488 Intelligence and Miscellaneous Articles. 



being very prevalent in quantity in the rhombohedral bibasic salt, its 

 chemical analogy with ammonia may be supposed to have been su- 

 perseded by the comparatively small proportion of soda combined 

 with it. In the absence of isomorphism in the strictest sense, there are 

 circumstances coming so near to it that the molecules of both sub- 

 stances still attract each other. sufficiently to effect regular superpo- 

 sition. The curved and disfigured planes of such crystals are at all 

 events indicative of their origin under abnormal and, as it were, com- 

 pulsory circumstances. — Proceedings of the Vienna Imperial Institute, 

 April 16, 1861. 



COMPARISON OF THE TEMPERATURE IN THE AIR AND OF THE 

 SOIL AT A DEPTH OF TWO METRES. BY M. POURIAU. 



From observations made during five consecutive years on the tem- 

 perature of the soil at a depth of 2 metres compared with that of the 

 air, it follows — 



1. That the mean temperature in the air was 10 o, 21, and in the 

 soil 12°'79. Difference in favour of the soil 2*58. 



2. That the mean temperature of the soil in winter and autumn is 

 higher than that of the air ; that in summer it is about 2 degrees 

 lower, and that in spring the mean temperatures are virtually equal . 



3. That the mean of the extreme maximum temperatures in the 

 air was 34°*5, in the soil it was 19 0, 75. On the other hand, the 

 mean of the extreme minima in air was — 12°T4; in the soil this 

 mean never sank below + 6°. 



4. While in air the mean of the total differences between the 

 extreme maxima and extreme minima reached 46°*64, in the soil 

 this mean was only 13°*74. 



5. In 1860 the temperature of the air sank to —20°, in the soil 

 the minimum was never less than +5 0, 47. 



6. While in the air the maximum temperature usually occurs in 

 July or August, and the minimum in December or January, the 

 maximum temperature in the soil always corresponds to the end of 

 August ; the minimum always occurs at the end of February, or on 

 the first days of March. 



7. The changes of temperature in the soil at a depth of 2 metres 

 may be thus stated : — 



While the mean temperature of the air usually begins to sink 

 towards the end of July, in the soil the heat continues to accumulate 

 in the superior layers under the influence of the intense solar radia- 

 tion, and to extend to the lower layers, until the end of August. 

 From this point the upper layers begin to lose more heat by radia- 

 tion than they receive ; the flow of heat changes its direction, it 

 passes from the lower to the upper layers and becomes lost in the 

 air ; and this ascending motion, continuing until February, is more 

 rapid as the external temperature is lower, that is, as the winter is 

 longer and more severe. Towards the middle of February or the 

 beginning of March the upper layers begin to become heated under 

 the influence of the solar rays, whose direction has become less 

 oblique ; the inferior layers give less and less heat to the upper 

 ones ; they begin, on the contrary, to receive some, and become 

 then reheated, which continues until the end of August. — Comptes 

 Rendu*, October 7, 1861. 



