NA TURE 



THURSDAY, FEBRUARY 4. 18S6 



ASTRONOMY DURING THE NINETEENTH 



CENTURY 

 A Popular History of Astronomy diirina; the Nineteenth 

 Century. By Agnes M. Gierke. (Edinburgh : Adam 

 and Charles Black, 18S5.) 

 \X /■£ have read this book with very great interest and 

 ^ with no little pleasure. The authoress (for this 

 learned volume is indeed the product of a lady's pen) has 

 modestly described her " History of Astronomy" as a 

 popular work. We certainly hope that the book will be 

 as popular as it deserves, and that it will be widely and 

 extensively read. We think, however, that few men of 

 science who use this book will think that it ought to be 

 classed as a popular work in the ordinary acceptation. 

 It might be more correctly described as a masterly expo- 

 sition of the results of modern astronomy in those depart- 

 ments now usually characterised as physical. 



Prof. Grant's " History of Astronomy," now more than 

 thirty years old, treated of astronomy prior to that re- 

 markable development of the science consequent on the 

 invention of the spectroscope ; Miss Gierke may thus 

 be said to have resumed the subject from the point 

 which Prof. Grant reached, and her present work is well 

 worthy of a place beside Grant's volume in every astro- 

 nomical library. 



In the opening pages of the introduction Miss Gierke 

 distinguishes the three great branches of the science of 

 astronomy. The primary branch is that known as " ob- 

 servational," which involves the art of observing the 

 returns and measuring the places of the heavenly bodies, 

 but is not concerned with schemes for harmonising these 

 facts into a compendious theory. The second kind of 

 astronomy is that founded by Newton, and is most ap- 

 propriately termed " gravitational." It seeks to account 

 for the main facts of astronomy, in so far as the move- 

 ments of the bodies are concerned, by the operation of 

 the law of gravitation. The third branch is that which 

 Miss Gierke terms "physical and descriptive." This 

 branch of astronomy embraces the detailed study of the 

 features of the different celestial bodies, and also the 

 examination of their actual character and chemical com- 

 position. The two first branches are the older and better- 

 known parts of astronomy. It is in the third branch that 

 the great developments of modern times have taken place. 

 It is especially in this department that Miss Gierke's 

 work will be found invaluable as giving a succinct and 

 accurate summary of our knowledge. 



The work is divided naturally into two portions. The 

 first part describes the progress of astronomy during the 

 first half of the nineteenth century. It opens with an 

 account of the career of Sir W. Herschel and his dis- 

 coveries. In subsequent chapters of the first part we 

 have the account of the memorable achievements of 

 Bessel and Struve in sidereal astronomy. We have also 

 a useful sketch of the earlier observations on and theories 

 with regard to the structure of the sun ; the discovery 

 of the minor planets ; the development of the cometary 

 discoveries so far as the laws of their motions are con- 

 VOL. xxxiii.— No. 849 



cerned ; and an account of the instrumental advances up 

 to the time of the great Rosse reflector. 



It is, however, in the second part, on " The Recent 

 Progress of Astronomy," that Miss Gierke has found a 

 new field, which she has occupied with great success. 

 The earlier chapters of the second part relate to the 

 foundations of astronomical physics. There is an admir- 

 able account of the state of our knowledge with respect to 

 sunspots, and of the results obtained from recent eclipses. 

 The spectroscopic work on the sun is discussed in an 

 able chapter, while the researches on the great constant 

 of the universe — the sun's distance— fitly occupy another. 

 Then we have an account of the recent discoveries with 

 respect to the planets and their satellites, and of the 

 theory of planetary evolution. Chapters X. and XL, on 

 comets, are especially good, and the spectroscopic labours 

 on stars and nebulx- are also well described. A chapter on 

 the methods of research concludes a volume of 468 pages. 

 The photographic and spectroscopic work is virtually 

 the theme of this book, and any one who desires to learn 

 .what has been done by Huggins and Lockyer, or by 

 Young, or Janssen, or Vogei, will find full and accurate 

 information, kn index is provided which might, however, 

 have been a little more extended with advantage. 



At nearly every point Miss Gierke is careful to 

 quote the references to the original authorities : this is 

 indeed so characteristic a feature in the work that it 

 would be valuable for these references alone, though in 

 saying this we do not imply the slightest disrespect to 

 Miss Gierke's able epitome of the results of each paper 

 she has quoted. Many years of labour must have been 

 required for the production of this work, for Miss Gierke 

 has evidently studied with elaborate care the original 

 writings on each subject. 



So far as we have seen Miss Gierke does not appear to 

 have been herself an observer of the heavens, and once 

 or twice remarks occur which would hardly have been 

 made by one who is familiar with astronomy in its prac- 

 tical sense. We are told, for instance, on page 103, that 

 Bessel when a boy, could see the components of e Lyrae 

 apart with the unaided eye ; no doubt he could, but the 

 remark would hardly have been made by one who knew 

 that everybody with tolerable vision can do the same. 



In some few places we think that it would have been 

 better to have allowed vague old speculations to pass 

 into oblivion than to furbish them up once again ; what, 

 for instance, is the advantage of reproducing Wright's 

 doctrines about the Milky Way, or the astronomical 

 theories of Kant? No astronomy is worth anything 

 which is not grounded on accurate observation or rigid 

 calculation. The " Central Sun " rubbish ought never 

 to have again been printed. We have however but few 

 criticisms to offer on a work so thorough and so carefully 

 written. Miss Gierke has expressly disclaimed any 

 intention of discussing the more abstract mathematical 

 researches relating to astronomy ; one of the few excep- 

 tions is to be found in a description of Prof. George 

 Darwin's now celebrated theory of tidal evolution ; the 

 account here given is both interesting and accurate so far 

 as it goes, but mathematicians do not like such expres- 

 sions as "wasting its momentum as heat dissipated 

 through space" (p. 316). 



The literary style of Miss Gierke's work is 'especially 



