On Vegetation and Soils . 285 



idea, that there rauft exift between thefe vegetables a dif- 

 ference Hill more important, and which ought to depend 

 more on the nature of the foil. Sauffiire therefore has 

 made a feries of experiments, with a view to afcertain the 

 difference which the nature of different foils produces in the 

 compofition of the vegetables which grow in them. That 

 thefe experiments might be conclufive, it was neceffary to 

 hiake them very much comparative, that is to fay, to take 

 the fame quantity of the fame vegetables, of the fame age, 

 growing under fimilar circumflances or in the fame expo- 

 fure, at a diftance from the courfe of ftreams, and beyond 

 the reach of cattle. 



It was neceffary alfo to repeat the fame experiments A 

 great number of times in order to obtain mean refill ts, and 

 to approach the truth by multiplying probabilities. This 

 C. de Sauffiire did. He began by analyfing the ftone that 

 compofed the mountains the plants of which he examined. 

 He then proceeded by the ufual chemical means, which he 

 defcribes in his memoir, to analyfe the vegetables, with a 

 view to afcertain the refpecVive quantities of natural water, 

 charcoal, earths, and falts which they contained. That he 

 might obtain more general refuUs he operated on different 

 kinds of plants, viz. the pinus abies ; pinus larix; rhodo-' 

 dendron ftrrugineum ; vaccinium myrtdlus ; jtcniperus com- 

 munis- All thofe vegetables which belonged to granitic 

 diftricts contained more water than thofe of calcareous coun- 

 tries. The fmallefr quantity of the extreme difference was 

 as 57 to 58, and the greateft as 52 to 59. Thefe differences 

 cannot be afcribed to the quantities of water which 'night 

 be retained in the mould of the granitic foil and thai of the*. 

 calcareous, for they are the inverie of thofe prefented by the 

 vegetables of thefe two foils. De Sauffiire concludes with 

 Duhamel, that the wood of calcareous countries is prefer- 

 able, in point offobdity, to that of granitic countries. 



Proceeding then to a companion of the quantities of 

 charcoal contained in vegetables, Sauffiire remarks how dif- 

 ficult it is to eltimate with precifion the abfolute quantities 

 of charcoal; the relative proportions of that principle can at 

 moft be known; and he found that it is more abundant in the 



Vol. VI II. BW salcarcou- 



