r 1158 ) 
le Several Microfcopicril Oh/erVatkm on the faniice^ 
Stone J Cord, SjmnpSj &cc» In a Letter from Mr 
Anthony Van Lcuweahock, F. ^ S. 
I Have for fome time made but few Obfervations^ fome 
of my llemarks madeia the beginning of the Summer 
concerning the Pumice-ftone, are as follows. I have feve- 
ral times heard fay that that Stone which fome People call 
DryfiothQTS Pumice- Jlfi^e^whkh 1 have feen the Silver fmiths 
ufe for fcouring their Hammers, wherewith they beat 
out their Silver, and which is likewife ufed by Hatrers ia 
their Trade, that the faid Pumice-ftone is found driving 
.in the Sea, and that the occafion of its lightnefs is, that 
it is calcined by the Fire before it is thrown out of the 
Burning Mountains, after fuch a manner, as to fit it for 
fwimming on the top of the Water. 
I have oftentimes obferved this Stone, but could never 
conceive that the Cavities which are found between the 
parts thereof (excepting thofe exceeding fmall Tubes or 
Pipes, fome of which appear to be hollow) could be oc- 
cafioned by Fire. - 
For if it were true, that fuch Stones were thrown out 
of the Volcanoes, or Burning Mountains, very high into 
the Air, for inftance, 20© Rods, according to all appear- 
ance, they would be red hot. 
This being granted, let us fuppofe likewife that thefe 
glowing Stones will be four Seconds of a minute in rifing 
to fuch a height^and four more feconds a falling into the 
Sea^ in which time, according to our Hypothefis, it 
would 
