Jan. 9, 1879] 



NATURE 



217 



si negligees," he has omitted all Capt, Jacob's measures 

 subsequent to 1848, and as instances where some 

 measures are wanting, may be mentioned y Argus, 

 /) Herculis, 8 Herculis, t Ophiuchi, 70 Opbiuchi, € Equulei 

 61 Cygni, 6 Indi, &c., &c. 



After exhibiting the measures of each object, M. 

 Flammarion, in the great majority of cases, appends his 

 o^vn conclusions with respect to the cause of the relative 

 changes of position, which have generally been carefully 

 considered, though there are some few in which we should 

 hardly be disposed to follow him. But the reader having 

 nearly all that is known of the different objects before 

 him, in M. Flammarion' s summary, will be able to form 

 his own inferences. If an observer he will be guided 

 thereby to a selection of objects most worthy of his atten- 

 tion, or most requiring further measures for the elucida- 

 tion of the cause of altered position. 



In a provisional examination of the volume ample 

 proof is afforded of the care taken by the author in his 

 work, which has no doubt been as he describes it long 

 and laborious. There are a few such oversights as 

 H2 3678 for H2 4087 ; and under Procyon, misled by a 

 measure of Secchi's in 1856 as printed, he refers to a 

 companion at 83°"6 and 33"'i6; this measure, however, 

 really belonged to Powell's distant companion, and 

 instead of 33" •16 the distance should be 33i"'6, as it is 

 given in another page of the same volume of Memoirs of 

 the Roman Observatory. There is no reference to some 

 of Argelander's determinations of proper motion, as in 

 the case of a distant companion of y Leonis, upon which 

 M. Flammarion enters into some detail. Omissions like 

 this, however, are perhaps unavoidable in the first prepa- 

 ration of such a work, but the author wiU doubtless have 

 his attention called to them, and will be able to make his 

 second edition a still more inclusive manual of double- 

 star astronomy, than even this first impression. 



Through the kindness of Leverrier, M. Flammarion 

 was allowed the use of one of the equatorials at the 

 Observatory of Paris during the year 1877 for the re- 

 measurement of a number of the double stars ; these 

 measures applying to about 130 objects are given at the 

 end of the preface to this volume : amongst them we 

 note the close pair of 40 Eridani, a rapidly revolving star 

 which has not received the attention it deserves from 

 observers. 



M. Flammarion's work will doubtless soon find its way 

 into the hands of every one who is interested in the 

 double and multiple stars, and he will certainly experience 

 the satisfaction of receiving the well-earned thanks of 

 many amateurs who have no convenient access to large 

 astronomical libraries and to whom his volume will be a 

 valuable vade-mecutn. 



OUR\ BOOK SHELF 



The Mtllusca of the Firth of Clyde; being a Catalogue of 

 Recent Marine Species Fotind in that Estuary. By 

 Alfred Brown. (Glasgow : Hugh Hopkins, 1878.) 

 Although the recent moUusca of this district have 

 during the last few years received a good deal of atten- 

 tion, especially from the labours of M'Andrew, Barlee, 

 and Merle Norman, still the various memoirs detailing 

 the results of these labours were only to be found widely 

 scattered through a number of scientific periodicals, and 

 Mr. Brown has in this neatly printed work given us not 



only a resutni of the labours of the naturalists we have 

 referred to, but also of all those who have collected on the 

 Firth of Clyde, and joined these to the labours of Mr. 

 David Robertson and his own. The result is, so far as 

 the testaceous mollusca go, a large and apparently accu- 

 rate catalogue, which will show not only what has been 

 done but also among the nudibranchs and cuttle-fish what 

 is yet to be done. The notes under the heading of Habitat 

 in this catalogue are often most interesting, giving details 

 not only of the exact localities for the species, but notes 

 also of their local names. 



Wanderings in Patagonia; or, Life among the Ostrich 

 Hunters. By Julius Beerbohm. Map and Illustra- 

 tions. (London: Chatto and Windus, 1879.) 

 The title of [this book is somewhat misleading, as the 

 author's "Wanderings" were of a very limited extent, 

 embracing only a small portion of the south-east coast 

 region of Patagonia. Its most important feature is the 

 account given of the life of the ostrich-hunters, and it 

 adds little to our knowledge of Patagonia in addition 

 to what has been told us by Musters and the one or 

 two others who have really "explored" more or less ol 

 the wild region. The author's story is pleasant to read. 



LETTERS TO THE EDITOR 

 ]_The Editor dees not hold himself responsible for opinions expressed 

 by his correspondents. Neither can he undertake to return, or 

 to correspond with the tvriters of, rejected manuscripts. Nb. 

 notice is taken of anonymous communications. 

 [The Editor urgently requests correspondents to keep their letters as 

 short as possible. 7he pressure on his space is so great that i^ 

 is impossible otherwise to ensure the appearaiue even of cont' 

 munications containing interesting and novel facts.'\ 



Tempel's Comet 



The well-known comet- and nebula-finder of the observatory 

 of Arcetri, Tempel, has just made an observation of grestt 

 interest in reference to his Comet No. II. of 1873, which, as 

 astronomers know, has an orbit between Earth and Jupiter. It 

 has no tail, but a nebular surrounding, which Tempel observed 

 to be gradually diminishing in luminousness v.ithout losing bulk, 

 and finally has entirely disappeared, leaving the comet perfectly 

 distinct, but with a slight scintillation or rather an appearance 

 of being composed of several masses having motion in the rest of 

 the nucleus ; probably an optical effect due to our own atmo- 

 sphere, but which is at all events seen quite distinctly enough to 

 make it certain that the disappearance of the nebulous surround- 

 ing is not due to failure of the telescope to show it. 



The comet was last observed on December 18, at 6h. 53m. 

 I2S. mean time of Arcetri in Right Ascension 23h. 3m. I4'i5s., 

 and in South Declination 19° 15' 54""8. It was seen on the 21st 

 but briefly, and no observation could be made. Since then the 

 continually cloudy sky has prevented it from being seen, but 

 Tempel is confident of being able to see it through January. It 

 is now amongst the asteroids. W. J. Stillman 



Florence, January i 



The Cosine Galvanometer 

 In Nature, vol. xix. p. 98, my name appears in a way that 

 might lead the reader to infer that I was the inventor of the 

 "cosine galvanometer." My knowledge of this useful instrument 

 was derived from Prof. Trowbridge, of Cambridge, U.S., who 

 described it in 1871 in the American fournal of Science, vol. cii, 

 p. 118. In my "Physical Manipulation" I omitted to mention. 

 Prof. Trowbridge's name, supposing that his connection with 

 the instrument was too well known to render it necessary. 



Edward C. Pickering 

 Harvard College Observatory, Cambridge, U.S., 

 December 20, 1878 



Force and Energy t- 



II. 



In passing it may be noticed that the plus sign thus deduced 



for a tensive force is otherwise convenient because tension results 



in a positive increase of the dimensions in the direction of th6 



tension of the body through which the tension is transmitted. 



* Continued from p. 196. 



