September 13, 1S94] 



NATURE 



473 



ELEMENTS OF COM ETA RY ORBITS. 

 Vcr:cichniss tier Eleineitte dcr bisher berechneien 



Comctcnbahnen. By Prof. Dr. J. G. Galle. (Leipzig : 

 1 Wilhelm Engelmann, 1S94.) 



I ' I 'HE volume which we have before us contains, as its 



-I- title indicates, a list of the orbits of all those comets 

 which have up to the present time been calculated. As 

 our readers may already be aware, this is not the first 

 " Verzeichniss " with which Prof. Galle has presented us, 

 for one has only to refer to the second edition of " Olber's 

 Methode zur Berechnung der Cometenbahnen," by 

 Encke, where will be found a collection of the orbits of 

 comets which had appeared up to the year 1847. In the 

 following or third edition, which came out in 1864, the 

 list was expanded, revised, and brought up to date. The 

 present " X'erzeichniss '' has, however, assumed larger 

 proportions than its predecessors, containing as it does 

 over 300 pages, and so is published as a separate work. 



In the introduction the author sums up in a few words 

 the chief points about the numerous lists of tometary 

 orbits which have be;n published from time to time, 

 referring chiefly to the different ways in which they have 

 been arranged and compiled. 



Several changes from preceding lists have been 

 adopted in the book before us, and we will chiefly re- 

 strict ourselves to a brief statement of the same. It 

 may be mentioned here that the order of the elements of 

 the same comet has been so chosen that the less accu- 

 rate elements precede those which have been considered 

 more correct, so that the last elements in every case are 

 those which approach nearest to the truth. 



Two important alterations concern the removal of the 

 distinction between direct and retrograde moving comets, 

 and the way of representing the inclinations of orbits 

 from o' to 180'. Instead of the Longitude of Perihelion 

 (ir) being adopted, Prof. Galle employs the angle between 

 the node and the perihelion point, that is, he introduces an 

 angle w, which equals the Longitude of I'erihelion minus 

 the node, so the relation may he represented by ii> = w - .a 

 The arc w has been termed the " Argument of Perihelion," 

 and is somewhat analogous to the "Argument of Lati- 

 tude" {u = v -\--rr- n), SO that wis the.-\rgument of Latitude 

 for v = o, or is Perihelion point. 



To pass from the "Argument of Perihelion" w, to the 

 "Longitude of Perihelion'' tt, without distinguishing 

 between direct and retrograde movement, the simple 

 relation tt = Q -f- w is used. On the other hand, if, after 

 the old style in the case of retrograde moving comets, 

 the Longitude of Perihelion is denoted by the difference 

 !2 — <■) and represents this by w', and if also / denotes the 

 value of the inclination in this case only as far as 90, 

 then the relation for the reduction is as follows : 

 n + n' = 2.0. z -f 2' = 180°. 



Following the columns dealing with the position of 

 I'erihelion, the Node, and the Inclination, are others 

 giving the logarithms of the Perihelion distance, and the 

 eccentricity, concluding with the names of the computers 

 of each of the orbits and the references in every case. 



in addition to the above, we have no less than 160 

 pages of remarks and literature references, which will be 

 found invaluable by those searching for special inform- 

 ation about any particular comet. Perhaps a brief note 

 NO. 1298, VOL. 50] 



will best serve to give the reader some idea of the style 

 in which the author has brought together the information. 

 The subjoined note, picked out at random, is typical of 

 the method followed. 



No. 3;6. 1SS3 II. Discovered 18S4. January 7, by 

 Ross in Elsternwick, at Melbourne, observed only for a 

 few days in the southern hemisphere and in Madras, by 

 Ellery in Melbourne until February 4, still approaching 

 February 7 and February 19. At first visible with the 

 naked eye, then afterwards dimmed quickly and difificult 

 to observe — A..V. cviii., cix. A/./V. xliv., xlv. Observ- 

 atory \\\. N.ATURE \K\x.~Te/i/iiilt's elements are com- 

 puted from the observations made on January 19, 23, 28. 

 Tcmtant's from those of January 17, 26, 30. Bryant's 

 from three normal positions January 19, 25, February 2. 

 Ellerfs from those of January 12, 18, 28. Oppenheim's 

 from those of January 12, iS, 28, 29, February 4. Three 

 computed ellipses, one by Tennant and the other two by 

 Bryant, in M.S. xlv. and xlvii., have been omitted, so 

 also an approximate orbit by Hind in Natl'RE xxix. — 

 All the above-mentioned orbits are referred to the M.E. 

 1S84, o. 



As a rule the notes are much longer than the above, 

 some, such as those which relate to comets 18S0 I., 

 1 88 1 III., 1882 I., 1SS2 II., 1889 v., &c., extending over a 

 page or more. 



In the compilation of this work, the thoroughness with 

 which it has been done is a striking feature throughout, 

 and Prof Galle deserves the thanks of all astronomers for 

 the completion of this volume. The information is 

 brought up to the beginning of this year, thus making 

 the book, besides the best, the most recent of all other 

 lists. W. J. L. 



OUR BOOK SHELF. 



Primary Geography. By A. E. Frye. Pp. 1 28. (Boston 

 U.S.A. : Ginn and Co., 1894.) 



We have never seen a class-book of geography more 

 profusely and admirably illustrated than the one under 

 review. Our only regret is that the book, being written 

 for schools in the United States, possesses the eccentric 

 or reformed orthography that obtains there. This, 

 in conjunction with the fact that the British Isles 

 are dismissed in less than a page of text, renders the 

 volume unsuitable for use in our schools. We hasten to 

 remark, however, that the author has not merely con- 

 cerned himself with the interests of the United States, as 

 a brief statement of the various sections in his work will 

 show. 



The book opens with what is called " Home Geography," 

 which section deals with elementary facts of physical 

 geography observable at any place. The earth is next 

 studied from an astronomical point of view: and then 

 follow descriptions of the slopes of the earth. After 

 describing the surface features of the different continents, 

 the author passes to an accovmt of the peoples of the 

 earth, and then to meteorological phenomena. This is 

 followed by sections on plants and animals, and finally 

 commercial geography is treated, the continents being 

 taken in succession. The book has so many excellent 

 points that we can only mention a few of them. One is 

 that the text on people refers to child-life, and must 

 therefore appeal to children more than references to 

 cheek-bones and the texture of hair. Plants and animals 

 are studied in their relations to climate and physical 

 features, and thus a clear idea as to the causes affecting 



