258 LOCALIZED ELECTRIZATION. 



not commence at zero. The feeble current which remains is 

 insignificant, when applied to the muscles of the trunk or of the 

 limbs. But it is no longer so when used for delicate operations, as 

 for faradization of the facial muscles, or of the membrana tympani, 

 and for these I use the water moderator already described. After 

 having diminished the intensity of the current, it becomes possible, 

 by making this weakened current pass through a stratum of uater 

 more or less thick, to divide it still further into infinitely feeble 

 doses. The combination of graduator and moderator has even 

 enabled me to measure the degree of excitability of each of the 

 muscles of the frog. 



E. — Magnetic Rheometer. 



The graduator tube divides into exact doses the current given 

 by either the primary or the secondary coil ; but it does not 

 measure the force of the initial current, — a force that is liable to 

 variation from numerous causes, and that therefore produces in- 

 evitable differences in the force of the induction. To endeavour 

 to apportion the electricity by the aid of the graduator alone, 

 seems to be as absurd as to weigh medicines in an accurate balance, 

 but with false weights. 



I employ a very simple means by which to measure the power 

 of the initial current, and the procedure also indicates the degree 

 of magnetization of tlie soft iron of the core. The action of that 

 magnetization upon a magnetic needle forms the basis of my 

 rheometer. The soft iron is differently magnetised at its extremi- 

 ties, according to the direction of the current. Let us suppose 

 tliat the extremity nearest the rheometer becomes the north pole. 

 The needle, placed as already described, will be made to deviate 

 from the magnetic meridian by the attraction between its south 

 pole and the magnetised core, and as the magnetization of the 

 core is directly as the intensity of the initial current, the degree of 

 deviation of the needle furnishes an index of both. 



I employ the rheometer to measure the force of the initial 

 current, and to keep it nearly at the same degree. The causes 

 which may weaken a pile are so various that no form of pile can 

 be called really and absolutely constant. The rheometer, there- 

 fore, not only measures the initial force, but renders it possible 

 always td' operate under the same conditions. The combined 

 action of the rheometer and the graduator enables us to administer 

 electric excitation in precise doses. It seems sufficient to enunciate 

 this proposition, and unnecessary to enter at large into considera- 

 tions which show that, although the graduator alone measures 

 nothing, yet its combination with the rheometer affords all the 



