402 JAMES CLERK MAXWELL. [CHAP. XII. 



3 '2 Sal Sylvii (potassium chloride). 

 2*3 Sal Amm. (ammonium chloride). 

 14-10 Calc. S.S.A. (?) 



2-21 Calcined Glauber's Salt (sodium sulphate). 

 3 '17 Quadrangular Nitre (sodium nitrate). 

 5-19 SaltD. (?) 

 The solutions were 3, 10, 12. 



I am going to try if this is Troy or Apothecaries' weight. 

 Saturated solution (1 in 3 '7 8) of common salt has 

 437,000 the resistance of iron wire. New distilled water 

 has more resistance than distilled water kept a year. 



All these results and many more were got by comparison 

 of the strength of shocks taken through Cavendish's body. 

 I think this series of experiments is the most wonderful of 

 them all, and well worth verification. 



Cavendish is the first verifier of Ohm's Law, for he 

 finds by successive series of experiments that the resistance 

 is as the following power of the velocity, 1'08, 1*03, '980, 

 and concludes that it is as the first power. All this by the 

 physiological galvanometer. 



. . . Can you solve the equation 



_ 



dx\dy 2 dxdy dy dx 2 dxdy 



A . 



= is a solution. Find the general ditto. 

 ay 



To PKOFESSOK, LEWIS CAMPBELL. 



11 Scroope Terrace, 

 Cambridge, 5th January 1878. 



46. It is more than a month that I have had your letter 

 lying by me. I am glad you like Chrystal. His departure 

 is a great loss to the laboratory, as it is difficult to find any 

 one to take up heavy work. W. D. Mven (brother of the 

 competitor) is going in for a heavy piece of work on 

 conduction of heat in gases. I am no judge of Greek plays, 



