1885.] 
Analyses of Books. 
549 
The remaining five parts or chapters, forming the larger por- 
tion of the book, deal with celestial spedtroscopy. Here, how- 
ever, there are also included sections on telescopic appearance 
ot the sun’s surface, and speculations as to the nature of the 
solai spots founded upon telescopic observation. 
Here, theiefore, we are landed on what is somewhat profanely 
called “ sunspottery.” The history of opinion on these much be- 
gossipped phenomena is briefly given. Pastor Schiilen, of 
^ssingen, in 177°* is said to have been the first who pronounced 
these spots to be depressions. The same view was held by A 
Wilson and the elder Herschel, and, though we find it stated in 
the text that “ opinions are still divided as to whether the spots 
aie cavities 01 not, . yet the Editor appends a note which seems 
to answer the question in the affirmative : — “ At Kew and Green- 
wich photogiaphs have been obtained when a spot was just at 
the limb. One or two photographs show notches cut out of the 
limb due to the depression of the spot.” The conflicting the- 
ories of Sporer and Zollner, on the one hand, and of Sscchi on 
the other, concerning the causes of the spots, are summarised, 
but no positive conclusion is drawn, — a judicious reservation. 
The question which is most closely linked with sun-spots in 
the public mind, — i.e., the connection, real or supposed, of their 
periodicity with a variety of terrestrial phenomena, — lies, strictly 
speaking, outside the plan of the present work, and is therefore 
not entered upon. On this subject we may refer to a brief note 
in our “ Correspondence ” department. 
The succeeding chapters treat of the applications of spedtrum 
analysis to the moon and planets, to the fixed stars, the nebula 
and clusters, comets and meteors, the zodiacal light, aurora 
borealis, and lightning. 
The value of this work to all who are interested in celestial 
phenomena— and who is not ?— is incontestable. On this part 
of the subjedt it may claim an almost encyclopaedic position. 
The illustrations are excellent and very numerous. There are 
fourteen maps and plates, five of which are coloured, and 
604 woodcuts introduced along with the text. 
The Wave of Translation in the Oceans of Water, Air, and 
Ether. By J. Scott Russell, F.R.SS. L. and E. London: 
Trtibner and Co. 
The author of this work divides water-waves into four orders. 
The first is the wave of translation, the second oscillating waves, 
the third capillary waves, and the fourth the corpuscular wave. 
As instances of the first order he mentions the tide-wave and the 
