The Potatoe Plague. 85 



these plans, which have been so much advocated, all resolve 

 themselves into one and only one process, which is, main- 

 taining dryness. 



The official circular of the Poor Law Commissioners, con- 

 tains an extract from an official paper published in the United 

 States, on the potatoe disease in 1843. It appears from this 

 document that the evil was ascribed to heavy rains and early 

 snows. 



An able writer in the Gardener's Chronicle, G. S. Mac- 

 kenzie, Bart., says : " I formerly suggested that an insect 

 had caused the disease of the potatoe. There now seems to 

 be some reason^ for believing that it has been injured by 

 various causes, and that there is more than one disease at 

 work. While examining a number of diseased tubers, in one 

 (and one only) I found two small maggots luxuriating in the 

 rotten matter. On mentioning this circumstance, I found 

 that some other persons had observed the same thing. In 

 many potatoes I noticed round holes and cavities connected 

 with them,, in which larvae had, no doubt, fed. But there 

 was no appearance of disease, the wounds having dried up 

 In many cases the substance of the potatoe had been con- 

 verted into matter of a corky consistence ; in the greatest 

 number the substance was a mass of wet rottenness. 



I now give the opinion of Professor Liebig, published 

 November 5. He says, " The researches I have undertaken 

 upon the sound and diseased potatoes of the, present year, have 

 disclosed to me the remarkable fact, that they contain, in the 

 sap, a considerable quantity of vegetable casein (cheese) pre- 

 cipitable by acids. This constituent I did not observe in my 

 previous researches. It would then appear that from the 

 influence of the weather, or generally speaking, from atmos- 

 pheric causes, a part of the vegetable albumen which prevails, 

 in the potatoe, has become converted into vegetable casein.. 

 The great instability of this last substance is well known ; 

 8 



