1902. J PUBLIC DOCUMENT — No. 33. 79 



necessary to treat the soil again. It requires no argu- 

 ment to show that the expense of §100 for treatment of the 

 house that would be worth $2,000 at 50 cents per dozen, 

 or even $1,000 at 25 cents per dozen, is a good invest- 

 ment, even if the treatment has to be repeated each year. 

 On the basis of a five-year treatment, which is, in our own 

 estimation, all that is required, the gain is nearly five times 

 as great. The increased value to the soil resulting from 

 such treatment, and the possibility of having less weeds 

 and fewer aphis, should also be taken into consideration in 

 estimating the benefits derived from the use of this method. 

 The oldest, most conservative and intelligent lettuce growers 

 were enthusiastic over the results of this experiment. 



Methods of SteviJizbuj. — The methods employed for 

 heating the soil have been by either hot water or steam, 

 with some variation in the mode of applying the latter. 

 Messrs. Hittenger Bros, of Belmont have made extensive 

 use of the hot-water method, and their later constructed 

 houses have special facilities for applying this in the most 

 economic manner. The hot-water method requires the treat- 

 ment of the soil previous to the putting in of each crop, 

 and only a few inches of the surface soil are sufl5cieutly 

 heated by this practice to kill the mycelium of th-e drop 

 fungus. 



The heating by steam is now done largely by the aid of 

 perforated pipe, and in some cases use is made of 2 inch 

 porous tile, though this method is not so applicable. If 

 finely perforated tiles could be obtained in the market at a 

 reasonable cost, their use would be much more valuable for 

 this purpose than at present. The various contrivances are 

 made out of perforated pipe, varying from 1 inch to 3 inches 

 in diameter, usually placed from 7 to 12 inches apart, and 

 made up into frames fi'om 10 to 20 feet or more in length 

 and into any dcsu'cd width. The size and number of the 

 perforations vary much in different appliances. When they 

 are rather large (l^ inch in diameter) they arc frequently 

 covered with burlap. In some appliances the perforations 

 are Vt inch in diameter and are only l^/l) inches apart each 

 way. In others the perforations may be only i/g inch in 



