68 Professor Abel [March 21, 



means of tubes ; thus, when a diaphragm of thin bibulous paper was 

 inserted into the glass tube about half-way between the two extremities, 

 detonation was not transmitted, even with the employment of about 

 six times the quantity of fulminate that gave the result with certainty 

 under ordinary conditions ; and similarly the transmission of deto- 

 nation by increased charges of mercuric fulminate and of gun-cotton 

 was prevented by the introduction into the tubes of light tufts of 

 carded cotton wool just sufficient in quantity to shut out the light in 

 looking through the tubes. 



Among several other interesting results furnished by an examina- 

 tion into the conditions governing and results attending the trans- 

 mission of detonation by tubes, a remarkable want of reciprocity was 

 found to exist between mercuric fulminate and gun-cotton. The latter 

 substance is more susceptible to the detonative power of mercuric 

 fulminate than of any other substance, as will presently be further 

 shown. The quality of fulminate required to detonate gun-cotton is 

 regulated by the degree to which the sharpness of its own detonation 

 is increased by the amount of resistance to rupture offered by the 

 envelope in which the fulminate is confined. From 20 to 30 grains 

 are required if the detonative agent is confined in a thin case of 

 wood, or in several wrappings of paper ; but as small a quantity as 

 2 grains of the fulminate suffices to effect the detonation of com- 

 pressed gun-cotton, provided the fulminate be confined in a case of 

 stout metal (sheet tin) and be closely surrounded by being tightly 

 imbedded in the mass of gun-cotton. If there be no close contact 

 between the two, the quantity of fulminate must be very considerably 

 increased to ensure the detonation of the gun-cotton, and, in attemj^t- 

 ing to transmit detonation from mercuric fulminate to gun-cotton by 

 means of tubes, it was found necessary to employ comparatively very 

 large quantities of fulminate in order to accomplish this, even through 

 short lengths of tubes. But when the quantity of fulminate used 

 reaches certain limits, the detonation may be transmitted from it to 

 gun-cotton through very long lengths of tube. In applying gun- 

 cotton, on the other hand, to accomplish the detonation of mercuric 

 fulminate, it was found that this result could be attained, and through 

 considerable lengths of tube (7 feet and upwards) by means of very 

 much smaller quantities of gun-cotton than is needed of fulminate 

 to induce the detonation of gun-cotton through the corresponding 

 distances. 



This want of reciprocity between two detonating agents corre- 

 sponds to one even more remarkable, which was observed by the 

 lecturer in his earlier investigations on this subject. In the first 

 place it was found that the detonation of \ oz. of gun-cotton (the 

 smallest quantity that can be thus applied) induced the simultaneous 

 detonation of nitro-glycerine, enclosed in a vessel of sheet tin and 

 placed at a distance of 1 inch from the gun-cotton ; while with \ oz. 

 of the latter, the same effect was produced with an intervening space 



