E 499 3 
jsortance to the pradtical mechanic, has been, of all others, the moft negledted, ibid, 
Muflchenbroeck’s, Helfham’s, and Fergufon’s opinions of the law by which the 
motions of bodies are retarded by fridtion, p, 166. Euler’s theory not true, ibid. 
Experiments to determine different properties of fridtion, ibid, p.167. The fridtioa 
of hard bodies in motion is a uniformly retarding force, p. 169. Experiments to deter- 
mine whether fridtion, ceteris parlous , varies in proportion to the weight or preffure, 
p. 170 — 172. Observations thereon, ibid. Experiments proving that the fridtioa 
of a body does net continue the fame when it has different furfaces applied to the plane 
on which it moves, but that the fmalleft furface will have the lead fridtion, p. 170 — - 
175. Refult of the author’s examination into the nature of the experiments which 
have been made by others, p. 176.. Theory eft ablilhed upon the principles already 
deduced, p. 178. Prop. I. to find the time of defeent and the number of revolutions 
of a cylinder, or that circular fedtion of a body on which it rods down an inclined 
plane in confequence of its fridtion, ibid. Cor. 1. p. 179. Cor. 2. ibid. Cor. 3. 
ibid. Cor. 4. p 180. Cor. 5. ibid. Prop. II. the body being projedted on an hori- 
zontal plane, with a given velocity, to determine the fpace through which the body 
will move before it flops, or before its motion becomes uniform, p. 1 8 r . Cafe I, 
ibid. Cafe II. p. i8z. Cafe III. p. 184. Definition of the centre of fridtion, p, 
186. Prop. III. to find the centre of fridtion, ibid. Prop. IV. given the vcdocity 
with which a body begins to revolve about the centre of its ba'e, to determine the 
number of revolutions which the body will make before all its motion be deftroyed, 
p. 187. Prop. V. to find the nature of a curve deferibed by any point of a b®dy 
affedted by fridtion, when it defeends down any declined plane, p. 188. 
G. 
Goodrich, John, Efq. See Variable Star « 
H. 
Hales , Dr. miftake of his, p. 271. 
Heat , diminilhes the attradtions of cohefion, chemiflry, magnettfm, and eledlricity, 
p. 364. 
Hell , Abbe. See Agronomical Obfervations . 
Hcljham. See Fridlion. 
Jlerfcbel , William, Efq. See Double Stars , Conjlrudiion of the HeavenU 
Home , Mr. Everard. See Marine Animal . 
Hope, John, M. D. See A/a Fcetida . . 
Hunter, John, Efq. See Marins Animal* 
U U U 2 D Injkif 
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