96 



THE EXPLOSIVE WAVE. 



errors exist in all processes of this nature, and their magnitude 

 must be estimated in each instance. In this case it amounted 

 to 2 '8 per cent, of the quantity measured, on an average, and 

 to 6 '6 in extreme cases. 



Some trials made with a vertical tube, shorter it is true, gave 

 the same velocities as with the hori- 

 zontal tube. 



The rectilinear arrangement of the 

 tube such as was employed at first, 

 required too extensive a space, and 

 could only be effected in the open air 

 and under conditions that were difficult 

 to maintain and vary in prolonged ex- 

 periments. For this reason the idea 

 was conceived of laying the tube in the 

 laboratory itself, in parallel horizontal 

 rows separated by bends with a con- 

 siderable radius of curvature ; the whole 

 was fixed upon a vertical frame (see 

 Fig. 9, p. 91). 



In this operation the length of the 



* ube was -'^dby ? of a metre . 



bringing it to 43135 metres. 

 The detonation was repeated under these new conditions, 

 which gave for the velocity per second 



Metres. 



2860-4 

 2712-9 

 2791-5 



Average ... 2788-3 



These figures are rather lower than in the preceding experi- 

 ment, but they do not fall below the mean limits of error. It 

 may therefore be assumed that the velocity is the same in the 

 bent tube as in the straight one, and the general mean, 2841 

 metres, will be adopted. 



Composition of the tube. The unexpected magnitude of 

 this velocity, which is intermediate between the velocity of 

 sound in the detonating gaseous compound and in the metal 

 constituting the tube, gave rise to some doubts. Was it really 

 the rate of propagation of the detonation that was being 

 measured, or was it not rather some particular vibratory 

 movement propagated by the metal, arising from the explosion, 

 produced at its extremity ? 



It seems, however, hardly probable that a propagation of this 

 nature could cause the detonation of the fulminate, when we 

 consider the weakness of the movement thus transmitted, and 

 again the intervention of the leather discs T, between the metal 



