The Potatoe Plague. 49 



where the entire vegetation may be destroyed by too wet or 

 too dry a season. 



These attempts to trace a general effect to partial causes 

 appear to me very like the deductions drawn from the pre- 

 tended rules of phrenology. I examine a stranger's head, and 

 find the bump of destructiveness, for example, fearfully prom- 

 inent. I therefore pronounce him a dangerous person ; but, 

 on inquiry, I learn that he is a man of remarkably benign 

 and quiet temperament. "That," says the phrenological the- 

 orist, " is because his organs of benevolence and reverence- 

 are equally developed, and neutralize his destructiveness." 

 What practical use can be cut out of a science that defines no- 

 limits or proportions ? 



In like manner, " one intelligent farmer (we quote from 

 the report above mentioned,) on his own farm, where the soil 

 was porous, lost none of a crop yielding two thousand bushels ; 

 while of a field he purchased on a neighboring farm, where- 

 the soil was clayey, and retained much water, he lost the 

 greater part of the crop." Hence he argues that the soil and 

 season together caused the injury, and so, undoubtedly they 

 did ; but, supposing there had been a drouth, the seed plant- 

 ed in clay must have fared best. No general rule can be 

 deduced from any such success or failure. From this and the 

 concurrences of many other like instances, however, I draw 

 the inference that a light soil is more congenial to the potatoe 

 family, generally, than a heavy one. 



Another set of theorists attribute the potatoe disease ta 

 flies, or other insects. These, however, as far as satisfacto- 

 rily observed, appear to be no other than have been always 

 found upon the potatoe, without producing any injurious 

 effects. They are the common aphis or vegetable louse, and 

 flies which confine their ravages to the leaves. It might be 

 argued in favor, or rather in disfavor of these parasites, thaty 

 by injuring the leaves, they deprive the tuber of its proper 

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