168 REPORT—1862. 
the air is upward or downward. A spring within the pencil-carrier con- 
stantly presses the pencil against a sheet of paper placed in front of it. This 
paper is for the present carried on a flat board, which is moved by a clock. 
The registering sheets are ruled with vertical hour lines and with horizontal 
lines which assist in estimating the angle of inclination to the horizon made 
by the disk during the action of an upward or downward impulse from the 
air. This follows because the tail and the wheel, d, revolve on the same 
centre, and each tooth in d describes an are similar to that described by the 
axis of the tail. An equal number of teeth in ¢ are raised or lowered, and 
thus the rack and the shaft, c, move through spaces proportional to ares de- 
‘scribed by the teeth of the wheel, d, and the axis of the tail, B. The board 
