56 MANUAL OF MODERN VITICULTURE. 



These indications are now considered as insufficient. In 

 the first place, they do not give any indication with regard to 

 new graft-bearers studied since, and which have real value ; 

 further, they do not give any information with regard to the 

 nature of the lime contained in the soils analyzed. We know 

 now that the peculiar state of limestones of different physical 

 nature affects American vines differently, assuming the per- 

 centage of carbonate of lime to be equal. They are more 

 affected by soft and friable limestone, such as chalky, pebbly, 

 or pulverized marl, and can, on the contrary, grow without 

 becoming yellow in soils containing a high percentage of lime 

 if tins lime is in a crystalline or saccharoidal state, forming a 

 sandy debris, and not paste or mud in the presence of water. 



It would seem that in this latter form limestone is 

 generally more soluble. Montdesir and Bernard have shown 

 that it is possible to gauge the assimilability of limestone by 

 the rate of disengagement of carbonic acid gas resulting from 

 the action of acids on it. Houdaille and Semichon have 

 continued this study, and made much progress. Bernard 

 invented a calcimeter (Fig. 22), with which it is possible to 

 rapidly ascertain the limestone contained in the soil, and to 

 judge approximately from the rate of disengagement of 

 carbonic acid gas, the more or less facility with which the 

 limestone is decomposed. 



This apparatus, which is easy to manipulate and costs very 

 little, should be in the hands of all viticulturists who wish 

 to study their soils themselves with the object of ascertain- 

 ing which graft-bearer will give the best results. Houdaille's 

 calcimeter is more complicated and provided with a self- 

 registering curve-marking device, with the aid of which it is 

 easy to ascertain the rate of disengagement of carbonic acid, 

 and, therefore, the rate of decomposition of the carbonate of 

 lime, but it is rather a laboratory instrument giving very 

 complete indications. 



The rate of decomposition, however, is not always sufficient 

 to explain certain facts, such as the presence in soils of 

 humus furnishing carbonic acid, decomposing limestone, and 

 water which dissolves it. Most of the soils of the Charentes, 

 in which vines become chlorosed, contained a high per- 

 centage of humus, which, according to the analysis of 

 Chauzit, varies between O412 and 0*803 per cent. 



Many other soils in which vines become chlorosed do not 

 contain a very high percentage of lime, but they always 



