3*4 Dr. Fordyce’s Account of 
black paint, fufficient to prevent the rays of the fun from 
penetrating either to the iron or pafteboard. 
On the 28th day of July, 1786, the fun {hilling on a room 
facing about S.W. the air not cloudy, but not very bright ; 
the air in the roomyi 0 ; at a quarter after twelve, thermo- 
meters being paiTed through the tubes below the plates of iron 
and pafteboard, after handing a quarter of an hour, fhewed 
the heat 67° in both apparatus’s. Both were nowexpofed to the 
fun, lo that the rays fell perpendicular on the paint covering 
the plates, in equal quantity on each as nearly as poffible. If 
there was any difference, rather more were thrown on the 
paheboard diaphragm. In five minutes the thermometer be- 
low the paheboard diaphragm fhewed 72 degrees; the ther- 
mometer under the iron had hardly rifen half a degree. 
Progrefs of the rifing of the thermometers . 
Under pafteboard diaphragm. 
Under iron diaphragm^ 
7 Z ° 
674 
75 
70 
80 
76 -f- 
s 5 
33 
90 
88-1- 
95 
94 
IOO 
IOO * 
io 5 
107 
no 
1 1 5 
After 20 minutes, 
1 10 
121 
* At this time thermometers were put through tubes into the chambers of the 
apparatus, between the glafles and diaphragms. The apparatus with the iron 
diaphragm railed this thermometer to 121 0 j that with, the pafteboard to 120 0 .. 
The 
