76 REPORT — 1892. 



Kow Messrs. Cooke's Barlow concave lens wants no help of that kind, 

 for it was constructed to magnify the first order of spectrum only, and 

 that has no red light of any other order intruding into its own ultra- 

 violet, or requiring some chemical liquid to dull its potency. Hence I 

 have actually found that I have been able to carry Messrs. Cooke's lenti- 

 cular magnifying of the first order of a Grating's spectrum, four plates 

 further into the invisible, than I was able to do with the second order of 

 the very same Grating's spectra, assisted in various chromatic modes. 

 As an illustration of which I beg to append a list of spectrum photographs 

 so obtained last autumn. 



(3) Lastly, my attention was kindly and earnestly directed by 

 Professor Liveing to keep on the look-out for possible changes in some 

 part or parts of the solar spectrum, depending on time and date only, 

 especially if their origin should appear to be in the Sun. 



Now it did so happen one morning that one of the glass negatives of 

 the H and K region of the solar .spectrum did show a very strange and 

 anomalous difference fi-om all the others, so different indeed that my 

 first impression was to throw it away as irretrievably spoilt by some acci- 

 dent. But on considering what such an accident could be, or how it 

 could be reproduced if desired, I was still more confounded and non- 

 plussed. Having, moreover. Professor Liveing's letter still before me, 

 the most respectful course seemed to be, on second thoughts, to describe 

 publicly how the anomaly brought itself forward so far as I knew, and to 

 leave gentlemen with more experience than myself to form their own 

 opinions, either for or against its being anything important. 



Now the main point of the anomaly is, that the whole space between 

 H and K is bright, while that outside them is dark, even very dark. To 

 understand which feature thoroughly and in the terms worked in by 

 Nature, it was necessary that there should be several plates employed, and 

 each of them should show, not only the whole space between those giant 

 lines or bands, but at least as much more on either side. 



Moreover, as good definition does not continue to hold all along even 

 so small a plate of glass as a quarter size, but has to be set and reset 

 several times in its course, while the appearance of the lines alters almost 

 radically on account of the mere curvature of the field, I enclose in an 

 album case in the first place thirteen ordinary photographs of the H and K 

 lines, taken at successive foci all across the field, and then three various 

 impressions from one and the same anomalous photograph. No. 14; 

 following that by Nos. 15 and 16, ordinary, but focussed to the right, 

 views : the whole eighteen now exhibited being enlarged on paper to six 

 times the size of the glasses, for convenience of examination. And I 

 should perhaps duly forewarn all and sundry that ' date ' plays no part 

 in the arrangement of this bundle of repetitions of the H and K lines — only 

 the continual progress from left to right of the place of sharpest definition. 



