40] A TOPOGRAPHICAL 



committed on turnip-fields by the caterpillar of this fly in the sum- 

 mer of 1785 ; when, after hot weather, they attacked the turnip 

 plants when full half grown, perforated the leaves into net-work, 

 and did not finally disappear till the frost set in : they have not 

 been very formidable since. Many farmers were alarmed, thinking 

 a new enemy to the crop had appeared : it is supposed that some 

 circumstances in the weather had been favourable to their increase, 

 and that their progeny was prematurely destroyed by frost. Ducks 

 were employed in large droves with some success in destroying this 

 caterpillar. They should be pent up all night, and driven early 

 in the morning, fasting, into the midst of the turnip-field, when they 

 will fill their craws as full as they will hold ; they will also devour 

 slugs and \worms : the former are said to be injurious, and some- 

 times destructive, to a turnip-crop. Mr. Vagg's grand secret of 

 jright-rolliftg is well known, and still recommended by some per- 

 sons, as tending to squeeze and destroy injurious insects better than 

 rolling in the day-time. 



Some persons are said to have soaked the seed, and made it 

 spurt before sowing, to promote a quick vegetation, which method 

 Dr. Darwin advises to be more attended to. He also advises to 

 prevent or destroy insects, that the ground be strewn with soot, and 

 thinks it probable that if infusions were made in hot water, or for a 

 longer time in cold water, of those leaves which no insects devour, 

 as of walnut, laurel, foxglove, henbane, hounds-tongue, ragwort, or 

 tobacco, and were sprinkled on the ground just after the young 

 plants spring up, it might prevent or destroy insects, without 

 injuring the crop. This, however, can be practised only on a 

 small scale. < 



Potatoes have been, and are a good deal, cultivated, both with 

 the spade and plough, in various ways, and the culture well under- 

 stood. They have been applied to the fattening of cattle, hogs, 

 and poultry, as well as for food for mankind. The refuse potatoes, 

 and inferior kinds, are generally applied to feeding hogs, which they 

 will bring on fast, when boiled and mixed with barley-meal, and 

 the inferior or damaged barley will do for this purpose. The 

 markets are principally supplied with potatoes by cottagers who 

 have large gardens, or who rent land for the purpose of growing 

 them : some also are grown for the market by farmers. 



The curl is now pretty well got rid of, the sorts liable to it 

 having been rejected, and new varieties raised in their stead. The 

 animal nutriment from potatoes is decidedly superior to that from 



