32 
GEOLOGICAL THEORIES. 
tured consideration. With respect indeed to the 
trappean rocks, notwithstanding I might have found 
authority and arguments, (as will subsequently be 
seen) for giving them a place among the transition 
series, and although their identity with these might 
be thought fixed, by even the solitary fact of that 
form of junction with slate called “ ribbon jasper” 
occurring here, yet, it happens that porphyry also, 
does itself in some places, run in veins through 
slate, or exhibit itself imbedded in fossiliferous 
sandstone ; mica-slate (by some ranked in the 
“ primitive” order) joins itself to the common mass 
of schistose rock, and even granite, as just said, has 
been seen much blended with slate in some situa-^ 
tions. Order therefore, and systematic lhan^ e moift 
in the positions and connexions of rocks, seem to 
be set at defiance, and perhaps geological theories 
will witness many more revolutions before such 
discrepancies will be reconciled. Continued accu¬ 
mulation of facts, with provisional theoretic state¬ 
ments seem to be the more eligible occupation of 
the geologist whilst surrounded with such perplex¬ 
ing phenomena. The kind of facts principally 
required are those affecting the natural connexions 
of strata in respect of mechanical union and chemical 
similarity, and the provisional theories in which it 
may be allowable to indulge, should invariably re¬ 
gard these data as their sole rational supports. With 
respect to chemistry applied to geological specula¬ 
tions however, it is but recently introduced as a 
means of investigation, and it is hardly known how 
far it may be carried into the detail of our science. 
Iii the perusal of the following remarks on the 
geology of our district, I trust the reader will perceive 
that though I have not called chemistry to my aid, 
I have framed my theories on such facts only, as I 
had it in my power to adduce. 
