produced by various kinds of electric discharge 427 



than a third of a maximum contraction. The discharges were made alternately 

 every 15 seconds, and when the resistances were 35,000 and 140,000 respectively, 

 the alternate contractions as recorded on the myograph were as follows: 



Small condenser Large condenser 



144 146 



147 148 



147 147 



146 146 



147 145 



Here the time-modulus was 1-05 x io~ B seconds for the small condenser 

 and 1-4 x io~ 2 for the large one, and the values of C were as I to 100, so that 

 p = -640. 



If we suppose that Cavendish took the shocks through pieces of metal held 

 in his hands, the resistance of the circuit would depend on the state of his skin. 

 He occasionally used a piece of apparatus, which he nowhere describes, but 

 which he names in three places* a shock-melter. 



From Art. 585 it would appear that it was filled with salt water, even when 

 fresh water was the subject of the experiment, and from Art. 637 Cavendish 

 seems to have considered it his last resource as a method of receiving shocks. 

 I therefore think that it must have been an apparatus by which his hands were 

 well wetted with salt water, so that the resistance of his body would be between 

 1000 and 2000 Ohms. 



The capacity of his battery of 49 jars was 321,000 glob, inc., which comes 

 to rather less than half a microfarad. 



The discharges of this through 2000 Ohms would have a time-modulus of 

 about one-thousandth of a second. 



The following table gives the different results obtained by Cavendish and 

 by myself, with the time-modulus of the discharges compared. The quantity p 

 is such that the ratio of the initial strength of the two discharges is inversely 

 as the p power of the ratio of the time-moduli when the shocks are equal in 

 intensity, or Q _ ^ 



'c, W <? 2 W w 2 W 



The number of jars among which a quantity of electricity must be divided 

 in order to give a shock of a given intensity through a given resistance, varies 



as the power of the quantity of electricity. 



Cavendish's experiments. 



TI T 2 P 



Art. 573 0-0000065 0-000026 0-5 + 



... 610 0-0000065 o-ooi 0-652 



... do. 0-00014 o-ooi 0-767 



... 613 0-00014 0-00042 0-697 



* Arts. 585, 622, 637. See facsimile at p. 317. 



