regarding the Rochs qftlie Red Sandstone Formation. 71 
creation, by constant laws, which have, in this particular case, 
produced at all times aqueous and igneous deposits, although 
the former are at present the most generally diffused, and the 
others much more limited. The same must also have happened 
at the period of formation of the red sandstone and grey-wacke; 
and in fact it did so, for the igneous rocks were then nearly of as 
local a nature as at present. But the old Neptunian rocks pre- 
sent some differences when compared with those in modern 
times, and the same may also happen with regard to the igneous 
rocks of different ages. Besides, as the aqueous rocks present 
differences between different localities, so, in like manner, the 
igneous rocks of all ages are not always identical in all the loca- 
lities of the same epoch ; thus, for example, the Mont d'Or and 
Cantal group is not identical in every particular with the group 
of Schemnitz or Tokay, although these two deposits are in all 
probability nearly of the same epoch. This being admitted, 
when we compare the pitchstones of the old red sandstones with 
those of the Cantal, instead of comparing them with those of the 
Hungarian group, we will perceive, that, excepting with regard 
to the crystals of quartz, the mineral ogical resemblance is still 
greater, for there we have no masses of pearlstone to embarrass 
us. Yet these pearlstones exist under the lithoid form in some 
localities of the ancient vitreous secondary rocks ; and although 
they are only found in small quantities, can this form a reason 
for not comparing these matters to the great deposites of trachy- 
tic pearlstones ? Could the comparison of a very recent arena- 
ceous bed with some old secondary sandstones be considered as 
extraordinary, when this similarity does truly exist ? 
If accessary circumstances, as the different extent of the sea, 
the vicinity of various formations, and many other causes, are 
enumerated, as having produced the differences in all the va^ 
rious arenaceous Neptunian deposites, why should we not employ 
the same arguments in explaining the anomalies observed be- 
tween old and modern igneous formations, especially as it is only 
necessary to explain the frequency or rarity of a particular circum- 
stance in two similar deposites ? Who can, besides, assure us 
that these pearlstones and porous rocks may not be found in 
much greater abundance in some old secondary pitchstone tracts 
of country ? 
