C 75 ] 
As the improved inttrument is like that already 
defcribed, except in the dial- plate, and part of the 
wheel work, I have made a drawing of the parts, 
only, wherein they differ. 
The fmaller index A. (Tab. IV.) fig. i. which 
moves in the circle b } b> b , b. about 4 inches diameter, 
is fixed on the axis of a double pulley B. fig. 2. 
nearly 1 inch diameter, which makes one revolution 
by a rife, or fall of 3 inches of the mercury in the 
tube. 
The pivots of the axis of the pulley B, are placed, 
each within 3 fridtion wheels, e , e , e 3 fig. 2. 2 inches 
diameter. 
The larger index E. fig. 1. which moves in the 
circle g,g,g,g, — 10 inches diameter is placed on 
the axis of the double pulley H, about 4. inch di- 
ameter, to make 3 revolutions exadtly, for 1 revo- 
lution of the pulley B. Each of the pivots of the 
axis of this pulley is placed on 2 fridtion wheels 
», fig- 2. 
The circle b , b 3 b , b 3 fig. 1. is divided into 3 equal 
parts ; one for each inch the mercury rifes or falls 
in the tube, and is marked 28, to 31 inches, with 
rain, changeable, fair, &c. infcribed, as other ba- 
rometers generally are. Each of thefe parts is fub- 
divided into 10. 
The larger circle g,gtg,g, is divided into 300 
equal parts, and marked 10, 20, &c. 
The ivory cone, d, which retts on the mercury in 
the tube, is fufpended by a filk thread k, fig. 2, which 
furrounds the outward pulley, B, and paffes alfo 4, or 
5 times round the outward pulley H, to which the 
end is fattened. 
L 2 
The 
