1879.] on Recent Detonating Agents. 67 



otlicr variable circumstances, upon the transmission of detonation. 

 Half a grain of silver fulminate freely exposed and ignited by a 

 heated body, will trwnsmit detonation to some of the compound placed 

 at a distance of 3 inches from it, but does not do so with certainty 

 through a distance of 4 inches. But when the quantity of the 

 fulminate is just inserted into one end of a stout glass tube 0*5 inch 

 in diameter, and 3 feet long, its detonation is invariably induced 

 by that of a similar quantity of the fulminate placed just inside the 

 other extremity of the tube ; this result is uncertain when the 

 length of the tubes of the same thickness and diameter exceerls 

 3 feet 3 inches. Glass tubes were found to transmit the detonation 

 of silver fulminate much more rapidly than tubes of several other 

 materials of the same diameter and thickness of substance. Thus, 

 with the employment of double the quantity of fulminate required to 

 transmit the detonation with certainty through a glass tube of the 

 kind described, 3 feet in length, it was only possible to obtain a 

 similar result through a pewter tube 31 '5 inches long, a brass tube 

 23-7 inches long, an indiarubber tube 15*8 inches long, and a paper 

 tube 11*8 inches long. The difference in the results obtained was 

 not ascribable to a difference in the escape of force on the instant of 

 detonation, in consequence of the fracture of the tube, nor to the 

 expenditure of force in work done upon the tube at the seat of deto- 

 nation, since the glass tubes were always destroyed by the first explo- 

 sion to a much greater distance along their length than any of the 

 others, and the brass tubes, which were in no way injur(;d at the seat 

 of the explosion, did not transmit detonation to so great a distance as 

 the pewter tubes, which were always deeply indented. The trans- 

 mission of detonation appeared also not to be favoured by the 

 sonorosity or the pitch of the tube employed, as the sonorous brass 

 tube was not found to favour the transmission to the same extent as 

 the pewter tube. Moreover the transmission of detonation by the 

 glass tubes was not found to be at all affected by coating these tubes 

 with several layers of paper, or by encasing them in tightly fitting 

 indiarubber tubes. These differences appeared on further investiga- 

 tion not to be ascribable, to any important extent, if at all, to the 

 difference in the nature of the material composing the tubes, but to be 

 simply, or at any rate almost entirely, due to differences in the 

 condition of the inner surfaces of the tubes. Thus, brass tubes, the 

 inner surfaces of which were highly polished, and paper tubes, when 

 coated inside with highly glazed paper, transmitted the detonation of 

 the silver fulminate to about the same distance as the glass tubes ; on 

 the other hand, when the inner surfaces of the latter were slightly 

 roughened by coating them with a film of fine powder, such as French 

 chalk, they no longer transmitted detonation to anything like the 

 distance which they did when the inner surfaces were in the normally 

 smooth condition. Other very slight obstacles to the unimpeded 

 passage of the gas wave through the tubes were found greatly to 

 reduce the facility with which detonation could be transmitted by 



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