of Projectiles thrown from Cannon, 225 



%Vith which the ball thrown from the infantry musket passed 

 over the interval between the one disk and the other, was 

 found at a mean value to be 343 metres per second instead 

 of 428. The diminution is in the ratio of 42 to 34. Tiie 

 experiments of the last kind are few in number, and we 

 shall deduce from them no conclusion : we shall not say 

 any thing either of some trials which were made to deter- 

 mine the loss of velocity which the ball experiences in 

 traversing the two Hrst leaves of the pasteboard j as the 

 principal object of our trials was not, as already said, to 

 employ this first apparatus for the advancement of the 

 science of arlillery, but to acquire some idea of the advan- 

 tage which this science might derive from it when con- 

 structed with that perfection of which it is susceptible. 



One of the most important changes which the author 

 proposes is, to increase the diameter of the disks and the 

 length of their axis in such a manner as to render them 

 proper for determining the initial velocities of cannon balls 

 of different calibres. It would be difficult to assign previ- 

 ously, and without preliminary trials, the term of tliis aug- 

 mentation compatible with the possibility and exactness of 

 experiments ; but there is no doubt that the apparatus we 

 used might be made of much greater dimensions, and such 

 as might render it fit to be employed for trials with caimon. 



Colonel Grobert proposes another change, which derives 

 its principal utility from that already mentioned. The ob- 

 ject of it is to afford the means of traversing the disks by 

 throwing balls in different directions, from the horizontal 

 to that which forms half a right angle with the vertical 

 line. To accomplish this end he has invented the follow- 

 ing mechanism, which is simple and easily constructed : — 

 He does not make the disks revolve around a common axis, 

 but gives to each of them a particular horizontal axis, to 

 which a pulley is affixed. The axis of the windlass has two 

 equal wheels corresponding to two pulleys, and two endless 

 chains, each of which passes round a wheel and a pulley. 

 The rotary motion which the windlass receives from the 

 descending weight is thus communicated to the disks, and 

 the dimensions of the wheels and pulleys nmst be well re- 

 gulated to make the disks turn together and to perform ex- 

 actly the same number of revolutions in the same period. 

 This condition being fulfilled, the supporter of one of the 

 disks (that which is furthest from the cannon) is disposed 

 in such a manner that it can rise vertically and fix itself at 

 different heights, fr)r each of which there are added some 

 links to the chain corresponding to that disk, '\a order to 



Vol. 22. No. 87. /higiist 1805. T '. give 



