PRELIMINARY CONSIDERATIONS. 
9 
that these comparisons between the rocks of the two countries were made before the applica¬ 
tion of organic remains to the identification of the age of rocks had become general, or even 
known here at all. Mineral or lithological characters were at that time the principal means 
of deciding this question, and it is well known how liable to error we become by depending 
upon this character, for the rocks even of different parts of this State ; how much more so, 
then, when attempting to identify those of distant continents. 
Again, while in Europe the older strata are much broken up and inclining at a high angle, 
those of the same age in New-York are very little disturbed, and throughout more than a 
thousand miles in extent westward, are nearly horizontal. Thus while seeking for these cha¬ 
racters in our rocks, we neglected much more important evidence; and it has sometimes 
happened that the same formation, in one place, from its horizontality referred to more recent 
deposits, has in other places, where disturbed and upheaved, been referred to older ones. 
This character of undisturbed horizontality over a great extent, in Europe and particularly 
in England, always considered as indicating deposits of a newer age, naturally led to the same 
conclusion here regarding our strata. At the present time, with all our guides, and which 
have only been afforded within a few years, we can scarcely conceive the condition of the 
subject during the earlier periods of observation in this country. From these facts, we learn 
that no condition of rocks, in regard to greater or less degrees of disturbance, can be consi¬ 
dered an indication of their age. We find in our country the oldest sedimentary rocks in their 
natural or horizontal position, unaltered and undisturbed; while in Europe, deposits much 
newer than the coal are so altered, that till recently they have been referred to the primary or 
hypogene. 
At the time our strata began to be studied, the doctrine of total destructions and renovations 
was generally admitted ; the termination of every geological period was supposed to be marked 
by the annihilation of every living thing, and the commencement of the next one as distinctly 
by a new and entirely different creation. Further observation has tended to the abandonment 
of this doctrine; and so far as our knowledge now goes, there seems to have been a gradual 
change from the first period of living things to the present time. Except in comparatively 
limited districts, no sudden destructions or violent catastrophes have occurred ; the loss of 
species appears to be due to their gradually dying out, as the climate and condition of the 
ocean became unfit for them ; and the appearance of new ones seems, in like manner, to be 
induced by changes causing a condition favorable to their existence. 
Of the extinction of species, we have an example on our own coast at the present time, and 
others might be enumerated. An extensive bed of the dead shells of the Pholas costata has 
recently been found at New-Bedford, while it is unknown as a living shell on the shores of the 
eastern or middle States.* It is thus evident that this shell at one time existed in great num¬ 
bers in a situation where, by some change unfavorable to its continuation, it has become 
extinct. 
Geol. 4th Dist. 
Dr. Gould’s Report on the Invertebrata of Massachusetts, p. 27. 
2 
