April %, 1 8 75 J 



NATURE 



453 



have afforded. Nor was this all. The assistance afforded 

 by the directors of the Peninsula and Oriental Steam 

 Navigation Company in aid of the grant from Government 

 was of so material a kind that the committee were enabled 

 to send no less than six fully equipped observers from 

 Europe to take part in the observations, as well as spare 

 instruments for the use of the Indian parties. 



"As a final result of all the efforts made, both in 

 England and India, the location and composition of the 

 i various parties this morning, so far as is known, are as 

 follows : — 



" Camorta, in the Nicobars. — Capt.Waterhouse, Messrs. 

 Meldola and Reynolds. 



" Mergui (British Burmah). — Professors Pedler, of Cal- 

 cutta ; Tacchini, of Palermo ; and Vogel, of Berlin, and 

 assistants. 



" Chulai Point (Siam). — Dr. Janssen and assistants, Dr. 

 Schuster, Messrs. Lott and Beasley. 



" The Royal Society Committee will certainly have to be 



congratulated if it has really been able to secure the 



valuable co-operation of all the distinguished foreign 



workers it has enrolled. We know that Herr Vogel 



joined at Suez, and that Prof. Tacchini, who was in India 



when the invitation reached him, joined at Calcutta, and 



that his instruments, which had been despatched to 



Europe, were only stopped by telegram at Aden ; but 



with regard to Dr. Janssen, it is not yet known whether 



he really joined at Singapore or not ; indeed, no telegram 



has yet been received from the Siam party since they left 



Galle, and there parted from the Camorta party, which 



was then transhipped to the Enterprise, a despatch boat 



j belonging to the Indian Government, which left Calcutta 



[ on the nth of March, having Capt. Waterhouse and 



I Professors Tacchini and Pedler, with their assistants, on 



j board. The Enterprise was to land the Camorta party 



' and then proceed to Mergui to establish a second station. 



1 We may also mention that the Siam party was to proceed 



j from Singapore to Siam on board the steamer belonging 



! to the Government of the Straits Settlement, the Chary bdis 



having been disabled by an accident. 



" From this digression as to arrangements we may return 

 to the question of personnel. In no eclipse expedition, 

 perhaps, has such a large percentage of the observers 

 been under fire before. Dr. Schuster and Mr. Meldola, 

 the chiefs of the Enghsh part of the Siam and Camorta 

 expeditions respectively, and Mr. Lott, are the only ones 

 who have not taken part in the observation of former 

 eclipses. Mr. Reynolds assisted Mr. De la Rue to photo- 

 graph the eclipse of iS6o. Professors Tacchini, Vogel, 

 Pedler, and Mr. Beasley formed part of the expeditions 

 of 1S70. Capt. Waterhouse assisted Major Tennant to 

 obtain the beautiful series of photographs of the eclipse 

 of 1871 at Ootacamund, which are so valuable when 

 taken in connection with those obtained at Baikul by the 

 British Association party. With regard to Dr. Janssen, 

 we are unable to say how many eclipses he has seen ; he 

 has certainly been at most which have occurred since 

 l86o, if not before that date. 



"With regard to the objects to be obtained and the 

 instruments to be employed, the Instructions drawn up by 

 the Royal Society, and issued to the observers by its 

 authority, come to our aid, and, by the minute and careful 

 references to each instrument and to each part of the 

 attack which they contain, enable us almost to picture to 

 ourselves each observing party with its complement of 

 telespectroscopes and prismatic cameras, the ' time- 

 teller' going through his terribly responsible task, the 

 silent activity of the photographic ' dark room,' and, 

 above all, the ever-sharpening ' cusps,' and final total 

 extinction of the Lord of Day — an extinction out of which, 

 however, is born one of those sights for gods and men, 

 which, once seen, so impress every power of the mind 

 that they can ever afterwards be recalled as transcendent 

 instances of the beauty and glory which attach themselves 



to some of the rarest as well as to some of the more 

 common phenomena of nature. 



" The most striking thing about the Royal Society pro- 

 gramme is its simplicity. For the first time in eclipse 

 expeditions, no eye observations are arranged for ; all 

 the phenomena are to be photographically recorded. 

 Here we see the enormous advance which has lately been 

 made in these studies ; for we may remind our readers 

 that in 1871, when the Astronomical Society were appealed 

 to to use their influence to secure observations of the 

 eclipse of that year, a committee of that Society would 

 not agree to employ photography at all ! 



" There is another point. It is now more than probable 

 that not even polariscopic observations will be attempted, 

 although, thanks to the care of Mr. Spottiswoode, arrange- 

 ments have been made for photographing the polariscopic 

 corona, as it may be called, if a spare observer presents 

 himself. 



" The ground has been cleared in yet another way. The 

 photographs of the corona, which were so strongly insisted 

 upon by Mr. Lockyer in the observations of the eclipse of 

 1S71, and objected to by the Astronomical Society, were 

 necessary to determine the solar or non-solar origin of 

 the corona. This question has now been set at rest by 

 showing that part of it is really at the sun, and this is now 

 termed the coronal atmosphere. When this was settled, 

 it was suggested by the same observer that this atmo- 

 sphere would be very likely found to vary in shape and 

 dimensions with the sun-spots. This is the question, 

 then, that is to be attacked in the old way on this occa- 

 sion ; and, on the suggestion of the Royal Society Com- 

 mittee, the Viceroy has charged Capt. Waterhouse with 

 this duty. He will use the same instrument that was 

 used by Major Tennant and himself in 187 1, on Doda- 



betta 



" The instruments termed ' prismatic cameras ' are ordi- 

 nary 32-inch achromatics, with a large prism of small 

 angle ouside the object-glass, and a camera replacing the 

 eye-piece. Such an instrument will give a spectra of 

 small dispersion. 



" Of course with such an instrument as this employed 

 on the full sun, the impression on the plate would be a 

 blurred spectrum containing no detail, but as the ad- 

 vancing moon reduces the part of the sun still remaining 

 visible to a thin silver crescent, then the instrument will 

 begin its work ; the actual shape and thickness of each 

 stratum of vapour above the photosphere will be im- 

 pressed by each coloured ray its light contains, and will 

 stand out on a band of continuous spectrum, which will 

 get feebler and narrower as the silver crescent thins to 

 nothingness. Then the whole ring of chromosphere and 

 coronal atmosphere which will burst upon the eye will be 

 sorted out, if all goes well, into its various metallic con- 

 stituents, by means of a chain o*^ rings of greater or less 

 thickness and regularity upon_the photographic film. The 

 vapours extending furthest outwards from the photosphere 

 will be represented by the broadest rings, those lying 

 closest to the photosphere by the narrowest. The Instruc- 

 tions are careful to insist upon complete rehearsals before 

 the day of the eclipse, so that we may be assured that 

 the simple programme we have sketched may be simply 

 carried out, and that the observers will not attempt too 

 much. It is as well to state this because persons unac- 

 customed to observations might imagine from the multi- 

 plicity of detail in the Instructions that the labours of the 

 observers will be more than ordinarily complicated. 



" Each party will have atelespectroscopeand a prismatic 

 camera. In addition to this equipment. Prof. Pedler will 

 use a heliostat, focussing the image of the sun on a spec- 

 troscope from which the slit has been removed. As a 

 camera, he uses a Janssen slide, which he has arranged 

 so as to get thirty pictures. 



" We are reminded incidentally by the Instructions on 

 ' the multiplication of results,' of the enormous advan- 



