NATURE 



[November 2, 189.^ 



species are exposed when grown in quantity, and so 

 forth. 



Some of the sections are notably long, and the author 

 gives signs of the discursive habit incidental to those who 

 read and transcribe much from German text-books ; 

 moreover, there are sentences which betray the German 

 method in their construction, and there is a distinctly 

 Teutonic sound about some of the terms and short 

 phrases, such as "soil-improving,"" free enjoyment of 

 light and air," "above-sketched method,'' "equal-aged 

 crops," and so on. 



With all its faults of diffuse writing, and a certain 

 amount of repetition, the work is likely to bs valuable to 

 students of forestry in this country, as setting forth the 

 experience of German and other continental authorities 

 in the growth and tending of mixed and other forests. 

 One or two misprints have come under our notice, ^,^. 

 an /has dropped on p. i6i ; and should not "prunosa" 

 (p. 328) be pruinosa ? Again, why adopt the antiquated 

 term " Scots Pine ''''i 



ASTRONOMY OF THE NINETEENTH 

 CENTURY. 



A Popular History of Astronomy during the. A'ineteenth 

 Ceniitiy. By Agnes M. Gierke. Third Edition. 

 (London : A. and C. Black', 1893.) 



DURING the six years that have elapsed since the 

 publication of the second edition of Miss Gierke's 

 classical history of astronomy, new light has been thrown 

 upon a number of old ideas, and many important dis- 

 coveries have been made. It became necessary, there- 

 fore, for the authoress to revise her work, to add here, 

 and substitute there, and in all cases to incorporate the 

 recently-acquired facts without breach of continuity. 

 There is no suggestion of interpolation, and nothing but 

 praise can be given for the manner in which the selected 

 material has been assimilated. 



Attention may be directed with advantage to one or 

 two points. On p. 199 a description is given of the 

 luminous outburst observed upon the sun in September, 

 1S59. The occurrence is supposed to have been followed 

 immediately by a break in the magnetic records at Kew, 

 and every astronomical text-book instances it in evidence 

 of the sun's ability to disturb terrestrial magnetism. Miss 

 Gierke's words with reference to the matter are as fol- 

 lows, the italicised expression being her own: — "^/ the 

 very instant of the solar outburst witnessed by Carring- 

 ton and Hodgson, the photographic apparatus at Kew 

 registered a marked disturbance of all the three mag- 

 netic elements." Now, at a meeting of the Physical 

 Society in 1S86, the late Mr. Whipple said that from an 

 examination of the magnetic curves, he believed " the 

 very slight notch in the record, many similar to which 

 have occurred since, was of an accidental nature, and a 

 mere coincidence." (Nature, vol. xxxiii. p. 621.) 

 Further, in a letter to the writer of this notice, Mr. 

 Whipple remarked "it was merely an insignificant 

 wriggle of the curves that was recorded at the time of the 

 Carrington and Hodgson observation, and the great 

 NO. 1253, VOL. 49] 



magnetic storm did not commence for some fifteen hours 

 later." Miss Gierke would do well to mention Mr. 

 Whipple's contention in a future edition, and if she 

 will look at the traces and decide the point— accepting 

 Sabine's interpretation of a magnetic disturbance (Phii. 

 Trans, vol. cliii. p. 274), she would do a good work. Possibly 

 the coincidence will be disproved before the appearance 

 of the next edition. Tenets of belief accepted quite as 

 implicitly have had to be given up in the interim be- 

 tween the publication of the second edition and the one 

 before U5. Thus, in the former edition we read (p. 437) 

 " the conspicuous bright line of the Draco nebula was 

 found to belong very probably to nitrogen"; whereas the 

 present rendering is " the conspicuous bright line of the 

 Draco nebula, although nearly accordant in position with 

 one belonging to nitrogen, has since proved to be 

 distinct from it." But for the suggestion that the 

 chief nebular line had its origin in magnesium, 

 the nitrogen origin would, in all probability, still be 

 accepted. The search for truth initiated by the sugges- 

 tion, has thus borne good fruit in disposing of the nitro- 

 gen-origin " for ever and for aye." One begins to wonder 

 why the idea remained above suspicion for so 

 many years. It is well known that the green line of 

 nitrogen is double, and it now appears that the mag- 

 nesium fluting is really nearer the true position of the 

 chief nebular line than the nitrogen double. What is 

 more, the magnesium origin was indicated by laboratory 

 experiments, whereas nitrogen had nothing but an 

 approximate coincidence to support it. 



In connection with the spectra of nebulae it may be 

 pointed out that no mention appears to be made of the 

 observation of the discontinuous character of the spec- 

 trum of the Andromeda nebula {Roy. Soc. Proc. vol. xlv. 

 p. 2 16), and of the white nebula in Draco, G.C. 4058 {Ibid. 

 vol. xlviii. p. 219). This is to be regretted, forthe obser- 

 vations are of importance, and, in all probability, many 

 of the spectra now classified as continuous are only irregu- 

 larly so; hence a study of these minute differences of 

 brightness may very considerably add to our knowledge 

 of stellar constitution. We also fail to find a description 

 of Prof Boys' work on the heat of the moon and stars 

 {Roy. Soc. Proc. vol. xlvii. p. 480). 



There are seventy-two more pages in the third edition 

 than in the previous one, and five plates have been 

 added. An extremely useful set of tables of astronomical 

 data has also been included. The chronological table 

 has, of course, been brought up to date, and it gives an 

 excellent digest of the work that has been done between 

 March 1774 and April 1893. It can hardly be said, ho vv- 

 ever, that the strict impartiality which should characterise 

 a history of astronomy has been exercised when an event 

 of such local interest as a " Lecture by Dr. Huggins, on 

 Nova AurigK, at the Royal Institution," is recorded as 

 having taken place on May 13, 1892, while the announce- 

 ment on February 8, 1892, of the duplex nature of the 

 lines in the spectrum of the same Nova is unmentioned 

 in the table. 



The merits of the volume are now so well known that 

 it is quite unnecessary to expatiate upon them. It seems 

 to us, however, that if Miss Gierke were more a historian 

 and less a partisan, her work would be of higher value. 



