94 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



volume by C. Wolling, whose investigations of this subject 

 are, we believe, almost the only ones at present accessible, 

 and form a portion of his work "On the Influence of Cover- 

 ing, etc., etc., on the Fertility of the Soil," Berlin, 18V 7. The 

 temperature observations were taken at 8 A.M. and 5 P.M., 

 at G .A.M., and 2 and 10 P.M., for three years at depths of 

 one tenth of a meter, or about 4 inches. Wolling finds that 

 during the warm season the ground that is shaded by plants 

 or otherwise is colder than the fully exposed : the daily vari- 

 ations are considerably less. In cold weather the snow-cov- 

 ered earth is considerably warmer than the naked earth : its 

 temperature changes are less decided. The earth freed from 

 all stones larger than peas is in summer slightly cooler than 

 that on which large stones are allowed to remain, but in win- 

 ter is slightly warmer. The temperature changes are greater 

 in the latter kind of earth, since at the time of the daily max- 

 imum the temperatures are higher, and at the time of mini- 

 mum are lower. 



Messrs. Ayrton and Perry communicate to the Philosoph- 

 ical Magazine the results of an elaborate determination of 

 the heat conductivity of stone. The methods of experiment 

 occurred to them during the lectures of Sir William Thomson 

 in Glasgow, in 18 74, and admit of highly accurate results. 

 The results bear directly on the accuracy of Fourier's equa- 

 tion for the flow of heat in solids of poor conductivity. The 

 authors acknowledge their indebtedness to the Japanese stu- 

 dents of the Tokio College of Eno-ineerino- for assistance in 

 their work. 



The distribution of heat in a homogeneous spherical shell, 

 whose surfaces have a temperature varying with the time, 

 has been studied as a mathematical problem in an inaugural 

 dissertation by Dr. P. Langer, of Jena. He elucidates many 

 details in a problem whose general solution has been already 

 treated of by Fourier, Poisson, and Riemann, and a modifica- 

 tion of it by Neumann. 



The temperature of the earth at St. Petersburg and Xukuss 

 has been discussed in a memoir by Wild. The observations 

 were made with an apparatus similar to that of Lamont. The 

 observations at Xukuss were made by Dohrandt, with a sim- 

 ilar apparatus, thrice daily for two years; and the tempera- 

 tures close to the surface were also observed every two hours, 



