November 22, 1894] 



NA TURE 



75 



modest observatory, at the equipment of which, con- 

 sisting only of small and portable instruments, any 

 modern amateur would turn up his nose. For years he 

 was obliged to correct his clock by tedious observations 

 of equal altitudes with a sextant and artificial horizon, 

 until he devised the simpler and quicker method of 

 watching the disappearance of stars behind a distant 

 tower. But his labours brought him a plentiful reward, 

 not only in the discovery of the planets Pallas and Vesta 

 and various comets, and in the renown which these and 

 his important publications procured him, but also in the 

 friendship of Schriiter, Zach, Gauss, Bessel, Schumacher, 

 Encke and others, who always in their letters and 

 published writings mention him with the greatest 

 veneration. 



The publications of Olbers are scattered through 

 many volumes of the various periodicals of his time, 

 some of which are not readily accessible now-a-days. 

 But most of them are still of the highest importance, 

 not only those describing the method which is practic- 

 ally the only one used for computing cometary orbits, 

 but also those in which Olbers has deposited the results 

 i>f his deep study of the literature of comets, ancient 

 and modern, as well as the many articles which bear 

 witness to his having possessed mathematical abilities of 

 no mean order. The appearance of the complete edition 

 of his works now before us will therefore be hailed with 

 pleasure by astronomers. It is to be followed by two 

 other volumes, containing the correspondence of Olbers 

 with Gauss, and a biography by the editor. 



The celebrated and epoch-making memoir on the 

 most convenient method of computing the orbit of a 

 comet was printed separately (in 1797), and it naturally 

 opens the volume now published. After it (and the 

 appendix published in the Jahrbuch for 1833) the editor 

 has placed twelve other papers under the common head- 

 ing " Abhandlungen." It is not easy to see why these 

 particular papers have been distinguished in this manner. 

 It is not because they are the longest, for some of them 

 occupy only a few pages, so it must be because the 

 editor considers them specially important. But if so, 

 why are others, fully as important, not put along with 

 them, as, for instance, the classical paper on the tail of 

 the great comet of iSi i ? The arrangement of the other 

 papers in six groups also frequently challenges criticism. 

 Under the heading " Comets " are given no less than 

 110 papers, but half a dozen notes on comets are 

 relegated to the group of " Miscellanea from letters," 

 near the end of the book, apparently simply because 

 they were written in the form of letters to the editors 

 of various journals. The useful index at the end of the 

 volume will, however, enable the reader to read these 

 notes in connection with the other papers on comets. 

 On the other hand, the papers on the comets of 1802 and 

 181 1 (pp. 293 and 315) are made up of pieces detached 

 from two editorial articles in the Monailiche Corre- 

 spondent, omitting all the observations not made by 

 Olbers ; and this patchwork might, perhaps, better have 

 been put among the miscellaneous notes. It would have 

 been much simpler, and apparently more satisfactory, if 

 all the papers (except the separately published book of 

 1797) had been printed in chronological order, as the 

 index would even then have made it easy to pick out 

 NO. 1308, VOL. 51] 



I 



papers on any special matter. It is, however, more to be 

 regretted that the editor has not seen fit to add some 

 explanatory notes, which would greatly have increased 

 the value of the book to young students of astronomy> 

 who cannot be supposed to be thoroughly acquainted 

 with its literature. We shall only point out a few cases 

 where such notes would have been particularly useful. 

 The first is Olbers' letter to Encke about the mysterious 

 comet alleged to have been observed by D'Angos at 

 Malta in 1784, reprinted here from Encke's well known 

 paper with the startling title, " Imposture astronomique 

 grossicre du Chevalier D'Angos." We certainly think 

 that the editor might in a short note have given refer- 

 ences to the more recent investigations on this matter by 

 d' Arrest and Gyldc'n, which render it at least very pos- 

 sible that D'Angos really found and on two nights 

 observed a comet. At any rate we cannot be certain 

 that the whole matter was nothing but a fraud, and a 

 different heading to the article might have been chosen. 

 On page 226 it should have been pointed out that the 

 orbit of the comet of 1558 has also been computed by 

 Hoek (from observations by Pa,ul Fabricius), whose 

 results differ considerably from those of Olbers. On p. 

 228, Olbers suggests that the manuscripts of Father 

 Schall in the Vatican might contain comet observations 

 from 161S. It would have been useful to have added a 

 note to the effect that these manuscripts have afterwards 

 been found not to contain any such observations [Corresp. 

 Astron. V. p. 143). .Similarly the article on Cacciatore's 

 supposed planet of 1835 (p. 526) should have been 

 accompanied by a note referring the reader to the calcu- 

 lations of Valz and Luther, as well as to Nature, voL 

 xviii. p. 260, which might prevent some rash student 

 from wasting his time on this object. 



The papers have been reprinted from the originals 

 without any alterations, so that even errors pointed out 

 in subsequent papers have been allowed to stand {c.i;. pp. 

 523 and 53S, compare pp. 649 and 542). Some papers 

 will be quite new to most readers, as they were published 

 in journals of limited circulation, such as Harding's 

 Kleine Ephemeriden, Gottingische Anzeigen, and Gruit- 

 huisen's Analekten and his Jahrbuch. The charming 

 character of Olbers is seen in his notes to Gruithuisen, 

 in which he frequently gently corrects mistakes in the 

 writings of this enthusiastic but somewhat erratic ob- 

 server. In an appendix are given two papers of 1787 

 and 178S on mesmerism. Olbers' dissertation for the 

 decree of M.D. (De oculi mutationibus internis, Got- 

 tingen 1780) is not reprinted. 



The book is well printed, and has as frontispiece an 

 excellent portrait of Olbers. In addition to a table of 

 contents and an index, it contains a list of all the papers, 

 arranged according to the journals in which they first 

 appeared. No mention is here made of the catalogue 

 of cometary orbits (published in Schumacher's Ahhattd- 

 liingcn) ; but this has not been reprinted, and is of course 

 long ago superseded. 



In laying aside this splendid volume, we cannot refrain 

 from making one more remark. We have now the 

 collected works of Laplace, Gauss, Bessel, Encke, 

 Olbers ; how long are we to wait for a complete edition 

 of the works of William Herschel ? 



J. L. E. D. 



