mi 
is only by following the slow operations of natural 
causes, that we are capable of making improve- 
ments. 
There is a number of chemical substances which 
are very offensive and even deadly to insects, which 
do not injure, and some of which even assist vege- 
tation. Several of these mixtures have been tried 
with various success ; a mixture of sulphur and 
lime, which is very destructive to slugs, does not 
prevent the ravages of the fly on the young turnip 
crop. His Grace the Duke of Bedford, at my sug- 
gestion, was so good as to order the experiment to 
be tried on a considerable scale at Woburn farm : 
the mixture of lime and sulphur was strewed over 
one part of a field sown with turnips ; nothing was 
applied to the other part, but both were attacked 
nearly in the same manner by the fly. 
Mixtures of soot and quicklime, and urine and 
quicklime, will probably be more efficacious. The 
volatile alkali given off by these mixtures is offensive 
to insects ; and they afford nourishment to the 
plant. Mr. T. A. Knight # informs me, that he 
* Mr. Knight has been so good as to furnish me with the 
following note on this subject. 
“ The experiment which I tried the year before last, and last 
year, to preserve turnips from the fly, has not been sufficiently 
often repeated to enable me to speak with any degree of deci- 
sion; and last year all my turnips succeeded perfectly well. 
In consequence of your suggestion, when I had the pleasure 
to meet you some years ago at Holkham, that lime slaked with 
urine might possibly be found to kill, or drive off, the insects 
from a turnip crop, I tried that preparation in mixture with three 
parts of soot, which was put into a small barrel, with gimblet 
holes round it, to permit a certain quantity of the composition, 
