[ 48 ] 
JIL Obfervations on the Affinity between Bafaltes and Granite . 
By Thomas Beddoes, M. D . ; communicated by Sir Jofeph 
Banks, Bart . P. R. S. 
Read January 27, 1791. 
A LL our opinions on the formation of rocks and mountains, 
except volcanic mountains, mud of neceffity reft upon 
analogical reafoning,fince we have no direct teftimony concerning 
their origin. Hence, whatever portion of the mineral kingdom 
is but little conneded with our experience of the adion of fire or 
water, muft be (lightly paffed over, or fet afide for future invefti- 
gation, while the partizans of the two oppofite hypothefes, 
which at prefent divide the philofophical obfervers of foffils, fix 
their whole attention, and lay all the ftrefs of their arguments, 
on fuch particulars as they are able to conned by fome ana- 
logy with the chemical operations in which either fire or wa- 
ter are principally concerned. For this reafon, bafaltes has been 
much more thefubjed of deputation than granite ; the former 
fpeciesof rock offering appearances that coincide in fome degree 
with both kinds of chemical procefles, while the latter feems 
to ftand aloof from the experiments that have given birth to 
our fciences. We do, indeed, find opinions on the produdion 
of granite by one or other of the caufes above mentioned ; but 
they are generally * loofe conjedures, thrown out at random, 
rather than philofophical proportions, laid down in precife 
* > 
# The only exceptions known to me are, Phil. Tranf. Vol. LXV, p. 5 “"”47* 
and Edinburgh Tranfadions, Vol. I. p. 255”” 2 57» 
r terms, 
