May 2, 1898.] 



KNOWLEDGE 



107 



original negative of that photograph with the one h^re 

 depicted, with the result that no obvious chin^e could be 

 detected to have taken place, either in the nebulie ihem- 

 selves, or in the relative position angles, or distances 

 between them and y, or of the surrounding stars. 



An interval of tive and three-quarter years is therefore 

 too short to show sensible changes to have taken place in 

 these objects. From this it follows that their distances 

 from the earth are great ; and we havi' jvt no unqu-ation- 

 able evidence to prove that the nebuhe are phy-<ically 

 connected with the star y, but their apparent distances 

 from the star are not too great for us to entertain the 

 possibility of sucli a physical connection. 



The diffused patch of light surrounding y mnst not be 

 mistaken for nebulosity ; for it is caused by the strong 

 light of the star illummating a part of the earth's atmo- 

 sphere afl'ecting the photographic plate during the exposure. 

 This atmospheric glare is of the same character as that 

 observed in forming halos round the sun, moon, and bright 

 stars ; but the possibility of the star having an extended 

 coronal light around it should not be omitted from con- 

 sideration, for, though it might exist, its structure would 

 be masked on the photograph, by the atmospheric glare, 

 as effectually as that of the solar corona is masked. 



There are many stars visible on the negative involved 

 in the patch of glare, but they cannot be reproduced on 

 the photo copies, for the reason that if the glare is printed 

 out so also are all the stars that differ but little from it in 

 density. 



A dense photo image of the star can be obtained with 

 the twenty-inch reflector in a small fraction of a second of 

 time ; but an exposure during an hour, or more, is required 

 to show the fainter parts of the nebulm, and the faint 

 stars, with clearness. 



THE RECENT ECLIPSE. 



By E. Walter Maunder, f.r.a.s. 



THE methods of investigation employed during the 

 late eclipse were so numerous, and their general 

 success so great, that it seems impossible to give 

 any adequate accoimt of the entire campaign in a 

 single paper. I have therefore thought it would 

 be better if I confined myself to the work on which my 

 wife and I were immediately engaged, and I have no 

 donbt that the editors will easily be able to arrange for a 

 succession of similar papers, contributed by observers 

 engaged in other departments. 



My wife and I, when we contemplated going to India 

 to take part in the eclipse observations, found ourselves 

 confronted by an extremely difficult problem. Our instru- 

 mental means were of the very smallest. They consisted 

 of a small binocular, one eyepiece of which was fitted 

 with a little direct-vision prism, and of a photographic 

 camera, the lens of which, though of high quality, had 

 but an aperture of one and a half inches, and a focal 

 length of nine inches. We could not but compare, with 

 something like a feeling of dismay, this almost microscopic 

 equipment with the magnificent instruments with which 

 the members of the official parties were furnished, or 

 which the directors of large observatories had at their 

 disposal. We were standing up in line, armed with our 

 little flint-headed arrows, whilst our comrades in the 

 battle were rejoicing in the possession of Maxims and 

 Lee-Metfords. 



Still, after looking the problem round, we concluded that 

 it was not one to lose heart over. We saw our way to at 

 least trying three lines of work. With the opera-glass and 



prism I intendt-d to ascert-iin the distribution of coroiiiurn 

 in the corona, and especially to see if it fhowed the rifts 

 and rays whicli form so sirkiog a feature of omnil 

 struciure as it ttppears to the ^ye. With the camera, we 

 thought that we might try, fir^t, by giving a v ry ioog 

 exposure to ob'ain an image of the long cor)n'il streamers, 

 and secondly to photograph the corona, if possible, after the 

 end of totaliiy. 



All three enterprises appear? d very hizirdons. It was 

 exoeediugly doubtful under t le first heid whether, with so 

 sm-ill a dispersion, the 1 171 K light would be snffi -.lenily 

 stioug to declare itself o^ar the continuous spectrum which 

 the corona also gives. Tne atiempt t > secure the long 

 extensions was less likely still. Only a week or two 

 before we left England Miss Gierke, whose admirable 

 judgment and exact insight in astronomical matters have 

 deservedly won such wide and general confidence, had 

 written : — " . . . the camera, owing to special difficul- 

 ties, has not yet been able to pursue them [the coronal 

 extensions so far as four solar diameters." (" Concise 

 Knowledge Library," Astronomy, p. 268.) And Mr. Albert 

 Taylor, in a paper read before the Royal Dublin Society in 

 1891 — a paper evidently most carefully thought out and 

 in the conclusions of which our own experience led us to 

 place great confidence — had laid down that the maximum 

 effective exposure for F 15 iu coronal photography was 

 thirty seconds — that is to say, for our camera five seconds. 

 Such exposures had on former eclipses failed to give any 

 great extensions ; indeed, had generally proved less 

 effective than shorter exposures, from the cause Mr. Taylor 

 so clearly points out — the great brilliance of the sky back- 

 ground. WhUat the last item on our programme seemed, 

 a fortiori, to be more doubtful still. 



It will be seen that our prospects did not appear too 

 brilliant. Nevertheless, we felt strongly that if new fields 

 of eclipse work were to be opened up it necessarily involved 

 the risk of failuVe in the first experiments, and those first 

 experiments might be made as effectively on a very re- 

 stricted scale as on a large one. Their success would be 

 no less indubitable, their failure far cheaper. 



And we felt that we were justified in undertaking this 

 risk. We received absolutely no financial help from 

 (lovemment or any other public body, either for our 

 equipment or for our personal expenses in our expedi- 

 tion, and we were therefore hampered by no restrictions 

 whatsoever. 



We had, moreover, groimds for hope. We had made a few 

 experiments in the use of the " Sandell " double and triple 

 coated plates, and had been convinced that they at least 

 offered us a chance over and above that which ordinary 

 dry plates afforded. It seemed to us that, by their use in 

 conjunction with a slow and prolonged development, it 

 might be possible to bring up the faint extensions of the 

 corona before the sky glare blotted them out ; whilst in view 

 of Prof. Wadsworth's recent papers, the very smallness of 

 the scale of our instrument formed an encouragement. 



One difficulty, however, remained. The second item in 

 our programme demanded an equatorial and driving clock. 

 These we were without, but the Council of the Royal 

 Astronomical Society very generously placed at our dis- 

 posal the pretty little equatorial and camera bequeathed 

 to it by the late Mr. Sidney Waters, f.r.a.s., and met the 

 expense of putting it into full working order. 



The camera attached to this equatorial was not suitable 



* The geaerositT of tTo members of the British Astronomical 

 Association enabled the iiehpse Committee of that body to undertake 

 the expense of insuring the instruments taken out by the members of 

 its two expeditions, and we have to thank them for our share iu this 

 benefit. 



