48 



As we have seeu above, the specific gravity of the soil is 1.14:. A 

 <3ubic foot of it therefore weighs 71.42 pounds, and a stratum of soil, 

 one foot in depth, extending over one acre, will contain 3,100,055 pounds. 

 This amount of soil is capable of yielding materials immediately avail- 

 able for plant food as follows : 



Pounds. 



Silica 1,331 



Peroxide of irou 651 



Phosphoric acid 440 



Potash ^. 2,077 



Magnesia 1, 395 



Lime 1,023 



Organic matter * 62, 001 



It will therefore be seen that the soil in question contains sufiBcient 

 material t« satisfy the immediate demands of a cotton crop, although 

 the quantity may be somewhat limited. The main trouble is undoubt- 

 edly due to the fact of the existence of proto-sulpliate of iron in the 

 subsoil, and probably free sulphuric acid also. Both of these sub- 

 stances have a poisonous influence upon plants. The planters of the 

 South Atlantic coast, who have this difficulty to contend with, must 

 necessarily adopt some means to remove this salt of iron, and to neutral- 

 ize the free sulphuric acid. The most economical method by which this 

 may be accomplished is a copious application of lime. In case of the 

 soil in question, about 150 bushels of lime per acre will probably be 

 required. I would also advise thorough under-draining where this is 

 deficient, and it is probable that this is the case wherever the difficulty 

 in question exists. 



Exhalation of moistlt^e by plants. — That plants emit moisture 

 during their growth is generally admitted, but whatarethecircumstances 

 •which are the most favorable to this action has never been fully deter- 

 mined until lately, when Mons. A. Barthelemy took ui> the subject. 

 Many observations have been made it is true, but it is probable that the 

 results obtained by the observer named above will be found more satis- 

 factory than any heretofore published. In some of his observations 

 3Ions. Barthelemy followed the method of Mariotte, which consists in 

 causing the branch to be experimented upon to penetrate a flask or 

 other closed vessel and weigh the condensed water. He took the pre- 

 caution, however, to introduce into the vessel a thermometer. When 

 the plants were enclosed in this manner and exposed to direct sunlight, 

 the temperature rose to 50° C, and small drops of moisture condensed 

 upon the cold parts of the receiver. When removed to the shade the 

 temperature rose slightly and the condensation almost entirely ceased. 



For certain reasons, however, he was inclined in further researches 

 to give preference to the method of M. Gareau, which consists in absorb- 

 ing the moisture in chemical substances, in order to determine the com- 

 parative quantities evaporated from each side of the leaf. The leafy 

 portion of the plant, with a weighed quantity of chloride of calcium is 

 placed under a carefully luted receiver, and in order that the plant may 

 have the same conditions as in the atmosphere, there was also inclosed 

 in the receiver a small quantity of bicarbonate of soda, which by disso- 

 ciation supplied the requisite quantity of carbonic acid. 



The complete results of his experiments are too lengthy to be given 

 in extenso, and we shall give only his conclusions, referring those of our 

 readers who may desire more comi)lete data with regard to this subject 

 to M. Barthelemy's report in Coraptes Kendus of November 10, 1873. 



