Mr W. S. HARRIS on a New Electrometer. 207 



the tube is bent a little forward, and then perpendicularly, and 

 is finally secured to a correctly divided scale be, sustained on a 

 convenient base, as seen in the figure. The point o on the scale, 

 corresponding to the level of the coloured fluid in the opposite 

 reservoir a, is marked zero. 



A metallic wire mn, Fig. 2, varying from the T^th to the 

 |th of an inch in diameter, according to the circumstances of the 

 experiment, is passed air-tight across the glass ball B by means 

 of small flanges of brass mn, cemented in and round two holes 

 drilled through the sides, and upon these are screwed two brass 

 balls rn in such way as to render the whole air-tight. The me- 

 thod of fixing the wire is extremely simple, the brass parts being 

 made quite clean internally ; the wire is passed directly through 

 them ; it is put gently on the stretch, and is then compressed in 

 the holes by small pegs of tough wood, so as to insure a good 

 contact : the pegs, and extremities of the wire, are allowed to 

 project a little, for the convenience of removal, and thus different 

 wires may be substituted with great expedition. The ball B, 

 being thus prepared, is screwed air-tight on the spherical reser- 

 voir a, Fig. 1, by the ordinary intervention of brass caps, which 

 should be closely cemented with good sealing-wax to the glass ; 

 hence, when the wire mn becomes heated by the voltaic action, 

 the fluid will be observed to ascend along the scale be. 



The contact with the battery, as in Figs. 1, 2, 3, &c., is made 

 by means of the small brass cups tt, Fig. 2, screwed in the balls 

 rn, in which is placed a little mercury ; and, to adjust the fluid 

 to zero of the scale, there is a small opening drilled through the 

 upper part of the bulb at q, Fig. 2, which, being covered also 

 with a ball and flange, admits of a communication being easily 

 made with the external air at pleasure *. 



* The fluid for marking the degrees of action may consist of rectified spirit one 

 part, distilled water three parts, coloured with tincture of cochineal ; to which may 



