5oo 
Mr. Babbage on electrical 
supported by three legs, two of which only, C and D, are re- 
presented in the figure ; these, by screwng into it, served to 
adjust its height. A cylinder of thick millboard F G, 5 inches 
high, was glued together, and was fastened to the board A B. 
In two very small recesses in its upper part rested a narrow 
bridge of glass or of wood b b, for the purpose of supporting 
a needle. A circular ring of pasteboard c c 9 was fixed near 
the top, which supported an engraved circle divided into 
degrees. A square piece of millboard P P, having a circular 
opening rather less than the diameter of the cylinder, rested 
on the top of it. Upon this was placed another millboard 
cylinder Q Q, of rather larger diameter, and 2J inches high. 
Another cylinder was fitted to the outside of this, in order to 
admit of fixing screens of muslin and various substances to 
the under side of the upper cylinder. 
Through the aperture in the centre of the wooden plate 
A B, a steel axis working in a brass frame passed up into the 
cylinder. The frame was supported by being screwed to 
a block of wood at S. On the lower end of this axis a pulley 
H, was fixed, to which motion was given by connecting it 
with a common jack. On the upper end of this axis a thin 
brass chuck K 2 inches in diameter, was fixed, to which was 
attached a wooden disc Z, 5 inches in diameter. Three 
wooden screws a a a, rose from this plate, and supported a 
disc M, of any substance on which experiments were to be 
made. 
A needle made of pasteboard covered with sealing-wax, 
and having an agate cap in its centre, was supported on the 
point of a steel sewing needle fixed in a wooden bridge 
.05 inch square. A plate of glass revolved below. The 
