Errata, &c. 



P. 145, line 17 from the bottom: the following reference ought to have 

 been inserted in this place : " An abstract of Prof. Faraday's Seventeenth 

 Series of Researches in Electricity appeared in vol. xvi. p. 336." 



P. 370, line 12 ; p. 372 line 15 ; and p. 374, line 8 from the bottom, 

 for H. G. AiiMSTKONG, readW. G. Armstrong. 



