MECHANICS. 



31 



insensible velocities was determined by 

 some of the foregoing experiments. The 

 ensuing table shows the results of the 

 experiments: the weights were made 



to run over a distance of 6 feet, and the 

 times of describing the first three and 

 the last three feet were measured by a 

 half- second pendulum. 



TABLE VI. 



" It appeared in the Table III., that 

 to bend the cord No. 3, of 30 threads 

 in a yarn, about a roller of 1 2 inches 

 diameter, and with a tension of 500 Ibs., 

 would require a weight of 14.4 Ibs. ; of 

 which weight the constant part due to 

 the fabrication of the cord is about 

 1 .4 Ibs : this value may be retained, but 

 it will be here proper to reduce the part 

 due to the tension of the cord by the 

 quintal to l (14.4 1.4)= i x 10 = 3'6 Ibs. 

 From these data the last column to the 

 right of the above table was computed." 



CHAPTER VIII. Works on Friction 

 and the Rigidity of Cordage. 



(38,) Ox the subjects of friction and the 

 rigidity of cordage, we are not able to 

 direct the student's attention to any ex- 

 cept those to which we have occasion- 

 ally referred in the preceding treatise. 

 The most extensive investigations on the 

 subject are those of Coulomb, contained 

 in the tenth volume des Memoires des 

 savans ct rangers. 

 A memoir on friction by Ximenes 



(Terria e Pentica delle Resist, de sol 

 ne* loro Attr. Pisa, 1 782), may also be 

 consulted. 



In the second volume of the Peters- 

 burgh Transactions, there is a memoir 

 on friction, by Bulfinger. 



In the transactions of the French 

 Academy, 1769, there is a paper on 

 friction by Perronet. 



The memoirs by Professor Vince, 

 with his theory of friction, will be found 

 in the 75th vol. of the Philosophical 

 Transactions, and also in Ti [loch's Phi- 

 losophical Magazine, Nos. 65, 66. 



In the latter of these numbers will be 

 found an account of a series of experi- 

 ments instituted by Mr. John Southern, 

 of Birmingham, an ingenious engineer. 

 These experiments were instituted with 

 mills turning grindstones, and the ob- 

 ject was to corroborate the principle, 

 that friction is an uniformly retarding 

 force. " These experiments," says Dr. 

 Gregory, " are the more worthy of 

 notice, as they were made on heavy ma- 

 chinery with considerable variation of 

 velocity of the rubbing surface, and 

 great spaces rubbed over : the weight 



