20 M. MELLONI ON THE FREE TRANSMISSION 
A 
the rays that are stopped. By performing these operations, and repre- 
senting the whole radiation by 1000, we obtain 
TABLE A. 
Order of the Transmitted 
screens. rays. a mays stopped: 
i 619 _ 381 
oD 576 4.24 
3. 558 442 
4. 549 451 
Let us imagine the thickest of the screens split into four equal layers ; _ 
the quantities of heat falling upon each will be 
1000, 619, 576, 558, 
and the quantities lost in successively traversing the four intervals 
381, 424—381, 442—424, 451—442; 
that is to say, 
381, 43, 18, 9. 
_ We shall then have for the ratios of the respective losses to the incident 
quantities, 
381 43 18 9 
1000. 619 - 576 558° 
or 
0°381, 0°071, 0°031, 0016. 
Thus the losses continue to decrease with great rapidity as the thickness 
increases by a constant quantity. 
We have seen that the action of the radiation on the thermomulti- 
plier commences at the instant when the communications are established, 
produces the greatest part of its effect in the first five or six seconds, 
and ceases entirely after a minute and a half. These facts, which are 
equally true of the direct rays and of those which reach the pile after 
having passed through screens of any thickness whatsoever, constitute 
the best proof that caloric is transmitted by radiation through the inte- 
rior of the diaphanous bodies. . If, nevertheless, a new confirmation of 
this truth were desired, it would be found in the successive diminution 
of the losses which the rays undergo in crossing the different layers of 
a transparent medium. Were the heat, which is the subject of our im- 
mediate inquiries, the effect of a species of conducting power, the losses 
would continually increase from layer to layer, or would remain con- 
stant, from the moment when the rays penetrated the medium, and 
could never follow the opposite law of decrease. 
The progressive diminution of the losses is, moreover, entirely pecu- 
liar to the calorific radiation, whose properties in this and in many other 
respects are altogether different from those of the luminous rays. In 
