Minnesota Plant Diseases. 239 



The various methods of treatment of timber to prolong its 

 usefulness consist entirely of impregnation processes. By 

 these, chemical compounds in solution or emulsion are forced 

 into the timbers or boiled in, so that they permeate the whole 

 timber or at least the surface portions. These substances must 

 be fungicides and antiseptic as well. They must prevent the 

 germination or growth of the fungi or bacteria and thus pre- 

 vent rotting. It is not always necessary that they penetrate to 

 the center of the timber, since the surface portions, if properly 

 impregnated, will keep out all decay-forming organisms. Of 

 course such a substance which would penetrate to the very cen- 

 ter would be of great advantage in the resistance towards the 

 leaching-out process. It must be kept in mind that many com- 

 mon fungicides are soluble in water and hence would leach out 

 under heavy rains. This is an important factor in the impreg- 

 nation of timber. A substance must also be selected which can 

 be injected with ease into woods. In the case of soluble salts, 

 the easier the injection the easier the leaching out. However, 

 in view of the cost this is an important factor. It will not be 

 many years when the price of timber will be such as to compel 

 the adoption of some methods of treatment for many timbers 

 and such is already the condition in European countries. It is 

 rapidly becoming imperative in certain classes of timber at 

 present and particularly those mentioned above as most liable 

 to decay, e. g., ties, poles, etc. At present, however, the cost 

 of impregnation is one of the first factors for consideration and 

 often of paramount interest. 



The following substances have been used with considera- 

 ble success. Creosote is sometimes forced hot into timbers 

 placed in tanks from which the air has largely been re- 

 moved. By this method a penetration of several inches may 

 be effected. This process has been described as the most 

 effective known, though on account of the considerable ex- 

 pense of the creosote is not generally applicable. A cheaper 

 but less effective method is that of the use of zinc chloride. 

 This has been more extensively used. Another process is 

 known as the Hasselman treatment. In this the timbers are 

 boiled in a solution of the sulphates of copper, iron and alu- 

 minum and a small amount of kainit for several hours. By this 



