REFLECTIONS ON DISEASE TREATMENT 167 
mass, otherwise there is danger of over-heating the soil, 
especially if it is too dry. Investigations with regard to 
the temperature details are now in progress at Cheshunt 
Experimental Station. Even with the crude methods at 
present in practice satisfactory results are generally 
obtained. In any case, it is advisable to bake the soil 
six weeks ahead of using it, and in the interval the heap 
should be well worked and watered to bring the soil into 
a suitable physical state for cultivation. 
Sterilization by means of Chemical Compounds 
The researches of Sir John Russell and his colleagues 
at Rothamsted Experimental Station have elucidated 
many problems of soil sterilization and led to the know- 
ledge that soil treatment with chemical compounds pro- 
duces partial soil sterilization effects. The intrinsic value 
of any method of soil sterilization depends upon the ease 
of application, thoroughness of sterilization, and the cost. 
Chemical treatment of soils has proved to be slightly 
cheaper and easier of application than that of heat treat- 
ment by steaming or baking ; but while the compounds at 
present on the market have proved successful for certain 
purposes, there is need for a more efficient and cheaper 
compound than is at present available to the practical man. 
Investigations conducted at Rothamsted indicate 
that such compounds will be available in the future. 
Caustic lime and cresylic acid are the only compounds 
used extensively in practice. Heavy dressings of caustic 
lime of from four to ten tons per acre are employed in the 
glasshouse industry with beneficial results. 
Sterilization with Cresylic Acid 
Pale straw-coloured “ carbolic”’ acid, composed of a 
mixture of ortho-, meta-, and para-cresols of 97 to 99 
per cent purity is used, one gallon being poured into a 
barrel containing 39 gallons of water. On light soils the 
