HISTORY, &c., OF INDUCTION INSTRUMENTS. 



291 



adding algebraically the ordinates of tlie superior curve to those 

 of the second, reduced to a certain ratio. The final result would 

 be to destroy the symmetry, and to displace the minima, as if 

 there were some impediment. 



C. — Apparatus of Saxton. — " We shall readily perceive that it 

 was not desirable, and that it was perhaps even objectionable, to 

 have so massive an electro-magnet as that of Pixii ; while, at 

 the same time, it was desirable to increase, as much as possible, the 

 power of the permanent magnet. It therefore became more con- 

 venient to fix the latter, and to render the former movable. This 

 was done by Saxton, who made Pixii's instrument approach 

 nearer to portability by 

 placing a fixed magnet hori- 

 zontally (see fig. 72), and 

 by causing the electro- 

 magnet, or induced reel, to 

 turn upon an axis parallel 

 to the plane of the magnet. 



" It is therefore still the 

 principle of Pixii that we 

 find in this instrument ; 

 which, although present- 

 inof an arrano-emeut less 

 desirable, in a theoretical point of view, has none the less prepared 

 the way for the employment of magneto-electric instruments in 

 medicine." ' 



In this instrument,- the handle causes the rotation upon its axis 

 of the armature of soft iron which carries the reels. 



D. — ClarTie^s apparatus. — There was yet a means of rendering 

 the instrument still less cumbrous, without occasioning any notable 

 diminution in its power : this was, to 

 render the magnet A vertical, and 

 to cause the electro-magnet to move 

 round a horizontal axis X X' (fig. 73) 

 in such a manner that the extremities 

 of the electro-magnet revolved in a 

 plane parallel to the branches of the 

 permanent magnet. 



" Such an arrangement was realized 

 by Clarke, and is shown in figure 74. 

 A represents the permanent magnet ; 

 and H is the axis on which the electro- *'«• f^.-cu.rke's inttn:mf ut 



72. — Saxton's instrument. 



* Le Eoux. I). T6. 



