SCIENCE. 



155 



obtained could be so classified that a series might 

 be made, each member of which would differ from the 

 next almost insensibly. This, of course, would take 

 a long time to do, as small stars can be examined only 

 in very fine weather. When it was done, however, the 

 results would be very valuable and interesting. 



a Grms. — This is a second-magnitude white star, 

 with the usual spectrum crossed by distinct hydrogen 

 lines. 



P Grids is a second-magnitude star, and nearly as 

 bright as the lucida of this constellation. Its color is 

 reddish-orange, and its spectrum is much like that of 

 y Crucis, but the groups of lines are not so distinct, and, 

 generally, there is a sort of approach to the appearance pre- 

 sented by the spectrum of Mzra Ceti, which I find thus 

 described in my note-book, under the date October 8th, 

 1878: "Saw to-night the spectrum of Mzra: it is really 

 wonderful — something like that of a Hcrcidis, as given by 

 Chambers. It seems to consist of bright broad bands, 

 with narrow ones in between. These bands are dark, 

 but hardly black. The effect produced is, as it were, that 

 of an irregular set of columus. The brightest part of the 

 spectrum is at the yellow and the green." 



a Piscis Australis {Fomalhaut). — This star is visible 

 at home sometimes, but its altitude there is so small that 

 it can scarcely be properly observed with the spectro- 

 scope. Fomalhaut is a first-class star of the most pro- 

 nounced type ; it is very remarkable for the great breadth 

 of the F hydrogen line. In Fomalhaut it is far broader 

 than it is even in Sirius. As an increase in the breadth 

 of the hydrogen lines has been shown to be due to in- 

 creased pressure, and as the increase in breadth is also 

 proportional to the pressure brought to bear upon the 

 gas which gives the lines in the spectrum, we may, I 

 would venture to suggest, conclude that the pressure at 

 the surface of this star is extremely great. That is to 

 say, Fomalhaut is either extremely dense and compact, 

 so that its radius is very small compared with its mass 

 (which is not very likely), or it is one of the very largest 

 stars in the sky. 



In conclusion, I would ask you to overlook any faults 

 of style that may be observable in this paper. It claims 

 to be nothing more than its title announces it to be — 

 " Notes on Southern Stars." 



SCIENTIFIC BOOKS. 



Mr. W. H. Farrington recently gave an interesting 

 Lectures on scientific books before the American Insti- 

 tute, a full report of which may be found in Engineering 

 News of March the 19th. He said that in spite of the 

 large number of scientific works published, there still 

 are constant enquiries for books on certain subjects, 

 which have yet to be written. This he explained was 

 due to various causes, one being that the demand for 

 certain books do not warrant their publication, and 

 secondly, that many works treating on manufactures are 

 withheld, it being the policy of those who could write 

 them, to keep from the public such information. He 

 stated that the English publishers seldom stereotype 

 their better class of books, but print from the type, 

 whereas in America it is the custom to print from such 

 plates, permitting a much smaller edition to be issued. 

 Those interested in the literature of Mechanics, and 

 " Engineering Science," should read Mr. Farrington's 

 Lecture from which they may gather many practical 

 hints respecting the purchase ot such books. 



ASTRONOMY. 



The March number of the America7i Journal of 

 Science contains a paper by T. C. Mendenhall, of Tokio, 

 Japan, ' On the Determination of the Coefficient of Ex- 

 pansion of a Deffraction Grating by Means of the Spec- 



trum." The object of the research was to find the 

 coefficient of expansion of the peculiar alloy of tin and 

 copper, now generally used for ruling gratings. The 

 value of the coefficient of expansion is independent of the 

 wave-length of the line upon which the measurements are 

 made and of the number of lines to the inch. The tem- 

 perature of the grating was altered by placing the plate in 

 one end of a small wooden box which could be filled with 

 water and brought to any given temperature. The re- 

 sultant value for the coefficient of expansion from the mean 

 of twenty measurements is 



E = .0000202 



Dr. Meyer, Assistant Astronomer at the Geneva Ob- 

 servatory, has employed the microphone in transmitting 

 the beats of the standard clock of the Observatory to dif- 

 ferent parts of the building, and also to the Regulating 

 Clock of the city Time Service. The microphone is fixed 

 upon the outside of the clock-case and placed in circuit 

 with a small battery and a telephone. The beats of the 

 clock can then be readily heard throughout the room. 



At the request of the Treasury of the Royal Astronom- 

 ical Society, a committee has been appointed to advise the 

 Government upon the steps which it is desirable to take in 

 order to secure observations of the Transit of Venus across 

 the sun's disk, 1882, December 6. The committee — which 

 consists of the Astronomer Royal, the President of the 

 Royal Astronomical Society, the President of the Royal 

 Society, Professor J. C. Adams, the Earl of Crawford and 

 Balcarres, Dr. De La Rue, Dr. Huggins, Professor H. J. 

 S. Smith, Professor Stokes and Mr. Stone- — has already 

 commenced its labors. 



About a year ago Admiral Moucher asked for a credit 

 of 4,000 francs per year in order to publish a monthly as- 

 tronomical review. M. Jules Ferry refused the grant, but 

 a similar review is now being published at Brussels under 

 the name del et Terre. It appears twice a month and is 

 devoted to meteorology and astronomy. 



The second number of Urania contains quite an elab- 

 orate article by H. C. F. C. Schjellerup, entitled, " Re- 

 cherches sur L'Astronomie des Anciens ; " also a short 

 communication upon Observations of the Spectrum of 

 Comet 1880 f. (Pechule) at Dun Echt, and a "Circular 

 from the Smithsonian Institution." 



A New Variable Star.— M. N. C. Dundr, of the 

 Lund Observatory, reports upon the 24th of February, 

 1 88 1, the discovery of a new, small variable. The star is 

 given in the Bonn Durchmusterung (1855.0) 

 9.4 mag. R. A. = 5 h , iy m , t,2\j. 

 Dec. = + 34' 2'. 1. 



The asteroid. No. 217, discovered by Coggia at Mar- 

 seilles on the 30th of August, 1880, has recently been 

 named " Eudora." 



Washington, March, 1881. w. C. W. 



We are informed by Professor Davidson that the fol- 

 lowing is the correct geographical position of the David- 

 son Astronomical Observatory, San Francisco, Cal.: 



Latitude = 370 47' — 22". 3 North. 



Longitude = 122° 24 — 39.0 West of Greenwich. 

 In time = 8 h 09"" 38 s . 6 

 This differs from the figures we recently gave at page 

 107, in the number of seconds in time. 



