180 Mr Robison's Description of 



tensive alluvion under whkh the towns of Herculaneum Itnd 

 Ponrrpeii were buried. 



The formation of Vesuvius ^ates probably from the saflie 

 epoch, for no tradition and no historical monument anterior to 

 that celebrated catastrophe points in any way to its existence. ^-^ 

 Extracted from the " Cmipte Rendu" of the Meeting of the 

 Academy of Sciences of the \^th Nov. 1835. 



Description and Drazving of a Nexv Pivot-Castor Jbr Furni" 

 i^re, possessing the advantage of retaining the Oil for an in- 

 definite length of time. By John Robiso>j, Esq., F. R. S. 3E., 

 Vic.e-Pres. Soc. Arts. * 



Read Wth December 1833. 



Among the various forms given to castors for furniture, none 

 is found to act so well, or to last so long, as that which is com- 

 monly called the pivot -castor, or sometimes (when of a large 

 size) the French castor. The objections to its general use are, 

 first its cost, and secondly its depth, which makes it inapplicable 

 in many cases. 



Another objection may be applied to it, as well as to all 

 the other forms commonly sold in the shops ; namely, that they 

 require constant oiling to prevent them from wearing out of 

 shape, and becoming incapable of turning round. 



The castor now about to be described has the advantage of 

 taking no more room than a common castor, while it turns on a 

 fixed pivot, sufficiently long to insure fair action ; and containing 

 a reservoir for oil, which will keep it in good order for an inde- 

 finite length of time. 



These advantages are gained by reversing the places hitherto 

 given to the pivot and the socket. In the pivot castor as usually 

 made, the pivot forms part of the lower portion of the castor, 

 and points upwards ; while the socket is in that portion of the 

 castor which is attached to the furniture, and consequently 

 points downwards, which prevents it from retaining more than 

 the film of oil which may adhere to the parts by capillary attrac- 

 tion. 



• The Society's Honorary Silver Medal was awarded, 12th August 1835. 



