Maclure on the Arrangement and Origin of Rocks. 263 © 
rently alternating with the transition class, though their 
relative position, from the smallness of the mass, exposed 
by the decomposition of the superincumbent transition, 
cannot be so easily ascertained. Col. Silvertope lately 
nown agent r ng water, may have 
made and aggregated the rest of the primitive rocks. 
hen we gaze through our largest magnifying telescopes, 
at the expanse of the heavens, or look into the past and 
dream of eternity ; on considering the small atom of space 
or time that exact observation has occupied, we must 
be convinced that we have no right to limit either, nor to 
tima’ i the operations 
ture. All compact lavas are smooth and unctuous, - losing 
great part of their characteristic roughness, even those full of 
nall imperceptible pores, which in their fresh state con- 
stitute that harsh feel, whi 
tible pores to the very centre, of the apparently solid 
rock. | first discovered this fact near Montpelie 
have since remarked it in different places. It is bec 
fore possible that a lava with small pores imperceptible 
