i88i.] 
The Radiograph and its Uses . 
221 
tilts, lifting the pencil up from the paper on the dial, which 
then continues to revolve without receiving a mark. In the 
example shown in our figure the sun began to shine a little 
after 6 a.m., and continued with short intervals till 4.15 p.m. 
An occultation, even of the length of a minute, was dis- 
tinctly recorded. 
The inventor of this most ingenious contrivance perceived, 
however, at once, that it was open to the same objection 
which we have already pointed out, giving duration of 
solar action, but not of intensity. He therefore went to 
Fig. 2. — Facsimile of a Record of the Duration of the Sunshine made 
by the Apparatus Winstanley. 
work again, and devised an apparatus to record both the 
quantities in a manner which leaves nothing to be wished 
for. 
This instrument, which Mr. Winstanley names the 
“ Radiograph,” is shown in the subjoined figure. It con- 
sists of a curved tube fixed along the greater part of the 
circumference of a brass wheel, and carrying at its ends the 
balls b and A, the former of which is blackened. The wheel 
turns at its centre on knife-edges of hardened steel resting 
on agate planes. The lower half of the tube is filled with 
mercury, and the bulbs are sealed so that the inclosed air 
cannot escape. The wheel carries a fine steel needle whiclt 
