38 HATCH EXPERIMENT STATION. [Jan. 



conclusion, it may be stated that it is not generally con- 

 ceded by tobacco growers who experimented with cucum- 

 jjers, etc., under tent cloth, that this method of culture will 

 be of any practical importance in the cultivation of garden 

 crops. It is quite evident, however, that it succeeds in pro- 

 ducing plants of better foliage, and, on the whole, it has a 

 value in certain cases of preventing infection. 



Experiments in Heating Soils. 

 The rather unusual interest taken in the problem of soil 

 sterilization within the last few years has been the means of 

 inducing growers to improvise various devices for heating 

 soil. Some of these appliances have been constructed for 

 personal use only, while others have been patented and 

 placed on the market. The diameter of the tubing and 

 method of perforating, together with the size and number 

 of the perforations, differ much in the various appliances. 

 The amount and pressure of steam and distance between 

 pipes in the soil also vary with different appliances, as does 

 the relative efEciency and cost of heating. Our experi- 

 ments, which were rather limited in extent, consisted in 

 testing the relative heating capacity of pipes one foot long 

 and of various diameters, which contained the same number 

 and area of perforations ; also of pipes of the same diameter, 

 containing various sizes and numbers of perforations. "We 

 made use of iron pipe, galvanized iron and tin tubing, and 

 porous tile. In order to test their relative efficiency, we 

 placed them in the centre of a keg that had a hole bored in 

 the side for a thermometer, which in each case was placed 

 about six inches from the tubes. The keg was filled with 

 soil, and steam entered into the tube. All of the tubes 

 except the tile were plugged at the lower end, and the 

 steam had to penetrate the soil through the perforations. 

 The table shows the result of these experiments : — 



