Page:Scientific Memoirs, Vol. 1 (1837).djvu/32

20 the rays that are stopped. By performing these operations, and representing the whole radiation by 1000, we obtain

Let us imagine the thickest of the screens split into four equal layers; the quantities of heat falling upon each will beand the quantities lost in successively traversing the four intervalsthat is to say,

We shall then have for the ratios of the respective losses to the incident quantities,or

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 thermomultiplier 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 interior 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 immediate inquiries, the effect of a species of conducting power, the losses would continually increase from layer to layer, or would remain constant, 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 peculiar to the calorific radiation, whose properties in this and in many other respects are altogether different from those of the luminous rays. In