ine to consider that they are all of animal origin, and that many of the so-called species were formed by one species of animal. Also that specific differences in the animals making them would not generally be shown in the casts of the burrows of trails." 1. c. 604.

In the two counties, Franklin and Chittenden, which are especially discussed in this volume, we have the best display of Cambrian strata which is found in the state and on this account it may be well to add to what has been said as to the rocks of this formation in these counties some general remarks on the Cambrian of the state as a whole.

Some repetition of what has already been given on foregoing pages is unavoidable, but no more of this than seems necessary to continuity of statement will appear.

The beds of rock that have been satisfactorily determined as Cambrian in Vermont form a narrow strip which extends through the western part of the state between the Green Mountains and Lake Champlain. From the Canadian border south for about fifty miles, the area occupied by them, they are never far from the shore of Lake Champlain and here and there they form cliffs or headlands. The formation extends northeasterly from the Vermont border to the Gulf of St. Lawrence and southward through Massachusetts and New York down to the middle of Alabama.

How large a part of the metamorphic rocks of the Green Mountains are altered Cambrian strata cannot be told, at any rate not at present, but it is most probable that these beds have contributed to the mountain masses. Most of the Cambrian of Vermont is to be placed in the lower division, or the "Olenellus Zone" of Walcott.

It is also very probable that there are Cambrian rocks east of the Green Mountains and between them and the Connecticut River, but much yet remains to be determined as to the age of the rocks of eastern Vermont and I do not feel like speaking positively as to them.

Three or four miles south of Burlington the Lake shore is occupied by Utica shale and nowhere south of this point do Cambrian rocks come to the shore or near it, all the rocks along the Lake being Ordovician south of that point. Ordovician rocks, mostly Utica, also form the northern shore from St. Albans twenty miles north.

As is well known there was for a long time discussion, and often quite earnest, as to the age of these rocks. As long ago as 1847, C. B. Adams placed certain portions of the Cambrian in the Medina sandstone and both Professor Adams and others, including the geol

ogists of the old Vermont survey which published its final report in 1861, held to this opinion. The first to move these beds towards their proper place was Dr. Emmons, who soon after Adams had assigned them to the Medina, asserted that they should be placed. lower, either in the Calciferous or Potsdam. Adams' views, however, appear to have prevailed at that time and for many years afterwards. Mr. Billings in 1862 from a study of the fossils concluded that Emmons was correct in his location of these beds, and that they belonged in the Potsdam. This view was generally accepted by geologists until Dr. Walcott took up the study of the Cambrian and showed at first that the Vermont red sandrock should be placed in the middle portion of that age and finally, after a study of the Newfoundland beds, that they belonged in the Lower Cambrian and here undoubtedly they will remain.

There is no doubt that the older geologists were puzzled and misled because in several localities, as Snake Mountain, Rock Point, Malletts Head and elsewhere, they found the sandrock beds resting conformably on a black shale which they identified as Utica or Hudson River. For this reason they supposed, naturally, that the Vermont beds must be newer than the Utica. I am not quite sure, but I think that it was Sir William Logan who first recognized a great fault that ran from Canada on for many miles southerly through Vermont, and that the location of what by that time were regarded as Potsdam strata above the Utica was a result of this fault and subsequent overthrust.

Even Mr. Billings did not recognize the true state of the beds, and it is interesting to find him writing in the American Journal of Science in 1862: "At the promontory called Sharpshins (Rock Point) on the lake shore near Burlington, the cliff seems to consist of black slate at the base, overlaid by what appears to be a whitish magnesian limestone. This place has been several times described, but what struck me as particularly worthy of notice is that the under side of the limestone where it is in contact with the slate is smoothed, presenting very much the appearance of slickensides. infer from this that, either there is a fault here, or that the limestone has moved on the surface of the slate." Mr. Billings' limestone is really a white calcareous sandstone.

Of course since this overthrust has been recognized, there has been no difficulty in assigning the superincumbent beds to their proper place.

In the Cambrian of western Vermont we find, as has been shown in some detail on previous pages, a variety of beds. There are numerous and thick beds of limestone, 1,000 feet or more, which seem to lie at the bottom of the series. Above these there are, according to Walcott, 8,000 or 9,000 feet of shales, sandstones, slates, quartzite conglomerates, breccia. Not only are these diverse in composition, but also in color. Red is the prevailing tint of the sandstones, varying from light pink to dark red brown, the limestones always very siliceous, are drab or gray, the shales are gray or brown or light, the quartzites are white or gray or bluish, the slates are purple, green and variegated and are the well known roofing slates sold all over the country.

As a rule the beds throughout the whole are not greatly disturbed. This is true even along the line of the great fault and overthrusts. Of course there are anticlinals, tiltings and foldings here and there, but altogether these form an inconsiderable part of the whole.

By far the greater number of the beds dip at a low angle, perhaps 20° on the average, though often much less, in an easterly direction, i. e., towards the Green Mountains. Some of the beds are thick and of deep water origin, but most appear to have been formed in shallow areas. Ripple marks, worm tracks, sun cracks, etc., are common everywhere in the shales and sandstone. Very few of the beds are prolific in fossils; most of them seem to be quite destitute of anything of the sort. Even where many fossils have, during past years, been found, they are never abundant. There are, however, thin layers in the shales, as we have seen, some of them of very recent discovery, in which fossils are very abundant. Generally only a few species are found in any one locality and, indeed, altogether the number found in the state is not large. I suppose not more than fifty.

As we have seen, some of the beds afford quite a variety of trilobites, brachiopods, etc., while others are very full of one species and scarcely any others.

Historically, the most interesting part of our Vermont Cambrian is what we call the Parker ledge. It is here that the first fossils of note were found and many have since been obtained, though not at any time very numerous. Olenellus thompsoni, Mesonacis vermontana, as well as smaller trilobites down to the tiny Microdiscus parkeri have made the locality somewhat famous. Most of the species collected here have been described and figured by Dr. Wal