232 



Sir [N'orman Lockver and ^Ir. A. Fowler. 



explosion; l3nt, on the other hand, cordite, although it contains as much 

 as 58 per cent, nitro-glycerine, owing to the fact that it contains also 

 vaseline, gives a temperature lower than that of ballistite containing 

 only 30 per cent, nitro-glycerine and no vaseline. Of course, the 

 minimum deflection is the one due to gun-cotton, which contains no 

 nitro-glycerine. 



Similar experiments have also been repeated with other explosives 

 and with cHfl'erent charges, and, in every case, the same comparative 

 results have been obtained. 



The above refers only to a part of the experiments which have been 

 carried out so far. Another series is now in progress for determining 

 the other necessary elements which will he recpired before we can 

 accurately express the value of these deflections of the galvanometer in 

 degrees of temperature. One important element which comes into play 

 is the inertia of the galvanometer itself in coimection ^vith the short- 

 ness of the time diu-ing which the maximum temperature exists, and 

 there are also other points which are being investigated, and these will 

 form the subject of a fiu-ther communication. 



We have, however, thought it advisable not to delay communicating 

 the above results, as already the described method shows the possibility 

 first of all of obtaining approximately an idea of the temperature 

 dming explosion, and, secondly, it shoM's a clear way by which the 

 comparative temperatures for various explosives can be determined. 

 These, taken in connection with the results shown in our former com- 

 mimication, will serve, we hope, to give a better knowledge of the 

 different modern explosives which are now commonh^ used. 



The Spectrum of a Aquil?e." By Sir Xoeman Lockyer, K.C.B., 

 F.E.S., and A. Fowlee. Pieceived January 18, — Piead Feb- 

 ruary 8, 1900. 



[Plate l.j 



The study of enhanced lines throws considerable light on the 

 spectrum of cc Aquilse, the peculiarities of which were first described 

 by Professor Pickering"^ and Dr. Scheinerf in 1889. In this spectrum 

 the lines of hydrogen are strong and broad, but the additional lines, 

 instead of being faint and sharp as in most other stars of this class, 

 are faint and diff'use. Dr. Scheiner stated that these apparent bands 

 were identical with the most conspicuous groups of lines in the solar 

 spectrum, and further that this appearance of the spectrum can be 



* Third Annual Eep. Henrv Draper Memorial, p. 5. 

 t ' Ast. 2facli.,' 2924. 



