cxc GENERAL SUMMARY OF SCIENTIFIC AND 



is so prone to set in with organic fluids, and thus, by preventing in- 

 cipient alteration, indirectly to improve the quality of the material. 



The practice of warming the dairy in winter-time, so as to main- 

 tain its atmosphere at a constant temperature of about 60, is there- 

 fore objectionable ; the pans should stand in running water at as low 

 a temperature as can be practically obtained. 



It is further suggested that the foregoing facts should be brought 

 prominently before the notice of those who are engaged in the manu- 

 facture of dairy products, in order that the many erroneous notions 

 on this subject may be gradually eliminated. Country Gentleman, 

 Novemler 23, 1875. 



RELATIONS OF CONSTITUENTS OF SOIL AND AIR TO PLANT- 

 GROWTH. 



Rendering Mineral PhosjjJiates SoluUe dy Co7Ji2)osting and Treating 

 icith Chemicals. Some interesting experiments on the effects of com- 

 posting in rendering soluble the phosphoric acid of mineral phos- 

 phates have been made by Holdefleiss at the experiment station at 

 Halle, Germany. Lahn phosj)horite, containing 28.86 per cent, of 

 phosphoric acid and 4.83 jDer cent, insoluble matters, was composted 

 with peat, earth, urine, dung, salts of ammonia and of potash, sej)a- 

 rately and mixed in various ways. The general plan of the experi- 

 ments consisted in mixing certain quantities of phosphorite with 

 weighed portions of earth or horse-manure, putting the mixture in 

 boxes, adding, in some cases, sulphate of ammonia, potash salts, or 

 carbonate of lime, and keeping each moistened with either water or 

 urine from the last of May until the fourth of the following January. 

 The total dry substance, total phosphoric acid, and jDhosphoric acid 

 soluble in citrate of ammonia, were determined in each case at the 

 beginning and at the end of the experiment. Sixteen different 

 mixtures, in as many boxes, were tested. In every case except one 

 there was a slight increase of soluble phosphoric acid, but in none 

 was this increase sufficient to be of practical moment. 



In a previous series of similar experiments nearly fifty per cent, of 

 the phosphoric acid of a phosphorite mixed with peat was render- 

 ed soluble. The explanation of this variation was found in the fact 

 that the peat of the first trial contained sulphur, which by oxida- 

 tion produced sulphuric acid, which in its turn rendered the phos- 

 phoric acid of the phosphate soluble. 



From these very carefully conducted experiments it seems that 

 there can be very little practical utility in the attempt to render 

 mineral phosphates more available as fertilizers by composting. 

 They would, of course, be still slower in becoming soluble when ap- 

 plied directly to the soil. These investigations coincide with gener- 

 al experience in indicating that mineral phosphates, however finely 

 ground, can not be of much value except when treated with acid. 



