VOL. LXVIII.] PHILOSOPHICAL TRANSACTIONS. '283 



manner of Mr. Robins were generally repeated by his commentators and others, 

 with universal satisfaction, the method being so just in theory, so simple in 

 practice, and altogether so ingenious, that it immediately gave the fullest con- 

 viction of its excellence, and of the abilities of its author. The use which that 

 gentleman made of this invention was, to obtain the actual velocities of bullets 

 experimentally, in order to compare them with those which he computed a 

 priori from his new theory, and thus to verify the principles on which it is 

 founded. The success was fully answerable to his expectations, and left no 

 doubt of the truth of his theory, when applied to such pieces and bullets as he 

 had used. But these were very small, being only musket balls of about 1 ounce 

 weight; for, on account of the great size of the machinery necessary for such 

 experiments, Mr. Robins and other ingenious gentlemen had not ventured to 

 extend their practice beyond bullets of that kind, but satisfied themselves with 

 earnestly wishing for experiments made in a similar manner with balls of a larger 

 sort. By the experiments in this paper I have endeavoured, in some degree, to 

 supply this defect, having made them with small cannon balls of above 20 times 

 the size, or from 1 lb, to near 3 lb. weight. These are the only experiments 

 that I know of which have been made with cannon balls for this purpose, 

 though the conclusions to be deduced from such are of the greatest importance 

 to those parts of natural philosophy which are dependent on the effects of fired 

 gunpowder; nor do I know of any other practical method of ascertaining the 

 initial velocities of military projectiles within any tolerable degree of the truth. 

 The knowledge of this velocity is of the utmost consequence in gunnery: by 

 means of it, together with the law of the resistance of the medium, every thing 

 is determinable relative to that business; for, besides its being an excellent 

 method of trying the strength of different sorts of powder, it gives us the law 

 relative to the different quantities of powder, to the different weights of shot, 

 and to the different lengths and sizes of guns. Besides these, there does not 

 seem to be any thing wanting to determine every inquiry that can be made con- 

 cerning the flight and ranges of shot, except the effects arising from the 

 resistance of the medium. 



Of the Nature of the Experiment, and of the Machinerij used in it. — The 

 intention of the experiment is to discover the actual velocity with which a ball 

 issues from a piece, in the usual practice of artillery. This velocity is very 

 great; from 1000 to 2000 feet in a second of time. For conveniently estimating 

 so great a velocity, the first thing necessary is to reduce it, in some known 

 proportion, to a small one. This we may conceive to be effected thus: suppose 

 the ball, with a great velocity, to strike some very heavy body, as a large block 

 of wood, from which it will not rebound, so that they may proceed forward 

 together after the stroke. By this means it is obvious, that the original velo- 



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