8. Phosphorescence at Low Temperatures.-RAOUL, PICTET and ALLSCHUL exposed tubes containing sulphides of calcium, strontium and barium to a strong sunlight for definite periods of time and then placed them in liquid nitrous oxide, the temperature of which was estimated at 140°. After remaining in the freezing mixture for twelve minutes they were taken out and the renewal of the phosphorescent appearance was observed. At first no light could be observed, gradually, however, light appeared in the warmer portions of the tubes and extended to lower portions. After five minutes the tubes became as bright as they were before they were placed in the freezing mixture. To determine the limits of the phenomena the tubes were placed in alcohol cooled to -80°, as the tubes took the temperature of the alcohol the phosphorescence diminished and totally disappeared at 65°. The portions of the tube above the alcohol phosphoresced strongly. Before the colored phosphorescence, whether blue, green or orange, entirely disappeared, the tubes assumed a yellow color.-Zeitschrift fur physikalishe Chemie, vol. xv, part 3, p. 386. J. T.

9. Telegraphing without wires.-At a meeting of the Physical Society held in Berlin, Nov. 16, Professor Rubens gave an account of experiments on this subject. On the banks of the Wannsee near Potsdam two electrodes were sunk in the water at a distance of 500 meters from each other and a current of fiftyfive accumulators was sent through them. From each of the boats connected by a cable an electrode was immersed in the water and a telephone inserted into the connection. When the current of the accumulators was broken an effect was perceived in the telephone at a distance of 45 kilometres. Small islands lying between the boats and the shore had no influence on the transmission of the signals.-Nature, Dec. 20, 1894.

J. T.

10. Calculation and measure of small coefficients of Self-induc tion. In the study of electric waves, the oscillators and resonators have, in general, small coefficients of self-induction and it becomes important to obtain an accurate value of these coefficients. Max Wien discusses the various mathematical formulæ for parallel wires, circles, rectangles, etc., and gives an experimental method also of determining the values of the coefficients. The student will find an interesting use of Maxwell's geometrical mean distance in the paper.-Ann. der Physik und Chemie, No. 13, 1894, pp. 928-947.

J. T.

11. Self-induction in iron wires.—KLEMENCIC shows that in general the magnetic permeability is different in the circular and axial directions. Iron wires may be said to be magnetically double refracting. In soft iron the permeability is smaller around the axis than in the direction of the axis. Hard iron in the process of drawing, obtains a stronger permeability axially than in the circular direction. This is also the case with Bessemer steel.— Ann. der Physik und Chemie, No. 13, 1894, pp. 1053-1061.

J. T.

12. "On the Photographic Spectrum of the Great Nebula in Orion," by J. NORMAN LOCKYER, C.B., F.R.S. Abstract from the Proc. Roy. Soc., lvi., 285.-The paper consists of a description and discussion of photographs of the spectrum of the Orion Nebula, taken with the 30 inch reflector at Westgate-on-Sea in February, 1890, of which a preliminary account was communicated to the Royal Society at the time. Fifty-four lines are tabulated as belonging to the spectrum of the nebula, nine of them being due to hydrogen. The complete discussion has led to the following general conclusions:

1. The spectrum of the nebula of Orion is a compound one consisting of hydrogen lines, low temperature metallic lines and flutings, and high temperature lines. The mean temperature, however, is relatively low.*

2. The spectrum is different in different parts of the nebula. 3. The spectrum bears a striking resemblance to that of the planetary nebula and bright line stars.

4. The suggestion, therefore, that these are bodies which must be closely associated in any valid scheme of classification, is confirmed.

5. Many of the lines which appear bright in the spectrum of the nebula appear dark in the spectra of stars of Groups II and III ; and in the earlier stars of Group IV, and a gradual change from bright to dark lines has been found.

6. The view, therefore, that bright line stars occupy an intermediate position between nebulæ and stars of Groups II and III is greatly strengthened by these researches.

13. Elementary Lessons in Electricity and Magnetism by SILVANUS P. THOMPSON. New edition, revised throughout with additions, 628 pp. New York and London, 1895 (Macmillan & Co.) The first edition of Thompson's Lessons, published in 1881, is well known as one of the best elementary books on Electricity and Magnetism ever presented and, with later reprints, it has had well deserved success. The present new edition contains all the good features of the earlier ones, while the large amount of new matter added makes it fresh and new throughout. Thus for example, to the subject of Electric waves a special chapter is devoted in which the work of Hertz and others is clearly, if briefly, presented. Many new illustrations are introduced; these representing the lines of force in various electric fields, e. g. in electrostatic induction, etc., will be particularly helpful to the student. The work in its present form deserves high commendation. A criticism might be offered by the teacher using the book to the arrangement of matter in some cases, but there may be room here for some difference of opinion.

* Roy. Soc. Proc., vol. xliii, p. 152, 1887.

II. GEOLOGY AND MINERALOGY.

1. Note on the Florida Reef; by A. AGASSIZ. (Letter to J. D. Dana dated Tampa Bay, Florida, Dec. 27, 1894)-You will be interested to hear that I have just returned from a ten days' trip to the Florida reefs, which I was anxious to examine again, in the light of the experience gained by my visit to the Bahamas and Bermudas; I think I shall be obliged materially to change my ideas of the mode of formation of the Keys, and to give up the Marquesas as a true Atoll. After having seen at the Bermudas the mode of formation of the Sounds, I have become satisfied that the Marquesas are a Sound. But the Florida Sounds do not, I think, owe their origin to subsidence, but merely to the mechanical and solvent action of the sea. It is interesting to trace on the large scale charts of the Coast Survey the mode of formation of Key Biscayne Bay, composed of two sounds, followed by Barns Sound, and finally to the westward, by the Bay of Florida, itself only a series of disconnected sounds indicated by isolated keys and bars. The same thing is going on at the Pine Islands, Key West, Boca Chica, Boca Grande, Ballast Key, and is especially well seen in Key Largo, the Marquesas, to the west of the principal line of Keys being a remarkably well preserved sound of an elliptical shape. To my great surprise I found that Lower Matecumbe was edged by an elevated reef about 2 feet above high water mark! and this elevated reef I was able to trace all along the shores of the Keys to the east of Indian Key as far as Soldiers Key, off the central part of Key Biscayne. I examined this elevated reef also at Indian Key where its highest point is 8 feet above high water mark, at several points on Key Largo, Old Rhodes, Elliott Key, and, as the most easterly point, Soldiers Key. No trace of this elevated reef could be detected north of Cape Florida, Key Biscayne being entirely covered by siliceous sands, just as the beaches of limestone sands cover great tracts of the Keys to the westward and hide the underlying elevated reef. Shaler speaks of having traced this reef at Old Rhode's and having followed it to the Miami River as an elevated reef. I was quite surprised on examining a bluff about ten feet in height, extending eastward from Cocoanut Point toward the mouth of the Miami River, to find that it consisted of aolian rocks which have covered the elevated reef in many places. On the low shores these æolian rocks are honeycombed and pitted and might be readily mistaken for decomposed reef rocks; but they contain no corals. This looks as if the lower southern extremity of Florida, the Everglade tracts, was a huge sink into which sands had been blown forming low dunes which have little by little been eroded, and which former observers had mistaken in some localities for reef rock. The material for these dunes coming from the (now elevated) reef at a time when it was either a fringing or a barrier reef along the former coast line of Florida, all of which, back of the reef, has little by little been eroded

by the mechanical and solvent action of the sea leaving only an occasional outcrop of the elevated reef as observed by Agassiz and Shaler. The outer line of reef has also been elevated. For I think Tuomey was right in looking upon the outcropping reef rock of Sand Key as an elevated reef, if I remember rightly what he says; while Professor Agassiz mistook it, as well as the traces of the elevated reef he saw along some of the Keys, for a recent reef consisting of beach rock into which large masses of corals had been thrown by hurricanes. But in this I now think both he and I were mistaken. It was however a natural view to take of the formation of that reef for one who was not familiar with the peculiar aspect of the elevated reefs of Cuba. From the Pine Keys and the Islands to the West, and including the Marquesas, there is nothing exposed but beach rock, stratified at a slight angle seaward on the sea faces of these Keys; and even that is only casually exposed,-the greater part of the southern beaches of the Keys being covered by coralline and coral sand completely hiding the substratum. Behind this beach rock, æolian rocks stretch northward and have formed the Keys.

2. The Geological Society of America. 7th Annual meeting.The winter meeting of the Geological Society was held in Baltimore Dec. 27, 28, and 29, 1894, in the geological rooms of the Johns Hopkins University. It was a representative gathering, geologists from all parts of the county east of the Rocky mountains attending; and the number of papers presented for reading (48) was so great that it was found necessary to make two sections in order to have them all read during the meeting. The Presidential address was delivered in Levering Hall at the evening session and was one of the most important contributions of the meeting. It was an account of his recent glacial studies in Northern Greenland, by Professsor T. C. Chamberlin as a member of the Peary expedition which went to Greenland during the last summer. The lecture was illustrated with some sixty stereopticon slides. "The feature that first impresses the observer on reaching the glaciers of the far North," said the lecturer, "is the verticality of their walls. Southern glaciers terminate in curving slopes. Next to the verticality of the edges, the most impressive feature is the pronounced stratification of the ice. It appears that stratification originated in the nucleus of deposition, emphasized by winds, rains and surface melting; that the extended stratification may have been intensified by the ordinary processes of consolidation; that shearings of the strata upon each other still further emphasized the stratification and developed new horizons under favorable conditions; that basal inequalities introduced new planes of stratification, accompanied by earthy debris, and that this process extended itself so far as even to form minute laminæ. A glacier is, essentially, made up of large, interlocking granules that have been developed from the snow crystals and pellets of the original snowfall. In the growth and the changes of these granules the secret of motion may lie. The glaciers drop

their material in front, and so sometimes build up their own pathway before them; thus, it is easy to understand how they may advance over sandy soils without abrading or disrupting them. All along the coast, from Southern Greenland to Inglefield Gulf, there are stretches of mountains that are very angular and irregular, and show no evidences of ever having been overridden by the ice. There are other stretches of the coast that seem to have been once covered by the ice, as their contours are subdued. It would appear, therefore, that the ice once pushed out to the coast line a portion of the western coast, and failed to do so along the other portion. The general conclusion is that no great extension of the Greenland ice has formerly taken place, and, hence, that the theory that the glaciation of our own region had its source in Greenland is without support."

G. F. WRIGHT, presented a paper on Observations on the Glacial Phenomena of Newfoundland, Labrador and Southern Greenland which is given in full in this Journal. H. F. REID discussed Variations in velocity of glaciers incident to varying amount of snow, pointing out vividly the effect of decrease in snow-fall in the withdrawal of the ice front with increasing rapidity, while increase of snow fall would result in advance of the glacier beginning only after considerable accumulations to the mass, and increasing in rate of advance as the increased snow fall continued. C. H. HITCHCOCK spoke on Highland level gravels in northern New England, which he interpreted as evidence of glacial lake beaches, 1000 and more feet in altitude in New Hampshire. WARREN UPHAM read papers on Discrimination of glacial accumulations and invasion, and Climatic conditions shown by North American interglacial deposits. Two papers based upon study of the altitudes of old beach lines and morainal drift in New York State were read by H. L. FAIRCHILD, of which the following abstracts are communicated by the author.

Glacial Lakes in western New York, Lake Newberry, the successor of Lake Warren, by H. L. FAIRCHILD.-If the reader will place before himself a map showing the hydrography of western and central New York, he will observe that the divide between the St. Lawrence and the Ohio-Susquehanna waters passes near the south ends of the so-called "Finger Lakes." The valleys of these present lakes with their northward drainage end abruptly in the high land south, the old valleys in that direction being choked with moraine drift. The same is true of several other valleys between the Tonawanda on the west and the Onondaga on the east, in which no water is now ponded.

All these north-south valleys were, during the retreat of the ice sheet, the site of extinct lakes, the water of which was held up by the barrier of ice on the north to the height of the col south, and so forced into southern drainage. Granting the capacity of glacial ice to serve as barrier to water, only a glance at the topography is sufficient to show the the necessity of such lakes. The positive evidence is found in the abandoned stream channels south