114 ^ [Assembly 
the gneiss loses its seams of stratification. The other rocks also fre- 
quently change their nnineralogical character, by taking into their 
connposition the nainerals of an adjacent rock. The most impor- 
tant of these rocks is the primitive limestone; this occurs in most 
of the towns we visited in the primitive district. But its frequent 
occurrence is just becoming known. We had occasion to point it 
out frequently, to individuals, who, till then, were ignorant of its 
existence in their neighborhood. In many places it contains foreign 
matter, as scapolite, augite, feldspar, tremolite, &c., which is in- 
jurious to it for burning into lime, or quarrying it into chimney 
pieces, monuments, &c. 
Another fault with the primitive limestone is, that it is too coarse 
and friable for a building stone in very many of the localities we 
examined, though this is not particularly injurious when it is to be 
used for making lime. The friable nature of this limestone, and 
the certain rapid disintegration of large masses of it, wdienever it 
is exposed to the w^eather, has suggested to our minds the proba- 
bility that this stratum was formerly much more extensive than it 
is at present. Hillocks of some size, and strata many rods in ex- 
tent, are often so friable, that masses may be easily broken to 
pieces in the hands. Masses, when they are formed of such ten- 
der materials, are rapidly worn down and washed into the valleys, 
in the form of sand, and are ultimately spread over the soil, or 
carried by small streams into the rivers, and finally find their way 
into the ocean, there to form a new stratum of limestone on its 
bottom, or, during its suspension and solution, to furnish matter 
for the shells of molluscous animals. 
Admitting the abundance of lime in the earlier times, we are 
able to account for its great preponderance in the later forma- 
tions. Some authors, when speaking of this fact, have proposed 
the question, whether the molluscous animals had not the power 
of secreting lime, as their shells are composed mostly of a carbo- 
nate, and finding their remains extremely abundant in all the lime- 
stone deposites, as well as in many others, they seem to have 
great diflficulties in accounting for the original source of the lime 
of their habitations. 
Limestone, when compared with gneiss, hornblende and granite, 
is comparatively soft, and when exposed with them to the same 
wearing and disintegrating agents, must be abraded and worn 
down at least twice as fast. Where do we find the boulders of 
