340 
THE ART OP REARING 
vator, and the progress of the art, make the 
rules which I have laid down indispensable. 
Chapter XV. 
OF THE NATIONAL AND INDIVIDUAL ADVANTAGES 
WHICH WOULD ACCRUE TO THE PUBLIC, THE 
PROPRIETORS, AND CULTIVATORS, BY IMPROV- 
ING THE METHOD AT PRESENT ADOPTED FOR 
THE REARING OF SILK-WORMS. 
The European soil offers a given number of natu- 
ral productions, everywhere the same, and every- 
where indispensable. 
The favourable or unfavourable changes which 
annually affect these productions, cause whole na- 
tions alternately to buy and sell, as often occurs in 
corn and other grain, 8c ,c. & c. 
Political calculation and financial interest regu- 
late in different states the exports, imports, and 
customs, according to circumstances. 
But when nature, favouring the soil, has en- 
dowed it with a faculty of yielding constantly, and 
in an indefinite degree, a production far exceeding 
its own wants, and necessary to those of other 
countries, or required by their luxury, jiolitical 
interest, and financial calculation should become 
