Scientific Intelligence — Geology. 193 



GEOLOGY. 



6. Movement of Heat in Terrestrial Strata of different Geological 

 Natures. By M. Dove. — In a work published in the Memoirs of 

 the Academy of Berlin for 1844, on the relation of the chano-es of 

 the temperature of the atmosphere and the development of plants, the 

 author has endeavoured to determine to what changes of temperature 

 a plant was subjected at different periods of the year. These inves- 

 tigations naturally divided themselves into two parts ; — to what 

 changes of temperature are the diffei'ent parts of plants subjected 

 whicli grow freely in the open air ; and what temperatures act upon 

 the ivots which penetrate deeply into the earth. The first point 

 could be determined pretty correctly, by a series of observations, car- 

 ried on for a great number of years in the Botanic Garden of Chis- 

 wick, for the jjurpose of comparing the calorific phenomena presented 

 by plants in the shade, with the temperatures indicated by plants 

 exposed on all sides, in a place open to the whole influence of the 

 sun, and of nocturnal radiation. With regard to the second part, 

 the decennial series of observations on the heat of the ground at 

 Brussels, presented valuable materials; but as the ground had always 

 been of the same nature, we could obtain from these only the differ- 

 ence between the shade and the radiation, and not the modifications 

 which might arise, in formations of diverse natures, from their dif- 

 ferent conducting power, their capacity of radiation and their speci- 

 fic heat, relatively to the movement of the heat in the interior of va- 

 riable strata. As these differences are by no means unimportant, a 

 comparison has been established between the observations of Heidel- 

 berg and those of Schwetzinger, the former of which were made on 

 a compact clayey soil, and the second, on a light sandy formation, 

 but which was not above five feet deep, and presented great irregu- 

 larities. The blanks may bo filled up by the calculation of observa- 

 tions which have been made, since 1837, at the depth of 3, 6, 12, 

 and 24 French feet, at Edinburgh, in the trap of the Calton Hill, 

 the sandstone of the coal-formation at Craigleith, and the sand of the 

 Experimental Gaiden. 



It follows from these calculations, that the extent of the changes, 

 whether periodical or non-periodical, is unimportant or insensible 

 in the trap, more considerable in the sand, and reaches its maxi- 

 mum in the sandstone ; so that the further the roots of a plant pe- 

 netrate into the soil, the more it lives in conditions appi-oaching these 

 of a maritime climate ; and, on the other hand, when the roots are 

 of equal depth, the same effect becomes so much the more sensible as 

 the roots penetrate into a soil of inferior conducting powers. Whence 

 it evidently follows, that the geological naturo of a formation is 

 important for the development of plants, not only in a chemical 

 point of view, but also in a physical. — (^V Instilut, No. 711, 



p. 169.; 



VOL. XLVII. NO. XCin. — .FULY 1849. K 



