Notices respecting New Books, 141 



from the mesh SGQ Ly 1 = y l Kr' 2 +y$ — (x— y)Q=y l Kr 2 , by 

 the condition PS = QR for the steady balance. 



The other case o£ the current beino- made is rendered 

 equally simple by the observation that the impulse \ E dt can 

 in itself have no effect on the galvanometer, if PS = QR, or 

 in general if it is placed in a link which is conjugate with 

 the battery branch. Or using Professor Lees's equations (12) 

 to (14), we may imagine them first solved leaving out the 

 second side of (13), i. e. with L = and K or r = ; this 

 gives PS = QR. Then subtract from the actual equations 

 when the second side of (12) disappears ; it is then seen that 

 the condition for the additional z being is Kr 2 = L, that 

 this condition is independent of PS = QR being satisfied, and 

 finally that it involves the disappearance of the additional 

 x and y. The additional current is thus confined to r as in 

 the previous case, L providing the necessary impulse. 



The principle that E cannot have any influence in the 

 induction experiment after the steady balance has been 

 obtained is of course of more general application ; in the 

 present instance it makes the writing down of the general 

 equations unnecessary, and the result follows immediately by 

 KirchhofFs laws as in the first case. 



XL VI. Notices respecting New Boohs. 



The Scientific Papers of Sir William Hugo ins. Edited by 

 Sir William and Ladv Huggiss. London : "William Wesley 

 & Son. Price .£1 lis. Ikl. net. 



r PllE book under review is the second volume of the Publications 

 -*- of Sir William Huggins's Observatory at Tulse Hill, and con- 

 tains a reprint of the published Papers on the work done in the 

 observatory since its foundation by Sir William Huggins in 1856. 

 It is complementary to the first volume, 'An Atlas of Representative 

 Stellar Spectra,' published in 1S99, which contains the later original 

 work of the observatory. 



The present volume is of extreme interest containing, as it does, 

 the record in contemporaneous documents by the pioneer himself 

 of the development of astronomical research in an entirely new 

 direction through the application of the Spectroscope to the 

 heavenly bodies other than the Sun, and supplying what is prac- 

 tically a history of the birth and development of the science of 

 Astrophysics. 



It is just fifty years since Kirchhoff's great discovery of the 

 true significance of the Fraunhofer lines in the Solar Spectrum, 

 and the deduction therefrom of the chemical constitution of the 



