30 On the Use of Charcoal Dust, $c. 



several experiments to prevent the disease taking place, but 

 none had the desired effect, until I made use of charcoal dust 

 (which is the refuse that is left at the bottom of a charcoal 

 pit after the charcoal for use is taken out), spread upon the 

 top of the ground intended for Onions, about half an inch 

 thick, before the seed is sown (the ground being previously 

 well dug and manured), and merely scuffled in with the 

 point of a spade, so as to mix the top soil and charcoal dust 

 together. Nothing more is after required beyond managing 

 the crop in the usual way. 



For these last six years, I have had most excellent crops of 

 Onions, and not the least appearance of any infection. My 

 first experiment was in the spring of 1818, upon a bed fifty 

 feet long, and five feet wide, prepared in the usual way, one 

 half the bed was dressed with charcoal dust, the other half 

 without it, the part on which the dust was laid had an excel- 

 lent crop of Onions, it remained quite clean and free from any 

 disease, whilst the part to which the dust was not applied, 

 was entirely destroyed by the grub and by mouldiness. i 



In 1819, I determined to try the effects of the dust upon 

 a larger scale, I therefore had the whole of the quarter pre- 

 pared for Onions, and divided it into eight beds of the same 

 size as before ; four of the beds were treated with dust, the 

 other four remained without it. The result was the same as 

 before ; the beds where the dust was applied bore a good 

 clean crop, whilst the others were affected. Having had 

 two years proof of the good effects of the charcoal dust, in 

 preventing the disease from taking place upon the Onion on 

 one quarter, I have since tried it upon different quarters, 

 with the best success. 



