162 Mr. F. A. Abel on the [Feb. 5, 



A great difference appeared, at first, to be established in the power pos- 

 sessed by tubes of different materials of favouring the transmission of 

 detonation, the glass tubes being far in advance of the others in this 

 respect. It was eventually established, very clearly, by a series of experi- 

 ments that this difference was not due, to any decisive extent, to the 

 physical peculiarities (in regard to sonorosity, elasticity, &c.) of the 

 materials composing the tubes, but chiefly to differences in the degree 

 of roughness of their inner surfaces, and in the consequent variation of 

 the resistance opposed by those surfaces to the gas-wave. Thus the 

 power of a glass tube to favour the transmission of detonation was 

 reduced, by about two thirds, by coating the inner surface with a film of 

 French chalk, while the facility of transmission, through a brass tube, was 

 nearly doubled by polishing its interior, and was increased threefold, 

 with a paper tube, by coating the interior with glazed paper. 



The following are some of the points established by these experiments 

 on the transmission of detonation by tubes : 



1. The distance to which detonation may be transmitted through the 

 agency of a tube to a distinct mass of explosive substance is regulated by 

 the following conditions : 



(a) by the nature and the quantity of the substance employed as the 

 initiative detonator, and by the nature of the substance to be detonated, 

 but not by the quantity of the latter, nor by the mechanical condition in 

 which it is exposed by the action of the detonation ; 



(>) by the relation which the diameter of the " detonator," and of the 

 charge to be detonated, bear to that of the tube employed ; 



(c) by the strength of the material composing the tube, and the conse- 

 quent resistance which it offers to the lateral transmission of the force 

 developed at the instant of detonation ; 



(d) by the amount of force expended in overcoming the friction between 

 the gas and the sides of the tubes, or other impediments introduced into 

 the latter ; 



(e) by the degree of completeness of the channel, and by the positions 

 assigned to the detonator and the charge to be detonated. 



2. The nature (apart from strength or power to resist opening up, or 

 disintegration) of the material composing the tube through which detona- 

 tion is transmitted, generally appears to exert no important influence 

 upon the result obtained. At any rate the differences with respect to 

 smoothness of the interior of the tubes far outweigh those which may 

 prove traceable to differences in the nature of the materials composing 

 them. 



In the tube experiments with gun-cotton many instances occurred in 

 which the mass operated upon was exploded, but with comparatively 

 little if any destructive effect, portions of the gun-cotton being at the 

 same time dispersed and occasionally inflamed. Similarly, the mercuric 



