524 Mr. Hinds on Climate in connexion 



water they will retain, calcareous come next, and siliceous the 

 last. It is by a judicious mixture of these that a fruitful 

 soil is made, for it is quite possible for a soil to be too moist 

 as well as too dry. Einhof, who has paid some attention to 

 soils, has named the variety which occurs in low meadows and 

 marshes, acid vegetable mould ; it is marked by excessive 

 moisture, and nourishes species of Juncus, Carex, Eriopho- 

 rum, Arundo, &c. : a notable quantity of the acetic and phos- 

 phoric acids exists in it. 



Nor are the effects on temperature to be overlooked ; dark- 

 coloured rocks and soils, as volcanic and slaty, are more easily 

 warmed by the sun from their superior power of absorbing 

 heat ; the clay-slate, on which the vineyards of the Rhine are 

 cultivated, owes its superiority to the dark colour ; and at Con- 

 stantia at the Cape of Good Hope, the excellence of the grape 

 has been attributed to the same. DeCandolle mentions that 

 the peasants in the valley of Chamouni are accustomed to re- 

 duce a black slaty rock to powder and sprinkle it over the 

 snow in spring ; the dark substance absorbs the sun's rays, 

 and by the melting of the snow beneath vegetation is accele- 

 rated from one to two weeks. The vegetation of the perennial 

 grasses commences at least a fortnight sooner on limestone 

 and sandy soils than on clay, or even deep rich moulds ; hence 

 has arisen the appellation of cold soils. The tenacity with 

 which a soil retains moisture is in some measure a guide to 

 its power of modifying temperature. Soils in which there is 

 much nutrient matter resist the effects of cold temperatures 

 better than poor or watery ones. Compact soils have the same 

 influence on low temperatures. 



Though these circumstances exert at times and seasons 

 their proper influence over the productiveness of soils, it must 

 still be held in mind that the latter are of very secondary im- 

 portance in the existence of the vegetable kingdom. The 

 cases where the condition of the soil decidedly defines the ve- 

 getation are the exceptions, and instances of plants being able 

 to thrive in a particular soil and no other are extremely rare. 

 Many of these exceptions are of interest, and an investigation 

 of them is not unlikely to make us better acquainted with the 

 relations between vegetation and soil. An examination of the 

 constituent parts of plants which have been growing on dif- 

 ferent soils shows that they vary with the mineral ingredients : 

 Saussure found that those which came from a granitic soil 

 contain certain quantities of silica and metallic oxides, and 

 others from a calcareous soil possessed little or none of these, 

 but their proportion of calcareous earth. There are some ex- 

 periments and observations which tend to prove that these 



