1888.] NATURAL SCIENCES OF PHILADELPHIA. 109 



-muscle as a fractional portion of E, the latter being the electro-motive 

 force of a Daniell element. To accomplish this let the circuit M 

 G P" IV III F' K M and the circuit D K I, III, IV II F F D, 

 be opened and the circuit D S IV II B P' D offering a resistance 

 W be closed, D being put in communication with IV by the 

 switcher S, B being a coil of Avire offering the same resistance as 

 F and brought sufficiently near the galvanometer G to slightly af- 

 fect it, the intensity of the current will then be equal to the ratio of 



E . 

 E to W or I = ^r^^ or if we call J the number of the divisions of the 



E 



scale corresponding to the deflection of the magnet, then J =^^ 



Let now D be put in communication by means of the switcher S, with 

 I, the beginning of the wire of the compensatoi', that is the Cur- 

 rent D K S I III IV II B P' D be closed and offering a resistance 

 W+L, L being the resistance offered by the wire I II of the compen- 

 sator, the intensity of the current will then be equal to the ratio of 



E 

 E to W+L, that is I == „ or if we call J^ the number of divis- 



E 



ions corresponding to the deffection of the magnet, then J^= 



W+L 

 or -jY= yr = T Y whence W^ — W+L or 



W+L 



W 1 J^ 



If now this value of _ be substituted in equation (2) we will obtain 



L 



X=^X^XE(3) 



in which equation 



X = the electro motive force of muscle. 



n = the number of divisions of the graduated scale of the wire 

 of the compensator necessary for compensation. 



N == 1000 ; the number of divisions of the wire of the compen- 

 sator. 



J = Number of divisions of scale corresponding to deflection 

 of magnet excluding the wire of the compensator. 



