THE TYNDALL FELLOWSHIPS.

AT the close of Professor Tyndall's brilliant tour as a lecturer on physics in various cities of this country during the winter of 1872-73, he devoted with unparalleled generosity the net results of all that he had earned to the encouragement of studies in physical science among young Americans. The amount thus set apart was somewhat more than thirteen thousand dollars ($13,033.34), and it was given to three trustees, Professor Henry of Washington; the founder's kinsman, Gen. Hector Tyndall of Philadelphia; and Dr. E. L. Youmans of New York. After the death of the first two named, President F. A. P. Barnard and Professor Lovering succeeded to the vacant places. In the deed of trust, which is dated Feb. 7, 1873, and may readily be found in the Smithsonian report for 1872 (p. 104), the giver declared his purpose to be the advancement of theoretic science, and the promotion of original research, especially in the department of physics. The method of employing the fund which he then proposed was to assist in supporting, at such European universities as they might consider most desirable, two American pupils who might evince decided talent in physics, and who might express a determination to devote their lives to this work. He added that it would be his desire to have each scholar spend four years at a German university, - three devoted to the acquisition of knowledge, and the fourth to original investigation.

For some reasons not publicly explained, and not difficult to conjecture, the trustees have been embarrassed in trying to carry out the precise wishes of Professor Tyndall; and consequently but a very small part of the income of his fund has been directed toward the assistance of young physicists. One of those who received encouragement from the fund generously returned to the trustees the sum advanced to him; another to whom the benefit of the scholarship was offered hesitated about pledging himself to remain four years in Europe, and declined the honor of an appoint

ment. Meanwhile the opportunities for studying physics in this country have rapidly improved. Excellent investigators in several universities have been provided with admirable laboratories, and with all the requisite apparatus for research. It is true that the opportunity to go abroad for a brief sojourn is still highly prized by our young men; but, if associated with an implied obligation to remain in Germany during four years, the value of the opportunity is seriously impaired. Meanwhile the trustees have been careful in the management of their fund, and, having added the unexpended income to the principal, are able to report that the original thirteen thousand dollars have grown to thirty-two thousand dollars, a remarkable record in these days of financial shrinkage.

Fortunately the donor of the fund is still living, and has been able to modify the original conditions of his gift. At the recent commencement of Harvard college, President Eliot announced that Professor Tyndall gave to Harvard one-third of the accumulated fund, another third to Columbia college, and the remainder to the University of Pennsylvania. The income is to be devoted to the maintenance by each institution of a graduate scholarship or fellowship in the department of physics.

Under these new conditions, the original purpose of this generous gift is sure to be accomplished. By the maintenance of a wise system of appointments, such as the experience of these three colleges will certainly devise, the hope of winning a Tyndall prize will prove a strong incentive to young American physicists. The foundation will have an influence upon scientific studies akin to that exerted upon classical studies for many generations by the prizes of Bishop Berkeley. It is also interesting to remember, that, as the name of Rumford, an American physicist, is associated indissolubly with the Royal institution of Great Britain, where Tyndall holds the commanding station, so the name of an English physicist, Tyndall, will always be remembered with gratitude in the land of Rumford's birth, for kindred generosity in the encouragement of kindred pursuits.

THE LATEST VOLCANIC ERUPTION IN THE UNITED STATES.

IN one of the volumes of the Proceedings of the California academy of sciences, Dr. H. W. Harkness describes the cinder-cone and lava-field at Feather Lake, Plumas county, Cal. Writing as I do in the field, and without access to books, I am unable to cite more accurately the description referred to. Dr. Harkness speaks of this volcano as being extremely recent, and mentions the fact that trees killed and half burned by the lava were still standing. Mr. John B. Trask also refers to it, with the statement that the eruption occurred in January, 1850; but he does not, so far as I recall, state the source of his information. I regret that I am obliged to depend upon memory alone in referring to these accounts of the outbreak. Within the last week I have had the pleasure of visiting Feather Lake in company with Mr. J. S. Diller, and can fully confirm Dr. Harkness's account of it, and feel confident that Trask's date, January, 1850, is quite in harmony with all appear

ances.

Feather Lake, prior to the eruption, was a sheet of water about four or five miles long, lying ten miles east-north-east of Lassen's Peak, say, in latitude 40° 34', and longitude 121° 19′; and its altitude is about 5,800 feet above the sea. The vent now covered by a large cinder-cone is situated a little above the western shore. From it there flowed a very thick sheet of basaltic lava, which nearly filled up the lake-basin. The thickness of the flow considerably exceeds 100 feet, and may be as great as 150 feet on the average. The lavafield is about three miles and one-fourth in length, and a mile in width, and half environs the base of the cinder-cone. The cone itself is nearly 600 feet high, and the diameter at the base is about 3,300 feet. It is perfect in form, with a crater in the summit which is not broken down on any side. It is built of scoria and lapilli, the outer layers of which are like coarse sand, giving a smoothness and finish to the surface of the cone which I have seldom seen equalled. Great quantities of fine lapilli and ashes' are spread out over the adjoining country to a distance of two miles, and over the lava-sheet itself, quite burying it in some places. The impression of recency is conveyed by every aspect of the cone, of the lava-flow, and of the country round about. The rains have not, as yet, produced even the first trace of a water-channel upon the wonderfully smooth surface of the cone; and the only vegetation

which has taken root is a single bush of Ceanothus, near the summit. The lava-sheet is rough and jagged in the extreme, but shows, as yet, no trace of weathering. For a space of four to five hundred yards from the cone, the trees were all killed. Most of them have fallen, and their decayed trunks are still lying on the ground, showing the marks of fire. In thirty-five years (the period assigned by Trask) such decay would be natural. Trees of the same species, felled certainly since 1850, show elsewhere in the vicinity an equally advanced stage of decay.

Whether the date assigned by Trask be the true one or not, the real date cannot be materially older. That the eruption was not at the time a matter of common fame, is readily intelligible; for the settlement of the northern part of the state did not begin until a year or two afterwards, and it is not probable that any observers except Indians could have witnessed it. Harkness adds, I believe, that it was still hot and feebly smoking' in 1852. This may be quite true; for the lava-sheet is an exceptionally thick one, and may have preserved its heat for a long time. And it may also have been seen by many white men in that year; for one of the routes by which overland emigrants poured into the state was laid in that year along the very base of the cone, and is known to this day as the Emigrant trail.'

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I am not aware of any volcanic eruption in the United States which is so recent as this one. Vague accounts have been given of eruptions in Oregon, Washington Territory, and southern California within the last twenty years; but they have not been authenticated or confirmed by subsequent observation of the localities. There are lava-flows and cones in Utah, Arizona, and New Mexico, and also in southern California, whose ages must lie within a very few hundred years, but not within the present century. Unless something of the kind more recent is found in some secluded spot hitherto unvisited by the geologist, I think we may safely regard the eruption at Feather Lake as the most recent of any in the country.

A word or two about the country in which this volcano is situated. It is a volcanic region of great extent, covering probably twelve thousand square miles; and Lassen's Peak is its culminating point, and nearly its geographic centre. It is thickly studded with great volcanic piles, and buried thousands of feet deep in ancient lavas. Most of the eruptions are of great antiquity, and those which built the central pile of Lassen's itself are among the

period, and observed apparently for the first time at this return. By short period is generally understood a period of somewhere in the neighborhood of five years, of which we have well-known examples in the comets of Encke (3.3 years), Brorsen (5.5 years), Winnecke (5.7 years), Faye (7.4

A

b

a

F.

FIG. 1.

F

P

comets II and III of 1884, the first discovered by E. E. Barnard of Nashville, Tenn.; and the second, by Max Wolf, a student at Heidelberg. Neither of these comets has been a conspicuous object, not even visible to the naked eye, I believe, but they are fair representatives of the class known as 'telescopic' comets.

As I have intimated, the orbit of comet 1884 II (Barnard), is elliptical with a period of about five and a half Making allowance for years. necessary uncertainty, the elements show a certain resemblance to those of DeVico's 'lost comet,' 1844 I, which, though certainly elliptical, has not been seen since, if we except a single rather doubtful observation made at Paris in 1855. The period agrees very well with that determined for DeVico's comet by Brünnow (5.469 years); but Berberich has pointed out that their identity cannot be assumed, for the time elapsed since 1884, forty years, does not correspond to any whole number of revolutions. He notes, also, that the physical appearance would seem to be against this identity; DeVico's comet, in a similar position with respect to the earth, having been visible to the naked eye. Leverrier thought it very probable that this comet of DeVico's was identical with one observed in 1678 by La Hire; and Laugier and Mauvais concluded that it was identical with the comets 1585, 1766 II, and 1819 III or IV.

i

=

5° 24' 48'.7

=

34° 51' 49.3

log a

= 0.474164.

Let me try to show how these elements represent the orbit of a comet, and to give an idea of the shape of this orbit, and its position in space with respect to the sun and earth. By far the most satisfactory way of doing this would be to construct from the elements a cardboard model, which I think can be done with little difficulty from the following directions.

We know, that, in obedience to the law of gravitation, comets must move about the sun in some form of conic section, the ellipse, parabola, or hyperbola. As a matter of fact, for the majority of comets, the orbit is given as a parabola; a few are known to be elliptic; but it cannot be said with certainty that any are hyperbolic.1

We are first to fix the shape and dimensions of the curve, and then its situation with reference to the plane

I might say that the linear distances a and e are usually expressed as decimal parts of the earth's mean distance from the sun. If a = 2.98 (as in the case of Barnard's comet), it means that the mean distance of the comet, or the semi-major axis of the orbit, is 2.98 times

that of the earth, or about two hundred and seventy-six million miles. So, generally, measurements expressed in this way are reduced to miles by multiplying by ninety-two and a half million.

Having settled the shape of the orbit, we must determine its position in space. For this purpose three more elements are required:

ORBIT OF

MAY 14, 1875.

6. Finally, we must state where the comet is in its orbit at some specified time. For comets we generally give the date of perihelion passage, T.

To these six elements there might be added the mean daily motion, μ, expressed in seconds of arc; and the period of revolution, sometimes called U, in days or years.

With the semi-axes a and b given (b is obtained from a and by means of the formula, b = a cos p), the curve is constructed to any scale we please. I have found it con

ORB

SEPT. 17, 1884

JULY 16,1884.

3. The longitude of the ascending node, the angular distance from the first point of Aries (Y, fig. 2) to the point in which the comet

venient to use a scale of two inches. The earth's orbit is then represented with sufficient

The next thing we want to know is how the major axis of the comet's orbit is pointing. This is determined by supposing that P and (fig. 2) at first coincide, and then that P is moved till P8 (in fig. 3 this angle is 300° 46', so that the acute angle OP is 59° 14'). The planes are inclined at the angle i (not shown in fig. 3, but given in fig. 2); and it only remains to fasten the two pieces of cardboard in this position, cutting a slit in either one, so that they will fit together. If the comet's motion is direct,' the comet and earth will be moving in the same quadrant, as they move away from the node. If its motion

6

become; and consequently a comet moving in such an orbit, will, if undisturbed, double' the sun, and then go off forever on its journey through space.

For the parabola, the elements are given in a little different form. The eccentricity is equal to 1. equal to 1. The major axis stretches out to infinity, and we give in its place the perihelion distance q, and the distance from the focus to the vertex of the curve PF (fig. 1). But five elements are then necessary to represent the parabola.

Collecting these symbols for reference, they are as follows: