POTATO DISEASE. 285 



which we may invariably defend the plant from its attacks, we 

 may nevertheless, by carefully recording the details of a series 

 of philosophical experiments, and by generalizing all the facts 

 thus developed, approach so near to the end desired as to 

 produce a potato crop with no more chances of failure than of 

 losing an Indian corn crop by summer rains and September 

 frosts. By the careful observation of such facts, obtained from 

 experiments extended through a series of years, we might 

 gather a sum of information, the value of which would more 

 than balance the expense of conducting them. 



It is a knowledge of the remedies, or preventives, of the dis- 

 ease, which it is desirable to seek ; the nature of it is of less 

 importance, except as a knowledge of it might point out the 

 means of extirpating it. The wide prevalence of the disease, 

 which occurs simultaneously in different parts of the country, 

 and in different countries widely separated, proves that its 

 cause is universal in its character. It does not commence in a 

 particular district, and gradually extend over the surrounding 

 country. Its sudden and simultaneous occurrence, as distin- 

 guished from any thing of a progressive character, proves it to 

 be no travelling epidemic. All this favors the idea that it is a 

 constitutional disease of the species, — whether it be the conse- 

 quence of " running out," or of any more hidden and mysteri- 

 ous cause. 



From the report of the committee of the Massachusetts 

 legislature, " On the Diseases of Vegetation," it appears that 

 out of a large number of communications relating to the 

 potato disease, from individuals claiming the premium to ,be 

 awarded to the person who should discover its remedy, twelve 

 of the experiments recommended, which were alone considered 

 worthy of being tested, were carefully tried on the State farm, 

 but " all failed to give any such results as would entitle them 

 in any way to the confidence of the community, or as answering 

 the requisitions of the law." The report of this committee is 

 an excellent specimen of philosophical reasoning, and ought to 

 be carefully studied by those numerous individuals who can 

 not distinguish between a principle and an hypothesis, or 

 between a conclusion based upon assumed premises and one 

 based upon facts. No man can be a good experimenter who 

 has not a logical mind, though he may be the best practitioner 



