C 499 ] 



portance to the practical mechanic, has been, of all others, the mod neglct'Ved, ibicJ, 

 Muflchenbroeck's, Helfham's, and Fergufon's opinions of the law by which the 

 motions of bodies are retarded by fridtion, p. i66. Euler's theory not true, ibid. 

 Experiments to determine different properties of friftion, ibid. p. 167. The fridioa 

 of hard bodies in motion is a uniformly retarding force, p. i6g. Experiments to deter- 

 mine whether fridion, ca^teris paribus^ varies in proportion to the weight or preflure, 

 p. 170 — 172. Obfeivations thereon, ibid. Experiments proving that the fridion 

 of a body does net continue the fame when it has different furtaces applied to the plane 

 on which it moves, but that the fniallefi fiirface will have "the leatt friftion, p. 170 — 

 175. Refult of the author's examination into the nature of the experiments whicb 

 have been made by others, p. 176. Theory eflabiifhea upon the principles already 

 deduced, p. 178. Prop. I. to find the time of defcent and the number of revolutions 

 of a cylinder, or that circular feftion of a body on which it rolls down an inclined 

 • plane in confequence of its fridion, ibid. Cor. i. p. 179. Cor. 2. ibid. Cor. 3. 

 ibid. Cor. 4. p. 180. Cor. 5. ibid. Prop. II. the body being projefted on an hori- 

 zontal plane, with a given velocity, to determine the fpace through which the bodj' 

 will move before it flops, or before its motion becomes uniform, p. i8r. Cafe I. 

 ibid. Cafe II. p. 182. Cafe HI. p. 184. Definition of the centre of fridion, p. 

 186. Prop. III. to find the centre of fridion, ibid. Prop. IV. given the velocity 

 with which a body begins to revolve about the centre of its bafe, to determine the 

 number of revolutions which the body will make before all its motion be dcftroyed, 

 p. 187. Prop. V. to find the nature of a curve defcribed by any point of a b«d/ 

 afFeded by fridion, when it defcends down any declined plane, p. 188. 



G. 



Goodrich, John, Efq. See VarlaUe Star, 



H. 



HaleSy Dr. miflake of his, p. 271. 



Hea/, diminiflies the attradions of cohefion, chemiflry, ttiagnetifm, and elcdricity, 



p. 364. 

 Hell, Abbe. See AJlronotnical OL/ervatiofi^, 

 Hclfoam. Sec FriSlion. 



Hcr/chel, William, Efq. See Douhle Sfa' s, ConJlruSlion 0/ the HeaveftJ, 

 Home, Mr. Kverard. See Marine AniraaL 

 Hrpe, John, M. D. See A/a Fa-tida. 

 Hunter, John, Efq. See Marine AnimaU 



J u 2 



\^ hJlM^, 



