58 Oi'iervations on the Processes of Tanii'nig. 



as 5 / and r r represent the ratio of" the velocities of the 



points s and r, they will be to eaeli other as I — ■ : 2 a 



or as m x CB : a x CA ; hence, when the body rolls 

 Vi.\ihout sl'tdi /I g, as : a r :: m x CB : « x CA. 



Cor. 4. The lime of descent down CA is = /- — ; but 



by the last Cor. when the body rolls without sUd'nig, a = 



"'Jll^^lS, hence the lime of descent in that case = AC 



J 



'X-^C 



; now the time of descent, it there were no 



friction, would be = -~7~ =:, hence the time of descent, 

 when the bodv rolls without sliding : time of free descent 



:: '\/sa : ^fr a. 



Cor. 5. Bv the last Cor. it appears, that when the body 

 just rolls without sliding, or when the friction is jii.st 

 equal to the aecelerativc force, the time of descent = AC 



— : now it is manifest that the time of descent 



x-v/) -xtJe ' 



vill continue the same, if the friction be increased; for the 



bod\' will still freely roll, as no increase of the friction actiuLj 



at a can affect the motion of the point s. 



If the bodv be projected from C with a velocitv, and at 



tlie same time have a rotatoiy motion, the lime of descent 



and the number of revolutions may be determined from the 



common principles of vmiformly accelerated motions. As 



we have alreadv investigated the aeeeleralive force of the 



bodv down the plane, and of its rotation about its axis, it 



pccms therefore unnecessary to lengthen out this paper with 



the investigations. 



[To be continued. J 



VII. Oheri'dtinns on the Processes of Tanning. Bi/llvM- 

 ■ PiiKV J)av'v, iJvey., Professor of Ckemislnj in the Roi/nl 



Jn addition. 



[Concluded from our last volume, p. 85.] 

 II. On th'.' Impregnation of Shin iiilli I lie Tanning Principle. 



-L HE tannino; lixivium or ooze is generally made in tlii*! 

 coumry, bv miusmg bruised or coarsely' powdered oak bark 

 ill v»atcr. 



bkius are tanned by 1 .eing successively immersL'd in li\i- 



viums. 



