425 Ohfervathns o?t Pumice Stonty 



pofe whatever. When it falls into the fea, it floats often 

 to a great diftance ; and it may be found fometimes on the 

 coaft of Sicily and Calabria *. It is in general' remarked, 

 thM the whiter pumice (lor.e \i<, it is always the lighter t. 



The moft common ufe of this kind of flone is for po- 

 lifliing almoft every kind of fiibftance ; and it is exceedingly 

 proper for the pnrpofe, as it is foft enough to be rubbed tof 

 a fine powder 5 and yet its fineft particles remain fo rough 

 tllat they can attack and wear down the furface of bodies 

 Vithout making fcratches. The powder of vitreous ftones 

 would alfo rub off particles by friftion, but, on account of 

 its acute edges, would leave fcratches ; and to pound it f© 

 fine as to prevent this inconvenience, would require much 

 more trouble and time than the pumice ftone ; and even 

 then, this fine powder of Aitrcous ftones w-ould fuffer itfelf 

 to pafs over the bodies to be polifhed almoft likelargillaceous 

 earth, without making any impreffion upon them. The 

 •workmen, who employ pumice ftone for this purpofe, ufe it 

 cither pounded, fifted and waihed, or in whole pieces, as the 

 hatmakers, curriers, and fome workers in metal. The laft 

 inuft choofe fuch pieces as have fine pores, and are fo large 

 that they ean affunie the form proper for rubbing or fcower- 

 ing. On this account preference is given, in commerce, la 

 that kind of pumice ftone which does not confift of too- 

 fi-nall pieces. In general, it muft be light, rough, friable,^ 

 of a grey colour, and free from fand or any other forcigr^ 



'* Popowitfch, in his Rtfeaycbes refpeHing the Sea, p. 3.47, obfcrves, 

 that this pumice iVcme is caft by the weft wind on the Calabiian ihores, 

 and by the north wind on thofe of Sicily and Greece. He was told there, 

 that it was a fubflance thrown op by the volcanoes of the Lipari iflands. 

 But it may be fcen, by Dolomieu's account, that it never can be aa article 

 ,«f comnurce, as Ptipouitfch thinks. 



\ Cronfledtiays, in his Mineralogy, that the white pumice ftone is pro- 

 duced' from the black, by its being bleached in the open air. But this is not 

 liie cafe : the white is of that eolour when it is thrown up. See Olafsen's 

 Rrije durcb Ijluntl, ii. p. 103. Linnceus, therefore, has been guilty of an 

 *rror ib his ^v-f, Nat, iii, p. 18 1. 



parts. 



