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I ing surface in which there are a few large groovings would move, the mass following the general surface, and the portions in the grooves nearly or quite the course of the grooves. The thickness of the ice that followed the course of the valley was at least 2000 feet; for the southerly scratches occur not only on the summits of Mt. Tom and Mt. Holyoke, but also on the top of Mt. Pocomptuck in Heath, 15 miles west of the Connecticut, the height of which, as stated, is 1888 feet.

As to the Lamoille, Winooski and Otter creek valleys, the case is somewhat different; for if the movement of the ice in the valleys took place when the great glacier was in full force, it was a movement in each up the valley. The valleys are, however, of gradual slope-that of Otter creek extremely gradualand facts show that the ice is often moved up slopes many hundreds of feet. Dr. A. S. Packard, Jr., mentions the occurrence of fossils in the drift on Mt. Katahdin (Maine) at a height of 4000 feet above the sea, which must have been brought from the low country to the north where such fossils are found in place. As Dr. Packard observes, such facts show that icebergs were not the transporting agents.

It is, however, possible that each of these three valleys had its independent glacier during the melting of the ice. But if so, the great glacier must have been removed wholly out of the way of the valley glacier, so as to be no impediment to its movement down the valley; and it seems probable, from the small extent of these valleys, that by the time the general glacier had got out of the way, the valley ice would also have mostly disappeared. It is quite probable that a careful study of the scratches along one or another of these valleys may decide this interesting question.

It seems to be a natural consequence of a gradual melting of the great glacier, that sooner or later parts of the ice should have become independent and taken independent movements. We should naturally look for this independence at least in the large valley of the Connecticut river. A thinning of the ice to 2000 feet would necessitate, it would seem, a valley movement southward. And yet, as has been observed, the evidences of such a glacier movement do not exist—that is, the scratches are confined to so narrow a band along the center of the Connecticut valley as to show that they were not made by an independent Connecticut valley glacier. How then can we reconcile the fact that the ice must have thinned down to 2000 feet, 1000 feet, and so on, and yet had no movement as a sepa rate glacier? The explanation is this:-The melting of the ice took place in the early part of the Champlain era—an era of subsidence for New England and a large part of the continent (and therefore favorable to the melting); and this subsidence was greatest in New England to the north, having been at least

325 feet in the latitude of Burlington; nearly 150 feet near the northern boundary of Massachusetts, one hundred miles from the termination of the valley (the highest terrace on the river in Hinsdale, New Hampshire, being 159 feet above the river, according to the Vermont Report); and 45 to 50 feet at New Haven, the southern end of the Connecticut valley. Such a subsidence would have diminished the average slope of the whole valley about one-and-a-half feet a mile. For the southern half, from northern Massachusetts to Long Island Sound-100 miles-the slope, which now averages two feet a mile, would have been reduced to one-and-one-tenth of a foot a mile; and from Springfield down, which is 60 miles from the Sound, and the height of the water level only 64 feet above the Sound, making the average slope below about one foot a mile, aud where the Champlain subsidence was at least 60 feet more than at New Haven on the Sound, there would have been no appreciable slope in the waters; the basin, as it is designated by Hitchcock, from Middletown in Connecticut to Holyoke in Massachusetts, would have been strictly a basin.* Under such circumstances the ice along the valley would have lost all motion. The same condition of rest would have belonged to the ice of other north-and-south valleys of as small rate of descent; but not necessarily to east-and-west valleys like the Lamoille and Winooski.

High up even the north-and-south valleys, where the slopes were not sensibly changed by such a subsidence, local glaciers might well have existed. Evidences of them in the region of the White Mountains have been pointed out by Dr. A. S. Packard, in an excellent memoir on the Glacial Phenomena of Labrador and Maine (94 pp. 4to), published in Volume I of the Memoirs of the Boston Society of Natural History (1867); also by Professor Agassiz, in the American Naturalist for November, 1870, who states that he observed the marks of local glaciers in the White Mountain region in the year 1847, soon after his arrival in this country.

In the foregoing pages the facts from the State of Maine have not been referred to. These are well discussed by Dr. Packard in the memoir just referred to, in which he recognizes and applies the principle discussed in this and the writer's former papers on the valley glaciers. He observes that of the eighty

*In order to deduce the amount of subsidence for any place on the river from the height of the highest terrace above the ordinary level of the river, it is necessary to deduct first the height of the lower flats. This would give for the amount at Hinsdale 138 feet, which is 88 to 93 greater than at New Haven; and for the amount at Springfield, where the highest terrace is 136 feet, it would give 115 feet, or 65 to 70 feet greater than at New Haven. Such calculations may be in error, and generally will give less than the actual amount, because the height of the terrace depends on the amount of excavation that has taken place since the land reached its present level; and this is in most cases less than the amount of elevation.

localities of scratches that have been noted in Maine, the scratches in sixty-two have a southeasterly course; that the southeasterly course of the glacial grooves and striæ is especially marked in the interior of the State on the high lands and low mountains; but, approaching the coast, the evidence shows that the glaciers moved down the river valleys, and thus assumed a more north-and-south course, and at times, owing to local trends in the depressions, were even deflected so as to flow in a direction a few degrees west of south. The facts in Maine are just such as are general to New England.

The same principle is recognized by Prof. N. S. Shaler in the Proceedings of the Boston Society of Natural History, for 1870. Other similar facts have been recently pointed out in States to the west of New England. When the applications of the principle are studied out over the whole continent, we shall understand better than we now do the sources of the varied movements in the great glacier.

ART. XXXIII.-The Paragenesis and Derivation of Copper and its associates on Lake Superior; by RAPHAEL PUMPELLY.

II. Paragenesis of the Minerals associated with Copper.

No. 1. CAPEN VEIN.-This is apparently a true fissure vein. It occurs in a compact and very tough melaphyr, which is exceedingly chloritic near the vein. All the joints within a distance of several yards from the vein are covered with a coating to inch thick, of dark-green and bluish-green chlorite, having a combined fibrous and foliated structure oblique to the joint surfaces. The melaphyr is rich in magnetite. Sheet copper was found in mining, but not in paying quantity.

1. Laumontite, in thin seams.

2. Prehnite, in seams which cut through those of laumontite, also between symmetrically arranged bands of laumontite.

3. Chlorite, as destroyer and replacer of prehnite, and as lining of cavities in the latter.

4. Analcite, in clear crystals on the prehnite and chlorite. 5. Calcite.

No. 2. HURON MINE.-1. Laumontite, in thin crystalline bands on the sides of a cavity; the free ends of the opposed crystals nearly meet.

2. Prehnite, filling the space between the bands of laumontite. No. 3.* COPPER FALLS MINE.-Fissure vein. 1. (?) Natrolite. 2. Laumontite. 3. Analcite.

No. 4.* SAME VEIN.-1. Apophyllite. 2. Copper. 3. Orthoclase. *Taken from a list given by Hilary Bauerman, Quart. Journ. Geol. Society, Nov., 1866.

No. 5. BAY STATE MINE.-1. Prehnite. 2. Quartz. 3. Copper. 4. (?) Laumontite.

No. 6.* PHOENIX MINE.-Fissure vein. 1. Laumontite. 2. Quartz. 3. "Green-Earth."

No. 7.* BAY STATE MINE.-Fissure vein. 1. Quartz. 2. Apophyllite. 3. Calcite.

*

No. 8. BOHEMIAN MINE.-1. Analcite. 2. Copper. 3. Orthoclase.

No. 9. AMYGDALOID MINE.-Fissure vein. 1. Prehnite, in its characteristic reniform shape.

2. Quartz, in small crystals on the prehnite. 3. Analcite crystals, covering the quartz.

On the soft

4. Orthoclase crystals, on the analcite and quartz. No. 10. BAY STATE MINE.-Fissure vein. brown gangue. 1. Analcite, lining part of a vugg. The crys tals are inch in diameter, often white and transparent, but very much fractured. Near the contact with the rock they are often reddened internally and much altered, and then surmounted by the next member.

2. Orthoclase, in the usual minute crystals, some of which are scattered over the altered analcites.

No. 11. AMYGDALOID MINE.-Fissure vein. 1. Prehnite, in the characteristic reniform shape, forming the body of the specimen; fresh-looking on the free surface, but on the under broken side somewhat porous, with earthy fracture, and then rather intimately associated with datolite and a soft green (chloritic ?) mineral.

2. Copper, in films traversing the prehnite, and molded to the reniform surface. While the under surface of the copper bears the impression of the prehnite, the upper surface, now free, bears that of some mineral that is gone; threads of copper rising from this free surface inch are crystallized at the tips, where they stood above the mineral that has disappeared.

3. Minute grains of a hard yellowish-white mineral, sprinkled like meal over the prehnite and copper; under the microscope appear to consist of sheaf-like clusters of minute rhomboidal plates; fuses with difficulty.

4. Datolite, in microscopic crystals on No. 3; others, one line in diameter, rosy, with suspended flakes of copper, lie upon the prehnite.

No. 12. AMYGDALOID MINE.--(Fissure vein.) On the gangue-here chloritic-lie, 1. Calcite, imbedded between the gangue and No. 2.

2. Prehnite, forming the greater part of the specimen, and having a tolerably fresh luster.

3. Copper, in grains, flakes and threads conforming to the radiating cleavage planes of the prehnite.

4. Datolite; compact amorphous, white translucent mass, covering the prehnite with a layer of which inch thickness, still remains. The copper threads do not penetrate it.

No. 13. PEWABIC COPPER-BEARING BED.-This specimenabout 2 inches by 3 by -is evidently from the interior of a druse, to whose wall it was attached by only a small part of its surface. The body of the specimen is copper, very cavernous, much of it pseudomorphous after laumontite. The copper is very thickly bestrewn with small green crystals of quartzprisms terminated at both ends,-which are however older than the copper. On the sides and around the edges of the specimen there are beautifully modified scalenohedrons of calcite. The successions are:

1. The rock or mineral to which the laumontite was originally attached, and which has disappeared.

2. Laumontite or leonhardite; has also disappeared; the prisms were to inch long, terminated at one end with a hemidome.

3. A mineral, now gone, which must have been present to support the quartz crystals (see Quartz). It may perhaps have been the alteration-product of the laumontite or an enclosing mineral; laumontite crystals occur frequently enveloped, except the base, in calcite.

4. Quartz, in prisms to inch long, often terminated at both ends. They occur on parts of nearly every one of the pseudomorphs after laumontite; the copper is moulded to them, giving casts even of the striæ on the prisms, and they frequently pass entirely through the pseudomorphs after laumontite, so that the two ends of a quartz prism frequently just appear on opposite sides of the pseudomorph and transmit light. In some instances the quartz crystals are so numerous as to touch each other, but they are often wholly isolated, and supported only by the copper which is younger.

The quartz crystals contain minute, brilliant particles of copper, wholly isolated, in the interior.

5. Copper, in the form of laumontite, preserving often the sharpness of the angles and smoothness of the faces of the original mineral, when seen by the naked eye; under the glass the surface is less even. The pseudomorphs are not solid copper, as will appear in describing other specimens.

6. Chlorite? a soft, light-green mineral in minute hemispherical forms, with radiating structure, scattered over the quartz and copper. Wherever this mineral lies upon the quartz crystals, these are more or less penetrated by it, and some of them are eaten through and through to such an extent that the crystalline form is no longer recognizable.

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