NATURE 



[March 2, 191 1 



KOMER'S ADVERSARIA. 



Ole Romer's Adversaria, med Understottelse af Carls- 

 bergfondet udgivne af det Kgl. Danske Videnska- 

 bcrnes Selskab. By Thyra Eibe and Kirstine 

 Meyer. Pp. v + 271. (Kobenhavn : Bianco Lunos 

 Bogtrykkeri, 1910.) 



AMONG astronomers Ole Romer (1644-1710) occu- 

 pies a peculiar position. He was held in high 

 repute among contemporary men of science, as may 

 be seen from the fact that Newton and he were the 

 first astronomers to be enrolled among the eight 

 foreign associates of the Paris Academy of Sciences, 

 and were elected on the same day. To posterity he is 

 known as the discoverer of the gradual propagation 

 of light, and as the man who introduced the use of 

 (if he did not invent) the transit instrument and the 

 transit circle. And yet his published writings only fill 

 a few pages, and the observations he made with instru- 

 ments far superior in design to those of his time, were 

 not printed, and nearly all of them perished not long 

 after his deafh. There is, therefore, every reason to 

 welcome the publication of his common-place book, 

 which has been brought out just two hundred years 

 after his death. 



Like every other book of its kind, the present book 

 of Adversaria deals in a scrappy way with a great 

 variety of subjects, and it shows what chiefly occu- 

 pied Romer's mind, especially during the last ten 

 years of his life. We see him as a practical 

 astronomer, as a physicist, and as a man who had 

 for many years served his country well by reorganis- 

 ing the system of weights and measures, getting the 

 Gregorian calendar introduced, and preparing a uni- 

 form system of land taxation. But though these 

 various occupations, which gradually came to fill 

 most of his time to the great loss of science, are now 

 and then alluded to in the present volume, they do not 

 fill many pages in it. It looks as if Romer was in 

 the habit of taking refuge in his commonplace book 

 when he wanted to refresh his mind after his hard 

 work as Burgomaster and Chief of Police of Copen- 

 hagen. To give a full account of the contents of his 

 notes is not possible in a limited space : we can only 

 give the reader some idea of the kind of subjects dealt 

 with. An important section on thermometers, dating 

 from 1702, has already been described in Nature, 

 (vol. Ixxxii., p. 296). Romer appears to have been 

 the first to construct thermometers with two fixed 

 points, marking the temperatures of melting snow and 

 of boiling water, and he was the inventor of the scale 

 known as Fahrenheit's. 



Turning to astronomical matters, we find Romer 

 to have been a follower of Descartes in his views on 

 the construction of the universe, though his own dis- 

 covery about light did not exactly harmonise with 

 Cartesian ideas. He inquires at what distance a 

 planet or satellite would have to be from the central 

 body according to the third law of Kepler in order 

 that its period of revolution may equal the period of 

 rotation of the central body. In the case of a planet 

 he finds the distance equal to 37 semidiameters of the 

 sun, in the case of a satellite of the earth 65, and 

 for a satellite of Jupiter 2 semidiameters of the respec- 

 NO. 2157, VCL, C-] 



tive planet. This, he thinks, may be made to agree 

 with the vortex theory by assuming that radiatiim 

 from the central body impedes the rotation of the 

 ether, and this radiation, being naturally much more 

 powerful from the sun, causes its influence to be felt 

 at a much greater distance than that at which the 

 radiation of a planet is perceptible. He shows him- 

 self interested in solar phenomena by calculating the. 

 apparent position of the sun's axis, and of the path 

 of sun-spots for every 7^° of longitude of the sun, 

 having first determined the inclination of the sun's 

 equator and the place of the node with fair accuracy 

 from his own and La Hire's observations. It will l^e 

 remembered that the sun's equator was in those days 

 often used as a fundamental plane or Via Regia ui 

 the solar system. He calculates the transit of M( r- 

 cury of May, 1707, from Kepler's elements and obs( r- 

 vations by Hevelius of the transit of May, 1661. He 

 calculates the solar eclipse of September 13, 1708, for 

 Copenhagen, and Holum in Iceland, and gives rules 

 for the prediction and graphic representation of an 

 eclipse. The transit instrument in the prime vertical, 

 of which he had introduced the use, is employed for 

 the determination of the vernal equinox of 1702, and 

 he examines the consequences of errors of observation 

 in the transit, and shows how to determine the error 

 of coUimation by reversing the instrument. 



The above examples, which could easily be multi- 

 plied, will show that the two ladies who have edited 

 this book have done good work by bringing it to 

 light. There is a useful index and an excellent table 

 of contents, and every care seems to have been taken 

 to produce an accurate edition of the old manuscript. 

 The few Danish words or sentences occurring here 

 and there might have been translated in foot-notes for 

 the convenience of readers not acquainted with that 

 language. J. L. E. D. 



GALL-FLIES AND OTHERS. 

 Das Tierreich. Eine Zusanimenstellung ufid Kenn- 

 zeichnung der rezenten Tierfortnen. Edited by 

 F. E. Schulze. 24 Lieferung. Hymenoptera. 

 Cynipidae. By Prof. K. W. von Dalla Torre and 

 Prof. J. J. Kieffer. Pp. xxxv + 891. (BerHn : R. 

 Friedlander and Son, 1910.) Price 56 marks. 



THIS work forms a worthy volume of the series 

 of zoological works published under the general 

 title of "Das Tierreich," by Messrs. R. Friedlander and 

 Son, of Berlin. It is an extension of the two volumes 

 by Dr. Kieffer in Andre's "Species des Hymenopteres 

 d'Europe et de I'Algerie." Dealing as it does with 

 the Cynipidae of the whole world, and containing 

 descriptions of all the known genera and species, the 

 book is indispensable to students of the Cynipidae. 

 Theodore Hartig was the pioneer of the scientific 

 study of the group. He placed the classification on a 

 proper basis, and was the first to point out the three- 

 fold habits of the species — gall-makers, inquilines, and 

 parasites. After him came Giraud, Schenk, and, 

 above all, G. L. Mayr, who made the identification 

 of the galls easy by the publication of beautifully 

 illustrated works on the species of Central Europe, as 

 well as a monograph on the guest-flies (Synergi). 



