8 Messrs. W. Maciiab and E. Rip tori. [May 10, 



parts of the corona in this way. All the photographs show a bright 

 continuous spectrum from the inner corona. 



Some of the plates taken out of totality show numerous bright 

 lines at the cusps of the crescent of the sun then visible, chief among 

 them being the lines of hydrogen and the H and K lines of calcium ; 

 others, farther removed from the second and third contacts, show 

 only the Fraunhofer lines. 



III. " Researches on Modern Explosives. Preliminary Com- 

 munication." By WILLIAM MAGNAB, F.I.C., F.C.S., and E. 

 RISTORI, Ass. M. Inst. C.E., F.R.A.S. Communicated by 

 Professor RAMSAY, F.R.S. Received February 28, 1894. 



During the last two years we have carried out a long series of ex- 

 periments with explosive compounds for the purpose of studying 

 chemical reactions at high temperatures and pressures, and of eluci- 

 dating certain thermal constants relating chiefly to the specific heat 

 of gases under such conditions. 



For these experiments we have principally used nitro-glyceriu, 

 nitro-cellulose, and several combinations of these two bodies which 

 are used as smokeless gunpowders, for the reason that such modern 

 explosives offer the advantage of not only presenting comparatively 

 simple chemical reactions, owing to the absence of solid residue, but 

 also of enabling considerable variations to be made in their composition 

 so as to vary the proportions of the elements reacting. 



We also expected that the results which we obtained would make 

 a small contribution to the knowledge of explosives in general, 

 following up the lines indicated by the published work of Noble and 

 Abel, Berthelot, Sarrau, Vieille, and others. 



In this preliminary communication we propose chiefly to indicate 

 the results obtained in the measurement of the heat evolved by ex- 

 plosion, and of the quantity and composition of the gases produced by 

 this metamorphosis. 



We have also made considerable progress towards the determina- 

 tion of the actual temperature of explosion, and we have succeeded in 

 recording these high temperatures by photographic means, but, as 

 this work is not yet completed, we shall not further refer to it in 

 this paper, but we hope it will make the subject of another commu- 

 nication at an early date. 



These modern explosives, and especially the smokeless powders, 

 have assumed of late such importance that it may be of general inte- 

 rest to give here a brief sketch of their development. 



About thirty years ago experiments were made in Austria with the 



