was, at your suggestion, so adjusted that one of its needle-points rested on the hydrogen line near G and the other on the line known as h. After the last ray of sunlight had disappeared, I took a few seconds of the precious time to observe the eclipse with the naked eye. The moon appeared intensely black, surrounded by a pinkish halo, extending to about two-fifths of a lunar diameter from the limb, and occupying the entire circumference. At two points this halo was expanded into radial streamers, one of which had parallel sides with a deeply indented or swallow-tailed end, extending westward of the sun and apparently lying in the ecliptic; the other appeared single, was on the eastern edge, and was inclined twenty degrees or more to the north of the ecliptic. The former of these streamers was traced to a distance of about a lunar diameter and a half from the edge, the latter to a somewhat less distance. No structure could be seen in the halo, but in the streamers traces of parallel rays appeared to be present. The amount of light emitted by the corona was a surprise to me. Preparations had been made for using artificial light for reading the circles, but this was found not to be at all necessary. The amount of light seemed to be nearly or quite equal to that given by the moon when ten days old. No protuberances were seen with the naked eye; nor were any streamers observed, other than those already described. A glance at the eclipsed sun was then taken through the finder of the equatorial. The magnifying power being low, the corona presented much the same appearance as to the naked eye; but the streamers showed much more distinct evidences of a radiated structure and a pale rosy protuberance was observed on the south-western edge of the dark disk. This was undoubtedly the same prominence which was observed previous to totality.

Turning my attention now to the spectroscope, upon the slit of which the coronal image had already been brought by means of the finder, the slit being placed radially, the first glance through the instrument showed me a bright, but an absolutely continuous spectrum. The region under examination was of course that portion of the spectrum which had been placed before totality between the needle-points of the micrometer. Totally unprepared for so unexpected a result, I moved the observing telescope so as to bring the green portion of the spectrum into the field, expecting certainly to see 1474 K, and by the appearance of this line to determine whether my instrument was out of adjustment; and if it were, to adjust it again. But no bright line was there; the green region appeared as continuous as the blue. I then gradually closed the slit—which had been previously adjusted on the solar spectrum so that the line D appeared nebulous on its edges-thinking that I might in this way improve the definition, but with no better results; no bright lines could be seen. To my great surprise, however, when the slit was thus narrowed, the region which was then under examination, that extending from b to G, appeared filled with dark lines on the brighter background, these dark lines being readily recognized from their general appearance as the solar lines of Fraunhofer. Still intent on getting bright lines, I opened the slit again gradually, moved the observing telescope over the entire length of the spectrum from red to violet, re

peating the operation three times and varying the width of the slit from time to time in each region; but not a single bright line could be detected. I then requested you to come and take a glance through my spectroscope, as had been previously agreed; saying that although I could see dark lines and a continuous spectrum, I was unable to detect a single bright line, and knew not what to make of it. You were then looking at the eclipse through your ingenious little telespectroscope of two inches aperture. You came to my instrument, looked at the spectrum, moved the observing telescope over its whole length and remarked that the results in my spectroscope agreed entirely with those in yours, and that in both the spectrum appeared continuous, showing no bright lines whatever.

My mind being thus relieved, I took my place again at the spectroscope, and this time, placing the slit tangential to the moon's limb, I moved the observing telescope from end to end of the spectrum, opening and closing the slit at intervals; but the spectrum appeared as continuous as before. Again the image was adjusted so that the slit was once more radial; and this time on a still different portion of the corona. On examining again the spectrum, no bright lines appeared, except once for an instant, when the slit passed over the small chromospheric prominence already noticed. Warned by Mrs. Draper's clear and distinct counting that the precious 165 seconds had two-thirds gone, I decided to devote the time still remaining to a more careful observation of the dark Fraunhofer lines. Now, for the first time, as I adjusted the width of the slit and its position on the corona with more care, I observed that these lines did not pass clear across the field, but were of a length corresponding to the width of the coronal image on the slit. At the base of the spectrum, which corresponded to the base of the corona, they appeared bright and sharp; certainly quite as much so as in the light of the moon similarly condensed; though the continuous spectrum which formed their background was relatively brighter than in moonlight. There was no difficulty in identifying them as Fraunhofer lines from their general appearance and position; but some of them could be identified beyond question. Such were b and F, which were especially distinct, D, E and G, which were considerably less so. They faded gradually out from the base of the spectrum upward, appearing to end where the continuous spectrum of the corona was limited above. While thus employed, a flash of sunlight told us that totality had ended and that the solar eclipse of 1878 was over.

In discussing the results of the spectroscopic observations which have now been detailed, I am, in the first place, quite at a loss to account for the fact that no bright lines were seen by me, notwithstanding the persistent efforts made to get them. The failure to observe them can be accounted for, as it would seem, only on the ground that with the dispersive power employed, the bright lines were too faint to be seen on the much brighter background of the continuous spectrum.

The lessons to be drawn from these spectroscopic observations appear to be few and simple. The absence of bright lines, or at least of any which

were at all brilliant, proves clearly the absence in the solar coronal region of any considerable mass of incandescent gas or vapor; which shining by its own light would of course give a bright line spectrum. The presence of Fraunhofer lines in the coronal spectrum shows conclusively the pres ence of reflected sunlight in the light of the corona and goes to establish the theory long ago suggested, that masses of meteoric matter raining down upon the solar surface from all directions, reflected to us the light of the sun and were therefore the essential cause of the coronal phenomena. And, finally, the fact of the increased brightness of the continuous spectrum, as compared with the intensity of the dark lines of Fraunhofer, goes to strengthen the probability that there is still other light in the corona which comes to us from the incandescent liquid or solid matter of these incandescent meteoric masses. These conclusions, deduced very simply from my own spectroscopic results, agree completely, I am happy to find, with those drawn from your most excellent photographs, as well as from the ingenious heat-measurements of Dr. Edison and the polariscopic determinations of Dr. Morton.

GENERAL CONCLUSION.

The general conclusion then, arrived at by the observations of our party upon this eclipse—a conclusion to which all the results point with singular unanimity-is that the solar corona consists of a mass of meteoric bodies falling in from space upon the solar surface, which meteors being intensely heated by the resistance encountered at their enornous velocity, as well as by radiation from the sun, become highly luminous, and emit a light which gives a continuous spectrum. Moreover, this mass of incandescent meteors is shown not to be equally extended in all directions around the sun, but appears to be ellipsoidal or at least spheroidal in form. That the larger part of the coronal light comes from the incandescence of these meteors, there can apparently, be but little doubt. But a considerable portion of it appears to have quite a distinct origin, and to be due to the reflection of solar light by these solid or liquid masses. Hence the appearance of the dark solar or Fraunhofer lines in the spectrum. A third, and in this eclipse an extremely small portion of the light of the corona, would seem to be due to incandescent gaseous matter, either injected into it from below, or produced from the meteoric masses themselves by the intense heat. This portion it is which gives the bright line spectrum, as feeble in this eclipse as it was strong in previous ones. Of the material composing this gas, there is yet, as it would appear, no indication.

From what has now been narrated, it must be conceded that the Draper Eclipse Expedition was singularly and exceptionally fortunate. No small part of this good fortune is due, as we believe, to the courtesy and liberality of the railroad and express companies over whose routes either the party or their instruments traveled. I desire to mention especially, in this connection, Col. Thos. A. Scott and Mr. Frank Thomson, of the Pennsylvania PROC. AMER. PHILOS. SOC. XVIII. 102. o. PRINTED JAN. 27, 1879.

Railroad; Mr. Henry Keep and Mr. M. L. Sykes, of the Chicago and Northwestern Railroad; Mr. Sidney Dillon and Mr. Jay Gould, of the Union Pacific Railroad; Mr. William H. Fargo, of the American Express Company; Mr. Frederic Lovejoy, of Adams' Express Company, and the Superintendent of the Union Pacific Express Company. The cordial appreciation by these gentlemen of the fact that the work in which we were engaged was one of a purely scientific character, and as such was one to which every reasonable facility should be furnished, was as gratifying to us as it was honorable to them. I should fail to do exact justice were I to omit mention of the service rendered us by Mr. J. J. Dickey, the Superintendent of the Union Pacific Telegraph; Mr. E. Dickenson, Superintendent of the Laramie Division; Mr. R. M. Galbraith, Superintendent of the Repair Shops at Rawlins; Major Thornburgh, Commanding Officer at Fort Fred Steele, with Capt. Bisbee and Surgeon De Witt, his associates in the service; Mr. Lawrence Hayes, of the Railroad Hotel, and to Mr. J. B. Silvis, of the photographic car. "Of the citizens of Rawlins," says Dr. Draper, "it is only necessary to say that we never even put the lock on the door of the observatory, and not a thing was disturbed or misplaced during our ten days of residence, though we had many visitors."

The agreeable party, the pleasant surroundings, the charming weather, the kindness of friends, and above all, the capital success of the observations, make the Draper Eclipse Expedition an exceedingly pleasant memory to us all.

Notes on a series of Analyses of the Dolomitic Limestone Rocks of Cumberland County, Pa., made by Messrs. Hartshorne and Hartranft in the Laboratory of the Second Geological Survey of Pennsylvania. By J. P. Lesley, State Geologist.

(Read before the American Philosophical Society, October 18th, 1878.)

At a meeting of the American Philosophical Society, Dec. 20, 1877, I described the progress of an elaborate investigation which I had instituted for the purpose of determining whether or not any fixed or rational order of deposition could be observed in our Lower Silurian, or Siluro-Cambrian Magnesian Formation (No. II).

I selected a fine exposure made by the rock cut of the Northern Central Railroad, on the west bank of the Susquehanna river, opposite Harrisburg, where a consecutive series of the beds, all conformable and all dipping regularly about 30° to the southward, afforded a good opportunity for collecting two sets of specimens for analysis, one at the bottom and the other at the top of the cut; and great care was taken to survey the cut, mark the beds (from 1 to 115) and range the specimens in two parallel series; so

1878.]

[Lesley.

that any lack of homogeneousness in any bed might be detected by analyses of two specimens taken from places in the edge of the bed from 5 to 30 feet apart, according to the depth of the cut, and sometimes by the selection of a third and intermediate specimen, many of the analyses of individual specimens being also repeated.

The investigation was continued throughout the winter by Mr. Henry Hartshorne, and completed during the summer by Mr. Hartranft; and I now find myself able to bring some of the results to the notice of the Society in the form of tables, (1) of analyses, and (2) of averages. At a future time I will be able to carry the discussion of averages still further, and can then venture to base upon them some hypothetical conclusions of great interest to geologists who occupy themselves with the problem of the genesis of our limestone deposits.

Table I, gives the whole series of analyses made; but includes only the determinations of Carbonate of Lime, Carbonate of Magnesia, and Insoluble Matter; omitting the determinations of oxide of iron, alumina, sulphur, phosphorus and carbon.

This table shows to the eye, without need of a diagram, the remarkable alternations of limestone beds with dolomitoid beds throughout the series.

TABLE I.

Analyses of specimens taken from railroad cuttings opposite Harrisburg; in two series: one at railroad grade; the other near the top of the cut.

NOTE, when the analysis was repeated, with slight difference, the average is given; but the instances of this are few.