ME. souly on the potato muerain. 35 



III. — Chemical Observations oh the cause of the Potato Murrain. 

 By Edward Solly, F.R.S., Experimental Chemist to the Hor- 

 ticultural Society, etc. 



[Communicated by order of the Chemical Committee, Dec. IG, 1845.] 



In the following brief observation on the potato rot, I propose 

 to consider tlie chemical nature of the changes which the potato 

 iin(!ergoes, the causes necessary to produce such changes, and the 

 peculiar conditions which probably led to the disease or epidemic 

 which lias so largely attacked tlie potato crop of the present year. 

 The subject is a very extensive one, including as it does many 

 practical considerations of high importance ; sucli as, the value 

 of sound and diseased potatoes as food ; the best modes of check- 

 ing the progress of the rot ; the processes for preserving the 

 starch, and economical modes of applying the products to useful 

 purposes ; the best method of storing and housing the crop ; the 

 prospects for next year's crop ; the precautions to be taken, the 

 manures and dressings to be employed. I shall, however, 

 confine myself entirely to the consideration of the cause from 

 which the disease originally sprung. 



It is unnecessary to say more respecting the potato disease, 

 and the mode in which it gradually appeared, than to remark, 

 that in the early part of the past season, the crops looked re- 

 markably healthy, and promised an abundant harvest : at a 

 particular period, namely, about the end of July, the plants 

 changed considerably iu appearance, looking as though they were 

 frost bitten. This change was by no means general, but appeared 

 in many places in various parts of tiie country, seeming to .spread, 

 or at least became apparent after a time, in fields which at first 

 had seemed not at all affected. About the same time that the 

 change was perceived in the leaves, it was observed that the 

 tubers also were aftected with a kind of rot, which commencing 

 either in the centre or towards the outside, gradually spread 

 throughout the whole substance of the tuber, and eventually 

 caused its entire putrefaction. This singular disease was not 

 confined to any one country, it appeared nearly at the same time 

 in most of the northern countries of the globe ; though it was 

 first observed in the more eastern countries, and almost immedi- 

 ately made its appearance in those to the west. The disease, 

 however, was not universal, as particular countries and districts, 

 even in the midst of those where the disease had made the 

 greatest ravages, were but partially attacked, or even wholly ex- 

 empt from its effects ; it was also not confined to particular soils, 

 or particular varieties of the plant ; though generally speaking 

 the plants which had nearly or wholly ripened their tubers at the 

 commencement of August, were those in which the disease made 



D 2 



