Зображення сторінки
PDF
ePub

tions which, in some localities, are from 25,000 to 30,000 feet in thickness.

Thus, we have brought before us certain facts and relations pertaining to the Primordial formations, which each person may observe for himself. In the light of these facts and relations, we are enabled to see the utter untenableness of the position that these beds are Lower Silurian, in the proper sense of that designation. According to the view suggested by the considerations presented, it may seem strange that any mistake should have been made in regard to these rocks. If, however, we look at the matter in another light, and remember that our geologists regarded the Red Sandstone as of Medina age, we can discover some excuse for the error ; for, according to that view, they would not be surprised to find the arenaceous formation, now known as Potsdam Sandstone, crowning the subjacent masses of slate.

We may next inquire briefly in regard to the fossil remains furnished by these rocks.

On this branch of the subject I can only speak in the most general terms, reserving for another occasion the detailed account of the organic forms which, from time to time, have been brought to light. It is still doubtful whether any fossils can be referred to the Lower Taconic beds of Vermont. The Paleotrochis major, and P. minor, found in great abundance by Dr. Emmons in the Quartzite of North Carolina, are not known to occur on any other horizon.* Passing to the next great division of the Taconic we find in the Swanton Group organic remains peculiar to itself. Of these the Atops punctatus (trilineatus] of Emmons is the best known. In the Georgia Slates there is a much larger variety of genera and species. Among these may be mentioned species of Obolella, Orthis, Orthisina, and Camerella; also, Olenellus Thompsoni, and 0. Vermontana, and Conocephalites Teucer. No one of these occurs, so far as is known, in any more recent rocks. When we come to the Potsdam Sandstone we meet with still other species. Among the various forms found in this rock I will simply cite the Conocephalites Adamsi, C. Vulcanus, and C. minutus. Now, the several species belonging to this period are distinct from all those that have been discovered in the earlier rocks, and they probably died out before the beginning of the next era. But while the several forms of Conocephalites peculiar to the Potsdam Group are different from, they are yet closely allied to, the species of Conocephalites found in the Georgia Slate, thus indicating just what stratigraphy seems to suggest, viz : the true order of succession in the beds. the same time it should be added, that while the species in these successive groups are different, they still have a common Primordial type; a type which distinguishes them from the organic forms of the Calciferous Sandrock, and of the several succeeding formations of the Lower Silurian, and thus shows that the Potsdam Sandstone is strictly Primordial, and may be properly reckoned as Upper Taconic.

* [These supposed corals have recently been shown by Prof. O. C. Marsh to be inorganic. This Journal, vol. xlv, p. 217.-EDS.]

In order to avoid all occasion for misapprehension, a supplementary remark should be made. It is sometimes urged as an objection, and the fact has been well known to the writer for years, that beds of Lower Silurian rocks are found within the generally admitted Taconic limits. These beds occupy troughs and depressions in the older formations, as would be natural, and occasionally crown uplifts which have survived the abrading force of ages. On these overlying strata I propose to dwell more at length when I come to speak of the formations of the Champlain Basin under other relations. I now simply remark that their occurrence, under existing circumstances, no more disproves the existence of the underlying Primordial series of rocks than would the presence of Carboniferous strata in a given district, militate against the fact of subjacent Silurian, or Devonian, formations on which they rest as overlying beds.

We thus are enabled to see, on the threefold ground of thickness, of stratigraphical relations, and of organic remains, to mention no other considerations, that the Taconic, or Primordial, series of rocks cannot be properly regarded as Lower Silurian in the legitimate sense of that term. The facts presented clearly show that the Swanton Group on which the Potsdam was in places laid down, and on which it still rests, cannot be Utica Slate or Lorrain Shales. If stratigraphy be of any account, it proves this in the most unmistakable man

And, on this relationship, as I may venture to say, the whole matter, at least from one point of view, virtually turns. If the Potsdam Sandstone rest unconformably, as it really does, on such a series of older beds, and if there have not been any inversion or overlapping of the Potsdam in the localities referred to, and there is the best evidence that there has not, then it clearly and certainly follows that these inferior rocks are not Lower Silurian ; that they are more ancient than the overlying discordant Potsdam ; and that there is series of formations of vast extent which may be known as Taconic or Primordial, and of which the Potsdam Sandstone legitimately constitutes the crowning group.

ner.

The view now presented reminds me of certain statements made by Dr. T. Sterry Hunt, in a paper read last August at the meeting of the American Association for the Advancement of Science in Chicago, and printed in the September number of this Journal. In that paper he asserts that the beds which I have designated as the Black or Swanton Slates are Hudson River formations, by which I suppose he means Utica Slate and Lorrain Shales. As he advances no argument in support of his declaration, no argument is needed in reply. So far as his assertion is concerned, I would simply wish it to be looked at in the light of the facts which have been presented. On the supposition that the slate referred to is Utica or Lorrain, we have the strange anomaly of a formation, at once belonging to the summit of the Lower Silurian, and yet originally and still overlaid by Potsdam Sandstone.

While touching this matter I ought perhaps to add, that with the Triarthrus Becki of Green, Dr. Hunt has confounded the Atops punctatus (trilineatus), a species which Dr. Emmons long ago described as having marks distinguishing it from the Triarthrus Becki; which a committee of the American Association for the Advancement of Science pronounced to be different; and which no less a paleontologist than M. Joachim Barrande evidently regards as distinct from the Utica species.

Again, Dr. Hunt says that the Triarthrus Becki has been found in the underlying Hudson River Slates at Sharpshins (Lone Rock Point), and Appletree Point, near Burlington. Being very familiar with these rocks, it may not be impertinence in me to suggest, that Dr. Hunt undoubtedly refers, in part, to fragments of organic remains long ago met with at Lone Rock Point, the specific affinities of which, however, were never accurately determined ; and, in part, to a specimen of Trilobite discovered at Appletree Point by Sir William Logan, but which was, unfortunately, as I happen to know, too indistinct for exact specific identification. At the latter point I have found, at different times, several specimens of Trilobites, probably of the same species ; also, other fossils both at the same place, and at Lone Rock Point, of which I have something more to say in the sequel.

Once more, Dr. Hunt declares that, “the Conocephalites Teucer,” which I have cited as characteristic of the Georgia Group, "is, according to Mr. Billings, common to the [Georgia] Slates, and to the associated Red Sandstone." The implications which tliis assertion involves rest, so far as they have truth, on a series of misapprehensions. In the first place, the Red (or Potsdam) Sandstone is not “associated,” in the sense

in which the term is here used, with the Georgia Slates. In the second place, the fossil just mentioned never occurs, so far as is known, in the Potsdam Sandstone. But, in the third place, while it is not met with in the Red Sandstone, it is found in a sandstone, in a slate, and, I may add, in a limestone-in each of these several beds; in other words, it belongs to the Georgia Group, which consists of brown slate, with interstratified masses of gray limestone and brown sandstone. But, if such be the case, how could any mistake arise? First, the rocks are very complicated, and cannot be mastered without much study and long continued observation. Next, nothing is easier than misunderstanding. In speaking to Mr. Billings of the Georgia Group as containing Conocephalites Teucer, Olenellus, etc., I said, among other things : These slates are interstratified with sandstone. From this he inferred, as was afterward evident from one of his articles, that I meant the Potsdam Sandstone, whereas I referred to the brown sandstone of the Georgia series. Receiving this wrong impression unconsciously, and desiring to give full credit to others, he cited me in connection with Dr. G. M. Hall as authority in the matter--as having made out, by personal inspection, the actual interstratification of the Georgia Slates and the Potsdam Sandstonemas may be seen by turning to this Journal for January, 1862, (vol. xxxii, p. 100.) In this he did what was very natural under the circumstances, since the Red Sandstone occurs in close proximity to the Trilobite locality; insomuch, also, as he was mainly intent on the fossils; while Dr. Hall and I lived in the neighborhood, and were very familiar with the “lay” of the rocks. Accordingly, from what was perhaps an inadequate statement on my part, from an accidental misunderstanding on the part of Mr. Billings, and, as I may presume, from an innocent misapprehension on the part of Dr. Hunt, the true relations of these rocks have been misconceived. Thus, as I may add, the cited proof of the specific identity of the Georgia Group and of the Potsdam Sandstone falls to the ground.

Such is a brief exposition of a single point in the Geology of Western Vermont. In due time other points may be expected.

ART. XXXI.- On some derivatives of Trichlormethyl-sul

phon-chlorid, (C CI,) SO,Cl; by 0. LOEW, Assistant in the Chemical Department of the College of the City of New York.

This chlorid, discovered by Berzelius and Marcet in 1812, was the subject of extended investigations by Kolbe. Since that time no investigations on this compound have been made, although it possesses many interesting properties. I find that the simplest way to prepare it, is the following : 300 grms, bichromate of potassium in pieces of the size of a pea, 500 grm. common hydrochloric acid, 200 grm. nitric acid of the common strength, and 30 grm. bisulphid of carbon are mixed in a flask, filling it to one-fourth of its capacity and loosely stoppered. It is kept cool in the beginning and shaken from time to time. In about eight days the process is finished. In direct sunlight only four days are required. By addition of water the chlorid and nitrate of potassium are dissolved, and there remains the insoluble trichlormethyl-sulphon-chlorid. It is filtered off, washed, and pressed between sheets of filter-paper.

When this chlorid is dissolved in absolute alcohol and treated with sulphuretted hydrogen, sulphur is deposited, and hydrochloric acid and another compound of an acid character remain in solution. By neutralization with dry carbonate of sodium, the sodium salt of this new acid remains dissolved in the alcohol, and crystallizes by evaporation in shining scales. 0:469 grm. yielded 0·146 grm, sulphate of sodium =11:33 per

cent Na. 0·236 grm. yielded 0:490 grm. AgCl =51:37 per cent Cl. 0:511 grm. yielded 0.605 grm. sulphate of barium =16-24 per

cent S. The sodium salt of the trichlormethyl-sulphurous acid requires: 11:14 per cent Na; 51.95 per cent Cl; 15:56 per cent S; 15:56 per cent 0 ; 5:81 per cent C.

To obtain the free trichlormethyl-sulphurous acid, the sodium salt is decomposed by dilute hydrochloric acid and agitated with ether. The ether yields by evaporation this new acid in radiating needles. Both the acid and its salts are not of great stability; at a moderate temperature, especially when water is present, decomposition takes place and a very offensive odor is evolved.

The formation of this acid takes place according to the following equation :

« НазадПродовжити »