248 



NATURE 



{July 12, 1883 



whilst the meteorological observations of Mr. Upton 

 showed a slight rise in barometric pressure, a rise in 

 humidity, and a fall of temperature, the latter reaching 

 e/en the nightly values, whilst radiation thermometers 

 showed that the heat received by the earth was almost 

 nil. 



The observations with the photoheliographs which the 

 English observers took out being taken in hand by Lieut. 

 Qualtrough of the American navy. 



Perhaps some details as to the work itself may be of 

 interest. 



First with regard to the work of Mr. Woods. A red- 

 end collodion plate was washed and placed by him in 

 one of the prismatic camera slides five minutes before 

 totality. Four minutes later he started the clockwork of 

 the integrating spectroscopic slide. Forty seconds before 

 totality exposures were made in the Rowland grating 

 cameras, and at totality the prismatic camera and slit 

 spectroscope were each opened. 



In the spectroscopes which were under the care of Mr. 

 Lawrence the exposures commenced ten minutes before 

 totality, his work continuing until ten minutes after 

 totality. 



The photoheliographs as we have said were looked 

 after by Lieut. Qualtrough, the plates which he exposed 

 in these instruments being given to Mr. Woods after the 

 eclipse. During the intervals in the exposures of the 

 plates the observers found time to note the corona. In 

 its general character it seems to have much resembled 

 that seen last year in Eg>pt, but its light was of a more 

 natural tone, the landscape lacking the weird colouring 

 so marked a feature in the Egyptian eclipse 



Mr. Lawrence examining the corona with the finder 

 was able to detect much delicate detail, especially in 

 those portions of it near the preceding limb of the moon. 

 He also examined it with a small pocket spectroscope 

 with lens. Taking out the prisms during mid totality he 

 could see the green ring, and very faintly towards the end 

 C and D 3 . After totality he still saw the 1474 ring, as 

 well as the red and yellow ones ; these latter, however, 

 being as before very faint. Replacing the prisms he 

 could see then only the 1474 line, that examined by Prof. 

 Hastings. The F line, for which he had specially 

 searched, was not seen by him at all. Mr. Lawrence 

 agrees in thinking that the coronal light was of a 

 more natural tint than it was in the eclipse last year. 

 Mr. Dixon of the American party made a careful sketch 

 of the corona, showing five well defined streamers. Soon 

 after totality the photoheliograph clock was stopped, and 

 an endeavour made to obtain the run of the sun's crescent 

 on the two cameras for the purpose of orientation, but, 

 owing to the prevalence of clouds, the attempt was only 

 successful with one, the smaller instrument, with which 

 two exposures were obtained on one plate. 



So much for the observations themselves. As to the 

 results we learn that the photographs taken with the small 

 photoheliograph are very good, that which had two minutes 

 exposure showing as much as those which M. Janssen 

 exposed during the whole of totality. The large photo- 

 heliograph has not given such good results, all the plates 

 taken showing signs of slight shifts. Still it is believed 

 that, by combining the photographs on each of the 

 nine plates, the whole structure of the corona from the 

 limb to its outmost limits will be obtained. 



With the first order grating H and K were obtained as 

 bright lines just before, and immediately after, totality, but 

 with the second order grating no result seems to have 

 been obtained ; at least the observers could see nothing 

 when they examined the plate on the island. The photo- 

 graphs taken with the dense prism spectroscope, like 

 those obtained with the first order grating, show bright 

 lines at the commencement and end of totality, particu- 

 larly at the end, the photograph taken then showing 

 H, K, /;, f and F very distinctly. 



The integrating spectroscope also did useful work. Al- 

 though no result was obtained during totality with this 

 instrument, the flash of bright lines before and again 

 after totality were successfully photographed by it. 

 The more prominent lines in these photographs are 

 those which belong to hydrogen and the lines H, K, and 



H74- 



The slit spectroscope was also successful, giving a good 

 photograph from the ultra violet to the green. This spec- 

 trum, whilst being in the main a continuous one, is not 

 the same on the two sides of the disk, nor are the lines 

 so numerous as those obtained last year in Egypt. H 

 and K are very strong in the present photograph, but in 

 this respect also the spectrum differs from that obtained 

 in Egypt, these lines then extending across the interval, 

 which is not so in the present photograph. The hydro- 

 gen line near G, however, extends over nearly a solar 

 diameter; and //, F, 1474,*, and other lines have also 

 been obtained. 



With regard to the gelatine red-end plates of the pris- 

 matic camera, although they gave good photographs, yet 

 the almost entire absence of prominences will diminish 

 their value. In the eclipse of last year, when many pro- 

 minences were visible, these plates were used with good 

 results. The Rowland grating, too, seems to have given 

 no useful result, but this is probably due, like the small 

 measure of success with the prismatic camera, to the 

 comparative absence of prominences. 



In developing the red-end plate immediately after 

 total ty Mr. Woods was unfortunate enough, owing to his 

 having to manipulate it almost entirely in the dark, to 

 get it torn, and nothing now remains but the gelatine 

 edging. 



The work now being complete, the things began to be 

 repacked for the homeward journey. The Hartford re- 

 turned to Caroline on the 8th, the work of reembarkation 

 commenced, and on the 9th the expedition left. 



The observers were almort sorry to leave the island, as 

 their sojourn there had been a most pleasant one. Like 

 most of its kind it is well wooded, the graceful outlines 

 of the cocoanut palms being characteristic features in the 

 pretty scenery which the island affords. 



By day the smaller hermit crab swarmed the sandy- 

 beach, feeding on what decayed animal matter it could 

 find, whilst at night the large red hermit crabs covered 

 the same beach in their hundreds, they preferring dead 

 vegetable matter. The lagoon too, around which the little 

 islets arrange themselves, was a never-failing source of 

 interest and amusement, and in boating there, and in the 

 deeper water off the reef, or in hunting the shore in search 

 of the brilliant-coloured shells and coral with which the 

 island abounds, the observers found much amusement. 



In deep water bivalve shells more than two feet 

 across were observed, whilst the reefs at low water 

 were covered with smaller representatives of the same 

 or a similar species, which threw jets of water into 

 the air. Several octopi were caught by the various 

 members of the expedition, and many beautiful sea- 

 urchins picked up by them in their daily walks. Thus 

 did they spend their spare hours, and it was therefore 

 with some regret that they saw the outlines of the island 

 disappear on their horizon. The Hartford was bound for 

 Honolulu in the Sandwich Islands. The voyage was 

 however broken at Hilo, Hawaii, in order that the mem- 

 bers of the expedition might visit the celebrated volcano 

 of Kilauea. Honolulu was reached on May 30. Here 

 Messrs. Preston and Brown, who were to continue their 

 pendulum observations remained, the rest of the expedi- 

 tion proceeding in the Zealandia for San Francisco. The 

 English observers left at Honolulu copies of the photo- 

 graphs they obtained, to be forwarded to England by the 

 next mail. They left San Francisco on June 15, and may 

 therefore be expected to arrive in England about the end 

 of the present month. 



