BACTERIZED PEAT 85 



that from the stable manure is a lightish brown, 

 while that from the treated peat is so concentrated 

 that it has the appearance of being black. In other 

 words, the water extract of untreated peat contains 

 only traces of soluble humus, that from stable 

 manure one of the best, if not the best, ordinary 

 source of humus contains relatively little, while 

 that obtained from treated peat is extremely rich in 

 the substance. Supposing now that these three 

 tubes are left standing for purposes of comparison 

 and the experiment is repeated, we have, by con- 

 tinuing it a stage farther, a very simple means of 

 getting a more precise measure of the difference 

 between our three samples. By adding Hydro- 

 chloric acid to the filtered liquids the soluble humus, 

 chiefly Ammonium humate, makes its appearance in 

 insoluble form as a brown flocculent precipitate of 

 Humic acid. When Hydrochloric acid is added to 

 the water extract of the untreated peat scarcely any 

 precipitate appears. When it is added to the water 

 extract of the manure a precipitate forms that may 

 settle down to occupy J- or inch of the test-tubes, 

 but when the acid is added to the water extract of 

 the treated peat a closely compacted precipitate 

 results that may be as much as 6 or 8 inches in depth. 

 To get an exact measure of the food values of the 

 three substances it is only necessary to filter off 

 these precipitates, to dry and weigh them. Experi- 

 ment has shown that the untreated peat gives almost 

 zero as its value, the manure a unit weight and the 

 treated peat as much as fifty or eighty times that 

 obtained from the manure. The following are the 



