BULLETIN OF THE BUSSEY INSTITUTION. 301 
all that could be wished. The Bs partinente with Dabney peat, on 
the other hand, were not successful and are hardly worth the pub- 
lishing. It appeared, after the experiment was started, that the 
jars devoted to the Dabney peat were not sufficiently filled, so that 
in watering them it was not easy to avoid pouring an undue 
amount of liquid which kept the materials soggy and drowned out 
the plants. This difficulty arose from the peculiar texture of the 
peat. It might readily have been overcome in a new trial, if the 
experiment had been worth repeating. 
The results obtained with the clays will be alluded to further on 
in another connection. 
It was still manifest in all these experiments that the presence 
of the nitrogen natural to the soil interfered very materially with 
the assay. Efforts to avoid this difficulty were made by calcining 
the loams in an iron muffle,* and by growing crops either in the 
calcined earths directly or in mixtures of the calcined earth and 
sand. ‘The calcined loams were moreover put in contrast with — 
various natural sands. In all these later trials the experiments 
were greatly simplified by using a much smaller number of jars 
and watering with fewer solutions than before. There was of 
course grave reason to fear that the process of roasting might alter 
the chemical composition of the loams to such an extent that they 
could not properly be used after calcination. It might readily 
happen, for example, in roasting some loams, no matter how 
carefully or at how low a temperature the process was conducted, 
that the inert potassic or phosphatic compounds contained in the 
earth might be broken up and made more available as plant-food 
than they were originally, while in other loams a precisely con- 
trary effect might be produced. But this was a matter which 
would be settled by the experiments, in so far as it bore upon the 
praticability of the assay. 
* A large muffle, one and a half feet long and eight inches wide, of very 
thin cast iron, was thrust into the upper door of the hot-air furnace used for 
warming the laboratory and miade to rest upon an iron bar placed across the 
pot of the furnace just above the glowing anthracite with which the pot was 
filled. The muffle had no opening but its mouth. It was heated to low red- 
ness and the loam in it was stirred continually until the last traces of 
glimmering from the carbonized organic matter had ceased. 
