ELECTRICAL APPARATUS. 203 



axis at the centre of the graduated plate, to the ferule at the 

 end of the stem ; and to its extremity is fixed a delicate 

 pith ball. This index rises as the charge increases, and the 

 strength is determined by the degree indicated on the gradu- 

 ated circle. Price, in box wood, $1.25. 

 " in ivory, $1.75 and $2.00. 



Fig. 282. Fig. 283. 



Bennett's Gold Leaf Electrometer. (Fig. 282, as above.) 

 Consists of a brass' foot, which supports a glass tube about 

 two and a half inches wide and five long. This has two 

 slips of tin foil pasted on the opposite sides, as represented. 

 The cylinder is closed at top by a brass cap, which fits 

 tight round the sides, but takes off and on, in order that 

 if the two slips of gold leaf which hang from the middle of 

 the cap in the inside should become broken, they may be 

 repaired. The cap should not in any other case be removed. 

 The gold leaves are about three inches long, and a quarter 

 of an inch wide ; they are best fastened on by a little piece 

 of flatted brass, soldered to the inner side of the cap, and 

 the leaves attached by gum water, gold size, paste, or any- 

 thing similar. They should hang so as to touch each other 

 when not in an electrified state, and when divergent, as 

 shown in the cut, they should approach to the slips of tin 

 foil on the glass. The cap has occasionally a point which 

 screws upon it, as shown ; this, however, is never used, except 

 in trying experiments upon the electricity of the atmosphere. 



Price, $2.50. 



Saussure's Gold Leaf Electroscope, which is represented in 

 Fig. 283, as above, differs from the former in the manner 



