VARIOUS FORCING METHODS. 85 



readily penetrates it, heating the whole bed uniformly; 

 whereas if the tunnels are heated by inclosed steam or 

 hot water pipes, the soil becomes too hot and dry close 

 to the tunnels while it is too cold midway between them. 

 Forcing steam into the tunnels keeps the soil moist and 

 maintains more continuous fermentation of the manure 

 mulch, thus promoting steady heat. 



The crop produced in this way was larger, of finer 

 quality, and the bed produced longer, than that forced by 

 any other method tried. The plants thus forced recuper- 

 ate by being allowed to grow one summer without cut- 

 ting, while plants transplanted for forcing are ruined 

 by the i:)rocess. 



The amount of soft coal used to force a plot 25 x 25 

 feet, in this way, from December 29 to February 25 (58 

 da3^s), was 2,308 pounds, costing $1.82, or an average of 

 39 pounds daily. During these 58 days, steam was turn- 

 ed into the six tunnels of this plot a total of I614 hours, 

 equivalent to 17 minutes daily, or less than three minutes 

 daily for each tunnel. The forced asparagus yielded, 

 during the 58 days, at the rate of 9,882 bunches, or 

 4,880 ponnds per acre. The yield of rhubarb has not 

 been stated. About five minutes at a time is as long 

 as steam can be forced into a tunnel without danger of 

 overheating the plants. 



Forcing the crops where they can be grown in the 

 field, has a twofold advantage; saving the trouble and 

 cost of transplanting, and avoiding the injury done 

 to the plants by transplanting. 



Exhausting steam into the bed, instead of returning 

 it to the boiler in an inclosed circuit, would, at first, 

 seem to be a wasteful process of heating. Experiment 

 showed, hoAvever, that the circumstances justified this 

 method. Heating a bed of this kind by a circuit of steam 

 pipes- or hot water pipes is very unsatisfactory. The 

 heat from pipes very soon dries out the soil around the; 

 tunnels, destroying its power to conduct heat. In this 

 way the bed becomes too hot and dry adjacent to the 

 tunnels, and too cold a short distance from them. It 

 also becomes necessary to maintain heat in the pipes 

 a good part of the time. 



