B. TEREESTRIAL PHYSICS AND METEOROLOGY. '77 



pare the quantity of water evaporated by the cultivated soil 

 with that which has been furnished to it by the rain. This 

 excess could, in fact, only be accounted for in great part 

 by the dew which covers the plants every clear night. 6 J?, 

 LXXX., 1357. 



ON THE TEMPERATURE OF THE SOIL. 



The Messrs. Becquerel have recently made a report to the 

 Paris Academy of Sciences on the results of observations 

 made in 1874 by means of a thermo-electric apparatus on the 

 temperature of the soil at various depths, from forty meters 

 up to the surface. The observations have been made many 

 times a day, but only those made at six and nine A.M., and 

 three P.M., come now into consideration. From a depth of 

 one hundred and ten feet up to a depth of eighty-five feet 

 the temperature was sensibly constant throughout the year. 

 Even at fifty feet the variations were barely perceptible, al- 

 though at this depth the effect of the penetration of surface 

 water into the soil is ordinarily quite sensible. The effect 

 of a covering of grass, as compared with that of a barren 

 soil, becomes quite perceptible at the depth of twenty inches, 

 where it is found that the covered soil experiences much less 

 violent changes of temperature than a sandy or barren soil ; 

 so that even from six o'clock in the mornino- to three o'clock 

 in the afternoon the protected soil is warmer than the bar- 

 ren soil. 



In the interest of terrestrial physics, it is to be hoped that 

 we shall be able to establish at still greater depths a similar 

 Becquerel apparatus, in order to discover at what point the 

 temperature of the solid earth experiences, or ceases to ex- 

 perience, any changes in a long interval of time, whether in 

 consequence of slow cooling, of earthquakes, or of internal 

 changes. 6 J?, LXXX., 773. 



INFLUENCE OF FORESTS ON WATER-FLOW AND ATMOSPHERIC 



MOISTURE. 



In order to contribute something to tlie controversy with 

 regard to the influence of forests upon atmospheric moisture, 

 Fautrat states that he has conducted certain observations in 

 the royal forests of Ilallette. He first measured the quan- 

 tity of rain both above and below the foliage of the trees, 



