EXPLOSIONS IN BLOCK OF LEAD. 375 



produced under the influence of equal weights of the various 

 explosives may be taken as comparative measurements of their 

 power. When the substance is too active, a system of rents is 

 produced, following almost a diagonal direction in any vertical 

 section passing through the axis of the block, and tending to 

 detach a kind of truncated cone in the total mass. This accident 

 can, however, be avoided by diminishing the weight of the 

 substance. 



It has been found that the relations of the increases of capacity 

 obtained with variable weights of different materials remain the 

 same, the weight being moreover very small in comparison with 

 that of the block. Here are some of these relations which 

 express the increase of capacity produced by I grin, of explosive 

 according to the experiments of the Commission des substances 

 explosives : 



cc. 



Nitromannite 43 



Nitroglycerin .. ... ... ... 35 



Dynamite 75% ... . .., ... 29 



Dry gun-cotton ... ... ... ... ... ... ... 34 



Ditto (0-40 grm.) + ammonium nitrate (0-60 grm.) ... ... 32 



Ditto (0-50 grm.) + potassium nitrate (0'50 grm.) 21 



Mercury fulminate ..13-5 



Ditto, eliminating the weight of the mercury by calculation ... 45 

 Panclastites : 1 vol. carbon disulphide + 1 vol. nitric peroxide 25 



2 vols. CS 2 + 1 vol. N0 2 ' 18 



3 vols. CS 2 + 5 vols. N0 2 (complete oxidation).,.. ... ... 28 



1 vol. essence of petroleum l + 1 vol. N0 2 28 



2 vols. essence of petroleum l + 1 vol. N0 2 ... 18 



1 vol. nitrotoluene + 1 vol. N0 2 ... 29 



This process furnishes very interesting comparative data, but 

 it does not apply to slow powders, such as black powder, as the 

 tamping is then driven forward before the chamber has been 

 enlarged. 



In the case of rapid powders the relations are not the same as 

 those resulting from the quantities of heat and of the gaseous 

 volumes. Thus these two quantities are nearly the same for 

 nitroglycerin and nitromannite, whereas the capacities are greater 

 by a fourth in the case of the latter substance, doubtless because 

 its explosion is effected in a shorter time. 



The classification of the relative force of explosives according 

 to their effects changes very much according as the operation 

 is carried out with or without tamping. Generally speaking, 

 studies of this kind are only fully valid for works, effects, and 

 materials comparable to those which formed the object of the 

 preliminary experiments. 



12. Such is the ensemble of the scientific data we must 

 endeavour to obtain before laying claim to the complete theory 

 of a given explosive substance. 



1 Containing one-tenth of its volume of carbon disulphide. 



