54 
ROCKS OLDER THAN THE TACONIC SYSTEM. 
lithological characters of any of its members are; still I consider that it tends to remove 
objections from the minds of some, to show how it happens that we find slates in the 
Taconic system so similar to those of the Gneiss or Primary system. If, however, the 
doctrine I have advanced in relation to the origin of these slates is objected to, or is not 
admitted as sound, I will ask on my part how it happens that talcose slate is found in the 
conglomerate of the Old Red sandstone % If there is any better answer than the one I have 
given ; if there is a better doctrine, let us have it. I say that if talcose slate, a sedimentary 
mass, can be made in the era of the Old Red sandstone, I see no objection to its being 
made at an earlier period by the same process.* 
§ 5. Position and relations of the taconic system. 
There is but one point which it is necessary to show, in order to prove that the Taconic 
rocks belong to a different period from those of the lower New-York system ; and this 
being proved, the doctrine of metamorphism, as usually applied and understood, is no 
longer important, or even of any consequence. The Taconic rocks may or may not be 
metamorphic; this may be admitted, or it may be denied : it has nothing to do with the 
question. Their texture may have been changed since their deposition; but if so, it by 
no means follows that they are of the period of the Hudson river slates, or of the lower 
Silurian rocks. 
In proceeding to show the position of the Taconic system, I shall repeat in part the facts 
stated in my report on the geology of the northern counties ; inasmuch as after a reexami¬ 
nation, I find but few instances in which I have had occasion to make corrections. These 
* In these remarks, as I have touched lightly upon the coal-field of Rhode-Island, I will permit myself to wander 
a little farther from the immediate subject of this essay. The doctrine that the anthracite of this small basin is a 
metamorphic coal, has been promulgated by some of the ablest geologists of this country and of Europe, particularly 
by Mr. Lyei.l. The hypothesis is, that the bitumen which it is supposed once formed a component part of these 
beds of coal, has been dissipated by heat, or, in other words, burnt out. To this doctrine the writer is not yet ready 
to yield his assent, for the following reasons: 1. The slates and conglomerate bear no marks of the action of heat 
(I speak only of those which I have seen). The fossils are similar in texture to those of other coal-fields, and they 
are perfectly free from all marks of fusion or induration by caloric. The Catamites are often in what some would 
call a talcose slate ; not so from heat, however, but in consequence of its origin. 2. If the bitumen was discharged 
by heat, then ought the sulphur of the sulpliuret of iron also to have disappeared. 3. If sufficient heat had been 
applied to volatilize the bitumen of the coal, then ought the slate also to exhibit marks of having been burnt. But 
it is said, farther, that the coal is changed into graphite. Admitting the fact, does it prove that heat was the agent of 
this change ? It does not necessarily follow, inasmuch as cast iron changes into graphite without this agency. The 
doctrine I wdsh to maintain, is, that if the coal has been thoroughly baked so as to dissipate all its volatile matter, 
then ought the rocks embracing the coal to exhibit signs of having been baked or burnt. In this connexion, too, I 
would inquire, if in the original formation of coal-beds, bitumen is a necessary element, one that will be invariably 
produced ? Admitting that bitumen is not a necessary product, does the coal of Rhode-Island possess characters so 
different from the western bituminous coal, that they cannot arise from pressure or other mechanical agencies ? The 
strongest evidence I have seen of the igneous action, is in the existence of seams of quartz, traversing the coal; not 
that they are injected in a melted state, but deposited from hot water or aqueous vapor holding silex in solution. 
