Green Mountains, I have found the rocks of Anglesea to offer remarkable lithological resemblances.

It may here be noticed that the gold-bearing quartz veins in North Wales are found in the Menevian beds, and also, according to Selwyn, throughout the Lingula-flags. These fossiliferous strata at the gold-mine near Dolgelly appear in direct contact with diorites and chloritic and talcose schists, which are more or less cupriferous, and themselves also contain gold-bearing quartz veins. [Mem. Geol. Survey, part 2, pp. 42; 45, and Siluria, 4th ed., 450, 547.]

The Table on page 312 gives a view of the lower paleozoic rocks of Great Britain and North America, together with the various nomenclatures and classifications referred to in the preceding pages. In the second column, the horizontal black lines indicate the positions of the three important paleontological and stratigraphical breaks signalized by Ramsay in the British succession. [Mem. Geol. Survey, III, part 2, page 2.] In a table by Dividson in the Geological Magazine for 1868 [V. 305] showing the distribution of organic remains in these lower rocks, he gives, as the Festiniog group of Sedgwick, only the Dolgelly and Maentwrog beds of Belt (the Upper and Middle Lingula-flags); and makes of the two divisions of the Tremadoc rocks a separate group; the whole being described as the Upper Cambrian of Sedgwick. This however is not the present grouping and nomenclature of Sedgwick, nor was it his earlier one. So far as regards Middle and Upper Cambrian, this discrepancy is explained by the fact already stated, that in 1843 Sedgwick proposed, as a compromise, the name of Cambro-Silurian for his Bala group, previously called Upper Cambrian; by which change the Festiniog or Middle Cambrian became Upper Cambrian. When the true relation between the Lower Silurian of Murchison and the Bala group was made known, Sedgwick, as we have seen, re-claimed for the latter his former name of Upper Cambrian; but this had meanwhile been adopted for the Festiniog group, in which sense it is still used by Lyell, Phillips, Davidson, Harkness and Hicks. The Festiniog group, or Middle Cambrian, as defined by Sedgwick, however, included not only the whole of the Lingula-flags but the Upper and Lower Tremadoc rocks. [Philos. Mag. IV. viii. 362.]

The only change which I have made in the groupings of the British rocks adopted by Sedgwick and by Murchison, is in separating the Menevian or Lower Lingula-flags from the Festiniog,

and uniting it with the Bangor group or Lower Cambrian. In this I follow, with Lyell and Davidson, the suggestion of Salter and Hicks.

In the third column, the sub-divisions are those of the New York and Canada Geological Surveys; in connection with which the reader is referred to a table published in 1863, in the Geology of Canada, page 932. Opposite the Menevian I have placed the names of its principal American localities; which are Braintree, Mass., St. John, New Brunswick, and St. John's, Newfoundland. The farther consideration of the American subdivisions is reserved for the third part of this paper. With regard to the classification of Angelin, it is to be remarked that although he designates II as Regio Olenorum, and III as Regio Conocorypharum, the position of these, according to Linnarsson, is to be reversed; the Conocoryphe beds with Paradoxides being below and not above those holding Olenus. The Regio Fucoidarum in Sweden has lately furnished a brachiopodous shell, Lingula monilifera, besides the curious plant-like fossil, Eophyton Linnæunum. [Linnarsson, Geol. Magazine, 1869, vi. 393.]

(The third and concluding part of this paper will appear in the next number of the Naturalist.)

REMARKS ON THE TACONIC CONTROVERSY.

BY E. BILLINGS, F.G.S.

TABLE of the Silurian formations of New York and Canada as recognized previously to 1859.

UPPER SILURIAN.

16 Lower Helderberg.

15 Onondaga.

14 Guelph.

13 Niagara.

12 Clinton.

11 Medina.

10 Oneida.

LOWER SILURIAN.

9 Grey sandstone.

8 Hudson River. 7 Utica.

6 Trenton.

5 Black River.

4 Birdseye. Chazy.

2 Calciferous.

I Potsdam.

The Red Sandrock of Vermont was originally placed about here by Dr. Emmons, followed by Adams, Rogers, and others. It was afterwards referred to a horizon near the Potsdam by Dr. Emmons and E. Billings.

Position of the Taconic rocks and Quebec group according to Prof. Hall and others. At first adopted, but rejected by the Canadian Survey in 1860,

Approximate horizon of the Quebec group as decided by SirW. E. Logan & E. Billings in 1860

Position of the Red Sandrock of Vermont (nearly)according to Dr. Emmons & E. Billings TACONIC SYSTEM. Position of the Taconic System according to Dr. Emmons.

It frequently happens that a science, such for instance as that of geology, possesses a sort of an aristocracy, consisting of the most talented, learned, active and influential of its devotees. The views of this body of men, on any difficult problem that may present itself, are usually regarded as conclusive, and are quietly adopted by the less distinguished members. Indeed, the opinion of any one of these latter, would be scarcely listened to, provided it should happen to be contrary to the established creed

of the dominant party. As a general rule the leading men are right, and yet it will sometimes happen that they are wrong. One of the most remarkable instances on record, is that of the great question in American Geology, relating to the age of the rocks which Dr. Emmons called "The Taconic System." Upon this question nearly all of the leading geologists of North America arranged themselves upon one side, and, as it turned out after more than twenty years discussion, on the wrong side. Although they were wrong, yet so overwhelming was the weight of their authority, that for nearly a quarter of a century, Dr. Emmons stood almost alone. He had a few followers, but they were not men who had made themselves sufficiently conspicuous and influential to contend successfully against an opinion that was supported by all the great geologists of the continent in one compact body. In consequence of this powerful opposition, the Taconic theory gradually sank so low in reputation, that it was at length considered to be scarcely worthy of the notice of a scientific man.

During the last thirteen years, a great revolution of opinion has occurred with regard to the views of Dr. Emmons. Although not entirely adopted, they are now considered to be, in a general way, well founded. The opposite theory, that all of those rocks which he placed in the Taconic System are above the Potsdam sandstone, instead of below it, as he maintained, is completely exploded. It is at this moment dead, more so than was the Taconic theory in 1859, the year in which the subject was reopened. As I understand it at present, some of the Taconic rocks are certainly more ancient than the Potsdam, others may be of the same age, and perhaps some of them more recent. The details are not yet worked out, and judging from the manner in which the strata are folded, broken up and thrown out of their original position by almost every kind of geological disarrange. ment, I venture to say that no man, at present living, will ever see a perfect map of the Taconic region.

The theory, that the Taconic rocks belonged to the Hudson River group, was an enormous error, that originated in the Geological Survey of New York, and thence found its way into the Canadian Survey. No doubt the mistake was due, in the first instance, to the extraordinary arrangement of the rocks, the more ancient strata being elevated and often shoved over the more recent. Thus, without the aid of paleontology, it was im