108 NATURAL HISTORY. [cH. V. 



are kept constantly dry and well aired, these sub- 

 stances will do no mischief, but keep the litter light, 

 and allow the air to circulate more freely through it. 



When the silkworms find any leaves that they do 

 not like, they leave them. There are some of a 

 dark hazel colour, which have fermented slightly ; 

 these the worms will eat, if they are not quite 

 spoiled, nor are they the worse for it ; from which 

 fact it would appear that the fermentation has not 

 affected the saccharine or resinous part of the leaf. 



The quantity of leaves, according to Dandolo, 

 taken from the tree, and employed for each ounce 

 of eggs, amounts to 1609 Ibs. 8 oz., divided in the 

 following manner: 



Ibs. oz. 



First age, sorted leaves, 6 



Second age, 18 



Third age, 60 



Fourth age, 180 



Fifth age, 1098 



1362 



But this leaf has lost by sorting much of its weight, 

 in the following proportion : 



Refuse picked from the leaves : 



Ibs. oz. 



First age, 1 8 



Second age, 3 



Third age, 9 



Fourth age, 27 



Fifth age, 102 



142 8 



Ibs. oz 



Sorted leaves, 1362 



Refuse picking, . . . . .142 8 



1504 8 



During the whole period of rearing the 

 silkworms, the 1609 Ibs. 8 oz. of the 

 leaves taken from the tree, have lost 



