I 70 DOVE ON THE ELECTRICITY OF INDUCTIOX. 



and III, when the Inserted wire is straight, is naturally only 

 then the case, when the intensity of the magnet is not very 

 great. If however the magnet used in the machine is a very 

 powerful one, then the influence of the human body as a se- 

 condary connexion upon the principal current is no longer un- 

 important. Very sensible shocks are perceived when a power- 

 ful magnet is used even with continuous sliding springs without 

 an inserted spiral. This however was not the case with the ma- 

 chine here described, for however powerful the shocks were with 

 an intermittent spring (quite unbearable when the rotation was 

 rapid), yet none were perceptible with one that slid uninterrupt- 

 edly. The influence of the body as long as it forms a secondary 

 connexion (0° to 90° and 180° to 270°) may therefore be here 

 disregarded. This facilitates very much the examination of the 

 complicated phtenomena in this department, for it follows di- 

 rectly from the absence of physiological action, when a straight 

 wire is inserted and connexion made between II and III, that 

 the powerful action obtained with the spii-ally coiled wire is solely 

 to be ascribed to the final extra current E. For other rheosco- 

 pical tests however, when connexion is made between II and 

 III, the current |; takes a greater or lesser part in the results 

 which are obtained. 



1. Physiological action. 

 72. Without insertion of the spiral more powerful shocks are 

 obtained, as well with one and twofold interruption (90° or 90° 

 and 270°), when the hand of the pachytrope is arranged for phy- 

 siological than when it is arranged for physical effects. The 

 whole of the following phtenomena, on the contrary, are much 

 more clearly perceived when the hand is arranged for physical 

 effects, in which case the primary current possesses the property 

 of magnetizing soft iron more powerfully*. If I and III (^ — A) 



* If the magnet of the Saxton's niiichine is removed, and instead of the 

 extra spiral between S and S a galvanic battery is inserted, we obtain from the 

 handles I and H and 1 and III, when the keeper is rotated, the incipient cur- 

 rent of the galvanic battery, for the keeper is by this arrangement converted 

 into a connecting electro-magnet to the galvanic battery, the magnetism of 

 which becomes evanescent as soon as the intermittent spring comes into contact 

 with the inserted piece of wood, and thus induces the extra current in the coils 

 i*f wire. This ind.iced current passes through the battery and the body when 

 connexion is made between I and If, and only through the body when I and 

 III are connected. The connexion II and III produces no shock, fur the 

 eleutro-magnet is then excluded, and the battery alone remains in the circuit. 

 This shock was more powerful with a keeper used in the machine when the 

 hand is arranged for physical than when it is arranged for physiological effects. 



I 



