but irregularly and slightly serrated, either by black or grayish points. This was particularly noticeable on the south preceding side, where the black disk seemed to be prolonged by a short grayish appendage. This peculiarity already observed in the morning soon after the first internal contact, was still visible during the afternoon when the sky was clear and the image steady; although it was not then so apparent.

A sharp watch was kept for the luminous ring, and I had almost lost all hope of seeing it, when soon after the sky cleared up, I saw a short and narrow arc of light hanging on the preceding side of the black disc, and a little larger and wider one on the following side. As a few small faculæ were scattered in the vicinity of the planet, I at first thought that Mercury was passing over some of these objects, but it soon became evident that these luminous arcs were really hanging to the dark disc, as I could soon see them passing over the solar granulations with the planet. Fig. 1.

The seeing having improved soon after, I distinctly saw a continuous ring of light encircling Mercury, and I continued to see the phenomenon for two hours longer, until the sky clouded up after five o'clock. I have not the least doubt as to the reality of the phenomenon, as it was well seen and carefully observed. During the most favorable moments it was very obvious that the ring had not the same degree of brightness throughout, the brighter parts being well defined on the sun, while the others were diffused. Taken as a whole, the ring appeared brighter than the surface of the sun, and for intensity it might have been compared to the narrow and faint faculæ sometimes seen at some distance from the sun's limb. It seemed to me that if instead of having been on the granulations, the planet had been projected over some brilliant faculæ, by contrast, it would have appeared surrounded by a grayish instead of a luminous ring. The outer edge of the ring did not appear sharply defined, except at its brightest parts, but its inner edge was much more apparent, and the irregularities of the black disc very visible on this luminous background.

The ring did not appear perfectly concentric with the black

disc, and this became very apparent a little before five o'clock when the seeing was at its best. Then it certainly appeared narrower on the preceding side than on the following. At this moment I estimated its width on the preceding side at about one-twentieth of the diameter of the disc, while on the following it was estimated at about one-fifteenth. Fig. 2.

Between four and five o'clock, Mercury was spectroscopically observed with an excellent diffraction grating which I owe to the kindness of Mr. Rutherfurd. The spectrum appeared of an intense black color, much darker than any of the absorption lines of the solar spectrum, and quite sharply defined on its edges. I attentively observed whether the absorption lines appeared thickened or deflected close to their point of contact with the spectrum of Mercury, but nothing was seen. I do not remember having seen the spectrum of the luminous ring forming a bright band on either side of the black spectrum, but unfortunately the thought of making this observation did not occur to me till after the transit was over. Judging from the bright appearance of the ring, it is quite likely that this spectrum would have been visible with a spectroscope of small dispersive power.

3.

After five o'clock the sky became partly cloudy, and observations were difficult. At 5h 51m the definition was rather bad, the image being unsteady and the limb of the sun wavey and boiling. A minute or two before the third contact, the sun disappeared behind a narrow, but opaque cloud, and when it emerged from it, internal contact had taken place and was consequently lost, the planet having then about half of its disc engaged on the sun's limb. While Mercury was thus passing over the limb, I easily and very distinctly saw that the two angles formed by the limb of the sun in apparent contact with Mercury had their corners rounded off. Fig. 3. This phenomenon which was very apparent seems to be of the same nature as the black drop, which I had not the good fortune to see. I do not remember having seen at this time any trace of the luminous ring either on, or outside the sun, but the seeing was bad at this moment, and my attention was so much occupied with the last contact that very likely it has escaped my notice.

As already stated, the sun's limb was wavey and boiling at the time of the two last contacts; it is undoubtedly owing to this fact that at 6h 0m 14s, Mercury completely disappeared from the limb of the sun, and last contact was recorded. However, a few seconds later, the planet reappeared and was seen still notching the sun's limb, it having probably been lost in the

trough of some deep wave of the sun's edge. The last contact occurred at 6h 0m 36-87, Harvard Coll. Observatory mean time. No trace of the planet was seen after it left the limb of the sun, but the sky was not very clear and the image was too unsteady to make delicate observations.

The luminous ring observed around Mercury in transit has generally been attributed to the horizontal refraction undergone by the rays of the sun in passing through the dense atmosphere which is supposed to envelop this planet. This explanation seems quite plausible, although it is difficult perhaps to conceive how atmospheric refraction alone can produce such a phenomenon, and it would seem that something else is wanting to fully explain it. Perhaps the refraction theory might somewhat be helped by the fact that the sun, having a vastly greater diameter than Mercury, must necessarily illuminate at all times more than one-half of the globe of this planet, and this surplus of illumination must be visible from the earth during transits, and appear as a thin luminous ring surrounding Mercury. Of course the distance between the sun and Mercury considerably reduces the apparent breadth of this ring; but still it is there; and this, combined with the horizontal refraction, may explain the observed phenomena.

Cambridge, May 8th, 1878.

ART. XIII.-Discovery of a new Planet; by Professor C. H. F. PETERS. From a letter to the Editors, dated Litchfield Observatory of Hamilton College, Clinton, N. Y., July 3, 1878.

ON June 13th I marked upon my chart, quite near to a star of the 11th magnitude, another of the 12th or 13th magnitude; and on June 19th this star was no more in its place. I therefore drew upon the chart all the small stars in the neighborhood; but before the one among these that had revealed itself by its motion as a planet, could be recognized, the sky had be come thick. On the following evening, June 20th, there was no difficulty in finding the planet. Its position was put down on the chart; but when the micrometer was arranged for observation, it had clouded up. So the sky remained until June 25th, when a complete determination of its position was obtained. Having notified Professor Pickering, I have received through his kindness also an observation of the same evening, made by Mr. Winslow Upton at the Cambridge observatory. The following are the positions of the new planet, I have succeeded in gathering here, including those graphically obtained from the chart.

THE

27, 11 9 54

15 36 45-74

15 36 29-20

28, 10 45 49
29, 10 11 32

15 36 14-82

30, 10 12 48

15 36 1.56

16 12

16 6 52.4

18 comp. by ring micr.

9 comp. by filar micr.

5.4

15 57

12 comp. by ring micr.

July 1, 10 28 13 15 35 50-10 -15 52 23.5

The comparison stars of June 28 and 30 require a re-determination by some meridian circle.

ART. XIV.-On "Indurated Bitumen" in cavities in the trap of the Connecticut valley. From the Report on the Geology of Connecticut, by Dr. J. G. PERCIVAL.

DR. PERCIVAL'S observations on the occurrence of what he called "indurated bitumen" in the trap of Connecticut valley, given in his Geological Report of Connecticut (1842) are briefly mentioned in Mr. I. C. Russell's paper, page 112 of this volume. Percival's notes are so full, and of so great interest, that we cite further from his Report.

Speaking, p. 315, of the common variety of amygdaloid accompanying the trap he says, that the "pores" [cavities] are sometimes occupied by a shining black indurated bitumen, somewhat resembling anthracite in appearance." Further, p. 318, that the metallic veins in the trap, whose ores are sulphides of copper, lead, zinc and iron, in a matrix of "sulphate of barytes, quartz and calcareous spar, ," "occasionally contain seams or nodules of indurated bitumen, similar to that already noticed" on p. 318, and that in the "altered rocks adjoining the trap"-the sandstonevarious minerals are often found, including "hyalite, epidote, chlorite, brown spar, fluor spar and indurated bitumen." Again, p. 320, he remarks that in the trap region of Berlin and Hartford, there are in the shale apparent dikes that consist of indurated shale, "through which points of bitumen are disseminated, as already noticed in a variety of amygdaloid;" and that in the brown and bituminous shale accompanying these dikes, there are "also included seams of bitumen with brown spar and sometimes with fluor."

The above are general statements as to the different modes of occurrence of the "indurated bitumen.” In the course of the following pages he mentions the facts at special localities.

On page 376, he observes that east of Farmington near the north point of a ridge of amygdaloid, "a quantity of indurated bitumen (considered as coal) was found on the back of the amygdaloid, the pores [amygdaloidal cavities] of which in the vicinity

were occupied partly by a similar bitumen, and partly by a dark green chlorite." Copper has been found in veins in the anterior amygdaloidal ridge west of the Hanging Hills," near Meriden, and "a similar bitumen is found in the matrix of the veins, which consists of quartz, calcareous spar and sulphate of barytes."

Page 382. In the trap range west of Middletown "where the stream (the Mattabesick) crosses the third (Eastern) ridge, considerable quantities of indurated bitumen have been found in the trap, occupying veins and the cavities of large quartz geodes"; and farther north, on the east side of the same ridge, where the trap appears as a dike and is bordered laterally by brown indurated shale small veins occur" in the trap and shale containing sulphurets of lead, zinc and iron, in a matrix of quartz, sulphate of barytes and cale spar, and also including seams of indurated bitumen. On page 384 he observes that in the line of the ridge passing through New Britain, at Hart's Mills, there is a wide bed of bituminous shale with interposed bands of a bluish compact subbituminous limestone," and here there is a dike of indurated clay with disseminated bitumen, "adjoining which the shale abounds in cross seams of brown spar with bitumen and fluor."

Page 385. Near the north point of Farmington Mountain west of north from New Britain, the amygdaloid "abounds in agates and has its pores partly occupied by indurated bitumen."

The localities above mentioned are within twenty-five miles of New Haven, to the northeast and north.

Page 388. South of Hartford, toward the southern end of the trap ridge called Rocky Hill, where it is nearly east and west in course, it" crosses a wide valley in which is a large bed of bituminous shale containing fish impressions, recently excavated for coal." The ridge terminates toward the north in low swells of amygdaloid; and just northeast is a mass of dark greenish indurated shale, highly contorted and disturbed in dip, with seams of bitumen and calcareous spar and traces of copper.

After speaking in several places, on pages 428 to 447, of outcrops of bituminous shale and limestone, forming part of the Triassic sandstone formation, and often containing fish remains, he mentions on page 451 the occurrence of similar bituminous shale and limestone in the small Triassic area of Southbury (which is quite independent of that of the Connecticut valley, and fifteen miles west of it); and adds that "seams of indurated bitumen and also of mineral caoutchouc occur in the bituminous shale and limestone, and the latter, particularly, is sometimes impregnated with naphtha."

Percival's facts thus have great importance toward settling the question as to the origin of the hydrocarbon of the amygdaloid. They show that the material occurs in the Triassic rocks as naphtha; as a flexible half-indurated material which he called caoutchouc; and as a firm, brittle coal-like material, which he calls indurated bitumen. Professor C. U. Shepard, his associate in the survey of Connecticut, mentions the "indurated bitumen" (Rep.