546 APPENDIX. 



about the highest temperatures known, 3000-4000 on the air 

 thermometer : 



(1) The same quantity of heat being supplied to a gaseous 

 system, the pressure of the system will vary in proportion to its 

 density. 



(2) The specific heat of gases is practically independent of the 

 density as well at high temperatures as at 0. 



(3) The pressure increases with the quantity of heat supplied 

 to the same system. 



(4) The apparent specific heat increases with this quantity of 

 heat. 



Referring to temperatures deduced from the expansion of a 

 given volume of air, M. Berthelot points out that the scale of 

 temperatures defined by the variations in volume at constant 

 pressure (or by the variations in pressure at constant volume) and 

 the scale of temperatures defined by the quantities of heat absorbed 

 will correspond between and 200, but will diverge more and 

 more as the temperature increases until when the temperature 

 deduced from the expansion indicates 4500, that calculated from 

 the heat absorbed will be 8815. 



Further, he says that the indications of an air and of a chlorine 

 or iodine thermometer differ greatly at high temperatures, and 

 that there is no valid reason for preferring the indications of an 

 air thermometer to those of a chlorine thermometer in the defini- 

 tion of temperatures. 



The rapidity of propagation of detonation in solid and liquid 

 explosives. 



In continuation of the experiments made with gaseous mixtures 

 while studying the explosive wave (p. 88), M. Berthelot, with 

 the assistance of members of the French Explosive Commission, 

 has extended his experiments to solid and liquid explosives. Full 

 details are to be found in " Annales de Chimie et de Physique," 6 

 serie, torn. vi. pp. 556-574. Trials were made with gun-cotton and 

 "starch powder" compressed in metallic tubes, and at different 

 densities of charge ; also on granulated gun-cotton, dynamite, 

 liquid nitroglycerin, and panclastite, a mixture formed of equal 

 parts of carbon disulphide and liquid nitric peroxide. 



I. COMPRESSED GUN-COTTON. 



(1) In a former series of experiments the velocity in leaden tubes 

 4 mm. exterior diameter, and about 100 m. in length, varied 



from 3903 4267 m. per second, 

 and from 4818 6238 m. per second 



in tin tubes of the same size. The density of charge, however, was 

 1'4 in the tin tubes, and varied from 0'9 to 1'2 in the lead tubes. 

 This may have occasioned the variation in velocity. 



(2) In a second series of experiments, made a few years after- 

 wards on similar gun-cotton, at densities of charge varying from 



