PREFACE. 
Vll 
The chances of failure increase, in fact, 
in proportion to the number of worms 
reared in any one place; and though a 
freer ventilation be created, the cold thus 
necessarily produced will be, if not 
guarded against, productive in this cli- 
mate of little less danger than the want of 
it. Hence the ill success that has hitherto 
accompanied attempts to rear the Silk- 
Worm on an extended scale. 
In Italy the practice of distributing the 
eggs intended to produce a certain quan- 
tity of Silk, amongst the several tenantry 
of a proprietor, has greatly diminished the 
ill effects arising from improper ventila- 
tion ; and the temperature of the climate 
is such as, generally speaking, to put the 
fear of cold out of the question. But 
even in that country, until within the last 
few years, it was a general and well-re- 
ceived opinion, that the mortality among 
a large number of worms was far greater 
in proportion than among a smaller quan- 
tity. 
The cause of this circumstance the fol- 
lowing work will be found to investigate 
