. 1 P.Uf. moo idis 10:30 loks iiho liis iho ifAs rJ.oo if.is is'.so isUs I'.oo i.ii —105' — o? —WO"- - / o y ^ -".^ ' a o '^O 0^>\0 yT ^S_ X O -9S- ^^ /° \^ D? / oS X /o /''' ' —go'. • • o \ °V y — • • ^^"^^ ex ^"^ / " •^ ' •"■-^ V / ,^ -7 - oP^^V V / •«''' '^ /^ / '' "^V \ / »? ^ -".5- •? "~~^.? \ / ° •''''° ^ ^'^^^ss /y:' -^ Black bulb freely exposed. «. > ,\v__ooji,--^'' • Brii-bt " " " ^-Q.0 -•-''■? -*-" 'o — — — — — • , iF" <^ • Separate observations of black bulb, o _ " bright ■' • % Denotes sun in clouds at tinie of reading Other readings were sonietinios alfiTted by clouds jn'ovions tc» the observation. 1 1 1 1 1 1 1 1 1 1 1 1 1 1 SOLAE ECLirSE, MAY G, 188.3. 67 Special observations in connection with solar eclipse — (Joiitiiiucd. SUNDAY, MAY G— ContiiiiuMl. ' Conjugate Vioi.i.e's bulbs. Ordinary tli ermometprs. Tiino. tlieriiiometcsrs. i». Black. Bright. Black. Gilt. Black. Bright. it< itKirks. No. 3. No.l. No. 742. No. 751. No. 1137. No. 1136. A. M. 11.40 82.0 81.0 27.0 27. o 82.0 81. 5 Sun cli'ar. 11.4.'-) 82.0 81.0 27. 0 27.5 82.0 81.5 Sun in cloud. 11.. 50 84.0 82.0 27.5 28.0 83.0 82.0 Sun clear. 11. .55 88.0 84.0 28. 5 2H. 5 84.5 83.0 Do. 12.00 90.0 85.0 29. 0 28. 5 84.0 83.0 Do. p. M. 12. 05 9:i.o Hfi. 0 29.5 29.0 85. 0 83. 0 Do. 12. 10 99.0 89. 0 30.5 30.0 89.0 85.0 Sun in <-1om(1. 12. 15 101.0 90.0 31.5 30. 5 90.0 86.0 Do. 12. 20 98.0 89.0 31.0 30. 5 85. 0 83.0 Do. 12. 25 109.0 94. 0 33. 5 31.5 93.0 87.0 Do. 12. :iO 113.0 94.0 34.0 32.0 92.0 87.0 Sun clear. 12. :!5 120.5 100.0 35. 0 33.0 94. 0 89.0 Do. 12. 40 124. 0 102. 0 3(5,5 34.0 93.0 88.0 Sun in cloud. 12. 45 124. 0 , 102. 0 3fi. 0 33.5 9.5.0 89.0 Suu clear. 12. 50 130. 0 105. 0 37. 5 34.5 97.0 90.0 Do. 12. 55 132. 0 100. 0 38.0 35.0 96.0 90.5 Do. 1.00 135.0 108.0 39. 0 3,5.5 98.5 91.0 Do. 1.05 138.0 110.0 40.0 36.0 101.0 92.0 Sun in cloud. 1.10 137.0 109.0 40.0 36.0 97. 0- 91.0 Sun clear. 1.15 139. 0 110. 5 40.0 3(;.o 98.0 91.5 Do. The detailed observations show with sufficient completeness the conditions nnder which they were made. The best days upon which to undertake radiation observations are those whicli are perfectly cloudless, and, if possible, only such should be selected. But during the whole stay ou Caroline Island there was no cloudless day, and consequently noue of the observations were made under the best circuiustances. However, on several days, there were iutervals of several hours wheu the sky was clear, and results of some value can be obtained at such times. The clouds, moreover, which so continuously prevailed were of the cumulus type, and these have, at least approximately, the effect of a screen placed before the sun, concealing it for the time being, but allowiug it to shine again with its former power when they have passed. The meteorological record shows that clouds of other varieties were rarely observed, though a haze was noted at times. The conjugate thermometers were very sensitive to a slight diminution in the sun's heat. It required only a very thin cloud to reduce the readings by many degrees, and it was some minutes after the passage of a cloud before the instruments rose to their proper temperature again. From fifteen minutes to half au hpur should be allowed after the temporary concealment of the sun before the readings may be considered reliable, and a longer time may be neces.sary in tlie case of the Violle bulbs, which are slower in their action on account of the time required for the bulbs of the thermometers within the spheres to be affected by changes in the temperature of their outer surfaces. If we select from the observations those in which the sun was clear at the time, and had been for at least fifteen minutes previously, we shall find a sufficient number to warrant a more extended examination. It is possible to obtain from them an estimate of the solar intensity by several methods, and to institute a comparison between them. It is also possible to obtain a value of the solar constant. In the computation which follows the solar intensity is obtained by the methods available for the conjugate thermometers, Yiolle's bulbs, and black and bright bulb thermom- eters, and a comiiarison made of the results, and in addition a value of the solar constant is determined from the observations with the conjugate thermometers. 08 MEMOIRS OP THE NATIONAL ACADEMY OF SCIENCES. 1. ItEDUCTION OF OBSEItTATIONti MADE WJTII THE CONJUGATE TEEItMOMETEBS. The bulletins of the Central Physical Observatory of Montsoiiris contain a general description of tlie instruments, but no rigid investigation of tbeir theory. The differences between the read- ings of the black and bright therniometers are taken as a measure of the sun's intensity, and are used in the formula T — t — dp', in which T', t are the readiug-s of the therniometers respectively, fi the solar constant, jj the diathermancy constant, and e the thickness of the layers of atmospheric air traversed by the solar rays. It is recognized, however, that the values of 0 obtained by this formula are not the true solar constant, but vary with the iustrnments used,* having a value of 17° in the instruments used at Moutsonris. For the purposes of comparison of the observations made from time to time, it is snggested that a conventional value of 100° be adopted for H, and that observations with different instruments be reduced to this standai'd by multiplying by a factor depending upon the value of H for each instrument. At Montsouris, where 6 = 17° for the ])nir of instruments described, the factor is Yt"- = ^-SS, and the product of the observed differences T' — t by this factor is called the "actimometric degree." In the case of observations made in 1873 and 1874 the ditt'erences 1' — t are published, but in observations since that time the acti- mometric degree is computed. Quite recently a rigid investigation of the theory of these instruments has been made by Prof. William Fekrkl, and is to be published in Professional Paper of the United States Sig- nal Service No. XIII. It assumes the law of Diilong and Petit, and derives formula? for deducing the solar intensities and also the solar constant. Through the courtesy of the author, the formula; have been furnished for this computation in advance of their publication. They are as follows: " Let ti = the temperature of the black bulb. ^'i = the temperature of the bright bulb. II' — the temperature of the inclosure (shade temp, approx.). I = the intensity of solar radiation (calorics per minute on square centimetre). n = constant 1.0077 (log tx — ., ^^ 1 ui = constant to be determined from observation. We have then the following relations: (1) I = 4.584 (yu»— ;u»') = 4.584 /^e'(;^»-e' — l) (2) I = 4.584 (//« — |<''')c= 4.584 /('" (yi^e_s._l)c (3) //e. = P/<''.+ (l-c)/A" From (1) the intensity is obtained from the readings of the black bulb in vacuo and the air temperatui'e, which is approximately equal to that of the inclosure, or from (2) the intensity is obtained from the readings of the black and bright bulbs in vacuo, the constant c being obtained from (3). The method assumes that c can be obtained from observation, and thus the readings of the black and bright bulbs in vacuo be used in computing the solar intensities; 0, o„ and o' are expressed in centigrade degrees. * Bull. Mens, de I'Obs. Phys. Centr. de Moutsomis, 1874, p. 189. SOLAR ECLIPSE, MAY 0, 1883. 69 It first becomes neces«ary to compute the constant c. From (3) we have — e "' *' 0 0, M — M 111 order to oI)tain Mie value of c under varying' conditions, observations were selected IVoiii difierent days and at dillerent times of tlie day. Tlic, following table contains the observations used and the resulting values : Computation of c. Diito. April 27 28 30 30 30 I 2 2 2 2 2 M.ay Time. 9. 00 a. 111. ; Vi. ir> p. ni. 9.35 a. 111. to 2. (IS p. m. 3. OOji. in. to .'•>. (lOp. n;. 7. 00 a. III. ; 5. 00 p. in. 9. 00 a. 111. ; 3. 00 p. ni. (i. ri.^> a. 111. to 10. 30 a., m. 10.30 a. ni. to 2. 30 p. in. 11.30 a. ni. to 12.3(1 p. in. 7.00 a. in. ; 5.011 p. in. 10.00 a. 111. ; 2. 00 p. ni. 8. 00 a. III. ; 4. 00 p. in. No. of olia. II (U t>' c. o o o 2 t>». 9 43.4 29.7 1.79 10 01.4 4.5.7 30. 3 1.87 5 .'•)2. 9 39. 0 2K.H 1.74 t) 44.8 34. () 28.2 1..59 2 58. 9 42.9 29. 7 1.74 10 53.3 39.7 29. 3 1.72 10 C3.8 40. 7 30. 7 1.82 3 G4. 8 46.9 3(1.9 1.78 2 45. 3 35.1 28.0 1.65 2 02. 5 46.1 30.3 1.85 2 55.2 40.2 28. 9 1.68 The resulting values of c arc quite discordant, and have a marked progression according to the values of 0, or according to the hour of observation. Tliey show that in the observations under discussion c is not strietlj^ a constant, but varies with the time of day. Tiiis may be true of the particular instruments used, or be due to some circumstance connected with the exposure of the instruments in these observations, or it may be inherent in this method of meas- uring solar radiation. Without further experiment it is impossible to discover the cause. It is therefore necessary to inquire what error is introduced by assuming a constant value of c. For his investigation the value c = 1.75 was assumed, and a computation of o' made for observations on May 1 and 2. The following table gives the result of the computation and a comparison with the observed values of the same quantity : Comparison of computed with observed shade temperatures {S'). MAY 1. Time. 0. 0. 0' obs. 0' comp. Obs. — comp. A. M. o o o o o 7.00 43.7 .33.4 28.2 2.5.0 4-3.2 7.30 .50. 2 37.3 28.6 26.7 + 1.9 8.30 54.3 40.5 29.7 29.1 + 0.6 9.00 57.2 42.2 29.8 29.7 + 0.1 9. 30 .59. 1 43.3 29.8 30.0 — 0.2 10. 00 60.6 44.6 30.0 31.1 — 1.1 10.30 62.1 45.4 30.3 31.3 - 1.0 11.00 03.6 46.3 29.9 31.6 - 1.7 12. 00 64.8 46.6 30.3 31.0 -(-1.7 { r. M. 1 1.00 63.5 46.6 30.4 32.2 — 1.8 2.00 t2.6 45.4 30.0 30.8 — 0.8 3.00 58. 8 43.3 29. 5 30.3 — 0.8 3.40 55.1 40.8 29.3 28.9 + 0.4 70 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. MAY 2. A. M. 7.00 43.9 34.1 27.8 20.2 + 1.0 7.40 49.9 37.0 28.5 20.4 + 2.1 8.00 54.1 39.3 28.9 27.0 + 1.9 8.:w .52. 4 39. 3 29.1 28. 5 + 0.6 9.00 58.0 42.3 29.3 29.1 + 0.2 10.00 62.2 45. 5 30.0 31.4 — 1.4 10. 30 03.2 40.2 30.7 31.8 — 1.1 1 11.00 (i4.2 40.7 30.0 31.8 — 1.2 11.30 65. 1 47.0 31.0 31.5 — 0. 5 12.00 64.7 40.8 31.0 31.5 — 0.5 p. M. 12.30 64.8 40.9 30.8 31.6 — 0.8 1.00 64.0 47.2 30.0 32.4 — 1.8 2.00 02.8 40.8 30.0 33.3 — 2.7 2.30 60.8 45.8 30.4 33.3 — 2.9 3.00 02.1 44.2 29.2 28.9 + 0.3 3. .30 58. 5 42.4 29.2 28.8 + 0.4 4.00 56.2 41.0 28.9 28.3 + 0.0 4. .30 52. 1 38.7 28.4 27.6 + 0.8 ."^.00 40.7 36.0 28.2 27.3 + 0.9 This table sliows the effect of using a coii.staiit value of c between the hour.s of 7.00 a. ni and .5.00 p. ui. Had the value c = 1.78 been employed, the computed values would have been diminished by about 0o.5, and the mean of the residuals would have been nearly 0. There still would have remained, as was expected, plus residuals for the morning and evening observations, and minus residuals for those taken near the middle of the day. The magnitude of the residuals, while larger than was hoped for, is not sufficient to prevent the use of the method, but it renders advisable the computation of the solar intensities by equation (1) as well as equation (2). In the latter equation it was decided to use the value c = 1.8. The following tiible contains the observations selected for the computation and the solar intensities obtained by equations (1) and (2). Those observations only were used in which the sun had been clear for some time before the observation. The mean of the corresponding readings with the two pairs of instruments was taken and the resulting values converted into centigrade degrees : Oomputation of solar intensities. [Conjugate thermometers.] APRIL 28. lutensity (I). Time. 6. 0,. 6'. 0-0,. 0 — 0'. a — 1). Mean. a. from (2). 6. from (1). A. M. 9.00 59.0 42.2 29.0 16.8 30.0 1. .570 1.483 + 0.09 1.53 9.30 58.8 42.6 29.3 16.2 29.5 1.515 1.458 + 0.06 1.49 9.35 59.4 43.1 29.3 16.3 30.1 1.530 1.401 + 0.04 1.51 10.00 59.2 43.1 29.4 16.1 29.8 1.512 1. 470 + 0.04 1.49 10. 35 59.9 43.9 29.9 10.0 30.0 1.509 1. 493 + 0.02 . 1.50 11.00 61.3 45.4 30.1 15.9 31.2 1. 517 1.502 — 0.04 1.54 11.30 60.9 4!>.6 30.4 15. 3 30.5 1.459 1. .527 — 0.07 1.49 12.00 62.6 46.1 30.7 10.5 31.9 1.587 1. 009 — 0.02 1.00 V. M. 12.30 04.5 47.9 31.0 10.6 33.5 1.619 1. 705 — 0.09 1.66 1.00 02.0 46.9 30.6 15.1 31.4 1.452 1.581 — 0.13 1.52 1.30 00.7 46.6 30.6 14.1 30.1 1.348 1. 506 — 0.16 1.43 SOLAli ECLIPSE, MAY (>, 1883. Computation of solar intensities — Ooutinucd. APEIL 29. 71 Intensity (I). Time. 0. e,. 0'. 0 — 01. e — ff. a — b. Mean. a. from (2). 6. from (1). A. M. 9.00 56.8 41.1 29.9 15.7 26.9 1.447 1. 323 + 0. 12 1.38 10.00 61.9 44.7 30.6 17.2 31.3 1. 640 1. 574 + 0. 07 1.61 11.00 61.2 44.6 30.8 16. 6 30.4 1. 578 1.525 + 0. 05 1. 55 11.15 02. 4 45. 7 30. 9 16.7 31.5 1.603 1.589 + 0.01 1. &.' 11. 30 62.9 46.1 31.0 16.8 31.9 1.618 1.612 + 0.01 1.62 11.45 63.1 46.3 30.7 16.8 32.4 1.620 1. 638 — 0. 02 1.63 12.00 62.6 46.3 30.6 16.3 32.0 1.568 1.614 — 0. 05 1.59 12. 15 63.0 46.6 30.8 16.4 32.2 1.583 1.627 — 0.04 1.60 12.30 63.1 46.9 31.1 16.2 32.0 1.566 1.621 — 0.06 1.59 1.30 60.4 46. 2 30.9 14.2 29. 5 1.353 1.476 — 0.12 1.41 2.10 59. 4 45. 9 30.9 13.5 28.5 1.281 1.421 — 0.14 1.35 2.30 58.9 45. 6 30.8 13.3 28.1 1.257 1.398 — 0.14 1.33 3.00 59. 1 44.5 30.6 14.6 28.5 1.378 1.417 — 0. 14 1.40 APEIL 30. A. M. 11.00 64. 9 46.7 30.4 18.2 34.5 1.771 1.755 + 0.02 1.76 11.30 64.9 47.4 30.5 17.5 34.4 1.706 1.751 — 0.04 1.73 11.45 64.7 47.3 30.4 17.4 34.3 1. 695 1.743 — 0.05 1.72 12. 00 64.9 47.7 30.4 17.2 34.5 1.678 1.755 — 0.08 1.72 12. 15 64.6 47.6 30.4 17.0 34.2 1. 658 1.737 — 0.08 1.70 3.00 58.4 43.0 29. 3 15.4 29.1 1. 439 1. 436 0. 00 1.44 3.30 56.4 41.7 29.2 14.7 27. 2 1.357 1. 332 + 0. 02 1.34 4.00 54.1 40.2 28.8 13.9 25.3 1. 264 1.225 + 0.04 1.24 4. 30 50.2 37. 9 28.4 12.3 21.8 1.093 1. 039 + 0.05 1.07 5.00 45.2 35.2 28.3 10.0 16.92 0.853 0.788 + 0.0(i 0.82 MAY 1. A. M. 6.45 39.8 31.1 28.0 8.7 11.8 0. 723 0. 538 + 0.18 0.63 7.00 43.7 33.4 28.2 10.3 15,5 0.876 0.719 + 0.16 0.80 7.15 46.6 35.1 28.4 11.5 18.2 0.996 0. 855 + 0.14 0. 93 7.30 50.2 37.3 28.6 12.9 21.6 1. 143 1. 029 + 0. 11 1.09 8.30 54.3 40.5 29.7 13.8 24.6 1.258 1. 196 + 0.06 1.23 8.45 57.3 41.9 29.8 15.4 27.5 1. 427 1. 355 + 0.07 1.39 9.00 57.2 42. 2 29.8 15.0 27.4 1.392 1.348 + 0.04 1.37 9.30 59.1 43.3 29.8 15.8 29.3 1.484 1.453 + 0.03 1.47 10.00 60.6 44.6 30.0 16.0 30.6 1.517 1. 528 — 0.01 1.52 10.30 62.1 45.4 30.3 16.7 31.8 1..596 1. 599 0.00 1.60 11.00 63.6 46.3 29.9 17.3 33.7 1.673 1.702 — 0.03 1.69 12.00 64.8 46.6 30.3 18.2 34.5 1.770 1.753 + 0.02 1.76 1.00 63.5 46.6 30.4 16.9 33.1 1.633 1.673 — 0.04 1.65 2.00 62. 6 45.4 30.0 17.2 32.6 1.649 1. 641 + 0.01 1.64 3.00 58.8 43.3 29. 5 15.5 29.3 1.454 1.450 0.00 1.45 3.40 55.1 40.8 29.3 14.3 25.8 1.310 1.257 + 0.05 1.28 72 MEMOIKS OF THE NATIONAL ACADEMY OF SCIENCES. A. M. 10.00 10.30 11.00 11.30 .'■)8. 6 61.4 CI. 2 G1.2 Computation of solar intensities — Contiuued. MAY 2. Intensity (I). Time. 0 fii. H'. O — Oi. 0 — 0'. a — h. Mean. a. from (2). 6. from (1). A. M. 7. 00 43. y 34.1 27.8 9.8 16.1 0.838 0.747 + 0.09 0.79 7.40 49. 9 37.0 28.5 12.9 21.4 1.141 1.018 + 0. 12 1.08 8.00 54.1 39.3 28. 9 14.8 25.2 1.341 1. 221 + 0.12 1.28 8.30 52.4 39. 3 29.1 13.1 23.3 1.181 1. 123 + 0.06 1. 15 U.OO 58.0 42. 3 29. 3 15.7 28. 7 1. 4(;i 1.415 + 0.05 1.44 10.00 C2. 2 45. 5 30. 0 16. 7 32.2 1.601 1.617 — 0.02 1.61 10.30 03.2 46.2 30.7 17.0 32.5 1.641 1.643 0.00 1.64 10. 45 63. G 46.2 30.6 17.4 33.0 1.681 1. 671 + 0.01 1.68 1 U.OO 64. 2 4"). 7 30.6 17.5 33.6 1.697 1.706 — 0.01 1.70 11.15 64. 9 47.1 31.1 17.8 33.8 1. 733 1.724 + 0.01 1.73 11.30 65.1 47.0 31.0 18.1 34.1 1.763 1.740 + 0.02 1.75 12.00 64.7 46.8 31.0 17.9 33.7 1.741 1.716 + 0.02 1.73 12. 30 64.8 46.9 30.8 17.9 34.0 1.743 1.731 + 0.01 1.74 1.00 (i4. 6 47.2 30.6 17.4 34.0 1. 694 1.728 — 0.03 1.71 2.00 62.8 46.8 30.0 16.0 32.2 1.542 1. 625 — 0.08 1. .58 2. 30 60. 8 45.8 30.4 15.0 30.4 1. 431 1. ,521 — 0. 09 1.48 3.00 62. 1 44.2 29. 2 17.9 32.9 1.707 1. 648 + 0.06 1.68 3.30 58.5 42.4 29.2 16.1 29.3 1.504 1.447 + 0.06 1.48 4.00 56.2 41.0 28.9 15.2 27.3 1.400 1. 334 + 0.07 1.37 4.30 52.1 38.7 28.4 13.4 23.7 1.204 1.137 + 0.07 1.17 4.45 49.1 37.2 28.3 11.9 20.8 1.051 0.985 + 0.07 1.02 5.00 46.7 36.0 28.2 10.7 18.5 0.932 0. 8G9 + O.OG 0.90 MAY 3. A. M. 10.30 61.6 44.8 30.4 16.8 31.2 1.601 1. .566 + 0.04 1.58 U.OO 64.3 46.4 30.8 17.9 33.5 1.736 1.703 + 0.03 1.72 11.30 G4. 1 46.1 30.1 18.0 34.0 1.741 1.721 + 0.02 1.73 12. 00 64.3 46.4 30.5 17.9 33.8 1.736 1.716 + 0.02 1.73 12.30 64.1 46. 6 30.0 17.5 34.1 1.695 1.727 — 0.03 1.71 1.00 63.9 46. 8 30.4 17.1 33.5 1. 6.58 1. 697 — 0.04 1.68 1.30 64.1 46.9 30.4 17.2 33.7 1.668 1.708 — 0.04 1.69 2. 00 62.7 45.9 30.3 16.8 32.4 1.G15 1.633 — 0. 02 1.G2 2.30 60.5 44.3 30.0 16.2 30.5 1.535 1.523 + 0.01 1.53 MAY 5. 43.0 44.7 44.3 44.6 24.6 25.6 26.7 27.2 15.6 16.7 16.9 16.6 34.0 35.8 34.5 34.0 1.460 1.591 1.605 1.578 1.650 1.764 1.70G 1.683 0.19 0.17 0.10 0.10 MAY 6. 1.56 1.68 1.66 1.63 p. M. 1.15 .59.4 43.5 29.4 15.9 30.0 1.495 1.487 + 0.01 1.49 1.30 59.4 43.8 29.4 15.6 30.0 1. 469 1.487 — 0. 02 1.48 2.00 57.6 43.4 29.4 14.2 28.2 1. 325 1. 388 — 0.06 1.36 3.00 58.2 41.8 29.0 16.4 29. 2 1.526 1.438 + 0.09 1.48 3.15 56.9 40.9 29.0 16.0 27.9 1.474 1.367 + 0.11 1.42 In the preceding table the sixth column contains the difference between the readings of the black bulb in vacuo (6) and the bright bulb in vacuo (^i), and the seventh column the difterences between the former and the shade temperatures (6"). The latter, which are given in the fifth column, have been obtained from the current meteorological record ; they are the reading of the SOLAR ECLIPSE, MAY (i, 1883, 73 mercurial thermometer in the instrument shelter, reduced to centigrade measures. In a few cnses tlie values were obtained by interpolation. The column of differences [a — b) shows the discrepancies between tln^ two methods. The signs are + for ruorniug and evening values, and — for those in the middle of the day, as should be the case by taking a constant value of c. A comparison of the two methods shows no reason for jtreferring one to the other. The one which introduces the value of c — equation (2) — is open to the objection that it assumes a constant value for c which it has been shown is only approximately true ; it is possible that the deviations from constancy are due to the circumstances of these particular observations, and that consequently the intensities are not strictly accurate as computed. On the other hand, the method which uses the shade temperatures — equation (1) — is open to the uncertain- ties in the observations of that quantity, and assumes that these temperatures may be adopted as the temperatures of the inclosure of the black bulb thermometer. There seemed to be no reason for giving preference to either of the reductions. The last column contains the 7nean of the two series of values, which are adopted as the solar intensities given by the conjugate thermometers. 2. RKDVCXION OF OBSERYATIOIfS MADE WITH VIOLLE'S BULBS. The theory of these instruments is given by the inventor in his work upon solar radiation, above referred to, pp. 17-22*. According to the method there explained, the intensities may be obtained bv the equation: M U' iu which M = the difference between the reading of the thermometer in the blackened sphere and the air temperature. . «' = the difference between the reading of the thermometer in the gilded sphere and the air temperature. a = the absorbing power of the gilded sphere in terms of that of the blackened sphere. K = a constant depending upon the instrument, and found by the methods explained, if K is undetermined, relative intensities can be obtained by the equation: uu' 1 = u'— au . In this equation the quantities u and n' are obtained directly from the observations, but the constant a must be derived experimentally. After the return of the expedition, a number of observations of this constant were made by screening the spheres and ol)serving the rate of cooling of each, and also by observing the rate of increase of temperature when full sunlight was allowed to fall upon them after they had assumed the shade temperature behind the screen. The experiments gave the value a =0.5, the large value being due to the tarnishing of the gilt, which was caused in ])artby the effect of the sea voyage. It is in part also apparently due to the poor manner in which the gilding has been done, as the same deterioration has been found in instruments which have never been used in actual work. Similar observations with a pair of instruments in which there was a good polisli on the gilded sphere gave the value a = 0.3. It was decided to use the value 0.1 in the reduction as probably representing nearly the correct value for the condition of the gilt at Caroline Island. An approximate value is sufficient for determining the relative intensities, which is the aim of the present investigation. The following table contains the computation for the same dates aiul times at which the readings of the conjugate thermometers were reduced. Other observations were reduced, but it is thought unnecessary to give the computation, as they sliow discordances due to the effect of passing clouds to a greater degree than those here given. * See also Annales de Chimie et de Physique, 5= s6rie, t. XVII, 187t>. S. Mis. 110 10 74 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. Computation of relative solar intensities. [Violle'.s Ijiilbs. ] APRIL -28. Time. Black. Gilt. Air. u. u'. I. A. M. 9.00 40.8 36.4 29.4 11.4 7.0 33.2 9.30 41.1 36.6 29.3 11.8 7.3 33.1 9.35 41.8 37.2 29.3 12.5 7.9 34.1 10.00 41.0 36.3 29.4 11.6 6.9 34.8 10. 35 43.0 38.2 29.9 13.1 8.3 35.1 11. 00 43.8 38.7 30.1 13.7 8.6 38.0 11.30 43.4 38.6 30.4 1.3.0 8.2 35. 5 12.00 44.4 39.2 30.7 13.7 8.5 38.8 p. M. 12.30 46.3 40.4 31.0 15.3 9.4 43.6 1.00 45.2 39.7 30.6 14.6 9.1 40.3 1.30 45.1 39.6 30.6 14.5 9.0 40.8 APEIL 29. A. M. 9.00 39.7 36.0 29.9 9.8 6.1 27.2 10.00 43.1 38.9 30.6 12.5 8.3 31.4 11.00 45.6 3H.2 30.8 14.8 7.4 73.0 11.15 45.6 38.7 30. 9 14.7 7.8 60.3 11.30 45.6 39.9 31.0 14.6 8.9 41.9 11.45 45.6 39.5 30.7 14.9 8.8 46.8 12.00 45:5 39.9 30.6 14.9 9.3 42.0 p. M. 12.15 45.5 39.8 30.8 14.7 9.0 42.7 12.30 45.5 40.2 31.1 14.4 9.1 39.7 1.30 46.0 39.5 30.9 15.1 8.6 49.9 2.10 46.0 39.7 30.9 15.1 8.8 47.5 2.30 46.0 39.7 30.8 1.5.2 8.9 48.3 3.00 46.0 39.2 30.6 15.4 8.6 5.5.2 APEIL 30. A. M. 11.00 46.7 42.6 30.4 16.3 12.2 34.9 11. 30 46.2 41.8 30.5 15.7 11.3 35.5 11,45 45.4 40.8 30.4 15.0 10.4 35.5 12.00 46.5 41.9 30.4 16.1 11.5 36.3 p. M. 12.15 45.5 40.5 30.4 15.1 10.1' 37.2 3.00 41.7 37.4 29.3 12.4 8.1 32.4 3.30 39.8 35.5 29.2 10.6 6.3 31.8 4.00 39.5 35.9 28.8 10.7 7.1 27.1 4.30 36.7 34.2 28.4 8.3 5.8 19.3 5.00 1 35.2 32.4 28.3 C.9 4.1 21.8 MAY 1. A. M. 7.00 33.5 31.3 28.2 5.3 3.1 16.4 7.15 34.4 32.0 28.4 6.0 3.6 18.0 7.30 37.5 34.1 28.6 8.9 5.5 25.8 8.30 40.8 36. 5 29.7 11.1 6.8 31.4 8.45 41.8 37.5 29.8 12.0 7.7 31.9 9.00 42.6 38.4 29.8 12.8 8.6 31.4 9.30 44.0 39.6 29.8 14.2 9.8 33.9 10.00 44.6 40.0 30.0 14.6 10.0 34.8 10.30 44.8 39.9 30.3 14.5 9.6 36.6 11.00 46.9 41.8 29.9 17.0 11.9 39.7 12.00 47.2 41.6 30.3 16.9 11.3 42.4 p. M. 1.00 46.7 41.3 30.4 16.3 10.9 40.4 2.00 46.2 40.7 30.0 16.2 10.7 41.3 3.00 45.4 40.3 29.5 15.9 10.8 39.0 3.40 43.0 38.7 29.3 13.7 9.4 33.0 SOLAR ECLIPSE, MAY G, 1883. 75 Computntion of relative solar intensities — Coutiuued. MAY 2. Time. Black. Gilt. Air. «. «'. I. A. M. 7.00 32.9 30.8 27.8 5.1 3.0 lii. 3 7.40 38.0 34.9 28.5 9.5 6.4 23. 4 8.00 40.3 36.5 28.9 11.4 7.6 28.9 8.30 39.8 36.5 29.1 10.7 7.4 25. 5 9.00 42.0 38.0 29.3 12.7 8.7 30.7 10.00 45.6 40.5 30.0 1.5.6 10. 5 38.1 10.30 45. 5 40.8 30.7 14.8 10.1 35. 6 10. ih 45.9 41.0 30.6 15.3 10.4 37. 0 11.00 46.3 41.3 30.6 15.7 10.7 38.2 11.15 47.0 41.7 31.1 15.9 10.6 40.1 11.30 46.9 41.7 31.0 15.9 10.7 39.6 12.00 46.2 41.1 31.0 15.2 10.1 38.4 p. M. 12.30 46.0 41.6 30.8 15.2 10.8 34.9 1.00 47.9 42.6 30.6 17.3 12.0 40.7 2.00 49.1 43.6 30.6 18.5 13.0 42.9 2.30 47.8 42.7 30.4 17.4 12.3 40.4 3.00 47.5 42.4 29. 2 lb. 3 13.2 40.9 3.30 44.8 40.4 29.2 15.6 11.2 34.9 4.00 43.9 39.6 28.9 15.0 10.7 34 1 4.30 40.0 36. 8- 28.4 11.6 8.4 25.6 4.45 37.0 34.1 28.3 8.7 5.8 21.9 5.00 35.9 33.3 28.2 7.7 5.1 19.6 MAY 3. A. M. 10.30 43.6 38.7 30.4 13.2 8.3 36.5 11.00 44.2 39.2 30.8 13.4 8.4 37.5 11.30 44.5 39.5 30.1 14.4 9.4 37.6 12. 00 44.9 39.8 30.5 14.4 9.3 38.3 p. M. 12.30 45.2 40.0 30 0 15.2 10.0 39.0 1.00 45.9 40.5 30.4 15.5 10.1 40.1 1.30 46.2 41.0 30.4 15.8 10.6 38.9 2.00 44.8 39.8 30.3 14.5 9.5 37.2 2.30 43.9 39.1 30.0 13.9 9.1 36.1 MAY 5. MAY 6. A. M. 10.00 39.7 35.7 24.6 15.1 11.1 32.9 10.30 41.7 37.2 25.6 16.1 11.6 35.9 11.00 40.8 36.3 26.7 14.1 9.6 33.8 11.30 41.4 36.7 27.2 14.2 9.5 35.5 p. M. 1 1.15 39.7 36.0 29.4 10.3 6.6 27.2 1.30 .39.8 .36.1 29.4 10.4 6.7 27.9 2.00 39.7 36.0 29.4 10.3 6.6 27.2 3.00 39.5 35.8 29.0 10.5 6.8 27.5 3.15 38.6 ;{5.3 29.0 9.6 6.3 24.2 It is evident from an examiuation of the values in the last column tbat observations were often made when the instruments had not recovered from the effect of passing clouds. This is especially true on April 29, which is here given as an illustration of the eflect of frequent clouds upon the indications of the instruments. This sluggishness seems to be greater than that of the conjugate thermometers. Further remarks on this point are given below iu the section devoted to a comparison of the results of the different computations. 76 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 3. REDUCTloy OF OlSSERyATIOSS MADE WITH THE BLACK AND BRIGHT THERMOMETERS EXPOSED IN FULL SUNLIGHT, DVT NOT IX TACVO. The snme forimila used for tlie reduction of observatiou.s with Violle's bulbs .serves for the computation of .'-•olar intensities from readiug.s of bhick and bright bulb thermometers not in vacuo. The absorption constant a i.s, however, different. In the computation, the results of which are given in the following table, the value a = \ is adopted as representing the theoretical value of the radiating jjower of the bright bulb in terms of that of the black bulb : Computation of relative solar intensities. [Black and bright bulbs not in vacuo.] APRIL 28. Time. 1137. 1136. Air. «. m'. I. A. M. 9.00 36.3 32.9 29.4 6.9 3.5 10.5 9.30 38.1 33.3 ■29. 3 8.8 4.0 14.1 9. 35 37.8 33.3 29. 3 8.5 4.0 13.1 10.00 38.2 33.0 29.4 8.8 3.6 15.1 10.35 39.1 34.6 29.9 9.2 4.7 13.5 11.00 39.2 34.6 30.1 9.1 4.5 13.6 11.30 38.3 34.4 30.4 7.9 4.0 11.7 12.00 40.6 35.7 30.7 9.9 5.0 14.6 p. M. 12.30 41.4 36.4 31.0 10.4 5.4 15.2 1.00 40.0 36.0 30.6 9.4 5.4 13.4 1.30 39.6 35.6 30.6 9.0 5.0 12.9 APRIL 30. A. M. 11.00 42.8 37.2 30.4 12.4 6.8 17.9 11.30 40.8 36.7 30.5 10.3 6.2 14.2 11.45 42.9 37.5 30.4 12. 5 7.1 17.8 12.00 43.3 38.1 30.4 12.9 7.7 18.1 P. M. 12. 15 43.0 37.7 30.4 12.6 7.3 17.7 3.00 36.9 33.9 29.3 7.6 4.6 10:6 3. 30 36.8 33.1 29.2 7.6 3.9 11.- 4 4.00 36.4 32.5 28.8 7.6 3.7 11.7 4.30 34.2 30.8 28.4 5.8 2.4 9.9 MAY 1. A. M. 7.00 31.8 29.2 28.2 3.6 1.0 . 9.0 7.15 32.5 29.6 28.4 4.1 1.2 9.8 7.30 33.4 30.6 28.6 4.8 2.0 8.0 8.30 36.7 33.3 29.7 7.0 3.6 10.5 8.45 36.8 32.9 29.8 7.0 3.1 11.4 9.00 37.5 33.6 29.8 7.7 3.8 11.7 9. 30 38.4 34.4 29.8 8.6 4.6 12.4 10.00 39.4 35.0 30.0 9.4 .5.0 13.8 10. 30 39.7 35.6 30.3 9.4 5.3 13.5 11.00 41.4 37.3 29.9 11.5 7.4 15.5 12.00 41.4 37.4 30.3 11.1 7.1 14.9 p. M. 1.00 41.9 37.3 30.4 11.5 6.9 15.9 2.00 41.2 36.1 30.0 11.2 6.1 16.3 3.00 39.2 35.0 29.5 9.7 5.5 13.7 3.40 37.5 33.6 29.3 8.2 4.3 12.2 SOLAK ECLIPSE, MAY 6, 1883. 77 Computation of relative solar intensities — (Jontimied. MAY 2. Time. 1137. 1136. Air. M. u>. I. A.- M. 7.00 30.7 28. 9 27.8 2.9 1.1 5. 3 7.40 32.9 30.6 28.5 4.4 2.1 6.6 8.00 34.7 31.7 28. 9 5.8 2.8 9.0 S.30 .36.8 32.8 29.1 7.7 3.7 11.9 9.00 38.3 33.6 29.3 9.0 4.3 13.8 10.00 40.4 35.6 30.0 10.4 5.6 14.9 10.30 39.4 35.4 30.7 8.7 4.7 12.4 10.45 40.8 35.8 30.6 10. 2 .5.2 15.2 11.00 41.1 36.1 30.6 10. 5 5.5 15.6 11.15 42.1 36.9 31.1 11.0 5.8 16.0 11.30 42.9 36.9 31.0 11.9 5.9 --18. 0 IS. 00 41.1 36.5 31.0 10.1 5.5 14.6 12. 30 41.8 36. 9 30.8 ii.o 6.1 15. 6 1.00 42.8 36.9 30.6 12. 2 6.3 17.9 2.00 41.8 37.1 30.6 11.2 6.5 15.8 2.30 40.3 36.4 30.4 9.9 6.0 13. 5 3.00 40.1 35.3 29.2 10.9 6.1 1.5.5 3.30 39.3 34.4 29.2 10.1 5.2 1.5.0 4.00 38.3 33.6 28.9 9.4 4.7 14.2 4.30 36.3 31.4 28.4 7.9 3.0 14.0 4.45 33.9 30.6 28.3 5.6 2.3 9.2 5.00 33.1 30.3 28.2 4.9 2.1 7.9 MAY 3. A. M. 10. 30 40.0 3,5.6 30.4 9.6 5.2 13.9 11.00 40.0 35.7 30.8 9.2 4.9 13.3 11. 30 40.8 36.1 30.1 10.7 6.0 15.3 12.00 40.8 36.4 30.5 10.3 5.9 14.5 12. 30 41.1 36.7 30.0 11.1 6.7 15.6 1.00 41.8 36.7 30.4 11.4 6.3 16.3 1.30 41.4 37.1 30.4 11.0 6.7 15.0 2.00 41.1 36.2 30.3 10.8 5.9 15.5 2.30 39.4 35.6 ■ 30.0 9.4 5.6 13.2 p. M. 1.15 1.30 2.00 3.00 3.15 36.7 37.1 36.8 36.2 35.4 33.1 33.2 33.1 32.9 32.2 MAY 6. 29.4 29.4 29.4 29.0 29.0 7.3 7.7 7.4 7.2 6.4 3.7 3.8 3.7 3.9 3.2 10.8 11.7 11.0 10.4 9.8 All ex;imiiiatioii of the values of tlie inteusity giveu in the last coluiiiii shows many iiregu- laiities. This is not due to the effect of passing clouds, as in the former methods, for the thermom- eters recover quickly their former condition after the clouds have passed, but to changes in the velocity of the wind. The method is confessedly approximate, since the least increase in the force of the wind which blows on the bulbs, or the least decrease, changes the effect of convection and so produces discordancies in the observations. The values obtained ai'e therefore more of interest for comparison than for their intrinsic merit. 4. COMPAEiaON OF THE KELATIYE INTENSITIES. It remains to make a comparison between the intensities obtained by the three methods in use. For this purpose they must be reduced to a common scale. The intensity at 12.00 on May 1 78 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. has beeu talven as 1, aud the intensities at otlier times divided by tlie intensities given by each method at the chosen time. lu the first two methods the relative values are less than 1, because the intensities at 12.00 on May 1 are the highest observed (with one or two exceptions) ; but in the last method there are values greater than 1, because this is not the case. The relatively small value at 12.00 on May 1 seems to be due to accidental conditions. The following table contains the relative intensities by the three methods : Comxi<(rison of relative intensities by the three methods. APRIL 28. Time. CODJ. Violle's Ordinary therius. bulbs. therms. A. M. 9.00 0.86 0.78 0.70 9.30 0. 85 0.78 0.95 i 9.35 0.86 0.80 0.88 ( 10.00 0.85 (1. 82 1.01 10.30 0.85 0.88 0.83 10.35 0.85 0.83 0.91 11.00 0.87 0.90 0.91 11.30 0.85 0.84 0.79 12.00 0.91 0.92 0.98 p. M. 12. 30 0.94 1.03 1.02 1.00 0.86 0. 95 0.90 1.30 0.81 0.96 0.87 APRIL 30. A. M. 11.00 1.00 0.82 1.20 11.30 0.98 0.84 0.95 11.45 0.98 0.84 1.19 12.00 0.98 0.86 1.21 p. M. 12.15 0.97 0.88 1.19 3.00 0. 82 0.76 0.71 3.30 0.76 0.75 0.77 4.00 0. 70 0.64 0.79 4.30 0.61 0.46 0.66 5.00 0.47 0.51 MAY 1. A. M. 7.00 0. 45 0. 39 0.60 7.15 0.53 0.42 0.66 7.30 0.62 0.61 0.54 8.30 0. 70 0.74 0.70 8.45 0. 79 0. 7:> 0.77 9.00 0.78 0.74 0.79 9. 30 0.84 0.80 0. 83 10.00 0. 86 0.82 0.93 10.30 0. 01 0.86 0.91 11.00 0. 96 0.94 1.04 12.00 1.00 1.00 1.00 p. M. 1.00 0.94 0.95 1.07 2.00 0. 93 0.97 1.09 3.00 0.82 0. 92 0.92 3.40 0.73 0.78 0.82 SOLAE ECLIPSE, MAY (i, 1883. 79 Comparison of relative intensities hy the three methods — Continued. MAY 2. Time. Conj. Violle's Ordiuarj' therms. bulbs. therms. A. M. 7.00 0.45 0.36 0. 36 7.40 0.61 0.55 0. 44 8.00 0.73 0.68 0.60 8.30 0.65 0.60 0.80 9.00 0.82 0.72 0.93 10.00 0.91 0. 90 1. 00 10.30 0.93 0.84 0.83 10. 45 0.95 0.87 1.02 11. 00 0.97 0.90 1. 05 > 11.15 0.98 0. 95 1. 07 1 11.30 0.99 0.93 1.21 12.00 0.98 0.91 0.98 p. M. 12.30 0.99 0.82 1.05 1.00 0.97 0.96 1.20 2.00 0.90 1.01 1.06 2.30 0.84 0.95 0.91 3.00 0.95 0.96 1.04 3.30 0.84 0.82 1.01 4.00 0.78 0.80 0.95 4.30 0.66 0.60 0.94 4.45 0.58 0.52 0.62 5.00 0. 51 0.46 0.53 MAY 3. MAY 6. A. M. 10.30 0.90 0.86 0.93 11.00 0.98 0.88 0.S9 11.30 0.98 0.89 1.03 12.00 0.98 0.90 0.97 P. M. 12. 30 0.97 0.92 1. 05 1.00 0.95 0.95 1.09 1.30 0.96 0.92 1.01 2.00 0.92 ■ 0. 88 1.04 2.30 0.87 0.85 0.89 P. M. 1.15 0.85 0.69 0.72 1.30 0.84 0.66 0.79 2.00 0.77 0.64 0.74 3.00 0.84 0.65 0.70 3.15 0.81 0.57 0.66 The above table shows phiinly the effect of temporary influences in modifying the observed intensities, and also that the different instruments are differently affected by the same influences. In order to eliminate the ac(;iden1al i)eculiarities and obtain a more reliable comparison of the methods the following table has been computed. It combines the observations made at the same hour on the different days, and uses tho.se times only at which observations on two or more days were made. 80 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. Mean relative intensities observed at the same Jionr on two or more (l((ys by the three methods. \ Hour. Conj. Violle's Ordinary therms. bulbs. therins. A. M. 7.00 0.45 0.38 0.48 8.30 0.68 0.67 0. 75 9.00 0.82 0.75 0.81 9.30 0.84 0.79 0.89 10.00 0.87 0.85 ■ 0.98 10.30 0.90 0.86 0.88 11.00 0.96 0.89 1.02 11.30 0.9.5 0.88 1.00 12. 00 0.97 0.92 1. 03 1 P. M. 12.30 0.97 0.92 1.04 1.00 0.93 0.95 1.06 1.30 0.88 0.94 0.94 2.00 0.92 0.95 1.06 2.30 0.86 0.90 0.90 3.00 0.86 0.88 0.89 3.30 0.80 0.78 0.89 4.00 0.74 0.72 0.87 4.30 0.64 0.53 0.80 The accompanyiDg chart represents graphically the values given in the above table. The full curve corresponds to the intensities given by the conjugate thermometers, the dotted curve to those given by V^iolle's bulbs, the broken curve to those giveu by the ordinary black and bright thermometers. The original values by which the curves wei'e drawn are represented by 0, •, and +, respectively. 5. SUMMARY OF RESULTS. The discussion given in the preceding pages has given us values of the solar intensities on the days of observation by three different methods. It has thus furnished incidentally a means of comparisou of the methods, in so far as the observations themselves allow this to be done. The uncertainties arising from the state of the sky have already been mentioned ; their effect is shown in the discordances which the results at different hours on the same day exhibit. By including favorable times only, the tables showing the relative intensities by the different methods rei^resent fairly the results obtained under the best conditions during the series of observations. The following summary gives the conclusions derived from an examination of the results : 1. The method of the black and bright bulb thermometers freely exposed in the air gives only an ajiproximate determination of the solar intensity. This was expected, and is due to the constantly varying conditions of exposure, caused by the effect of the winds on convection currents. 2. Violle's, bulbs are affected by convection, but the effect is shown less than in freely exposed thermometers, on account of the i)osition of the thermometer.s within. The observation.s on the afternoon of May 2, when the air was almost perfectly still, show higher intensities than tlie corresponding times on other days, but the observations are not sufficient to indicate how much the results are intluenced by this cause. 3. The intensities by the conjugate thermometers seem also to be affected bj' the varying influence of convection, but in this case (and in the preceding also) direct experiments would give more information as to this effect than any examination of these observations. 4. The intensities by Violle's bulbs (see the curves) are smaller in the morning and greater in the afternoon than tho.se by the conjugate thermometers. There is a marked difference rig. 13. CHART OF RELATIVE INTENSITIES. 1 1 1 A.M. \TLtTU! of OhservatiorL \ P.M. | 8.00 SOO 10 00 ll.OO 12.00 T.OO 2.00 3.00 1 1 700 ReZattue. —120 •^ 4.00 J.OO - + + t, • + ^ '*" "^ ^^ ^' "-'•^ '1.00 ~O.S0 .//° .'"''' '\.'^^^^ ^ ^'^^ - / 4 ,' . e \ \- \ ' /o -'' \ ^ '^ +- ' / ^' ' ® ^\ ® ^\ /' -0.80 ///' \ L \ / / / +' / f f / / \ \ 0.70 / / / \ \ \ \ ^ \ \ \ \ © \ \ -0.60 1 1 / 1 1 1 1 1 1 1 1 1 1 ' 1 \ \ \ \ \ \ \ \ \ \ \ \ —O.oO 1 / * VhiIIp'a liiilhq ._-_ ___- \ \ f / / / / / / / / / / V IV'llU M UUlltH. _ — - — — _ — — _ — lihick ami bright bulbs. \ \ \ \ \ \ \ \ -o.40; \ 1 - i 1 1 1 1 1 1 1 1 1 1 SOLAR ECLirSE, MAY 6, 1883. 81 ill (lie times of the inaxiiiiiiin readings, the Violle bulbs reaching the niaxiinuiu one hour hiter than the conjugate theriiioiiieters. This shows that the former are sluggish in their action, and at any given time show the intensity not for that time but for a time already past by many minutes. The sluggishness of the Violle bulbs was also indicated by the long time which was required after the passage of a cloud before their return to a normal condition. 5. The curve corresponding to the intensities given by the conjugate thermometers represents the relative solar intensities as accurately as the observations permit for the period April 28 to May 3. It is impossible to give any mathematical estimate of the uncertainty of the numerical values which would be obtained from this curve. It is probable that the values are liable to an uncertainty of several hundredths, but not as great as a tenth. They may' be accepted as the final values of the relative solar intensity obtained at Caroline Island. Expressed in terms of the 12.00 value they are as follows: Relative solar intensity at Caroline Island, April 28 to May 3, 1883. Time. luteDsity. Time. Intensity. Time. Intensity. A. M. A. M. • p. M. 7.00 0.47 10.30 0.94 2.00 0.9S 7.30 0.57 11.00 0.97 2.30 0.90 8.00 0.66 11.30 0.99 3.00 0.87 8.30 0.73 12.00 1.00 3.30 0.82 9.00 0.80 p. M. 4.00 0.76 9.30 0.87 12.30 1.00 4.30 0.66 10.00 0.91 : 1.00 0.98 5.00 0.46 1.30 0.96 6. DETERMINATION OF TEE SOLAR CONSTANT. The investigation upon the theory of the conjugate thermometers made by Prof. William Feerel (Professional Papers of the U. S. Signal Service, No. XIII) contains formulfe for the derivation of the solar constant from the solar intensities given by the observations. Adopting his notation, and referring to the Professional Paper itself for an explanation of the method of deriving the formulae, we have the following: Let A = the solar constant,* p = the diathermancy constant, I = the solar intensity at any given hour of the day, Ai,ih ly = assumed values of the above, SA, Spi dl — the corrections to the assumed values. Then— (1) A = Ai + dA (2) P = Pi+ Sp (3) I = Ii + Sl Let £ = the thickness of the atmosphere through which the sun's rays pass (e = 1 when sun is in zenith). Then — (4) I,= A,(i;i' + 0.025fc^j>r^) (5) SI=pi'3A + Aiepi('-'^Sp • The solar constant iu Professor Fekrel's investigation is the amount of heat received on a square centimetre of snrface at the upper limits of the atmosphere, exjiressed in calories. The calorie is the amount of heat necessary to raise the temperature of one gramme of water 1° centigrade. By these definitions the constant = 2 j^ a decimal. S. Mis. 110 11 82 MEMOIRS OF THE NATIONAL ACADEMY OP SCIENCES. If 2^ is not constant during the day then dp + t S'p must be substituted for Sj) in the hist equation. In § 1 there have been given values of the solar intensities obtained from the readings of the conjugate thermometers. These, after the rejection of a few discordant observations, were used in the above formulae for deriving values of A and p. The first step in the computation con- sisted in the computation of the values of e for different hours of the day by means of the well- known formuliB — e = sec « cos z = sin jc sin 5 + cos

were then obtained by trial computations with equation (4), using a few of the observations on each day. The following were adopted : J. P- April 28 1.96 0. 859 29 2.18 0.760 30 2.27 0.776 May 1 3.02 0.614 2 2.20 0.805 3 2.20 0.805 With these values^ equation (4) was used to give computed values of I, for comparison with the observed values. The resulting residuals were used in equation (5) to give the corrections SA and 3p by the method of least squares. It was found by the computation that the observa- tions on April 28 were discordant, and also were not of suflicient range to give successful results since they extend from 9.00 a. m. to 1.30 only. Observations taken at early or late hours are necessary to give sufficiently large values of £ for the computation. .It was also found that the assumed values of A and p on April 30, May 1, 2, 3 were not near enough to reduce the residuals satisfactorily. Consequently a second approximation was mnde for these dates, using the values of A and p derived from the first computation for the dates April 30 and May 2, but deriving new trial-values for May 1 and 3. The coefficients ^^i^ and Ai, s^^/^-D were recomputed on the second approximation for greater accuracy. The labor involved in these computations was very great; the results obtained are given in the following tables : Table I. — -Values of A and p at each approximation. April 29 30 May 1 2 3 A. p. Ist approx. Assumed for 2d approx. 2d approx. 1st approx. .^-;^| 2d approx. 1 2.194 2.358 1.983 2.315 2.611 2.358 2.25 2.315 2.40 2. 337 2. 327 8.303 2.576 0.745 0.745 ' 0.751 0.756 0.756 ; 0.737 0.760 0.760 1 0.764 0.665 0 730 1 0.690 SOLAR ECLIPSE, MAY 6, 1883. 83 Table II. — Compariso^i of computed and observed solar intensities, APEIL 2<). Intensities. Residuals (obs. — comp.) Time. Observed. Computed. I. II. III. I. 11. III. A. M. 9.00 1.38 1.45 1 1.38 - _ _ 0.07 0.00 . . - _ 10.00 1.61 1. 55 . 1. 50 . . _ + .06 + .11 .... 11. OC 1.55 1.60 1.55 - - _ .05 .00 .... 11.15 1.60 1.61 1.56 _ - _ .01 + ■ .04 . - - . .11. 30 1.62 1.62 1.57 - - - .00 + .05 - . - . 11.45 1.63 1.62 1.57 ... + .01 + .06 .... 12.00 1.59 1.62 1.57 .03 + .02 . . . - p. M. 12. 15 1.60 1.62 1.57 . . . : .02 + .03 - - . - 12.30 1.59 1.61 1.56 ... 1 .02 + .03 - - . _ 1.30 1.41 1..58 1.52 ... 1 .17 — .11 . . - _ 2.10 1.35 1.53 1.47 .18 — .12 . . . - 2.30 1.33 1..50 1.44 ... .17 — .11 . - - . 3.00 1.40 1.43 1.37 ■ " " 1 ~ .03 + .03 - - - - APRIL 30. MAY 1. A. M. 11.00 1.76 1.71 1.69 1.69 + n.05 + 0.07 + 0.07 11.30 1.73 1.72 1.70 1.71 + .01 + .03 + .02 11.45 1.72 1.72 1.71 1.71 .00 + .01 + .01 12.00 1.72 1.72 1.71 1.71 .00 + .01 + .01 p. M. 12. 16 1.70 1.72 1.71 1.71 — .02 — .01 — .01 3.00 1.44 1.54 1.50 1..50 .10 __ .06 — .06 3.30 1.34 1.45 1.40 1.41 — .11 — .06 — .07 4.00 1.24 1.33 1.26 1.27 — .09 — .02 — .03 4. .30 1.07 1.15 1.02 1.07 — .08 + .05 .00 5.00 0.&2 0.88 0.75 0.78 — , .06 -f .07 + .04 A. M. 7.00 0.80 0.48 0.74 0.77 + 0.32 + 0.06 + 0.03 7.15 0.93 0.67 0.87 0.93 + .26 + .06 .00 7.30 1.09 0.83 0.97 1.05 + .26 + .12 + .04 •8.30 1.23 1.29 1.23 . . . .06 .00 . - 8.45 1.39 1.38 1.27 1.42 + .01 + .12 — .03 •9.00 1.37 1.44 1.31 . . . .07 + .06 . . . - 9.30 1.47 1.56 1.36 1.54 — .09 + .11 — .07 10.00 1.52 1.64 1.40 1.59 — .12 + .12 — .07 10.30 1.60 1.70 1.43 1.62 — .10 + .17 — .02 11.00 1.69 1.74 1.45 1. 65 — .05 + .24 + .04 12.00 1.76 1.77 1.47 1.67 — .01 + .29 + .09 P. M. 1.00 1.65 1.73 1.44 1.64 — .08 + .21 + .01 2.00 1.64 1.63 1.40 1.58 + .01 + .24 + .06 ' Rejected on second approximation. 84 MEMOIRS OF THE NATIONAL ACADEMY OP SUIENCES. Table II. — Comparison of computed and observed solar intensities — Continued. MAY 2. Intensities. Residuals (obs.— comp.) Time. Computed. Observed. I. II. III. I. II. III. A. M. 7.00 0.79 1.06 0.88 0.89 — 0.27 — 0.09 — 0.10 7.40 1.08 1.33 1.21 1.22 — .25 — .13 — .14 8.00 1.28 1.42 1.32 1.32 — .14 — .04 — .04 10.00 1.61 1.68 1.64 1.64 — .07 — .03 — .03 10.30 1.64 1.71 1.68 1.68 — .07 — .04 — .04 10.45 1.68 1.72 1.69 1.69 , — .04 — .01 — .01 11.00 1.70 1.72 1.70 1.70 _ .01 .00 .00 11.15 1.73 1.73 1.71 1.71 .00 + .02 + .02 11.30 1.75 1.73 1.71 1.71 + .02 + .04 + .04 12.00 1.73 1.74 1.72 1.72 .01 + -01 + .01 p. M. 12.30 1.74 1.73 1.71 1.71 + .01 + .03 + .03 1.00 1.71 1.72 1.70 1.70 .01 + .01 + .01 2.00 1.58 1.67 1.63 1.64 - 09 — .05 — .06 2.30 1.48 1.63 1.59 1.59 .15 — .13 — .11 3.00 1.68 1.58 1..52 1.52 + .10 + .16 + .16 3.30 1.48 1.50 1.42 1.42 .02 + .06 + .06 4.00 1.37 1.40 1.29 1.30 — .03 + .08 + .07 4.30 1.17 1.24 1.09 1.10 — .07 + .08 + .07 5.00 0.90 1.00 0.80 0.82 — .10 + .10 + .08 MAY 3. A. M. 10.30 1.58 1.70 1.61 1.66 — 0.12 0.03 — 0.08 11.00 1.72 1.72 1.64 1.69 .00 + .08 + .03 11.30 1.73 1.73 1.66 1.71 .00 + .07 + .02 12.00 1.73 1.73 1.67 1.71 .00 + .06 + .02 P. M. 12.30 1.71 1.73 1.66 1.71 - .02 + .05 .00 1.00 1.68 1.72 1.64 1.68 - .04 + .04 .00 1.30 1.69 1.70 1.60 1.65 — .01 + .09 + .04 2.00 1.62 1.67 1.55 1.61 - .05 + .07 4- .01 2.30 1.53 1.63 1.48 1.54 - .10 + .05 — .01 In the above table the columns I, II, III of intensities and residuals refer to the first com- putation, with the assumed values of A and p, the result of the first approximation, and the result of the second approximation respectively. An examination of the last column of residuals shows how nearly the second approximation represents the original observations. There are a few large residuals, but on the whole the agreement is very satisfactory. The resulting values of the solar constant have been given in Table I, and show excellent agreement. Collecting them here, with the interval of time covered by the observations on each day, we have the following results : SOLAR CONSTANT. Date. Interval. A. April 29 30 May 1 2 3 9.00 a. m. to 3. 00 p. m. 11. 00 a. ra. to 5. 00 p. m. 7.00 a. ra. to 2. 00 p. m. 7. 00 a. ra. to 5. 00 p. ra. 10. 30 a. m. to 2. 30 p. m. 2.194 2.337 2.327 2. 303 2.576 Mean of all, 2.347. Mean of April 30 to May 2, 2.322. SOLAR ECLIPSE, MAY 6, 1883. 85 The corresponding values of p are 0.735 and"t).751, respectively. Early morning and evening observations are wanting on April 29 and May 3, and wben this is the case values of A between 2.2 and 2.0 will satisfy the observations with nearly equal accuracy. It seemed best, therefore, to adopt for the final value that obtaiue;ible of liigh polisli, No. 8." MALTACEtE. Sida fallax, Walp., Eel. Meyen., 306. '' Only one specimen found, No. G." SlMARUBE^. Suriana maritima, L., Spec, 284. Passiflore^. Carica papaya, L., Sp., 1466. Cultivated for its fruit. *{Gucurbita pepo., L., Spec, 1435.) Recosfuized iu cultivation. Cucurbitace^. KtJBIACEiE. *Morinda citrifolia, L., Spec, 250, " Height of tree, 15-20 feet ; branches low ; No. 1." BORAGINE^. *Gordia subcordata, Lam., 111., 1899. "Tree, soft, high; lower branches touching the ground." *Tournefortia argentea, L. lil., Suppl., 133. " Eight feet high, clumpy, light green." * Hcliotropium anomalum, Hook, and Arn., Bot. Beech. Voy., 66. " Six inches to 18 inches iu height ; flowers white ; No. 3." SCROPHULARINE^. *Busselia juncea, Zncc, Flora, 1832, II., Beibl., p. 99. " One specimen only. Ground, and over tree stumps ; No. 2." A native of Mexico, probably introduced for its flowers, as it is widely cultivated. Nyctagine^. *Boerhaavia, Sp. ? "Vine creeping over ground and coral rock; leaves light green." Represented by a frag- meut which does not admit of further identification. *risoma grandis, R. Br., Prodr., 422. " A large tree, 40 or 50 feet high, with a trunk 4 feet in diameter." Chenopodiaceje. *Boussingaultia baselloides, H. B. K., Nov. Gen. et Spec, VII., 194. "Vine climbing over portico." EXJPHORBIACE^. * Euphorbia piluUJcra, L., Amoen. Acad., III., 114. *PhyUanthus Niruri, L., Spec. PI., 1392, Drticaoe^. *Ficus carica, L. Cultivated for its fruit. Fleurya ruderalis, Gaud., Voy. Urania, 497. S. Mis. 110 12 90 MEMOIES OV TUE NATIONAL ACADEMY OE SCIENCES. Bromeliace^, * Ananas sativa, Schult., Syst. "Veg., VII., 1283. Kecoguized in cultivation. Palm:^. *{Cocos nucifera, L., Flor. Zeyl., 391.) Eecognized in cultivation. Pandaneje. {Pandanus, Sp.) No specimens were collected, but I learn from the notes of the collector, and from Professor HoLDEN, that one or more of the screw pines were found growing in various parts of the island. Geamineje. * ? Panicum [Digitaria) marginata, Lk. ? Apparently identical with No. 6 of Wilkes Expl. Exp., from Cape Verde Island, in the Gray herbarium, but in poor condition. *Meimne Indica, Gaertn., Fruct., I., 8. *Eragro8ti8 plumosa, Lk. *Lcpturus repens, E. Br., Prodr., I., 207. FiLICES. *Polypodium phymatodes, L., Mantissa plant., 3G0. Alg^. *IIalimeda triloba, Deng, f One specimen collected by Mr. Upton. FuNai. * Olwosjwriuin GalophyUi, n. sp. On fruit of Calopliyllum inopliyllum, L. Spores unicellular, elliptical or oblong, straight or somewhat curved, obtuse at both ends ; coarsely granular or with a few large oil globules; 4x18 /j, oozing out in salmon-colored masses." 4 fi. NOTES ON THE ZOOLOGY OF CAROLINE ISLAND BY DR. DIXON, U. S. N. The following notes on the zoology of the island were furnished by Dr. Dixon. "Although remotely situated and rarely visited by man, these insignificant points of land — mere dots upon the bosom of the broad Pacific — are, in some particulars, well stocked with rei)resenta- tives of the animal kingdom. They cover a wide I'ange in class, order, genus, and species. An enormous number of birds occupy several of the islets; and being devoid of fear, or perhaps ignorant of human enemies, a few of them permitted handling without an effort on their part to escape until after their capture had been effected. While nature has been lavish in the bestowal of gorgeous colors to almost everything about these coral formations, yet the plumage of the birds is renuirkably plain. The members of the feathery tribe, covering a small scope, may be classified thus : Order : Orallatores : Plover. Heron (probably Ardeajugularis, two varieties, brown and white.) Curlew. Snipe. Order : Longipennes : Seagull, two species. Terns, two species (one with all the feathers white, and the noddy.) SOLAR ECLIPSE, MAY C, 1883. 91 Oeder : fotipalmes : Gaunet. Booby. Frigate bird. There were great numbers of the frigate bird on several of the islets ; and there appeared to be two distinct varieties, one with a large red ponch, the throat being white. The pouch could be wrinkled to a very small size. One, with pouch, was seen to swoop down from a high tree, in which were numerous nests, to the lagoon, make three distinct scoops in water and then return homewards with pouch enlarged. Professor Holden reports hearing the notes of a singing bird, but he did not see the bird. The insects are numerous, but cover a limited range. Order : Coleoptera : Beetle. Weevil. Order: Orthoptera: Cockroach. Croton bug. The Eclipse Expedition is probably responsible for adding at least one member to the insect family, for many croton bugs appeared when stores and instruments were impacked. House cricket. Grasshopper. Order : Hymenoptera : Ants, two varieties, and very numerous. Order : Lcpidoptera : Butterfly, a dozen or more varieties. A collection of the butterflies was made by M. Palisa and presented to Professor Holden.* Moth, several species and very numerous. Order : Homoptera : Plant lice. Order : Biptera : Gnat. Flesh fly. Domestic fly. Very numerous; a small fly; yellowish; very quick in its movements and generally found in the presence of decaying animal matter. The Saurian reptiles have but one representative, the lizard, of which there are three species. The Chelonian reptiles are represented by one family of sea-tortoise or turtle, which, however, is not very numerous. The Arachnidans make also but a single exhibit in the spider, of which there are two species. Contrary to expectations, only one centipede was seen, the giant representative. The brown rat has a foot-hold, but is not numerous. Their nests were made in the cocoa-nut trees, just at the base of the fronds. There must be some connection between color and tropical heat, because even the most contemptible things possess chromatic gifts that make them attractive. Fish are given the most marvellous embellishment, the variety of color combinations being infinite. Not a tint is out of pla<;e, nothing is harsh or strained, and the quiet pools within the outer reef, occupied by living * A memorandum on the butterflies follows this section. — E. S. H. 92 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. gems of blue, gold, silver, and green, make a picture never to be forgotten. Many of the fish are timid, and dart quickly away upon the slightest provocation, while others appear indilferent to capture, and may be easily caught with the hand. The basins and indentations of the outer reef afford safe retreats for many wonderful forms that live in these warm seas. A view of such a grotto, with its growing coral and brilliant and gaudy fish, fully confirms the praise bestowed by nearly all visitors to these South Sea Islands. Even the shark, eel, gar-fish, and other common forms have their charming gifts, only in less degree than the chaitodou and parrot-fish. The coral reef is a field pregnant with life, and offering the most beautiful and curious forms imaginable for observation and study. Detached pieces of coral form the hiding places of hosts of small fish, crabs, shrimps, star-fish, mollusks, etc., and myriads of microscopic beings. The following list is only a partial inventory of the different forms observed : EcMnoderms : Brittle stars {opMurida;), several varieties. r sun star. Star-fish (Asteridw) \ cross fish. I knotty cushion star. Sea urchins (echini), six varieties. Sea cucumbers (holothuriw), three varieties. Crustaceans : Ordek: Decapoda: Sea crayfish. Shrimp. Racer crab (Ocypoda). Land crab (gecarcinus). Hermit crab, three species, which occupied eight varieties of moUusk shells. Their number is enormous. They were found even near the tops of small trees, whither they had gone carrying a shell of several times their own weight. Of the Cephalopods the only one seen belonged to the family of the Octopodidae, the eight- armed cuttle. Although the habitat of many varieties of mollusks, we had not the facilities for procuring many of their shells, and some seen could not be identified. The following list, therefore, is not a complete one : Sea trumpet (Triton). Frog shell (Eanella). Spindle shell (Fusus). Spotted needle shell (Terebra). Cowrie (Cyprseidae), eight varieties. Common top shell (Trochus). Pinna (Pinna). Scallop (Pecter), several varieties. Cui) and saucer limpet (Calyptnea). Clams (Tridacuidto), and others. Stromb shells (Strombus), several varieties. Whelks, volutes, etc." MEMORANDUM OF THE BUTTERB^LIES, ETC., OF CAROLINE ISLAND. (Collectiou by Dr. Palisa; iilontifications liy Dr. AuTiiUK BuiXEii auil Mr. Hermann Strecker.) Dr. Palisa, of the French expedition, made a complete collection of the lepidoptera of the island, which he has taken to Vienna for identification. At my request, he was kind enough to make as comiilete a collectiou as was possible of duplicates, which were presented to us. This SOLAR ECLIPSE, MAY 6, 1883. 93 latter collectiou contained thirteen specimens, and throngh the kindness of my colleague. Professor Owen, of tbe University of Wisconsin, it was submitted to Dr. Hermann Strecker, of Heading, Pennsylvania. Dr. Strecker was prevented from making a careful study of tiie collection, and returned it with the identification of five specimens, viz : 1 Utethesia palchella, L. 4 Diademu bolina, 3 5,19. One of the latter (a male) and the other eight specimens were sent by me to Dr. Arthur (K Butler, assistant keeper of the zoological department of the British Museum. The remaining four were presented to Professor Owen's collection. Dr. Butler kindly undertook the identification of the nine specimens sent him, and his report on the subject follows. These specimens are now in the collectiou of the British Museum. It will be seen that Dr. Streckbr's Diadema bolina has been made a new species by Dr. Butler, who has also found in this small collection three other new species, one representing a new genus. I desire to express here the thanks of the expedition to these gentlemen for their kindly interest, and especially to Dr. Butler for his full report, which follows : THE LEPIDOPIERA COLLECTED ISY HERR I'ALISA AT CAROLINE ISLAND IN IIAT, 1883. By Arthur G. Butlkr, assistant keeper of the zoological tlepartmeiit, British Museum. "The collection contains one butterfly of the family Nymplmlidm ; the moths are represented by a new species of Maeroglossa, three species of NocUue, and sexes of one species of Pyrales. butterflies. Nymphalidji;. Hypolimnas Roldeni. sp. n.'(No. Gl). 7 Per cent. 0. 220 0. 220 0. 220 0. 203 Per cent. 0. 219 0.236 0. 2-.il 0.218 "Very re.spectfully, - " STILLW ELL & GLADDING. "Mr. WiNSLOW Upton, Washington. T). C." Mr. Upton has kindly forwarded this note, with the following niemorandinn: "The analysis was liniited to the fonr principal constituents on account of the small quantity ot water available. It will he seen that the essential ditt'erence between the analysis and the others given is the amount of chlorine, which was estimated twice by very careful du]dicate analyses. Tlie lagoon water is more like that from the Irish Channel than like ocean water; that is, it is slightly /)e.s/(e>-. Since the lagoon has free outlets it is presumable that a similar analysis would have resulted from water taken from the ocean in the vicinity." v.— OBSERVATIONS OF L'3 NEW DOUBLE STARS BY MESSRS. HOLDEN AND HASTINGS. During our stay on the island Dr. Hastings and myself spent two or three hours of each clear night (with a few exceptions) in examining the southern sky, which is tilled with objects of great interest to an observer who has only seen the stars visible from northern latitudes. In the course of this examination the following list of 23 new double and ."> new red stars was found. Our days were usually full of work, and more time was not spent in the observatories at night as it wa.'? impossible to liave a quiet sleep in the day-time, owing to our contracted quarters. It is clear, however, from this short list, that a stay of a year or two in the southern hemi- sphere would yield a rich retui-n to an observer who went proiterly equipped. Probably Quito or Santiago de Chili would be the most eligible station. During the voyage from Callao to Caroline Island, and from the island to Honolulu, Mr. Upton made a number of observations of variable stars, which will be communicated by him to the Harvard College Observatory. S. Mis. 110 13 98 MEMOIES OF THE NATIONAL ACADEMY OF SCIENCES. Lifit of 23 new double .stars discovered at Caroline Island betivcen Ajyril 27 and May 7, 1883, hij E. S. HoLDEN and C. S. Hastings. Star. a 1880.0. 5 1880.0. P- B. Mags. Observer. Date, 1383. Stone 5791 A. m. 8. 10 28 35 o ' — 54 46 o 250 II 2 8.5—9 HOLDEN. May 1. Anon. 11 31 28 — 60 14 350 H 8. 5— 9. 5 HOLDEN. April 28. Lac. 49.36 11 48 58 — 55 25 230 2 7.5— 8 HOLDEN. May 1. Anon. 11 57 40 — 57 5 240 H 8. 5— 9. 5 HOLDEN. May 4. • Lac. 5223 12 31 24 — .'^5 16 205 u 7. 3— 9. 3 HOLDEN. May 1. Anon. 13 1 16 — 52 5 200 li 9. 5— 9. 5 HOLDEN. May 4. Lac. 5434 13 6 59 — 62 57 40 i-i 7. 5—10 HOI.DEN. May 6. S 348 \ 290 1 5—6 Russell No. 227. Mav 2 A. B. Lac. 5738 13 48 28 — 53 33 25 6. 5—13 HOLDEN. May 2A.C. Lac. 5817 13 59 56 — 49 18 30 t 7,5— 7.5 Hastings. May I. Lac. 5844 14 6 14 — 61 9 180 34 7—9 Hastings. May 2. Lac. 6066 14 41 16 — 72 42 90 14 6—8 Hastings. May 2. Lac. 6136 14 50 35 — 67 30 0 5 7 —10 Hastings. April 27. Auou. 15 2 18 — 40 31 70 4 7—8 Hastings. May 4. Stone 8250 15 3 33 — .51 38 220 3 7.5— 9 HOLDEN. May 2. Lac. 6259 15 6 36 — 60 27 300 12 6. 5—13 Hastings. April 27. Anon. 15 7 20 — 68 8 0 n 7.5— 9 Hastings. May 2. Anon. 15 8 40 — .53 50 170 3 8 —10 Hastings. May 1. Stone 8348 15 14 18 — 47 29 225 14 8. 0— 8. 5 Hastings. May 1. £ Lupi 15 14 32 — 44 15 175 * 3—6 Hastings. Apfil 27. 1 Lac. 6488 15 36 11 — 50 24 alO 2 7-9 HOLDEN. May 4. Lac. 6540 15 44 44 — 60 23 85 1 6.5—9 Hastings. MaV 2. Stone 9221 16 50 15 — 56 25 125 2 7.5—10 HOLDEN. May 7. Lac. 7315 17 23 16 — 40 57 95 1 8. 0— 8. 5 HOLDEN. May 7. List of 5 neiD colored stars discovered at Caroline Island by E. S. Holden. Star. a 1880. 5 1880. Remarks. Stoue's mag. Lac. 5384 Anon. d Apodis. Lac. 7152 Lac. 7638 II. VI. s. 12 58 2S 13 10 24 13 53 41 17 4 5 18 12 10 o ' — 51 28 — 63 57 — 76 13 — 56 44 — 61 33 Reddisli ; 7. 5 magnitnde. Brick-red; 7. 7 magnitude. Kiiie orange red ; 5 magnitude. Red ; 7. 0 uiaguitude. Orange red ; 6. 0 magnitude. 6 5 6 5.4 It will be observed that my estimates of magnitude are in general about one magnitude smaller than Stoue's. The latter are to be preferred, as I was not familiar with the appearance of stars in the G-iuch telescope. VI.— PLANS FOR WORK ON THE DAY OF THE ECLIPSE, ETC. (By Prof. E. S. Holden.) General instructions as to the plan of work were given to me by the committee of the National Academy of Sciences, but the details of carrying out their intentions were left to me. It is my opinion that the very short time of the totality of a solar eclipse should be utilized by any one observer iu making a single observation, or at least a single kind of observation. The time, even of the longest totality, is all too short, and if it is further diminished by the times required to move from one instrument to another, or to change apparatus, the real value of the observations which are made is seriously lessened. It was, therefore, my effort to assign to each observer one single piece of work, which he could reasonably hope to accomplish, so that his re- sults would have a perfectly defiuite meaning. SOLAR ECLIPSE, MAY (i, 188,}. 99 I very much regret that the excellent photographic apparatus constructed under the direction of Prof. W. Hakkness, (J. S. N., for the Naval Oliscrvatory, was not utilized 0:1 this expedition. From the results obtained with it in 1878, even before its moditication into its present form, I have no doubt but that observations of great value could have been secured. As it was, the entire field of iihotography was left to the English party wliich accompaTiied our own, and I must refer to the memorandum of Mr. Lawbance, which accompanies this rei>ort, for a preliminary account of their preparations and valuable results. Photography of the corona, etc., was also employed in a very successful way by the French expedition under M. Janssen. The plan of the American party proper- comprehended — (A.) A search for the interior planet (or planets) Vulcan, reported by Professor Watson and also by J'rofessor Swift. This was assigned by your committee to me. (B.) Spectroscopic observations of the inner and outer corona. This was undertaken by four observers, namely Dr. Hastings, Mi-. Kockwell, Mr. TJi'Ton, and Ensign Brown. The general plan of the specti-oscopic and polariscopic observations was discussed by Dr. Hastings and myself with the other observers, but the entire credit for the details of the observations belongs to Dr. Hastings and to the observers themselves who were placed under his directions. (C.) Polariscopic observations of the corona. At my request Dr. Hastings brought with him the polariscope which he used at the eclipse of 1878, for the purpose of attaching it to one of the spare telescopes of the party, and it was my hope that a satisfactory set of observations might be obtained, especially because the observa- tions with this instrument in 1878 had led to the conclusion of tangential polarization. Mr. Preston was placed under the exclusive direction of Dr. Hastings for this duty, his observations to be made during that i^art of totality after his observations of the time of second contact and before his observation of third contact. The telescope was pointed by Midshipman Doyle, and during totality Mr. Preston made 11- pointings. When these were reduced they showed that the apparatus itself, /. e., the c )mbination of the telescope and the polariscope, was not suitable to its object, as a subseriueiit examination convinced Dr. Hastings and myself. I regret that this should not have been found out before- hand, so that the services of such a competent observer as Mr. Preston might have been utilized. The observations are not here printed. (D.) Telescopic examination of the details of the inner corona. This was made by Dr. W. S. Dixon, U. S. JST., with the 3.i-inch Clark telescope lent to us by the Nautical Almanac office. A drawing of the corona with a descriptiou is given in Dr. Dixon's report. (E.) Observation of the contacts. The^rs^ contact was observed by Messrs. Upton, Preston, and Brown. The second by Mr. Preston. The third by Mr. Preston. The fourth by Messrs. Holden, Rockwell, Upton, Presion, and Brown. The observation of the contacts was made entirely subordinate to more important work. (F.) The determination of the latitude. This was determined on four nights by IG pairs of stars, by Talcott's method, by Messrs. Preston and Brown. Mr. Upton also determined a preliminary value with the sextant. ^G.) The determination of the longitude. 100 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. Ist. By transport of cbronoincters. Five chronometers were carried hy the expedition from New York to San Francisco, and kept running constiintly. These were in cliar • * • • / \ / / \ 1 • • • * / \ « 1 / /• > • / • • • • 1 • • • • • / • • 1 • / • ./ • / • ■ / 1 • • • • / • / • • J / • • 1 • / • • • • • • • • • • • • / 1 / • • • • • • i •— • • • • • • /• • • • • « • • * • < • • Us, A 1 / 1 — « • • • •• » • •• ■/ / • «• • / / \ \ • • / • z • < • (/I J &< SOLAR ECLIPSE, MAY 6, 1883. 101 power of 44 (liaiiieter.s and a Held ol' view 54' (in declination) l)y -'.'57** (in riyiit aseensiim). Tliis ina{>iiifyin<;' power ntilizestlie whole apertnre of the ohjecitivc. I i)iepaied a map of tlie planets and stars in the nei};'hl>orlio(i(l of tlic sun on May <>, wlii(^ii was iiublislicd in Science No. 3, for February -3, 1883. I arranged my i)laii of observation so that 1 coidd make sweeps in right ascension, each sweep being about .54' wide in declination. To tiiis end 1 memorized all the stars in each sweep iu order and in magnilndii. Some of the sweeps were longer than others, so that the ecliptic and its neighborh(jod siioiild be covered without wasting time. In order that theeutire time of the totality nnght be available lor tlie search, I did not observe the second and third contacts; and 1 did not observe the first contact, as tiiis ol>servation would have made it necessary to take otf my /.one eye-i>iece and thus to lose the adjustment for parallel and focus 1 had made on the night of May 5. I need not describe the mechanical arrixngements 1 had i)rt>vided for detern)ining the |)osition of any object not on my star luaj), since these were not employed. Tlicy were, however, adequate for the purpose. On May (i I began sweeping a few seconds after totality commenced, and swept carefully and deliberately over the space marked on the accomi)anying map without finding any new object. I am positive that uo star as bright as five and a half magnitude could have escaped me. I saw all the sixth magnitude stars within this space except the three nearest the sun. I saw uo seventh magnitude stars anywhere. The star U. M. (19'=, 477), in right a.scensiou 3'' n" 21", and declination + I'J'^ 11, was very bright indeed, and uo star half or even a third as bright coidd have by any possibility escaped observation. This star is of four and two-tenths magnitude ; the same as the brighter of the two plauets reported by Professor Watson iu 1878. At the eclipse of 187S it was a question whether the planet Vidcioi of Le Verrier existed or uo. At the eclipse of that year I searched for such a planet over a space of 320 square degrees and found none. The Vulcan of Le Verrier should have been at least of the third magnitude. My instrumental means were sufiicieut to have detected it had it existed. At the same eclipse Professor Watson reported the existence of two new aud much smaller bodies which he saw with a 4-inch telescope with a magnifying power of 45. Professor Swift also reported the existence of two different (aud uew) bodies. > At the present eclipse I looked for these with a maguifyiug power purposely chosen the same as Professor Watson's, and with aii objective giving more than twice the light of a 4-inch. No such new bodies existed within the space marked on the map. It is my opinion, therefore, that at future eclipses it will not be necessary to devote an observer and a telescope to the further pros- ecutiou of this search, and I must regard the fact of the nou-existeuce of Vulcan as definitively settled by Dr. Palisa's observations aud my own. CONTACTS. I observed the fourth contact with an aperture of (i inches, power 57, at 4'' 0'" 34^8 of chronometer 1536 Negus. Its correction to Caroline Island sidereal time was + 1'" 5"J».5; so "hat the fourth contact occurred for me at 4'' 8"' 34'.3 Caroline sidereal time = 1'' 10" 43' .8 Caroline mean time. OBSERVATION OF THE UIFFRACTION-BANUS BEFORE AND AFTER THE TOTAL PHASE. I had a white tenttly stretched fiat on the ground a few feet south of my observatory, and 1 employed the two carpeuters of our party in observing the direction and the distance apart of the bauds. 102 MEMOIRS OF THE NATIONAL AOAUEMY OF SCIENCES. The seams of the tent were phiiiily visible during the totality; they were 20 inches apart and ran exactly north and south. Carpenter's Mate Charles Emms, of the Hartford, stood near the tent and compared the dis- tance between the centers of two adjacent diifraction-bands with the distance between the seams and with a foot-rule which he held in his hands. He estimated this distance before totality to be 12 indies, and after totality to be IS inches. I have great confidence that the truth lies between these limits. He also estimated the number of bands passing a given line per minute to be SO. From my recollection of the same plieiunuenon in 1878, I should think this estimated number too small. The shadows or bauds lasted about one and one-quarter minutes, both before and after totality. While Emms. was observing the distance apart of the bands. Carpenter Peter Murphy, of the Hartford, observed their direction. This he did by laying a 10-foot pole on the tent in a direction perpendicular to the bands. After he was satisfied with the direction of the pole he marked its position on the tent with a pencil. To avoid mistakes the observations before totality were made on the south side of the tent, and those after on the north side. After the total phase bad passed I laid out an east and west line on the tent and compared the directions of the i^rogress of the shadows with this. Before totality the shadows moved along a line whose azimuth was north 60° east. After totality the shadows moved along a line whose azimuth was 92° northwest. The general direction of motion was west to east before totality and east to west after totality. The radius of the moon's shadow was about G9 miles. The (observed) direction of motion of the bands before totality was about 16^° to the east of the direction of that radius of the moon's shadow which passed through Caroline Island at second contact. The (observed) direction of the bands after totality was only 2° to the west of the radius of the moon's shadow which passed through Caroline Island at third contact. It is possible that the first observations are erroneous by 16°, but I do not regard it as probable. The other scientific work of the expedition is detailed in the following reports. I am, my dear Professor Young, very sincerely yours, EDWARD S. HOLDEN. (b). RFA'OBT OF PliOF C. S. HASTINGS. Prof. E. S. HoLDEN : Dear Sir: The late date at which it was definitively determined that the writer should be a member of the Eclipse Expedition rendered the preparation of the apparatus a laborious as well as a most hurried one. The task would, however, have been far more difficult had not the trust- ees of the Johns Hopkins University generouslj' placed all the facilities of the jihysical laboratory and the services of the university mechanic at my command. Fortunately much useful apparatus was already in my own possession. This, with that lent either by the university or by Mr. Rockwell, one of the members of the party, was all that could be successfully used by the five observers assigned to my instructions. The following is the list of apparatus used, with the essential constants: APPARATUS. 1. rolariscope. — This was the same instrument which the writer used at Central City in 1878 ; it is fully described in the report on that eclipse published by the United States Naval Observatory. Time did not admit of trying the instrument or even of adapting it to its SOLAR ECLIPSE, MAY 0, 18S;5. 103 telescope before our arriviil at the island, bat Mr. Upton took witli liini a small telescope aud its inoiuitiug, which there formed a part of the complete apparatus. After the oljservations on the day of the eclipse it was found that the mounting was too unsteady to admit of the recpiisit** accuracy in pointing, so that, although Mr. Prkston found polarization in all parts of the corona, the angles of polarization were thoroughly discordant. Of the greatest theoretical importance, however, was tlie observation that with greater brightness of the field the Savart's bands were more intense. As the instrument is specially devised for the examination of isolated ]>ortions of the corona, the inference is that the intensity of polarization does not decrease in approaching the moou's limb. 2. Prismatic telescope. — This was composed of a large flint-glass prism of 30° before the ob- jective of a telescope lent by Mr. Rockwell. The essential constants were as follows: Clear ap- perture, 2i inches; apparent length of spectrum (A to H), 32|o ; magnifying power used, 20. The instrument was used by Mr. Upton, aud the results are given in his report. 3. Integrating spectroscope. — The instrument belongs to the writer; its constants are given in the report of Ensign Brown, who observed with it. Tiiere is, however, one novelty in its con- struction which is worthy of notice, because it seems to me better adapted to the end in view than any arrangement before used. The angular aperture of a small telescope lens, such as would be used for a spectroscope col- limator, is rarely less than five or six degrees ; consequently, if such a collimator is directed towards a source of light as small as the suu, only -^ or i\ of the whole aperture is utilized. The ordinary method used for correcting this fault since the eclipse of 1870, when Professor Young employed it for the lirst time, has been to place a small telescope before the slit directed towards the sun. The effect of this addition is obviously to increase the apparent magnitude of the object ; it is also evident that the magnifying power of the auxiliary telescope should be, in tlie case of a total eclipse, about three or four diameters. The only objections to the method are that it requires at least two lenses, aud that the system admits of no range of adjustment. I used a single concave lens in- troduced between the slit and objective of the collimator. It is clear that such a lens would reduce the apparent magnitude of the objective as seen from the slit, ann)i)agation of the liglit. Tlien, for this case _1 1_ 1 u A V ^ a L = F — « + V Thus, in tlie instruiiitMit wliich Mr. Brown used A = 6o and I wished to make A = 2°; moreover, F = 113 inches ; — /= 2 inches. These constants substituted gave u = — 4 inches; r = — L\ inches; L=14[\ inches, and the brightness of the spectrum, with a slit of the same angular width, was three times what it would ha\ c been without the additional lens. It is evident that the apjiaratus admits of large variation; for exami)le, had 1 chosen then I should have had V = — 0 inches; r = — li inches; L=1G:J inches, and the brightness would have been increased four times. I should have ]>referred the latter pro- portions had the tubing at our disposal admitted. 4. 6ratme, but that light from regions to the right and left of the sun, up to a distance determined by the length (in this case 1.5') of the slit or the dimensions of the prism, would so appear; moreover, it is obvious that the spectra formed of the two halves of the slit would be adja- cent. In fact, these two spectra, one that of the region to the right of the sun and the other that of the region to the left, were separated by a narrow black line about as distinct as the G line of the spectrum.. Although all angles of reflection in the prisms were greater than the critical angle, the sides a, b, a', and b' were silvered, to avoid trouble in keeping them clean. It will be recognized that this spectroscope, which was specially devised for the work in view, was most carefully considered in all points so as to be of the highest efficiency, i^or do I see now, after Iiaving used it, how it could be bettered if the same large scale of 1 .6 inches available aperture were not to be surpassed. OBSBEVATIONS. The observations made with all the instruments described, except the last, are given in the in- dividual reports of the observers. Here I shall give my own only, though I shall have occasion to discuss some of the others. A few minutes before the first contact the spectroscope slit was adjusted for parallelism with the utmost care, since the essence of the method was the comparison of two spectra formed by different halves of the slit. xVn ideally more perfect way of eliminating errors due to the slit would be to rotate the spectroscope by ISOo on the axis of collimation of the equatorial at each observation, but as I found no difficulty in so adjusting that it was quite imi>ossible to distinguish a difference in the twohalves of the spectrum with any useful slit- width, I definitively abandoned the inconvenient reversals. After this adjustment the slit was given the maximum width compatible with sharp definition ; that is, the spectrum was made as bright as possible under the limitation that the line D should be just recognizable as double. The group b was of course under these conditions, triple. It was expected that it would be unnecessary to alter this adjustment during the eclipse, and it was so found. A short time before second contact the spectroscope was rotated on the axis of its collimator until the direction of its slit became sensibly normal to the edge of the solar image at the point of second tangency. As I was engaged in this way I noticed on the white card-board which cov- ered the slit-plate a sudden alteration in the aspect of the image by the growth of arcs of light from the cusps of the sun, which quickly joined and formed a complete ring. The phenomenon occurred, as I found from Mr. Fletcher's counting,Jl seconds before totalit\% It is only of scieu. S. Mis. 1 10 14 106 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. tiflc importance as showing that the coioim could have been seen much eailier by employing a more delicate method. Just before second contact 1 put my eye to the spectroscope. The right-hand side of the spectrum, corresponding to the eastern limb of the sun, exhibited a long brilliant line in the place of 1474, extending 10' or 12' from the edge of the sun ; on the other half, however, the line was much fiiinter and not more than 3' or 4' in length. The magnitude of the difference was so great a surprise to me that, although the appearance of the spectrum itself would have betrayed any fault in adjustment, I immediately tested it by giving the equatorial a slight motion east and west. The effect was what I anticipated— the shortening of alternately one and the other at the base, but no other change. I had intended to examine all parts of the corona by rotating the spectroscope gradually through 180° on the axis of collimation, but the phenomenon observed was so important that I at once resohed to leave the spectroscope unchanged and to note the changes due to the moon's motion alone. This exaggerated difference on the opposite sides of the sun lasted but a short time. I observed the rapid equalization, but only made the single eutry in my note-book of equality at 200 seconds after beginning of totality. Just at the beginning of totality I had seen the lines C, D3, F, and near G extremely brilliant, but very short. This was, of course, just at the middle of my spectrum band, along a line extend- ing from red to ^'iolet, and they were confined to that side of the line corresponding to the eastern limb of the sun. It is possible that some or all of these lines extended away from the middle of the band as very faint bright lines, but I could not be sure of the fact after the eclipse from a recollection of the hasty examination which I gave it. At 200 seconds from the beginning, experieuce had showu that all the significant changes could be looked for only in the last few seconds of totality, and, as more than two minutes remained, I set myself to a deliberate examination of the spectrum of the corona exclusive of 1474. That which first struck me was the intensity of the colors: none were too feeble to give a vivid impression of their hues, except perhaps the upper violet, which I ftiil to remember. Not less striking was the marked difl'erence between this spectrum and one equally brilliant of sky- light. Two lines only were seen, the bright 1474 and the dark D line, rather faint. The latter, however, was so distinct that it could hardly liave been regarded as a single line even if unfa- miliar; but the other familiar groups, C, E, h, F, and less certainly G as being much fainter, were wanting. A streakiuess at first suspected in the green was not rendered more probable by subse- quent inspection. This observation was made with the utmost care and deliberation, as I was aware that it differed from the spectroscopic results reported at some former eclipses. I also made a single estimate of the extent to which the coronal line could be traced from the limb of the moon, and found it about 15 minutes of arc. As the end of totality approached I again turned my attention to the 1 474 line. At 280 sec- onds I recorded the line on the left side of the spectrum brighter and on the right side shorter^ that is, the line had now become longer and brighter on the western side. This difference increased until returning sunlight put au end to the observations. At a time estimated as 20 seconds after Mr. Fletcher ceased counting, that is, at 320 seconds from the beginning of totality, I noted C, P3, and F as appearing but very short. I cannot recall seeing the hydrogen line near G. The conclusions to be derived from these observations are interesting. It is obvious that the enormous change in the exteut to which the 1474 line could be traced east and west of the sun, with very slight change of the moon's place, at once precludes the explanation hitherto accepted of a, SOLAR EGLirSE, MAY C, 1883. 107 gaseous atmospliere extemliii*;' as far as implied by the spectroscope. On the other hauil, we can find no explanation in difliision by our own atmosphere, for diffusion was absolutely insensible. Still, as an einineut autliority has suggested that this might be an adequate explanation of the phenomenon, it is well for inc to give categorically the reasons for rejecting it. First. The skj- was extremely clear, aud the moon during the eclipse sensibly black. Of course, if there had been any considerable diffusion, the moon would have looked less dark near the limb. Second. The bright lines of the chromosphere and corona stopped abruptly at the moon's limb, although the diffusion here should have been more sensible than towards the outer corona, because at the place where the change in illumination was most I'apid. It will be recognized that my examination of this point was a careful one, for by it I assured myself of the adjustment of the apparatus in the beginning of the observations. Third. All the photographs taken by the English and French observers showed a sensibly black moon. Fourth. In a photograph of the coronal lines H and K, taken by the English observers, these lines ended abruptly at the moon's edge, although the instrumental diffusion must have been much greater than in mj- own apparatus because thej- made use of a heliostat. Before attempting any explanation of the observed pheuomeno7i, however, it is well to review briefly all that study has taught us concerning the corona, for it is evident that no theory is tenable which is contradicted by any established fact. la this review I shall depend implicitly upon Ran- yard's "Observations made during total solar eclipses, " which forms Vol. XLI of the Memoirs ot the Royal Astronomical Society, and my references will be to the pages of that work. This ad- mirable work, for which students of solar physics owe Mr. Ranyabd a debt of gratitude, includes all useful observations to the eclipse of 1875 inclusive. For those of later date I shall refer to the original publications. GENERAL HETIEW OF THE ItESVLlS OF OBSEETATIOSS ON THE COliONA. I. — Spectroscopic Observations. As we shall find much contradictory evidence in these observations, and many cases of negative evidence even on occasions when definite advances in our knowledge have been made, it is necessary in a general discussion to establish some criterion by which this evidence may be weighted. Un- questionably the best method of determining the relative values of the observations is from the efficiency of the apparatus used in each case. To do this we must first discuss the theory of the spectroscope as applied to such work. This step seems to me advisable, not alone on account of the reason given, but also because the apparatus used is often so badly devised that the theory is evidently not generally known. The frequent description of non-essential constants of the spec- troscopes used when the. essential ones are omi^tted is another proof of inadequate ai)prehension of the optical principles involved. Of the three forms of spectroscope used in corona observations we will discuss, in order, [a] the prismatic telescope; {b) the integrating spectroscope; (c) the analyzing spectroscope. (a) Prismatic telescope. — This consists of a system of prisms or a grating before the objective ot a telescope or the naked eye. The office of the dispersive system is to form a virtual spectrum ot the corona at an infinite distance. This image is to be observed by means of the telescope. It is clear that a high magnifying power is not requisite for observing the coronal ring, since it measures a half degree in its inside diameter; on the other hand, it is equally evident that the image should appear as brilliant as possible. This last condition limits the magnifying power. According to the well-known law governing telescopic vision of a surface, the power for maximum brightness 108 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. should be equivalent to the quotient obtained by dividing the diameter of the object-glass by the diameter of the pupil of the eye. If we assume tlie diameter of the pupil at | of an inch, which cannot be far from the truth unless special precautions have been taken to dilate it, we should choose a power equal to eight times the numerical value of the available aperture in inches. If the coronal light contains an excess of definite wave-lengths, the fact will be indicated by colored images of the corona arranged according to their wavelengths upon an impure spectrum as a back- ground. It is well known that such rings are ordinarily seen corresponding iu place to the lines C, D:i, 1474rK, and F. With a dispersive power less than that of a 60° flint-glass imsm they over- lap; with a much greater power they are distiuct rings. With a high dispersive power, also, the contrast between the rings and the background is increased, at least until the absolute loss of light incident to all highly dispersive apparatus becomes considerable. It is veiy important to observe, however, that the C ring alone is free from admixture. with light of other refraugibilities, and that only on the side farthest removed from the blue end of the spectrum. On the other hand, the green ring, the liTJtK, is least favorably situated for distinctness. We must expect, therefore, to find in such an instrument the C ring relatively much too strong. This peculiarity evidently makes the instrument a defective one for observing the corona; but the defect is partly balanced by its show- ing large surfaces instead of narrow spectral lines, thus enabling the observer to sometimes recog- nize the presence of light of definite wave-lengths, which the ordinary spectroscoiie would fail to re- veal. There are a number of cases on record where just this advantage has been rendered evident. (b) Integrating spectroscope. — This term has been applied to that form of instrameut where the spectrum is that of the sum of all tbe sources from which raj^s passing through the slit fall upon any x>oint of the effective aperture. Bearing iu miud that the effective aperture is determined by the angular dimensions of the source of light, as well as by the linear aperture and focal length of the collimator, the theory does not differ from that of the analyzing spectroscope. The proper ratio of focal length to aperture has been discussed in the description of the instrument used by Ensign Brown. From what I shall prove in the theory of the remaining form of spectroscope, it follows that an integrating spectroscoi)e with large available aperture is far superior for this particular purpose to oue with equivalent dispersive power and smaller lenses. (c) Analyzing spectroscope. — This differs from the instrument just described only in having an additional lens, which forms an image of the source of light upon the slit-plate. This lens is ordi- narily called the " condensing lens." The term is objectionable, not only because it fails to define the function of the lens, but because it is misleading. For example, if we may speak of the " con- densing" power of a lens, it is evidently a measure of the brightness of the image formed by it, and this depends solely upon the angular aperture of the lens. Now, I shall show that the bright- ness of the spectrum in the instrument under discussion is absolutely independent of the angular aperture of the " condensing lens." It follows, then, that the use of the lens is not to " condense" light upon the slit. It seems that a much better name for this lens is one which describes its office at once, namely, " image lens." This name I shall venture to use to replace the old term in the following discussion : Let A — effective aperture of image lens. F = focal length of image lens. a ~ effective apertui'e of collimating lens. /= focal length of collimating lens. d = diameter of pupil of eye. g — quantity of light incident on unit surface of image lens from one minute square of source. SOLAR ECLIPSE, MAY 6, 1883, 109 We see at once that A_a for if this is not so, either some portions of the image lens can never send liglit to any portion of the collimating lens, or some parts of the latter never receive liglit from the image lens; in snch cases either A or a ceases to be the effective aperture. The quantity of light (Q) falling on a minute square of slit, measured from the image lens, is evidently, Q=i^A'^5. To find the quantity falling on a unit surface of the slit we must divide Q by the value of a minute square expressed in area. If we denote this quantity by Q/ we may write The function of the collimating lens is to form a distant vertical image of the slit. The bright- ness of this image may be expressed in the same way as that which we have chosen to exi)ress the brightness of the source, namely, by the quantity of light from a minute square of its area falling upon a unit surface. Let us denote this quantity, which is a measure of the brightness of the image, by q'. Now, we have already obtained an expression for the total quantity of light, Q', falling upon the whole of the collimating lens from a unit area of the slit. To find q', then, we have only to divide Q' by the area of the collimating lens and by the value of a unit area of the slit expressed in minutes square. The first of these divisions is \ -«'-, the second is ^r^, whence O' A'' f- that is to say, the brightness of the image is the same as that of the source, and this perfectly independently of the apertures of the system used. We may arrive at the same couclusion, by a process of reduciio ad ahsurdum, very briefly, thus: Suppose q' less than q, then, since there are no limitations as to the values of F and /, we may make them infinite without change of angular apertures. In this case we have reduced the quan- tity of light by introducing media which are assumed to have no action on light, which is absurd. Again, suppose q' greater than q, then we have simply to regard the image as the source of light in a similar apparatus in which the image will be brighter than ris'm with aperture na as regards con- trast between bright lines, of the same apparent width in each case, and their background. This, however, is not all that we demand in a spectroscope for observing the corona. There are dark lines in the spectrum the width of which does not depend upon the width of the slit, con- sequently their visability does not depend upon the laws which we have just considered. In order to render such lines visible with any dispersive power the slit must have a very moderate angular width, hence with a small aperture it might be impossible to have the slit wide enough to show the bright lines and at the same time the dark ones. Suppose, for example, that the bright lines are so faint that in order to be distinctly visible they must not be less than 10' in width. If no telescope were used with the prisms, a form which has often been employed, this would render all but the strongest lines of the solar spectrum invisible ; if on the other baud a dispersive mem- ber of a tenth of the power but tenfold the aperture the same apparent spectrum would be ob- tained with a slit 1' in width. This admits of a sharply defined spectrum. That a considerable angular width in the bands, with the exception of 1474 K, is requisite, has been proved in many observations of past eclipses, as well as in my own observations. In the latter, bands correspond- ing to C, D3, and F were not seen, although Mr. Upton's observations prove that they were pres- ent. Since they were carefully looked for and must have been as intrinsically brilliant as in the prismatic telescope, the only explanation is the wholly sufficient one of too narrow a slit. Had it been wider, however, the more important observations as regards dark lines would have been un- satisfactory. We see from these last considerations that for corona observations a spectroscope of large aperture is far superior to one of small aperture which would be regarded as equivalent to it by the rule in the preceding paragraph. The principles developed above will be valuable to us in explaining the apparently contra- dictory evidence on record as to the spectroscopic nature of the corona. They can only be regarded as novel in so far as they direct attention to the fact that the conditions which must be satisfied in an apparatus designed for this particular use differ from those governing other spetroscopic observations ; nor should I venture to give them here were there not most positive proof that they are not universally understood. Not oidy have some eminent authorities mistakenly laid stress aOLAli ECLIPSE, MAY (i, 188^!. Ill iijioii tbe viilue of largo iiiigultir aperture in the image lens, in their published prograninies for e(;Iii)se observations, l)ut guided by this erroneous theory they have too often failed to make the most of rare opportuuities. This is a misfortune which would correct itself in time, but, unfor- tunately, the time for such observations is restricted. Moreover, the results derived from elaborate apparatus, even if based upon false theory, are apt to have undue weight accorded to them. In our examination of the existing spectroscopic evidence relating to the corona we may group the observations, first, according to the date of the eclipse to which tliey pertain, and secondly, according to the character of the instrument used, taking in order the prismatic telescope, inte- grating spectroscope, and analyzing telescope. 18C8. Of the four observers who directed their attention to the spectrum of the corona not one gives the essential elements of the apparatus used. Ehia used a " Bunsen's spectral apparatus of the simplest construction" with a single prism. The magnifying power of 20 was certainly far too high. Only a continuous spectrum was recog- nized ; but the observer was confident that he would have seen dark lines in a solar spectrum of the same brightness. Tennant's spectroscope is described as having a collimator of " short focus and considerable aperture." As his image lens had a focus of 5 feet and an aperture of 4.0 inches, the effective aperture of his spectroscope was probably very small. The dispersion was produced by a single prism. Faint continuous spectrum observed. PoGSON observed faint continuous spectrum. Instrument not described. Eayet gives us sufticient data to enable us to make a fairly probable guess as to the dimen- sions of his spectroscope. Por an image lens he used a reflecting telescoiie. His spectroscope was a direct-vision instrument 40 cm. in length with collimator lens so calculated as to receive all the light transmitted by the slit. If we suppose the reflecting telescope had an angular aperture of about -^ this would imply an effective aperture of not far from 4 inch. As the direct-vision prism probably had as large a dispersive power as two ordinary 00° prisms, we must conclude that Eayet employed a very efficacious instrument. He observed three bright lines in the corona spectrum which were doubttess D3 1474 K and F. 1869. Pickering used an integrating spectroscope with angular a2)erture of 7°. Two bright lines were seen, one near C and the other near E. Haekness gives the constants of his apparatus with great exactness, and, as he failed to get the spectrum of the corona at first, but after widening the slit saw the coronal line with sufficient distinctness to determine its position on the illuminated scale, his experience affords a valuable guide in interpreting other records. According to his data the effective aperture of his single prism spectroscope was 0.45 inch with a magnifying power of 5.7. This tailed to show anything of the corona spectrum with a slit-width which had been used in recording the spectra of three prominences. We may then fairly conclude that a spectroscope of less than i inch effective aper- ture is ill suited for such observations. Young used an analyzing spectroscope with an effective aperture of ^V of an inch and a mag- nifying j»ower of 18 ; but as it had five 45° prisms it was a very effective apparatus for bright lines. "With it he determined with great accuracy the iiosition of the bright coronal green line, ^o dark lines were seen though looked for. 112 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 1870. Of those observers who used integrating spectroscopes, Hammonb (p. 424) saw a spectrum in whicli blue and violet were wauting, otherwise characterized by a red line — doubtless C. His in- fitrunieut was a Browning's direct-vision spectroscope, and therefore presumably without a tel escope. In all probability the observer's eye was not in the proper place ; at least such a supposi- tion is the only plausible one which explains the anomalous observations. Of course, such an explanation is only tenable if the spectroscope was used without a telescope. Abbay (p. 425) used a spectroscope with two 45° prisms and an effective aperture of not far from i inch, supposing the corona to have been i° in breadth. He saw 1474 K and F during the whole of totality. Pye (p. 427) used a spectroscope of about .§ inch effective aperture (according to the assumption just made) with a 60° j)rism of dense glass. He observed, as did Abbay, the lines C, D3, 1474 K and F, but unlike that observer, he saw them during the whole duration of totality. The remainder of the observers used integrating spectroscopes. Brown (p. 419), Burton (p. 437), Denza (p. 438), Lorenzoni (p. 444), and Nobile (p. 445) give no data as to their instru- ments. The first named saw nothing; all of the others saw 1474 K. CARP3IEA.L (p. 415). Spectroscope 00° prism with /„ inch effective aperture ; power 5. At first nothing was seen, but as the slit was widened three bright lines appeared. Clouds interfered with accurate determination of places. Maclear (p. 420) does not describe his instrument. He saw five bright lines which he called- C, D, E, b and F ; these were also seen, less intense, on the body of the moon. Perry (p. 423) leaves undescribed the essential constants of bis instrument, but as the Casse grainian telescope which he used for an image lens had an angular aperture of only IgO it is highly probable that the eilective aperture was too small for the moderately wide slit. He saw nothing. WiNLOCK (p. 430) employed a spectroscope with two prisms, otlierwise not described. The observer recorded the positions of bright lines C, near D, 1474 K and F. He traced 1474 K to a distance of 25' from the moon, ai.d the others nearly as far. No dark lines were seen though the whole region, above F was most critically examined. Young (p. 432). Instrument, a spectroscope with 13 prisms of 55°, with effective aperture a little less than i inch. The line 1474 K was traced from 10' to 13' from the sun ; C and D to 4' or 5', and even on the disc of the moon. No dai'k lines were seen, though carefully looked for. Harkness (p. 441) used the same apparatus which he had employed in 1S69 with much the same result. 1474 K was estimated as extending 10' to 15' from the moon. Two less refrangible lines were suspected. 1871. At this eclipse the " prismatic telescope" was first used. The two observers who made use of them employed widely different forms. LocKYER (p. 447) looked through five prisms of 45° each with the unassisted eye. He saw three hydrogeu rings, together with a ring corresponding to 1474 K. The last-named was esti- mated as the least bright. All were regarded as of equal width, not more than 2'. Eesmghi's (p. 462) instrument had an aperture of 4J inches, a single prism of about 13°, and a power of 40. He saw three rings corresi)onding to C, 1474 K, and F. Of these the second was the brightest and the last the faintest. The width of the green zone was estimated at C or 7'. Of those who used integrating spectroscopes Saxton (p. 500) and Tupman (p. 469) both saw 1474 K and both fail to describe their apjiaratus. SOLAK ECLIPSE, MAY 0, 1883. 113 Fyeks (]>. 107) observed with an iiitegTiitiiig spectroscope of about 1% of an inch aperture and a single (iO^ ])risni. The bright lines C, 1);;, 1474 K, and K were seen. Ferguson (p. 470), with au apparatus similar to the hust, saw the same Hues as did Fyers, with four other faint ones, the positions of which were merely estimated. The following observers employed analyzing spectroscopes : LocKYEK (p. 44ti) with a (W° prism of 14 inches eflective aperture sa\v a vivid hydrogen si)ec- trum and the 1474 K line. He " was astonished at the vividness of the 0 line and of the continu- ous spectrum." Macleab (p. 447) with a '• Gprism spectroscope of great dispersive power" and a " 7-prism direct-vision spectroscope," saw nothing whatever. Jassen (p. 4.50) fails to describe the essential constants of his apparatus, but emiihasizes the tact that the image lens was of large angular aperture, thus, in the opinion of the observer, yield- ing exceptionally brilliant spectra. We may be permitted to discuss this apparatus somewhat minutely, not only as a good illustration of the theory given above, but on account of the impor- tance of the observations made with it. A silvered mirror of 15 inches aperture and 60 inches focus was used as an " image lens." The dispersive member consisted of two direct-visiouprisms. No telescope was used.* Nothing is said about the aperture of the collimator and prisms except that they were so constructed as to transmit the whole pencil from the mirror. Let us suppose the collimator 4 intihes in length, which would correspond to an effective aperture of 1 inch. Then we should have a beam of light 1 inch in diameter from the prisms, but only that portion falls upon the retina which can pass through the pnpillar aperture. If we suppose the diameter of the pupil to be J of an inch, then all the light which reaches the retina comes from a portion of the image mirror 2 inches in diameter, and the remainder is useless. Again, since such prisms are usually equivalent to two or three prisms of 60°, we see that the apparatus is inferior to a single-i^rism spectroscope of f of au inch eft'ective aperture even for observing bright lines; and, in accoi dance with the principles exi^lained in the theory of the instrument, it is greatly inferior to such a single-prism spectroscope for detect- ing dark lines. It is clear that any other assumption as regards the focal length of the collimator would not affect the conclusion ; for, suppose the length twice as great, then, since the effective aperture of 1 inch is not altered, only one- fourth as much of the mirror would be utilized; but, at the same time, a slit of the same angular dimensions would have four times the area; thus an exact compensation would i-esult.t The observer saw the hydrogen lines bright, as well as 1474 K. Besides these, D was seen as a (larii line, with some faint ones in the green. The bright lines were traced to a distance of 10' to 12' from the limb of the moon. Herschel and Tennant (p. 454) give no description of the spectroscope used. They saw 1474 K only, and saw it at a distance of 8' from the moon. Moseley (p. 471). Captain Tupman describes the spectroscope used as having a collimator 5 inches focal length, 0.7 inch aperture, with a direct-vision prism of 2 flint and 3 crown prisms. The image lens was of 3i inches aperture and 33 inches focus. " Tower of the whole combination about 40." This gives effective aperture of 0.53 inch and magnifying power of 6. This should •• This fact was overlooked by Mr. Eanyard in liis discussiou of the same instruiuent. tMr. Kanyard, at p. 4.51, calls attention to M. Jannskn's fallacious reasouiu}; in a footnote. As, however, ho not only conchules that tliis sjiecial apparatus was after all very efficacious, but also computes the "intensity of the inuige" (pp. 375-378) for all the instruments used, we are driven to the conclusion that he overlooked the full force of his logic. lu this connection his remarks on p. 37.') are very instructive. S. Mis. 110 15 1 14 MEMOIliS OV THE NATIONAL ACADEMY OF SCIENCES. have been a very eft'ective apparatus had the telescope iustead of the slit been movable ; but, as the observer tells us that with his adjustment " the center of the slit was far from coinciding with the axis of the telescope," the ettective aperture may have been much less, lie saw 1474 K and traced it to a distance of 22' ± 5' from the moon's limb. 1874. Stone (p. 475). It is especially to be regretted that this obser\'er fails to give the constants of his instrument, not only on account of the value of his observations, but because he was the only spectroscopic observer of this eclii^se. He saw the hydrogen spectrum with 1474 K bright on a continuous s])ectrum in the inner corona, and traced the last-named line in the outer corona to a distance of more than 1° from the moon. He also detected dark lines in the siiectrum of the outer corona, though they were seen with great dififlculty. 1875. Nothing of the siiectroscopic nature of the corona was learned at this eclipse. 1878. Professor Brackett (Amer. Jour. Sci., vol. xvi, p. 287) used a very efiBcient prismatic telescope, but failed to recognize otlii r than a continuous spectrum of the corona. Other observers with prisms or gratings used without telescopes saw no more. Mr. Bennet (Amer. Jour. Sci., vol. xvi, p. 287), with a very eflicient integrating spectroscope saw 1474 K and F for a few seconds after the beginning of totality and again for a few seconds before its termination. Professor Bakkee (Proc. Amer. Ass. Adv. Sci., 1878, p. 113) used a direct- vision analyzing spec- troscope, with telescope and collimator having 4inch focal lengths and finch apertures. The dis- persive power was nearlj- equivalent to that of two 00° prisms. This instrument was attached to a 4-iuch telescojje by Jones, of London, not otherwise described. If we assume the ordinary ratio of aperture to focal length in the image lens, i. e.. jVi ^^ fi"'l that the effective aperture of the si»ectroscope was only about ^ of an inch. No bright lines, but numerous dark lines were seen Of these, h and F were esitecially distinct,* and D, E, and G considerably less so. They were all faiuter than in an ordiiuiry solar spectrum of the same brightness. Professor Eastman (U. S. N. Obs. Eep., 1878, p. 299) employed a siugle prism instrument with an effective aperture of 0.9 of an inch ; power not stated. With a wide slit he traced 1474 K to a distance of from 10' to 14' froui the moon's limb. No other lines were seen. Professor Harkness (U. S. N. Obs. Eept., 1878) confined his attention to the ultra-violet region of the spectrum, where he tailed to find any lines. Commander Sampson (U. S. N. Obs. Kept , 1878, p. 113) does not give the essential constants of his instrument. Using a narrow^ slit, the observer failed to see either bright or dark lines in the continuous spectrum exhibited. Professor Young (Amer. Jour. Sci., vol. xvi, p. 285) employed a single-prism spectroscope with a fluorescent eye-piece. The field of view extended from about C to above F. C, D3, 1474 K and F, were visible throughout totality. Of these, C was traced to a height of 10' and F of 5' from the moon's limb. * It will be seen that Professsor Young found F a bright coronal Hue tlironyhont this eclipse. SOLAK ECLIPSE, MAY G, 1883. 115 SUMMARY OP SPECTROSCOPIC EVIDENCE. This review, in wliicli all the available spectroscopic evidence concerning the natnre of the corona is collected, is most instrnctive. Leaving ont of account tlie integrating spectroscopes, l>ecanse they do not distingnisii between the lines due to the corona alone and those which have their origin in chromospheric light, we find that not a single observer, who has made nse of an instrument which by description is as efiQcient as a single- prism si)e(!troscope of i-inch aperture, has failed to see the bright 1471 K line in the spectrum of the corona. As to the height to which this line could be traced, at no eclipse when the effort has been made has this been less than 25' as a maximum except dnring that of 1878, when a single observer only (Eastman) attempted to find its limits ; he found 14' for a maximum. The evidence of the existence of the hydrogen-spectrum in the coronal light i y, really not less conclusive. Ten of the fifteen observers who saw 1474K also saw the hydrogen lines. But what adds indefinitely to the strength of the evidence is the fact that all the observers wbo describe their apparatus as of greater efficiency than a single prism of 'i inch aperture saw the bright hydrogen lines, with the exception of two. Of these two, one (Young, in 18Gfl) may have had too narrow a slit, as he was looking particularly for dark lines ; the other (Eastman, 1878) was observing at a time when all the bright lines were exceptionally feint. The height to which the hydrogen lines have been traced varies from 5' or 6' up to nearly 25'. The line D3 is to be classed with those of Lydrogen. All the evidence, some of it most decisive, goes to show that the distribution of the light which yields this line spectrum has no relation to the rifts and streamers which characterize the various coronas. As to the presence of dark lines in the spectrum of the corona, the evidence is more conflicting. It is evidentthat the integrating spectroscope is, if properly designed, as well suited for the detection of such lines as the analyzing, but with the exception of Brown, in 1883, who reported D as a dark line, no one has detected any with this form of instrument. With analyzing spectroscopes, Janssen, in 1871, saw D with some faint lines in the green, and the writer 1) alone in the recent eclipse. Besides these, a single observer (Barker, in 1878) has reported all the prominent Fraunhofer lines as evident. On the other hand, many of the most experienced observers with the most efficient apparatus have foiled to detect them, even when looking specially for them. The observations of Mr. Stone in 1874 are not included here, as they applied to the outer corona only. Whatever in- terjiretation be placed upon the presence or total absence of dark lines, the conclusion is inevitable that the proportion of true solar light in that of the corona within 5' or G' of the moon's limb is so small that all but the strongest of the Fraunhofer lines are invisible in any spectroscope which lias hitherto been employed. Here wehave a starting point from which we can, by means of experiment, determine tbe minimum limit of the ratio of snnligbt in the corona. It is only necessary to mix light which yields a continuous spectrum with sunlight until we can secure a spectrum which re- sembles that of the corona. This experiment I have tried in the following manner : Before the slit of the same spectroscope used at Caroline Island I placed a number of glass plates, varying from one to twelve, at an angle of 450. In front of these was a screen of white paper upon which fell a beam of sunlight from a heliostat. A gas-flame was placed in such a position that a portion of its light was reflected into tlie collimator by the glass plates. Two small movable screens were so adjusted that, at will, one- lialf of the slit could receive sunlight alone, while the other half was illuminated by gaslightonly, or, the whole slit could receive both kinds of light simultaneously. The quantity of sunlight which 116 MEMOIRS OF TUE NATIONAL ACADEMY OP SCIENCES. entered could be regulated by the oiiacity of the paper selected for the screen, and the quantity of gaslight by the number of glass plates used in the retlector before the slit. 1. By means of the movable screens it was easy to adjust the apparatus so that the quantity of light from the two sources should be sensibly equal; then, when the two small screens before the slit were removed, the spectrum was that of sunlight mixed with an equal (juantity of light yielding a continuous spectrum. This was found to show in the central portion of the spectrum the lines U, E, b, F, and very many distinct but fainter lines in the green. This proves that in the corona less than half the light giving the continuous spectrum is retlected suidight. 2. The relative quantity of light from the tiame was successively increased. When two or tliree times as great as the proportion of sunlight the fainter lines disappeared and onlj' those remained which are named above ; then, still increasing the relative amount of gas-light, F, E, and D disai)peared, leaving b distinctly visible long after. This can hardly excite surprise, for the h group is obviously the strongest line in a faint solar spectrum. But the necessary deduction from the experiment is a very important one. Since there was enough sunlight in the-coronal spectrum to render visible the weaker line D while the b group was invisible, there must have been present an excess of light of the wavelengths of the b group ; in other words, if the corona had been deprived of all purely solar light the brightest of the magnesium lines would have been added to those of hydrogen and 1474K. II. Polarization of the Coronal Light. It is unnecessary to review the observations on this point with such minuteness as we have employed in discussion of the spectroscopic evidence. This is owing not only to the thorough manner in which Mr. Eanyard has done it, but also because there is no room for doubt, esxiecially since Professor "Wright's admirable work at the eclipse of 1878, that the coronal light is strongly polarized radially. The intensity of polarization and its distribution with i-eference to the sun are, however, of the greatest theoretical importance. Thus all evidence bearing on these points deserves our critical examination. Unfortunately, there are few observations to guide us here, though some are of great value. There are certain observei's who have given estimates of the percentage of polarization in the coronal light or of its variation in passing from the moon's limb outwards. They are Prazmowski ( 1860), Langley (1870), Blaseena (1870), and Hastings (1878). Mr. Prazmowski writes (p. 281), as nearly as I can recall, the portion of the corona most " stronglj^ colored did not correspond to the most brilliant part, but was situated at a certain distance froin the edge of the moon." This, as a mere recollection, and differing from all others who have used the same method (notably Eanyard, in 1871), has necessarily little weight. Professor Langley (U. S. Coast Survey Report, 1S70, pp. 158-164) concluded that the polari zation diminished near the moon's limb, because the bands in his Savart i)olariscope did extend to that limit. But from the i^eculiarity of the api)aratus this conclusion does not follow. The bands were about 1° 50' apart, v.-hile the apparent diameter of the moon was oidy 6° in his instrument, so that successive bauds would fall on widely ditt'ereut regions of the corona. In short, even if the polarization had been 30 per cent, at the limb, the bands, other than the central one, would have taded out before reaching the limb. * Professor Blaseena, in the eclipse of 1870 (j). 309), estimated the strength of the polarization near the limb as equal to that of a clear sky at 50° from the sun. This corresponds to a per- centage of about 30. Dr. Hastings (U. S. Naval Obs. Report, 1878, p. 158), by an apparatus which did not admit of * The theory of this instrument has been discussed more fully in the U. S. N. Report, 1878, p. 161, by the writer. SOLAR ECLIPSE, MAY 6, 1883. 117 his knowing the portion of the, corona under observation, found the polarization increasing- uj) to the limb. That of the light from an area .3' in diameter and close to the limb of the moon was estimated as not less than .'>() per cent. ^ Two observers have made quantitative measurement, namely, Winter in 1871, anesides these components of the envelope, there is present .matter which reflects or diffuses light much as our own atmosphere does. To this is attributed the partial radial i>olarization of the corona. d. The streamers and rifts in the corona indicate matter repelled, in various quantities, from the sun by forces which may be electrical. 118 MEMOIES OF THE NATIONAL ACADEMY OF SCIENCES. This neglects no one of the established features of the corona and has apparently contented most writers. It is essentially the explanation given by Professor Young in his work on The Sun, though he does not fail to note grave diiiiculties in the way of accepting it. When, however, we demand of the theory a quantitative agreement with observation, we find that it utterly breaks down. Some of the assumptions involved are so exceedingly improbable that we refuse to regard as plausible a hyi)othesis resting on them, while others equally as essential are absolutely nega- tived by the observations. We will consider these points in turn : First («). Since the sijectroscope demonstrates that the gaseous pressure at the limit of the chromosphere is very small, probably far less than that of an inch of mercury, this supposition requires that the pressure of the assumed atmosphere from 000,000 to 1,200,000 miles deep shall be thus inconsiderable, notwithstanding that the force of gravity is more than twenty-seven times as great at the surface of the sun as at the surface of the earth. As improbable as this consideration renders the assumption of a gaseous atmosphere, we find a still stronger objection in the motion of comets. All optical evidence of the existence of our own atmosphere ceases at a height of about 4.5 miles ; still, the density at more than twice that altitude is sufficient to offer a resistance to bodies moving with velocities averaging 1.4 times that of the earth in its orbit, such as to render them incandescent almost instantly. Now, the illumination of a particle in the corona is not indefinitely greater than that of one in our own atmosphere, the ratio being that of the angular area of the sun as measured from the two points. It follows, then, that the density of a visible atmosphere near the sun cannot be indefinitely less than that of our own at 45 miles from the earth. But we have the clearest evidence that far within the limits of the corona the density must be almost infin- itely less than that of our atmosphere at even CO miles above the earth's surface : for the great comet of the last year passed at a distance of 300,000 miles of the sun, hence deep within the assumed coronal atmosphere, for a space of several millions of miles and with a velocity 180 times that of the earth in its orbit, not only without being stopped and precipitated upon the surface of the sun, but without having been checked in the least. This was proved by the fact that the orbit deriv^ed from observations after perihelion passage was sensibly the same as that before. Still more con- clusive pi-oof is offered by the comet of 1843, since it passed still nearer the surface of the sun. It is true that its oi'bit before and after perihelion passage does not admit of such comparison as iu the more recent case, but we are forbidden by every law of probability, just because of its small perihelion distance, to assume a higher velocity before nearest approach than that due to a para- bolic orbit ; this it had after leaving the neighborhood of the sun. We must not, iu weighing this evidence, overlook the fact that the resistance offered by an atmosphere increases with enormous I'apidity with increasing velocity of motion. Surely, no more decisive argument against the exist- ence of an atmosphere extending as far as the perihelion distance of either of these comets could be imagined. But the assumption of an extensive atmosphere leads to a contradiction to our experience wholly indepeudently of such considerations which would render it untenable. According to theory, as well as observation, the upper limits of the gaseous envelopes of the sun ought to be ordered according to their densities. The material which i)roduces the 1474 K line, and which m.ay always be seen iu the chromosphere spectrum, is, according to this criterion, as unmistakably denser than hydrogen as is magnesium vapor, or of iron vapor; but if we accept the coronal spec- trum as evidence of the existence of an atmosphere, we are, bj' exactly the same principle, driven to the conclusion that the 1474 K material is far less dense than hydrogen. The contradiction could not be more abrui>t and inexiilicable. There are two other arguments of not inconsiderable weight which are opposed to the suppo- SOLAll ECJLirSE, MAY 0, 18So. 119 sitiou of a ooroiial iitmosphei'e. First, the pliotographs indicate wliat may be styled a flat arrangement of the corona, as though the forces whicli produce its irregularities act only in a l)laue at right angles to the line of vision. That is to say, the rifts and streamers seem to have their origin at or uear the limb of the sun and are often narrowly limited in width. Such a char- acter might well exist if the corona were determined by the disk of the sun, but would be highly improbable if it were distributed about the solar globe; secondly, we are compelled by this theoj-y to assume most improbable changes in the hypothetical atmosphere. For example, the line 1474 K was traced to a distance of 1,200,000 miles from the sun in 1874, while four years later it was so feeble as to have eluded all but two of the observers, notwithstanding that the conditions of vision were probably better then than ever before. If the line demonstrates the existence of an atmosphere, it demonstrates also inconceivable changes in it. In regard to the matter (6) which emits the white light, our statements must be a little less positive. That it is not of solid or liquid particles suspended in an atmosphere after the nature of our clouds is pretty evident from the necessary rarity of such an atmosi)here.* The sui)position tlmt a large quantity of meteoric matter is falling into the sun otters almost as great difficulties. We must conclude that it is falling nearly vertically downwards in the immediate neighborhood of the sun, because the necessary orbital velocities to check this precipitation could not exist within an atmosphere, eveu if we disregard the difficulties in the way of accepting a theory which implies a swarm of satellites whose orbital poles are distributed uniformly over the heavens; hence there must be a continuous supply from without. This supply cannot come from parabolic comets unless those of small perihelion distances are more abundant thau those of great. I am uot aware that there is any evidence, founded either on theory or observation, which cannot be ex- plained by the greater brightness of comets near the sun, and hence their greater liability to dis- covery, for such a distribution of perihelion distances. It is true that such a law for periodic comets might be probable, but as these are likely to have the poles of their orbits uear the poles of the ecliptic, they, although they serve admirably to explain the zodiacal light, could not give such a corona as we observe. Perhaps the assumption of an inter[)lanetary resisting medium would help the hypothesis of a nieteoric constitution, but it would be another hypothesis. The possibility of matter ejected from the suu we will consider with the structure of the corona. The polarization (c), when considered quantitatively, is even more incompatible witii the accepted theory than either of the phenomena previously discussed. It is clear, as has been pointed out by a number of writers, that the polarization of light retlected from a i^article at the surface of the suu is nil, because the luminous source there is a surface with an angular subtense of 180°. It is also easy to see that therefore the polarization of the corona near the limb of the moon must be small, eveu if all the light is diffused by matter in such a state of subdivision as to give a maxi- mum effect. At a greater distance from the moon the percentage of polarization should be greater. But this is quite contrary to the observed law. In 1878 I mnde a number of approximate calcula- tions as to the percentages of polarization at various distances from the moon, and found them widely at variance with the estimated values in my own observations. In December, 1879, Dr. Schustert published an elaborate analytical discussion of the problem. We will make use of the results of his investigation. These, under various assumptions as to the law of distribution of matter about the sun which should diffuse light so as to give the maximum amount of polarization, are given in the accompanying table : * It is perhaps worth noting that whatever argument can he drawn from the independence of the viscosity of a gas or pressure and its increase with temperature cease to apply when the mean free path is large compared to the dimensions of the hody considered. « tR. A. Soc. Month. Not., vol. 40, p. 36. 120 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. Table I.t d. )•». »— 2. )-• '. )-'■'. r" — )—-. ,—2 ,— 4_ r" -f ai^2. 1 0.00 11.1 12.9 12.0 10.9 9.1 16.4 12.9 0.14 12.1 14.8 14.1 13.3 9.4 16.7 14.6 0.5G 13.9 18.3 18.5 18.0 10.1 18.1 18.1 1 31 16.3 22.9 24.0 24.1 11.7 21.0 22.5 2.46 18. y 28.2 30.5 31.3 14.0 25.3 27.5 4.18 21.7 33.8 37.4 39.1 16.8 30.5 32. 7 6.6 24.3 39.5 44.6 47.1 20.0 36.5 37.9 10.3 26.7 44.9 51.6 55.0 23.3 42.6 42. (i 16. 29.0 49. 9 58.1 62.5 26.5 48.1 45.9 26. 30.8 .'■)4. 3 63.7 69.1 29.1 52.9 47.2 46. 32.3 57.4 67.8 72.6 31.5 56.8 45.4 t This is Table IV of the article cited, altered to give percentages and distances from the limb. The first column, under rf, gives tbe angular distance from the limb of the sun ; the next, under r", gives the corresponding percentages of polarization for an atmosphere of unvarying- density, while the other columns give the values for different laws of atmospheric density ; e. (/., the fifth column contains the results of calculation under the assumption that the density decreases as the the sixth power of the distance from the sun's center. It will be seen that it makes little difference what laws of distribution be assumed for the neighborhood of the limb ; the polarization is there feeble, not far from 12 per cent., and increases continuously outwaixls. Since we have seen, how- ever, that not more than one-fourth or one-fifth of the light of the lower corona cau be diffused sunlight, even eight times the polarization theoretically possible would not yield the percentage observed. Again, the polarization must, if due to reflection by an atmosphere, increase continuously with increasing distance from the sun. That it does not do so is established beyond question. The only inuiginable explanation for this is the admixture of increasing quantities of nonpolarized light at higher altitudes, which, as we have just seen, cannot be admitted near the sun. But if "■we decline to accept any values for polarization other than those yielded by direct measurements, we have enough in Professor Weight's observations of 1878 to demonstrate that the assumed explanation is untenable, notwithstanding that his measures did not come nearer than C from the moon. It is easy to calculate from the last table what must be the relative quantity of mixed light from other sources, in order to i educe the theoretical numbers to correspond with his observations. If we represent this quantity for any point in the corona by A, the quantity of diffused light for the same poiut being unity, then the values for A are given in the following table : Table II. Law of density. A, d = 6'. A,