vi WORK AT MANCHESTER 141 



third edition I was assisted by my friend Professor 

 Schuster in describing the newest developments of 

 this fascinating branch of science. 



I have always tried to make the illustrations in my 

 books worthy of the subject. This was especially the 

 case with the Spectrum Analysis and with the Treat- 

 ise. In the latter I not only endeavoured to obtain 

 the best drawings of the most modern plant used in 

 chemical industries, but I also took photographs of the 

 actual apparatus used in my own lectures. These were 

 admirably engraved by Messrs. Vieweg and appeared 

 both in the English and in the German editions. 

 With regard to the book on Spectrum Analysis I 

 received the following letter from Sir John Herschel : 



COLLINGWOOD, May 2%th, 1869. 

 MY DEAR SIR, 



Accept my very best thanks for your exceedingly beautiful 

 book, and not less interesting than it is beautiful. There was 

 wanted just such a work to embody the vast mass of new 

 experiment discovery and speculation which " Spectrum 

 Analysis" is grown into and the whole scientific world is 

 under a real obligation to you for its production. I have 

 only dipped here and there into it, but enough to perceive 

 that it is a real treasury of information. (Among things 

 perfectly new to me those curious properties of Erbium and 

 Didymium on p. 176 are peculiarly striking.) The list of 

 Memoirs, &c., at the end is also most valuable, and it is really 

 astonishing to see so assembled such a mass of laborious 

 research on a subject so very new. 



Once more expressing my thanks for this kindness, believe 



me, 



My dear Sir, 



Yours very faithfully, 



J. F. W. HERSCHEL. 



In the year 1865 I was asked to visit the copper 

 mines at Mottram, near Alderley Edge, in Cheshire. 

 Copper occurs there together with a large number of 



