VOL. LXX.] PHILOSOPHICAL TKANSACTIONS. tJOa 



easily receives a strong electricity, I make no doubt but a good use might be made 

 of them, by exposing a great surface of them to friction. I have attempted 

 more than one method of constructing such a machine; but as I tried it only in 

 small, I have not pursued the object far enough, and therefore I think I have no 

 right to throw out hints unsupported by experience. 



END OF THE SIXTY-NINTH VOLUME OP THE ORIGINAL. 



1. Calculations to determine at what Point in the Side of a Hill its Attraction 



will be the Greatest, &c. By Charles Hutton, LL.D., and F. R. S. Anno 



1780, Fol. LXX. p. 1. 



1. The great success of the experiment, lately made by the k. s., on the hill 

 Schihallien, to determine the universal attraction of matter, and the important 

 consequences that have resulted from it, may probably give occasion to other ex- 

 periments of the same kind to be made elsewhere: and as all possible means of 

 accuracy and facility are to be desired in so delicate and laborious an undertaking; 

 it may not be unuseful to add, by way of supplement to the paper of calculations 

 relative to the above-mentioned experiment, in the 68th volume, an investigation 

 of the height above the bottom of a hill, at which its horizontal attraction shall 

 be the greatest; since that is the height at which commonly the observations 

 ought to be made, and since this best point of observation has never been any 

 where yet determined, but has been variously spoken of or guessed at, it being 

 sometimes accounted at ^, and sometimes at i of the height of the hill; whereas 

 from these investigations it is found to be generally at about only J- of the altitude 

 from the bottom. 



2. Let ABCEDA be part of a cuneus or pyramid of matter, its sides or faces 

 being the 1 similar right-angled triangles abc, ade meeting in the point a, and 

 forming the indefinitely small angle bad. Then, of any section bced, fig. lo, 

 pi. t), perpendicular to the planes abd and ade, the attraction on a body at a 

 in the direction ab, is equal to the constant quantity Si; where s =: sin. < bac 

 and s = sin. < bad, to the radius 1 . For, first, the magnitude of the flowing 

 section being every where as xU^, and the attraction of the particles of matter 

 inversely as the same, or as — ; therefore their product, -r-, or 1, a constant 

 quantity, is as the force of attraction of bced, whatever its distance may be from 

 the point a. And to find what the quantity of that attraction really is, the 

 author, by a very simple fluxionary process, determines its actual quantity to be 

 ss, as above stated.* 



* As this paper will be found at large, among many others, in the author's collection of his original 

 ■works, we shall limit our abstract here to an account of the method of process, and of the final results. 



4 h2 



