MEASURE OP MOISTURE IN SOIL. 69 



" On the other hand, in the palus of Bordeaux, the vine is seen 

 growing, so to speak, with its feet in the water. 



" It is then probable that vegetables, or at least some of them, are 

 endowed with an eclectic power ; they take water where they find it, 

 they distil away subterranean water when it is in excess, and they 

 know also how to condense and absorb water from the atmosphere." 



I accept the facts, but demur to the reasoning. I think all can be 

 otherwise accounted for. M. Cezanne cites in a foot-note, in illustration, 

 the description given by Mr Thomas Baiues of the Markivhoe, a large 

 watery root, measuring in its greatest circumference 40 inches and 

 in its smallest 30, with the statement of Mr Baines that when he and 

 his party, travelling in an arid district of South Africa, felt thirsty the 

 Bushmen would pull up some of those roots, and by eating of them they 

 would quench their thirst. I have heard of several different kinds of 

 such juicy plants growing in the most arid districts of South Africa ; 

 but never have I heard anything in regard to their natural history, 

 or their structure, which would warrant the conjecture advanced ; 

 while the proved afl&nity of soil for moisture supplies a satisfactory 

 explanation of all the phenomena referred to. 



From experiment and observation it has been deduced that pure 

 sand has little affinity for moisture ; but that such afiinity is 

 manifested both by clay and by humus in a high degree, and to 

 these conjointly may be attributed the attractive affinity of the soils 

 for moisture, indicated by the gain of weight in the second set of 

 experiments, when the desiccated soils were exposed for a long time 

 to the air. 



To this affinity of soil for moisture attention is given in analyses 

 of soil in agricultural chemistry. It is in generaV inversely propor- 

 tionate to the proportion of sand, and directly proportionate to the 

 quantity of clay in the composition of soil taken from the open country, 

 in which these constituents greatly preponderate ; but it is also 

 proportionate in a much higher ration to the quantity of humus in 

 the soil, and the quantity of this can easily be determined. 



If the two parcels of earth last referred to as subjects of experiment 

 be raised to a red heat in iron spoons, and after all appearance of 

 brighter incandesence in portions of the mass has ceased, they be 

 weighed, care being taken to remove all scales of iron or of iron rust, 

 they will again be found to have sustained a loss of weight ; this is 

 attributable to the combustion of organic matter, most of which was 

 humus, or capable of becoming humus, and the loss sustained by the 

 forest soil will be found much greater than the loss sustained by the 



