19 Temperature of the Terrestrial Globe. 



The effect of solar heat upon air confined within transparent cov- 

 erings, has long since been observed. The object of the apparatus 

 we have just described, is to carry the acquired heat to its maximum; 

 and especially to compare the effect of the solar ray upon very high 

 mountains, with what is observed in plains below. This experiment 

 is chiefly worthy of remark on account of the just and extensive 

 inferences drawn from it by the inventor. It has been repeated sev- 

 eral times at Paris and Edinburgh, and with analogous results. 



The theory of the instrument is easily understood. It is sufficient 

 to remark, 1st, that the acquired heat is concentrated, because it is 

 not dissipated immediately by renewing the air ; 2d, that the heat of 

 the sun, has properties different from those of heat without light. 

 The rays of that body are transmitted in considerable quantity 

 through the glass plates into all the intervals, even to the bottom of 

 the vessel. They heat the air and the partitions which contain it. 

 Their heat thus communicated ceases to be luminous, and preserves 

 only the properties of non-luminous radiating heat. In this state 

 it cannot pass through the plates of glass covering the vessel. 



It is accumulated more and more in the interval which is sur- 

 rounded by substances of small conducting power, and the tempera- 

 ture rises till the heat flowing in, shall exactly equal that which is 

 dissipated. This explanation might be verified, and the results 

 made more apparent, by varying the conditions and employing col- 

 ored or blackened glasses, and exhausting the air from the intervals 

 which contain the thermometers. When this effect is examined by 

 the calculus, results are obtained in exact accordance with those of 

 observation. It is necessary to consider attentively this order of 

 facts, and the results of the calculus when we would ascertain the 

 influence of the atmosphere and waters upon the thermometrical 

 state of our globe. 



In short, if all the strata of air of which the atmosphere is formed, 

 preserved their density with their transparency, and lost only the 

 mobility which is peculiar to them, this mass of air, thus become 

 solid, on being exposed to the rays of the sun, would produce an 

 effect the same in kind with that we have just described. The heat, 

 coming in the state of light to the solid earth, would lose all at 

 once, and almost entirely, its power of passing through transparent 

 solids : it would accumulate in the lower strata of the atmosphere, 

 which would thus acquire very high temperatures. We should ob- 

 serve at the same time a diminution of the degree of acquired heat, 

 as we go from the surface of the earth. 



