APPENDIX. 349 



a little saturated solution of zinc sulphate (z. s) is 

 poured with a fine pipette into tube above the plug 

 of clay; into the zinc sulphate solution dips the 

 thoroughly amalgamated end of a thin rod of zinc- 



z.s 

 c&c 



Oscillating rod. 



This is a thin band of steel about 9 inches long and 

 in. wide ; at one end at right angles to the band 

 is fixed a pointer one to two inches long. The band 

 can be fixed at any part of its length by a wide 

 brass clamp ; connected with the clamp is a binding 

 screw. A cup containing mercury is placed under- 

 neath the pointer and the clamp is arranged on the 

 stand at such a height that when the band descends 

 in oscillation, the pointer dips a millimetre or so into 

 the mercury; it is well to cover the mercury with a 

 thin layer of alcohol. A piece of main-spring bent 

 at one end will serve the purpose of the steel band. 



Lever for the Frog's Heart. 



The lever used is like that given at (1) Fig. 1, but 



