May 2, 1898.1 



KNOWLEDGE. 



109 



precision by the presence upon them of Venus, which 

 burned like a lamp some six degrees away from the sun. 

 The plates were amply large enough to take in the planet, 

 since they were sixteen centimetres square ; and the focal 

 length of the lens being nine inches, six and one-third 

 degrees correspond to an inch, and the solar diameter is 

 almost exactly one-twelfth of an inch. 



We learn at once by this means that the great south- 

 west ray, so far from coinciding with the sun's equator, 

 lay in thirty-five degrees south latitude. The two rays 

 which composed the " fishtail " on the eastern side of the 

 sun, lay some twenty-four degrees north and south of the 

 equator respectively, the equator itself therefore being 

 void of any great streamer. 



It will be seen that, in disregarding Taylor's limit, we 

 have been abundantly vindicated by the result. Never- 

 theless, the considerations Mr. Taylor urged in the paper 

 alluded to substantially held good. In developing these 

 plates, even the one with only five seconds exposure, the 

 general sky glare came up deep and black at an early stage. 

 Here we owe our success to the fact that we exposed two 

 plates for each given exposure. The companion plate to 

 the Ilford five seconds was in itself a comparative failure, 

 but its development gave us the experience and courage 

 necessary to push the development of its more fortunate 

 comrade to a successful conclusion. 



Our last photograph was the most important. Totality 

 was over by nearly two minutes when we exposed a plate 

 with our little camera for a second and a half. This on 

 development yielded us not only the brilliant arc of sun- 

 light, but showed an unmistakable coronal ring, for the 

 entire dark disc of the moon is seen upon it. 



This success, we may well hope, will have far-reaching 

 effects. It is a very long way from realizing that ambition 

 of so many astronomers, the photographing the corona 

 in full sunlight. But the corona has never before been 

 photographed unmistakably and beyond challenge in so 

 mucit sunlight. And even should it never lead on to the 

 desired goal, something has at least been done to lift large 

 partial eclipses from the category of being astronomical 

 mere waste material. It will be a distinct advance if in 

 future we can fix the 

 positions of the roots 

 of the great coronal 

 rays on such more 

 frequent occasions : a 

 most necessary advance 

 if we are to learn the 

 true nature of coronal 

 change and motion. 



Our experiments, 

 therefore, were success- 

 ful beyond our hopes, 

 and their success seems 

 to justify us in having 

 made them. Yet had 

 they failed we feel that we should have been not one 

 whit less justified. 



But our photographs are on an almost microscopic 

 scale, and although sufficient to prove the practicability of 

 our methods it is much to be desired that they should be 

 repeated on the next occasion with ampler means. We 

 feel it incumbent on us, if any way possible, to take part 

 in the observation of the next eclipse, that of May 28th, 

 1900. ^Ve want to photograph the sun during the entire 

 period of the partial phases, to give a considerable range 

 of exposures, and to try the efiect of various developments. 

 We want, in short, to follow the corona to the utmost 

 extent which the sunlight permits. We want also to 



obtain the greatest possible extension of it. We want also 

 to give two exposures during totality of much greater 

 length than the longest we gave in India. These experi- 

 ments we are prepared to carry out with the little camera 

 which has just done us such yeoman service, but we 

 earnestly hope that we may also be entrusted with in- 

 struments that may enable us to duplicate this programme, 

 but on a much larger scale. 



The accompanying pictures are reproduced from drawings 

 which Mr. W. H. Wesley has most kindly made from the 

 original long-exposed photographs. Amongst other details 

 of interest Mr. Wesley especially remarks on the cor- 

 roboration which these negatives aft'ord of certain well- 

 known drawings of the corona. Hitherto there has been 

 a wide difference between the corona as presented us on 

 the sensitive plate and in drawings even of the most trust- 

 worthy observers, and this fact has thrown a good deal of 

 doubt upon the value of such drawings. A comparison 

 of the corona as here shown with the well-known drawing, 

 by Captain Bullock, of the eclipse of 1868, shows a most 

 remarkable resemblance between the two. If the two 

 were representations of the same eclipse one could not ask 

 a more complete correspondence. 



Noti»0 of Boolts. 



A New Astronomy for Bt;iinners. By David P. Todd, 

 M.A., PH.D. (The American Book Company, New York. 

 1898.) This book deserves an appreciative welcome. It 

 is moderate in compass, precise in plan, succinct in treat- 

 ment. There is a freshness about it, too, that pleasantly 

 reminds one of its origin in a "new" continent. Loci 

 commuufs are few : the topics introduced are mostly dis- 

 cussed from an original point of view ; students are made 

 to feel the i)uranlne<is of them. A " pedagogic purpose" 

 is throughout kept in view. The fundamental idea of the 

 volume is to teach astronomy as a science of observation — 

 to inculcate principles and indicate modes of working 

 them out in practice, no matter how roughly, were the 

 available equipment " but a yard stick, a pinhole, and the 

 rule of three." One recalls — ^be it said without prejudice 

 — the system in vogue at Dotheboys Hall of learning 

 botany by planting cabbages. For, apart from the 

 rigorous sic ros non fohi.s code there enforced, that system 

 possesses high excellences and manifold resources, which 

 Prof. Todd's sixteen years' experience as a teacher enables 

 him to develop to the full. With resourceful ingenuity, 

 he makes the " appeal to observation which can alone," 

 as Huxley wrote, " give scientific conceptions firmness and 

 reality." In the pages before us, precepts are given for 

 pursuing a "laboratory course" in the study of the 

 heavenly bodies ; the construction of home-made apparatus, 

 needing only " moderate mechanical deftness,' is de- 

 scribed preferably to the latest refinements of modern 

 instrumental methods ; nor can we doubt that its use, 

 while flattering the instinctive egotism of beginners, tends 

 at the same time to develop in them both mental alacrity 

 and manual aptitude. The present author, while rightly 

 dwelling upon " the importance of thinking rather than 

 memorizing," lets them ofi' with perhaps undue ease from 

 the stem necessity of confronting mathematical difficulties. 

 Yet we cannot find it in our hearts to quarrel with the 

 capital illustration at page 398, where an instantaneous 

 photograph of a " foul ball " at cricket replaces a formal 

 demonstration that "a projectile's path is a parabola." 

 The book is to a most praiseworthy extent "up to date." 

 The newest results in every department are included in it — 

 included, perhaps, with too slight an allowance of grains 



