C 89 ] 
equal length, interfering each other at right angles 
in the middle; hung it, horizontally, on a central 
pin, and fet a light horfe, with his rider, upon each 
extremity ; whereupon, the whole being nicely bal- 
anced, and each courfer urged on by an ele&rifed 
point, inftead of a pair of fpurs, I was entertained 
with an electrical horfe-race. 
I have contrived an eleCtrical air thermometer, and 
made feveral experiments with it, that have afforded 
me much fatisfaCtion and pleafure. • It is extremely 
fenfible of any alteration in the date of the included 
air, and fully determines that controverted point, 
whether there be any heat in the eledtric fire. By the 
Plate [Tab. IV.] and the following defcription, you 
will readily apprehend the conftrudtion of it. 
A. B. is a glafs tube about eleven inches long, and 
one inch diameter in the bore. It has a brafs feril ce- 
mented on each end, with a top and bottom part, C 
and D to be ferewed on, air-tight, and taken off 
at pleafure. In the center of the bottom part D, is 
a male ferew, which goes into a brafs nut in the ma- 
hogany pedeftal E. The wires F and G are for the 
eleCtric fire to pafs through, darting from one to the 
other. The wire G extends through the pedeflal to 
H ; and may be raifed or lowered by means of a male 
ferew on it. The wire F may be taken out, and the 
hook I be ferewed into the place of it. K is a glafs 
tube with a fmall bore, open at both ends, cemented 
in the brafs tube L, which ferews into the top part 
C. The lower end of the tube K is immerfed in wa- 
ter, coloured with cocheneal, at the bottom of the 
tube A B. (I ufed at firft coloured fpirits of wine ; 
but, in one of the experiments I made, it took fire.) 
Vol. LIII. O Oa 
