54 ROCKS OLDER THAN THE TACONIC SYSTEM. 



lithological characters of any of its iiiemljcrs are; still I consider that it tends to remove 

 objections from the minds of some, to show how it happens that we tind 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 tlie Old Red sandstone 1 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 llie same process.* 



^ 6. 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 l)elong to a dillerent 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 liglitly 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. Lyelj.. 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 absent, 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 sulphuret 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 wish 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 (piartz, traversin" the coal ■ not 

 that they are injected in a melted state, but deposited from hot water or aqueous vapor holding silex in solution. 



