6oo 



NA TURE 



[November 4, 1922 



Narni to the Tiber. Bertarelli's " Guida itineraria del 

 Touring Club italiano," route 180, puts the true aspect 

 of this dissected country before the geographic tourist- 

 Such tourists will receive much encouragement from 

 the broad views of western lands provided in the book 

 before us. Perhaps in another volume the author will 

 show how intensive studies of equal value may be 

 carried on by easy deviations from frequented ways. 

 The piazza of Todi, 1350 feet above the sea, Foix on 

 the Ariege, guarding one of the few passes into Spain, 

 or Radstadt, tinkling with cattle-bells, on the high 

 pastures of the Tauern, may serve as epitomes of their 

 regions and of the reaction of environment on man. 

 But Dr. Newbigin certainly does not need suggestions. 

 Grenville A. J. Cole. 



History of Astronomy. 



Histoire de V Astronomic Par E. Doublet. (Encyclo- 

 pedic scientifique.) Pp. 572. (Paris : G. Doin, 

 1922.) 17 francs. 



IN his first chapter the author passes in review the 

 principal works on the history of astronomy, 

 beginning with Weidler's book and ending with the 

 great work by Duhem on the cosmical systems. Of the 

 valuable books of Grant and R. Wolf, only the titles 

 are given, and several others are omitted altogether. 

 Of monographs, only Schiaparelli's first two papers are 

 mentioned. This is natural enough, since there is 

 plenty of evidence that the author is quite unacquainted 

 with the rich literature of memoirs and short papers 

 on the history of astronomy which has appeared within 

 the last fifty years. Whenever a fact is not mentioned 

 by Delambre, Duhem, etc., it will be looked for in vain 

 in M. Doublet's pages, and whenever fresh light has 

 been thrown on any subject since they wrote, he is 

 not aware of it. Take, for example, the paragraph on 

 Hipparchus. We are told that his diopter was in the 

 Middle Ages called a Jacob's staff ; in reality the former 

 had a cursor with a round hole in it, and was used only 

 for measuring small angles such as the diameters of 

 sun or moon, while the latter was shaped like a cross, 

 with the shorter arm movable (on p. 152 the invention 

 of the baculus is correctly attributed to Levi ben Gerson 

 of Avignon, as Duhem had also done). The star of 

 Hipparchus is compared to the new star of 1572, 

 whereas there can be no doubt that it was nothing but 

 the comet of 134 B.C. The star-catalogue of Hip- 

 parchus is said to contain 1025 stars and to have been 

 handed down to us by Ptolemy, but it has been shown 

 by Boll that the catalogue probably contained only 

 about 850 stars, while it is now universally recognised 

 that Ptolemy's catalogue is not a mere reproduction 

 of that of Hipparchus. Next it is stated that Hip- 

 NO. 2/66, VOL. I lo] 



parchus put the solar parallax equal to 3'; it was Ptolemy 

 who did that, whereas Hipparchus said that it was at 

 most a minute and a half. On the same page we read 

 that Hipparchus determined the principal lunar in- 

 equalities with admirable precision. Hipparchus knew 

 only one inequality, the equation of the centre ; but 

 that is, perhaps, a slip, as it is elsewhere (p. no) 

 mentioned that Ptolemy discovered the evection. 



The most valuable part of Duhem's work is his 

 account of Latin astronomy in the later Middle Ages, 

 as he was able to make use of many manuscript sources. 

 M. Doublet has done right in quoting him largely ; but 

 here, as everywhere else, the consequences of never 

 referring to the original sources are evident. Duhem 

 gives a very unsatisfactory account of the planetary 

 system of Al Betrugi, which was very much discussed 

 in the thirteenth century both at Paris and at Oxford. 

 The account of it by M. Doublet similarly misses the 

 most important part of the system. In the same way, 

 the account of King Alfonso and his Tables reproduces 

 all the old misstatements which have been refuted long 

 ago. The tables were not published at the time of the 

 King's accession, but some twenty years later, and no 

 change was made in them as regards precession ; they 

 were not prepared by a " numerous commission," for 

 it would have been necessary to raise the dead, since 

 the alleged members of that Royal Commission lived 

 long before King Alfonso's time. The " Libros del 

 Saber " were never translated into Latin, and were 

 quite unknown until they were at last printed some 

 sixty years ago, and the last edition of the tables was 

 not printed then, but in 1641. 



The author's account of the progress of astronomy 

 from the "end of the Middle Ages to the time of Newton 

 does not differ much in extent or quality from the 

 earlier chapters. We have only space to direct atten- 

 tion to a misunderstanding on p. 255, with regard to 

 Kepler's work on Mars. What produced errors of 8' 

 was not the use of the Tychonic system (for that, of 

 course, made no difference whatever, being merely the 

 Copernican system with the origin of co-ordinates 

 transferred to the earth), but the use of an excentric 

 circle with " bisected excentricity," after the manner 

 of Ptolemy. 



Having found the first two-thirds of the book rather 

 disappointing, we are glad to say that the chapters on 

 French astronomers in the eighteenth and first half 

 of the nineteenth century are very interesting and 

 pleasant to read. They do not go into details as to 

 the work of these astronomers, any more than do the 

 earlier chapters, but they tell a good deal about the 

 Cassinis, the Maraldis, etc., down to Arago and Lever- 

 rier, which will be new to most readers. 



J. L. E. D. 



