490 
Oil the Potato Disease. 
it proceeded down one side of the stem. In some cases I ob- 
served that these had lengthened in the course of 24 hours 
2 inches; the first tuber I observed affected was on the 8th of 
August, but it was impossible to make any one believe there was 
anything the matter beyond what is the case every year. On 
the 23rd complaints came in from all parts of the country, fol- 
lowed next week by contradictions and assurances that the crop 
were healthy as usual, with the exceptions of a few spots on the 
leaves, and that the tuber was quite sound. Very many people 
deceived themselves on this point ; I amongst the rest had several 
rows of different varieties turned out, and could discover nothing 
particular except a sort of livid smooth skin, which I attributed to 
the unripe state of the tuber. I picked out every one that I con- 
sidered affected, and left the remainder on the ground during four 
or five warm days, when I intended to have had them taken up 
and stored, but on examination T found the whole of the late 
varieties badly affected, the warm sunshine, together with the 
previous dampness of the ground, favouring and accelerating the 
fermentation already began. This taught me to adopt quite a 
different method with the main crop ; I immediately had them 
taken up and laid in small heaps two or three days, shading 
them from the hot sun, but allowing them plenty of air; I then 
had them taken into a dry loft after having had them carefully 
picked over : in a few days they were picked over again, after 
which they were stored away in different situations, for experiment 
sake, the result of which will be seen when we come to consider 
the mode of storing. 
The partially diseased potatoes were boiled, the best for table, 
and those further advanced for the pigs, which throve remarkably 
well upon them when mixed with meal after being well mashed. 
We now come to consider the precautions which afford the 
best hope of averting the disease. First, then, choose sound 
tubers for sets : for although it is by no means certain that diseased 
seed will invariably produce diseased progeny, yet it seems likely 
that the new plant will inherit a predisposition to decay, which 
would require many seasons to outgrow. 
Secondly, choose well prepared ground in a dry situation and 
not over rich; this point is of great iniportance, as has been seen 
by my experiments in taking up the crop of 1845. 
Thirdly. In choosing manures apply such as seem to arrest 
fermentation and putrefaction, such as charcoal dust, peat-ashes, 
&c. ; for while those substances add vigour to the plant they seem 
not to overstimulate its growth. 
In an experiment I made in 1843 on Swedish turnips with 
charcoal dust and ashes against seven other varieties of manure, 
I found that the least per-centage of rotten or diseased bulbs was 
