Vjt On the. Velocity of Water Wheels. 



in all poflible directions, and adhering to one another by a cer- 

 tain degree Qi'coheiive force. He thought that if he could, 

 by anv proctfs, deitroy that adherence, without altering much 

 the iblidity of the cryftals themfelves, he might thus obtain 

 a loofe, but entire, ftony aggregate, which would become 

 flexible on account of the relative mobility of the integrant 

 cryftals, but keep its folidity and preferve its form in con- 

 fequence of their being deeply implicated and interwoven 

 among themfelves. 



According to that theory, he undertook a feries of expe- 

 riments by expofing flips of marble to the action of fire in 

 fand- baths of regularly graduated and well afcertained tem- 

 peratures : he thus found a point where the adhefion of the 

 cry Hals was loofened, without any material alteration in their 

 hardnefs. He gave to his friends fome fpeeimens of Carrara 

 marble thus rendered flexible. I have one of them in my 

 poflfeffion here in London, which may be feen by any 

 perfon who {hould yet entertain any doubts as to the poffi- 

 bility of the fa&. 



Now, a volcanic fire may have a6fed on a large mafs of 

 marble nearly as my friend's furnace has done on his fmall 

 fpeeimens ; and this explanation of the natural phenome- 

 non I confider as being as near to truth as moft of our con- 

 jectures on fimilar fubje6ts can be. 



I am, Sir, with true regard, 

 Your moil obedient humble Servant, 

 Mr. Tillocb. M. A. Pictet, f.r.s, 



Lond. et Edinb. 



XLT. On the Velocity of Water Wheels. By Mr. Robertson 

 Buchanan, Engineer. Communicated in a Letter to 

 the Editor. 



PEAR SIR, London, No. 75, Piccadilly, 



Ti4th Avgutt, 1 So;. 

 HE accompanying paper was read in May 1799, in 

 a Philofophit-al Society at Edinburgh. I offer it to you with 

 diffidence, knowing that it contains things contrary to re- 

 ceived opinions. Having, however, made no wilful error, if 

 you think proper to pubhfti it in your Magazine, it may in- 

 duce thofe ^vho have leifure and abilities to enter more fully 

 into the investigation of the fubjeei. 



I am, dear Sir, 

 Your very humble Servant, 

 JXr. THlcch* Robertson £ u c h a n a x. 



