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but left it to a simple shepherd to discover the gold. They are some- 

 times wrong ; and in the potato disease they have been most unfortu- 

 nately and pertinaciously so, as I apprehend, very much from want 

 of opportunities for making observations. Thus, when they recom- 

 mended the taking up of the crop, I left mine in the ground, and came 

 oflf better than many of my neighbours who lifted theirs. As they did 

 not come in contact in the earth as they would in pits, the disease did 

 not spread. I have made some experiments, to test the power of 

 infection, and found, the first year, that in a few hours a sound tuber 

 would be tainted, when in contact with an unsound one ; and I con- 

 sider it a good sign that this year the disease is but slightly infectious. 

 To suppose that the same species of insect could not have caused the 

 disease in other parts of the world, is, to say the least, absurd, as every 

 naturalist knows that many of these creatures are common to almost 

 every country, and that some are migratory. The locust, that often 

 lays waste whole provinces in Asia and Africa, has before now visited 

 England. As to the power of insects, look to the formation of coral, 

 see, also, the perforation of the hardest rocks ; and as to the extent of 

 their doings, look to the destruction caused by the cane-fly in the 

 West Indies, another which destroys the meadows of Sweden, and 

 the almost total defoliation and other ruin of vast forests by Aphides. 

 Their fecundity is prodigious ; but I shall not take upon me to say 

 the exact number of fresh eggs they lay in the morning. My friend 

 Mr. Andrews will remember the injury caused by one of the Erio- 

 soma to the silver fir in the county of Wicklow, in 1845, and so well 

 described by him at the time. His plan for banishing them was sim- 

 ple, and most efiicacious, and more practicable than that of picking 

 them off, as had been recommended. Soon after the planting of 

 larch-trees in Scotland, they were attacked in a similar way ; and far- 

 mers know what the turnip-fly can do in this country. For the last 

 two years, a plant of the Araucaria imbricata with me has been 

 attacked by an insect, much resembling, except in colour, the potato 

 enemy, and blackened the leaves of it, and, I think, would have killed 

 the plant, had I not banished them, by dusting with soot. Another 

 was partly blackened ; and, remarking one branch quite green, I was 

 pleased to find that the cause was, that a spider had covered it with 

 his web, and was busily employed with them. Now, I observed a 

 webless spider, last year, very numerous on the potato. Its mission 

 appeared to me to be the destruction of the former insect. I put one 

 in a bottle with about thirty of them, which he killed in an incredibly 

 short time. I have many reasons to hope that, as far as the potato is 



