280 Notices respecting New Books. 



ledge of the Sun during the first half of the century is related ; and 

 the Herschelian theory of the solar constitution explained and dis- 

 cussed in a way which shows that Miss Clerke is quite familiar with 

 current ideas and theories on the constitution of the Sun and his 

 appendages. The first discovery of minor planets and the circum- 

 stances which immediately led up to that event are gone into at 

 length, as well as the great services rendered by Gauss in the 

 emergency caused by these discoveries. We fear, however, that 

 the method of Least Squares is not very felicitously referred to as 

 that which "enabled him to extract the utmost amount of probable 

 truth from a given set of observations;" but such subjects are 

 avowedly outside the scope of Miss Gierke's book. The history of 

 the discovery of Neptune is given with great impartiality, and a 

 full discussion of the observations of, and theories relating to, 

 Comets anterior to the application to them of the methods of spec- 

 trum analysis. The first part of the work concludes with a chapter 

 on the important subject of the improvements effected in astrono- 

 mical instruments during the period to which it refers. 



Part II. may be divided into four sections, consisting of the 

 chapters referring to (1) the Sun, (2) Planets and Satellites, 

 (3) Comets, and (4) Stars and Nebulae. Of these we think that 

 the chapters devoted to the Sun are the best. Miss Clerke has 

 evidently given much attention and thought to the subject, and has 

 drawn a very clear and accurate picture of the state of our know- 

 ledge of, and of the various theories which have been advanced 

 regarding, the Sun. Starting from Schwabe's discovery of a decen- 

 nial Sun-spot period, she goes on to trace the rise and development 

 of Spectrum Analysis, and to point out the various ways in which 

 the spectroscope has increased or originated knowledge in the 

 several departments of solar physics. Of the chapters on the Sun, 

 that which pleases us best is the one on Eecent Solar Eclipses. 

 This, to our mind, gives a remarkably clear and able account of the 

 various questions successively raised and answered, completely or 

 partially, by the series of total solar eclipses extending from I860 

 to 1883 ; and we know not where else, in popular literature, such 

 an account is to be found. In discussing Sun-spot theories, Miss 

 Clerke manages very judiciously to steer a middle course between 

 " Sun-spottery " and scepticism. She even finds space for reference 

 to the attempt which has been made to arrive at the period of an 

 unknown planet through the observation of sun-spots ; but, some- 

 what drily, adds, " The prediction still awaits fulfilment." "We 

 venture to think that the author is much more successful when 

 discussing theories (e. g. when engaged on the subject of Mr. 

 Lockyer's " basic lines ") than when describing appearances : 

 thus the chapters on the Planets and Satellites, which are mainly 

 concerned with descriptive Astronomy, appear to us to be the 

 least satisfactory of any in the book, and not calculated to fix 

 the reader's attention in the same way as the following ones 

 dealing with Comets or with Stars and Nebulae, in which a much 

 greater amount of speculative matter is introduced. In speak- 

 ing of the rotation-period of Mars, Miss Clerke appears to claim 

 for Mr. Proctor's result an undue amount of accuracy : it is un- 



