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the epochs of great eccentricity might have had may be inferred from the fact that, adopting Mr. Croll's method of estimating solar temperature, the mid-summer heat of the northern hemisphere due to solar radiation, was from 40° to 50° higher than it now is. His layer of snow must therefore resist, not merely our present heats, but temperatures ranging from 100° to 150° Fahrenheit.

The remainder of the argument can be dealt with quite briefly, because it is based on the utterly fallacious results we have just described. The northern hemisphere being cooler the trade winds are thrown farther south. The Gulf Stream being caused, in part, by the trade winds, is thrown into the southern hemisphere, and thus the northern hemisphere is deprived of this latent source of heat and its temperature falls to a point far below the normal astronomical temperature. Considering separately the propositions that a cooler northern hemisphere would throw the trade winds south, and that this change in the winds would change the Gulf Stream, they both rest on too slender a basis to be worth consideration. We cannot therefore regard Mr. Croll's theory of a connection between the form and position of the earth's orbit and the Glacial epoch as having any reasonable show of foundation. The working out of such complex theories is of the less importance that there is no astronomical reason to believe that the solar radiation has been constant during a period of a million of years. Washington, February 21, 1876.

ART. XXXIII.—On crystals of Tourmaline with enveloped Orthoclase; by EDWARD H. WILLIAMS, Jr.

[Read before the Chemical and Natural History Society of Lehigh University.]

WHILE at Port Henry, N. Y., last July, visiting the newly constructed furnace at Cedar Point, I noticed large sized crystals of tourmaline in some heaps of quartz and feldspar in process of shipment up the lake.

The feldspar was orthoclase, and of two varieties: one white and compact; the other reddish and much weather-stained; the cleavage planes, especially the basal, were more or less covered with a film of sesquioxide of iron. The crystals of tourmaline in the quartz were simple prisms. Those in the feldspar, and in the second variety in particular, were peculiar; when the feldspathic matrix was fractured they readily separated from it, and proved to be mere shells of tourmaline filled with feldspar. From want of time I was then unable to visit the locality from which they were taken. When again at Port Henry I

found that the minerals came from a quarry worked by Messrs. Roe and Witherbee, five miles west of the town, and about 1500 feet above the lake.

The tourmaline which presented the peculiarity was mainly in the reddish feldspar, that in the white variety being, as a rule, solid. The tourmaline occurs in long prisms with rarely more than one termination. The observed faces are: Rhombohedral, 1, 1(R), -; scalenohedral, -5; prisms, I, -2, -. The common form is shown in Fig. 1. The crystals are commonly distorted, and are frequently terminated by but a single rhombohedral plane. Specific gravity, 3:11. Fuses before the blowpipe easily, with intumescence, to a dark bead.

In the specimens obtained, there seem to be two varieties of combination of the feldspar with the tourmaline: in the first, the tourmaline has imposed its form upon the feldspar; in the second, each has influenced the other.

[blocks in formation]

There are two types of the first variety. Fig. 1 shows the tourmaline with a solid termination, and the enclosed feldspar pierced with small tourmaline prisms which descend from the solid end with their vertical axes parallel to that of the a enclosing shell. These shafts, as well as the shell, decrease in thickness as they recede from the head. The tourmaline has thus a pyramidal cavity filled with feldspar; and in one instance this cavity is terminated by a face of -1. The shell is absent in places, with the feldspar apparently crystallized according to the prismatic planes of the tourmaline. In figure 1, the dark and light parts represent tourmaline and feldspar respectively;

[graphic]
[blocks in formation]
[graphic]

figs. 1a, 16, 1c are sections of the same crystal (fig. 1) parallel to the basal plane of the tourmaline, and taken at the points indicated by the letters a, b, c; they show the gradual disappearance downward of the tourmaline.

In the second type the rhombohedral faces, as well as those of the prism, are shells, and the tourmaline does not seem to decrease in thickness with its distance from the termination. After removing the shell from these combinations the enclosed feldspar has been obtained having the form of a distorted tourmaline crystal.

2.

Under this second variety there are cases in which the tourmaline prism encloses the feldspar and has no terminations. The feldspar often replaces the tourmaline, as is seen in Fig. 2, where the angles between the prismatic faces are distorted; one face is found parallel to a cleavage plane, usually i- of the orthoclase. In the figure the angles aßy and Bay are respectively 45° and 90°; the tourmaline prism is perpendicular to the basal plane of the feldspar; the edge toward the eye

[graphic]

3.

has been replaced by the orthoclase, while the tourmaline makes a re-entering angle behind it at the arrow-point; the plane abc is the cleavage plane parallel to I of the feldspar. These prisms are readily separated from their feldspathic matrix, and cleave parallel to its basal plane; each section thus given shows an uneven shell of tourmaline that in places entirely disappears. In all the cases mentioned the cleavage of the enclosed feldspar is parallel to that outside.

Fig. 3 shows where the tourmaline has been deposited on a cleavage face of the feldspar, and covers about one square inch;

the vertical edge toward the observer is rounded, and presents no measurable angle; the plane abcd is a cleavage plane parallel to i- of the feldspar. In one instance the feldspar inside the tourmaline encloses another shell of tourmaline filled with orthoclase.

The few specimens thus far obtained seem to point to simultaneous crystallization. There is no law governing the relations in position of the two minerals; for, in the same mass of matrix, there are crystals of tourmaline whose vertical axes make with the basal plane of the orthoclase angles varying from 0° to 90°. Some of these enclose the feldspar in prisms whose angles correspond exactly with those of theory, while others are distorted and are found between the cleavage planes of the feldspar. more extended study of these interesting forms, afforded by a greater number of specimens, may throw more light on this singular combination.

[graphic]

Philadelphia, Dec. 28, 1875.

A

ART. XXXIV.-The Conglomerate Series of West Virginia; by WILLIAM M. FONTAINE.

IN the May and June numbers of this Journal for 1874, I gave some account of the strata which, on New River, West Virginia, underlie the massive sandstone exposed at the Falls of the Kanawha. This account was necessarily imperfect, since at the point examined the base of the series was not exposed, and the exposures were very unfavorable for a detailed examination.

During the past summer I revisited this field, and made further examinations, at points more to the east, with such success that I am now able to present a detailed section of this field. Since the white sandstone of the Falls is the equivalent of what is everywhere called "the Conglomerate" of the Coal Measures, it might to some seem more fitting to call the rocks in question "Sub-conglomerate," or "Lower Carboniferous." In West Virginia, the strata which occupy the interval between the floor of the productive coals and the Devonian, are so greatly expanded, and so much diversified, that these terms are not definite enough to distinguish them. Besides, this New River system occupies precisely the horizon which is elsewhere commonly filled by conglomeritic sandstone alone, lying, as it does, between the red shales of the Umbral, and the lower productive coals. For these reasons I prefer to use the name "Conglomerate Series" for it. For like reasons it will be necessary to retain the names "Vespertine" and "Umbral," of the first Pennsylvania Survey, in describing rocks equivalent to those bearing these titles in the above named survey. A single instance will show this necessity. The system about to be described contains important coals. We find also far below them, in the Vespertine of Montgomery County, Virginia, near the White Sulphur, West Virginia, and elsewhere, well developed coals. To call these Sub-conglomerate or Lower Carboniferous coals would fail to distinguish them.

In my second visit to this region I made a re-examination of the strata at Sewell Station, the point at which most of the facts given in my first paper were obtained. In this last visit I found the strata quite well disclosed in the cuttings of the "Incline," made since my previous inspection. I also made a careful and detailed examination of the same strata at Quinnimont, a point on the Chesapeake and Ohio Railroad, distant by railroad twenty-one miles to the east of Sewell Station, but about ten miles by air line.

While the base of the series is not exposed at Sewell Station, yet, owing to the fact that the westerly dip is more rapid than

the fall of the river, even the underlying Umbral red shales are fully disclosed, and the entire series in question is contained in the lofty hills at Quinnimont, while in their summits they still retain a small remnant of the lower productive coals, with one and sometimes two coal beds.

While making my examination at Quinnimont I received valuable aid from Mr. S. F. Morris, C. E, and I take this opportunity to make my acknowledgments to him. Mr. Morris had, by levelling, determined the height of many points, and examined the character of the strata around Quinnimont, in behalf of the company owning the furnace and coal mine at that point. The data which he kindly put at my disposal were of great assistance in checking my own observations.

During the same summer I also made an examination of the country to the east of the Quinnimont, especially that portion in the vicinity of the White Sulphur Springs, Greenbrier County. It will perhaps be well to give here some of the facts thus obtained, bearing on the general geology of the region, in order more clearly to define the relations of the series to be described in this paper. In order to do this I will commence at the east and proceed west along the line of the Chesapeake and Ohio Railroad, whose general course is across the strike of all the strata underlying the rocks in question.

We may for a clearer exposition commence at Lewis Tunnel, a point six miles east of the White Sulphur. Here we find Vespertine strata which run in a narrow belt along the east face of the main Alleghany range, and contain the small coal beds, and plant-bearing shales, found near the Tunnel. The main range and the country westward for twelve miles is occupied by highly disturbed Devonian strata, mainly Hamilton. Portage, and Chemung, with probably the Catskill group. In the center of this belt the Springs are situated. Six miles west of the Springs, we find, on the east side of a small creek, highly contorted Devonian strata, and on the west side within 100 yards, the upper portion of the Vespertine, dipping gently eastward toward the contorted Devonian. Just above the Vespertine, in the hill across this stream, the base of the Umbral or Lewisburg limestone may be seen. The contortions and other evidences of great disturbance which follow us from the east up to this point now cease, and throughout the wide belt of country lying between this point and the Ohio River, the strata undulate more and more gently, until before Quinnimont is reached the rolls cease to reverse the dip, but serve to keep the strata longer at the surface than they would otherwise remain. in that position.

This sudden change in structure is not found here alone, although it seems to be more marked here than elsewhere. It

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