1878.] Mr. J. N. Lockyer. Use of Reflection Grating. 107 



(No other organisms appeared in these cultivations.) These were again 

 used to inoculate other preparations of aqueous humour, and so on, 

 until 1 succeeded in obtaining considerable quantities of liquid, con- 

 taining only bacillus and its spores. The last-named animals were 

 infected with liquid of this kind. 



Seeing that splenic fever, pneumo-enteritis, and specific septicaemia 

 possess a great affinity in anatomical respects, and seeing that in 

 splenic fever and pneumo-enteritis the materies morbi is a definite 

 species of bacillus — the difference of species being sufficiently great 

 to account for the differences in the two diseases — we may with some 

 probability expect that also the third of the group, viz., specific septi- 

 caemia, is due to a bacillus. This, however, remains to be demon- 

 strated. It seems, finally, justifiable to speculate whether or not we 

 have in these three varieties of disease " a variation of species " in 

 the sense of the evolution theory. 



IV. " On the Use of the Reflection Grating in Eclipse Photo- 

 graphy." By J. Norman Lockyer, F.R.S. Received 

 February 8, 1878. 



The results obtained by the Eclipse Expedition to Siam have lead 

 me to think that, possibly, the method of using the Coronal atmosphere 

 as a circular slit, suggested by Professor Young and myself for the 

 Indian Eclipse of 1871, might be applied under very favourable condi- 

 tions, if the prism, or train of prisms, hitherto employed, were replaced 

 by one of those reflection gratings with which the generosity of 

 Mr. Rutherfurd has endowed so many of our observers. 



To test this notion I have made some experiments with a grating, 

 which I owe to Mr. Rutherfurd's kindness, containing 17,280 lines to 

 the inch. The results of these observations I have now the honour of 

 laying before the Royal Society. 



In front of the lens of an ordinary electric lamp, which lens was 

 adjusted to throw a parallel beam, I introduced a circular aperture, cut 

 in cardboard, forming an almost complete ring, some 2 inches in 

 interior diameter, the breadth of the ring being about -§- inch. This 

 was my artificial eclipse. 



At a distance from the lamp of about 13 yards, I mounted a 3f inch 

 Cooke telescope, of 54 inches focal length. Some distance short of 

 this focus I placed Mr. Rutherfurd's grating, and, where the first 

 order spectrum fell, I placed a focussing screen. To adjust for sharp 

 focus, in the first instance, the grating was so inclined to the axis of 



is also in accordance with the observations of Professor Cohn, for this authority 

 states (1. c, p. 265) " Die Sporen schwolien etwas an und trieben an einem Ende einen 

 kurzen Keimschlauch." 



