OF RADIANT HEAT THROUGH DIFFERENT BODIES. 23 
oil of colza*, and after having waited until the needle recovered its ori- 
ginal position we reestablished the calorific communication. 
The deviations obtained through the different thicknesses of the li- 
quid are exhibited in the following table. 
Degrees of thickness of Deviations of the galva- 
the liquid layer. nometer. 
mm oO 
6°767 15°642 
13°535 12°83] 
27-069 10°389 
54°139 9°540 
81-209 8-988 
108°279 8°512 
The free radiation being always represented by 1000, the respective 
quantities of the rays transmitted and those stopped are found to be : 
TABLE B. 
en a Rays transmitted. Rays stopped. 
mm 
6°767- 443 5ST 
13°535 363 637 
27-069 294 "06 
54°139 270 730 
108-279 244: 756 
If we suppose the last layer (of 108™"-274:) subdivided into six paral- 
lel slices of the following degrees of thickness : 6™*767, 6°767, 13°535, 
27-069, 27:069, and 27-069, we shall be able to determine, by means 
of the numbers contained in the two last columns, the quantity of heat 
incident to the first surface of each of these slices and the quantity lost 
in the passage. Dividing the second by the first we shall ascertain the 
loss. It is unnecessary to exhibit the operations in detail, as they are in 
all respects similar to those which have been performed in reference to 
the screens of glass. Here are the final results: 
Degrees of thickness of the six Losses in the respective transmissions 
successive slices into which referred to the quantities of 
we suppose the layer of rays which arrive at the 
108™™:274 to be divided. surface of each slice. 
mm 
6°767 0°557 
6°767 0°180 
1S°535 0°190 
27-069 0:082 
27:069 0°056 
27:069 0:040 
[* It may be proper to inform the English reader that “oil of colza”’ is an oil 
expressed from the seeds of the Chou Colza of the French, Brassica arvensis, Linn. 
It must not be confounded with the rape oil of England, obtained from the Rape, 
Brassica Napus.—Ev1t. | 
