ally increasing from 1.25 to 11.4 tenth meters, corresponding to a motion of recession increasing in two minutes from 36 to 330 miles a second. Thirteen sun-spots have been examined on 20 days with reference to the broadening of the lines in their spectra. The strong black lines or bands in the part of the spectrum between b and F, first noticed in the spectrum of a spot on November 27, 1880, have been generally observed to be present in the spectra of spots during the last twelve months, besides several fine lines in the same region of the spectrum to which there is nothing corresponding in the solar spectrum.

For the determination of motions of stars in the line of sight, 177 measures have been made of the displacement of the F line in the spectra of 41 stars, 68 of the b1 line in 19 stars, and 9 of the b, line in 5 stars. Of the 61 stars observed, 15 had not previously been examined, and the total number of stars of which the motions have been spectroscopically determined is now 106. In the case of three of the stars observed in the last year, a dispersive power equivalent to that given by sixteen prisms of 60° has been used. A comparison of the successive determinations of the motion of Sirius indicates a progressive diminution from about 22 miles a second, in 1877 and 1878, to about 7 miles a second or less this year, and as other stars do not show any. thing similar, it appears likely that the change is due to the orbital motion of Sirius. Further observations will, however, be required to settle the point."

THE SUN.

Solar radiation.-Prof. S. P. Langley has submitted to the Chief Signal Officer an abstract of the results of the Mount Whitney Expedition to determine the amount of heat the sun sends to the earth; in techni cal terms, the solar constant. Mount Whitney, in Southern California, was selected for the observation because it combined the advantages of great elevation, extreme dryness of atmosphere, and abrupt rise from the plain. The party of observation consisted of Capt. O. E. Michaelis, United States Army; two non-commissioned officers of the Signal Serv ice, six soldiers acting as an escort, four civilian assistants, and Professor Langley. Systematic work did not commence until the last days of August, 1881. Professor Langley summarizes the results obtained as fol lows:

"The approximate estimate of the solar constant is from 2.6 to 3.0 calories, by which is meant that the direct solar radiation before absorption by the earth's atmosphere would in falling for one minute, normally, upon an area of a square centimeter, raise the temperature of one gramme of water 20.6 or 30 centigrade. This implies its ability to melt annually a crust of ice covering the whole earth over 150 feet thick. This amount is one-half greater than the received value of Pouillet, and greater than the latest determinations of Messrs. Crova and Violle."

On the summit of Mount Whitney an ordinary black-bulb thermom

eter, in vacuo, rose 130° Fahrenheit, while the temperature in a blackened copper vessel, covered by two sheets of common window glass, rose above the boiling point. With such a vessel water could be boiled among the snow-fields of Mount Whitney by the direct solar rays.

While the influence of the atmosphere is to shut off from the earth's surface a considerable portion of the sun's heat by absorbing it, the capacity of the air to store heat and prevent its radiation into space serves to make the earth habitable. Otherwise, the surface temperature, even under the tropics, would be lower than the lowest recorded degrees of Arctic cold. Another effect of the selective absorption of the atmosphere is to change the apparent color of the sun. In a transparent atmosphere the now golden sun would appear blue.

Subsequently to this report, Professor Langley read a paper to the Brit. Assoc. A. S., giving an outline of the results he has reached. It is impossible to condense this paper, which is itself a highly condensed account of work extending over several years and covering a varied field.

Solar parallax from observation of minor planets.-Mr. David Gill, H. M. astronomer at the Royal Observatory, Cape of Good Hope, has arranged with a number of observatories in both hemispheres for corresponding observations of the minor planets Victoria and Sappho about the time of their oppositions in the present year. Victoria, in opposition on August 24, will be distant from the earth 0.89 of the earth's mean distance from the sun; and Sappho, which comes into opposition in R. A. on September 24, will be within 0.85; so that we have in each case a favorable opportunity of applying the method of determining the sun's parallax which was advocated and also applied by Professor Galle, the director of the observatory at Breslau. In a communication to the Astronomische Nachrichten, Mr. Gill states that the necessary extra-meridian observations will be made in the southern hemisphere at the Cape, Natal, Melbourne, and Rio de Janeiro, and in the northern hemisphere at Dunsink (Dublin), Strasbourg, Berlin, Bothkamp, Leipsic, Upsala, Moscow, Clinton, U. S., and probably at Kiel. From the clearer skies of the southern hemisphere, he believes that a fully corresponding number of observations will be secured there, notwithstanding the smaller number of observatories, and he invites co-operation from other establishments in the northern hemisphere on this ground. A list of the proposed stars of comparison is given in his letter.

Maskelyne's value of the solar parallax.-Several inquiries have been lately made with regard to the authenticity of a value of the sun's parallax, attributed in many works to Maskelyne, the former Astronomer Royal. These are answered as follows in Nature:

"This value (8".723) was deduced by Maskelyne in an application of what he calls a new method of determining the effect of parallax on transits of the inferior planets, and is given in an article which appears to have communicated to Vince, Plumian Professor of Astronomy

at Cambridge, who published it both in his large work, 'A Complete System of Astronomy,' and in his elementary treatise intended for the use of students in the university. We have not been able to consult the earlier editions of these works to ascertain whether, as is probably the case, the article was published in Maskelyne's lifetime, but it is found in Vol. I of the System of Astronomy,' which appeared in 1814, and is dedicated to Maskelyne, and also in the fourth edition of the Elements of Astronomy,' Cambridge, 1816. The article is entitled 'A new method of computing the effect of parallax, in accelerating or retarding the time of the beginning or end of a transit of Venus or Mercury over the sun's disk, by Nevil Maskelyne, D. D., F. R. S., and Astronomer Royal.' After explaining his method and how an approximate value may be corrected, as a numerical example he compares the duration of the transit of Venus in 1769 as observed at Wardhus and Otaheite, assuming as an approximate value of the mean horizontal parallax 8.83 (nearly that found by Du Sejour), and concludes: Hence the mean horizontal parallax of the sun=8".83 × (1 – 0.0121) 8.72316. In the Elements of Astronomy' there is the additional sentence: We assume, therefore, the mean horizontal parallax of the sun = 83';' but this does not appear in Vince's larger work, nor is it quite clear whether it is an addition of Maskelyne's or his own. "Lalande says the first edition of Vince's 'Elements of Astronomy' was published in 1790, and Vol. I of the larger work in 1797. Probably some of our readers may be able to refer to the earlier editions."

=

6

Solar eclipses.-The British scientific expedition sent to the banks of the Upper Nile to make observations of the total eclipse of the sun, June 17, was every way successful. The chief members of the party were Norman Lockyer, Arthur Schuster, Mr. Woods, assistant, Mr. Lawrence, and Mr. Black. The special correspondent to the London Daily News summarizes the results as follows:

"This eventful morning was the finest we have yet had, cool and without a cloud. A great crowd of natives in picturesque costumes lined the road and the hill between the camp and Sohag. The shore of the Nile, except before the observatories, was packed with dahabiyebs bringing the governors of the provinces and other notables to observe the eclipse and do honor to the strangers. Thanks to Moktar Bey, in charge of the camp, and a force of soldiery, there was no confusion. Along a line of three hundred yards the French, English, and Italian observers were left in undisturbed possession of tents and observatories. Nevertheless, while the sky darkened and assumed a leaden hue, the hills bounding the Nile bathed in purple, the great silence gave way, and from the river and palm-shaded slope arose a shout of wonder and fear, which reached its climax at the moment of the sun's disappearance; nor ceased then, for in addition to the horror of an eclipse (which the natives here in Africa attribute to the act of a dragon) there appeared

in the heavens on the right of the sun an unmistakable scimetar. The eclipse had indeed revealed the existence of a new comet. Despite the short totality (one minute and twelve seconds) many valuable results have been obtained. I am permitted to send a copy of the collective telegram sent to the various Governments, showing many new facts touching the sun's atmosphere, though matters have not become much simpler, which means more work. The layer to which much absorption has been ascribed seems vanishing from existence. The band K in the spectrum of the corona fully explains the eclipse coloring.

"Among the results, the most satisfactory are photographs of the corona, and a complete spectrum obtained by Schuster on Abney's plates. H and K are the most intense lines. A study of the red end of the spec.rum of corona and protuberances was made by Tacchini. A comet near the sun was a striking object; it was photographed, and was observed by the naked eye. Bright lines were observed before and after totality at different heights by Lockyer, with intensities differing from Fraunhofer's lines; by Lockyer and Trepied an absolute determination was made of the place of the coronal line 1474 in Kirchhoff's scale; by Thollon and Trepied the absence of dark lines from the coronal spectrum was noted. Tacchini and Thollon, with very different dispersions, noted many bright lines in the violet. Thollon observed the spectrum of the corona, and Schuster photographed it. The hydrogen and coronal lines were studied in the grating spectroscope of Buisieux, and with direct-vision prism by Thollon. Rings were observed in the grating by Lockyer, of the first, second, and third order. The continuous spectrum is fainter than in 1878, stronger than in 1871. An intensification of the absorption lines was observed in group B, at the moon's edge, by Trepied and Thollon. The whole spectrum, with blue lines on a continuous background, has been photographed. The prominences were photographed with the prismatic camera (showing, of course, ring spectrum). Three photographs were taken of the corona. The comet close to the sun was photographed with the prismatic and also with ordinary cameras."

Solar eclipse of May, 1883.-The following is a summary of a paper prepared by Mr. C. H. Rockwell, New York, and read at the meeting of the American Association:

"The great astronomical event for 1883 will be the solar eclipse to occur on the 6th day of May. At the points of greatest obscuration the totality will last nearly six minutes. Unfortunately, the line of totality is almost exclusively a water track, running from a point about 200 miles back of the east coast of Australia, going northeasterly to 90 south latitude, 1300 west longitude, thence toward the coast of South America, terminating about 500 miles from the coast.

"The only island crossed by this line is a small coral reef called Car oline Island; this was discovered by Captain Nares, the Arctic explorer, in 1874, who gave its length at nine miles and width at one mile. H. Mis. 26--19

"This point is in 10° south latitude, 150° west longitude, and is proba bly the only point where the eclipse could be observed. To reach this island a schooner or steamer would have to be chartered especially for the voyage; the expense of such a vessel suitable for the purpose would be about $6,000."

It is now probable that this eclipse will be observed by an expedition sent out under the auspices of the National Academy of Sciences and the United States Coast Survey. The party will probably consist of Professor Holden, of the Washburn Observatory, Professor Hastings, of Johns Hopkins University, of Mr. Rockwell, and Prof. C. S. Peirce, of the Coast Survey. Two photographers sent by the Royal Society of London will also join the party.

Solar spectrum.-A new map of the solar spectrum, containing a much larger number of lines than are shown in Angstrom's normal spectrum, has been published by Dr. H. C. Vogel, of Potsdam. Particular attention has been given by Dr. Vogel to the characters as well as to the positions of the lines.

Transit of Venus, December 6, 1882.-It is yet too soon to speak of the success of the various observing parties sent out to observe this transit. From reports already received, it appears that the observations were, on the whole, quite successful, although the weather in Europe was bad. Mr. Stone, director of the Radcliffe Observatory, regards the contact observations as alone sufficient for the solution of the problem of the solar parallax, and it is certain that enough photographs have been secured by the United States Government parties and by the Lick Ob servatory party to insure a good determination by this means also. The following are the stations of the different parties:

Cape of Good Hope:

Chief astronomer, Prof. S. Newcomb, U. S. N.

Assistant astronomer, Lieut. T. L. Casey, jr., U. S. Engineers.
Additional assistant astronomer, Engineer J. H. L. Holcombe,
U.S. N.

Photographer, Mr. Julius Ulke.

Santa Cruz, Patagonia:

Chief astronomer, Lieut. Samuel W. Very, U. S. N.

Assistant astronomer, Mr. O. B. Wheeler.

Photographer, Mr. William Bell.

Assistant photographer, Mr. Irvin Stanley.

New Zealand:

Chief astronomer, Mr. Edwin Smith, United States Coast and Geodetic Survey.

Assistant astronomer, Mr. Henry S. Pritchett.

Photographer, Mr. Augustus Story.

Assistant photographer, Mr. Gustav Theilkuhl.