I. AGRICULTURE AND RURAL ECONOMY. 405 



ment than a cause ; or, in other words, that it is due to cer- 

 tain climatic conditions, such as excessive moisture, and par- 

 ticular changes or stages of temperature, which, while weak- 

 ening the plant, render it an easy prey to the fungus which 

 is developed simultaneously. According to Mr. Hibberd, 

 whenever there are sudden and positive alternations of unu- 

 sual cold and great heat, accompanied by a copious rain-fall, 

 the disease is always developed ; and if, by any artificial 

 means, it were possible to prevent these agencies from influ- 

 encing the potato, we should measurably secure it from de- 

 struction. 



The potato, more than any other plant under cultivation in 

 Great Britain, according to Mr. Hibberd, is dependent for its 

 health on continued solar heat ; and if we can produce arti- 

 ficial sunshine above the surface of the ground, and artificial 

 heat below, we shall save the crop at times when sunshine 

 fails, and the ground is disastrously cooled by a heavy rain- 

 fall. This forms the suo-o-estion of a method of treatment of 

 the potato which, according to the author, has resulted in the 

 most advantageous manner. It is well known that a favor- 

 able method of treating potatoes is to cultivate them in 

 ridges, so that their roots may enjoy a maximum of ground 

 heat, and be quickly drained of superfluous moisture by means 

 of the trough between the ridges. If, now, every ridge were 

 pierced with a tunnel, the advantage would be increased, 

 since this would insure, beneath the plants, a body of impris- 

 oned air, the non-conducting property of which would render 

 it a storehouse of solar heat, maintaining the temperature 

 of the soil nearly at the point it had attained before the 

 weather changed, and, while favoring the rapid escape of 

 surplus moisture, acting medicinally as well as nutritively 

 to sustain the health of the plant. 



Acting upon this suggestion, the author procured a quan- 

 tity of common roofing tiles, laid them in lines in hard ground, 

 and laid potato sets upon them, and then covered the who?e 

 with prepared soil, so as to form a long ridge, covering a 

 shallow tunnel. The result was a remarkably heavy crop, 

 the texture finer than the average, and without a trace of 

 disease. 



He then resolved to improve upon the plan by providing 

 abetter tunnel than was possible with the nearly flat roofing 



