THE SOURCES OF THE NITKOGEN OF VEGETATION, ETC. 499 



Series 1. — Experiments on the decomposition of nitrogenous organic matter, 



made in 1857. 



Wheat-meal, Barley-meal, and Bean-meal were the nitrogenous organic substances 

 submitted to decomposition. A quantity of each of these was mixed respectively 

 with burnt soil and with pumice, making in all six separate experiments. About 100 

 grammes of soil, or about 60 grammes of pumice, were used — these quantities, together 

 with the meal, filling the bottles B to the depth of about 2 inches. Sufficient water 

 was added to bring the mixture into an agglutinated condition. The materials being so 

 prepared, the apparatus was put together according to the arrangement above described. 

 The six sets were then placed in a light room before a large window, so that, during the 

 middle of the day, the sun shone directly upon them. 



The experiments commenced on June 10, and terminated on October 8, 1857. Several 

 litres of air were drawn through each apparatus daily, by applying the mouth to the 

 tube E. After the first day the gas possessed a more or less disagreeable taste, and the 

 odour of decomposing organic matter. 



The following statement of the condition of the several mixtures, at the termination 

 of the experiment, is condensed from the notes then made : — 



1. Wheat-meal and ignited Pumice. — The meal slightly mouldy; the odour that of 

 decomposing organic matter; quite moist, so that the particles of pumice adhered 

 together. 



2. Wheat-meal and ignited Soil. — A slight mouldy coating on the surface ; odour like 

 that of No. 1 ; the mass moist, but not sufficiently so for the particles of soil to aggluti- 

 nate. 



3. Barley-meal and ignited Pumice. — No mouldy coating on the surface ; odour similar 

 to that of the wheat but more intense, and sour, much like that of fermenting malt ; 

 the mass wet and clammy. 



4. Barley-meal and ignited Soil. — No mouldy coating on the surface ; odour like that 

 of barley No. 3 ; sufficiently moist to agglutinate. 



5. Bean-meal and ignited Pumice. — A little mould upon the surface, but not quite so 

 much as with the wheat and soil (No. 2) ; odour very disagreeable and putrescent ; the 

 mass wet and clammy. 



6. Bean-meal and ignited Soil. Very similar to the bean-meal and ignited pumice 

 (No 5), but a little more wet and pasty. 



In every case, carbonic acid was evolved on the addition of oxalic acid, preparatory to 

 evaporating to dryness. The evolution was the greatest from the bean-meal with soil. 



A known proportion, about one-half, of each dried mass, was burnt with soda-lime, 

 and the Nitrogen capable of estimation in that way determined. The remainder was 

 reserved for the determination of nitrates, provided any were present. On examination, 

 however, no nitric acid was detected. To put the validity of the qualitative test for 

 nitric acid beyond doubt, 0-001 gramme of nitric acid was added to the portion of sub- 

 stance which had been already exhausted to test for nitric acid, and had yielded a nega- 



