160 DOVE ON THE ELECTRICITY OF INDUCTION. 



electro-dynamic and magneto-electric induction are combined, 

 then currents of higher orders can be examined as if this com- 

 bination had not been etfected. For machine-electricity the 

 following arrangement was made : — The battery was discharged 

 by the inner spiral a ^ of the differential inductor (fig. 3). 

 The spiral enclosing this, a /3, was connected with the second 

 inner spiral c d, and the spiral surroundingthis, 7 8, was connected 

 with the flat spiral A^ described before (66), whilst on the spiral 

 Bp parallel with this last, the shocks were tested, when solid 

 iron rods or bundles of wires were inserted in a 6 and c d. We 

 thus obtain — 



in a b the primary current, 

 in «;S and c d the current of the second order, 

 in 7 S and A, the current of the third order, 

 in By the current of the fourth order. 

 The currents of the fifth order, produced by smaller flat spirals 

 Cy Dy, could not be proved to exist physiologically. This how- 

 ever succeeded easily with Saxton's machine, or when the primary 

 current was that of a galvanic battery ; for although the inner 

 spirals for higher orders had often only two lengths of wire, one 

 over the other, yet they nevertheless acted powerfully upon fresh 

 preparations of the frog, and were distinctly perceptible with the 

 moistened hands. As each higher order requires two new spirals, 

 itwas often necessaryin these experiments to employ spirals which 

 had originally been intended for other purposes, and were often 

 coiled in an unfavourable manner for the object here in view, the 

 distance between the inner and outer spiral being often very con- 

 siderable. The augmenting action of inserted bundles of ironwii'es 

 was here exerted with the greatest energy, for by their means cur- 

 rents became very perceptible, when in the case of electi'o-dyna- 

 mic induction no trace of any action was discernible. The weak- 

 ening influence of enclosing tubes or closed surrounding spirals 

 is therefore here exceedingly prominent. The needle of the gal- 

 vanometer oscillated at last with the higher orders of galvanic 

 induction and with the Saxton's machine, as if driven by the 

 shortest possible impulse, and was not affected at all by the cur- 

 rents of the fifth order, which exerted distinct physiological ac- 

 tion. Probably these induced currents of the higher orders 

 approach more and more to the momentary discharges of fric- 

 tional electricity. Success however did not attend the endea- 

 vours to prove this empirically, i. e. to obtain a decrease of the 



