1 -46 1 
*culiar to tliefe waters, having never feen nor heard of 
•them in any others. They are remarkably fmall, fcarcely 
exceeding, a line or two in length, and are perhaps the 
fmalled: univalve or teftaceous animal of any fuch kind 
hitherto difcovered. It.is mentioned and figured by van- 
•DELLi in his treatife 'fhermis Patavinis\ but the fi- 
gures are not good, and much too large; as may -be feen 
,by the original fpecimens herewith fent. 
Such are the obfervations, which I have the honour 
to prefent to you, sir, and to the other learned members 
of the Royal Society upon the prefent occafion. I fhall 
.think myfelf very happy if they afford any fatisfaiiion; 
and more particularly fo, fhould they be found condu- 
xive to the advancement of fo interefting a j:)rovince of 
-Science as that of Phylical Geography, which being 
grounded upon fa6ts, that require obfervation, feems hi- 
therto to have fuffered for the want of it. If, contrary to 
the common opinion, I have infilled on the local origin 
of moft vulcanic tra61s, it may further be confidered, that 
this feems full as confiflent with the principle of their 
.origin, as it is agreeable to the ph'^nomena themfelves. 
For fire not only. penetrates, pervades, defiroys, and new 
modifies the texture of the molt folid bodies ; but is alfo 
often generated in thefe bodies, without the previous in- 
tervention of other fire ; which coiifideration alone might 
lead us to the opinion I have advanced, were there not 
fuch evident proofs in fupport of it. Thefe will, I hope, 
receive a llronger confirmation from a more particular 
^account of the vulcanic phaenomena of Auvergne and 
Velay, 
