[ 1V5 3 90 



When strav/ or shavings are burnt, the ventilator should be opened 

 for the circulation of the air. If the exterior temperature be not cold, 

 and the Vy-eather calm, the doors and windows may also be opened ; 

 when the interior temperature by these means is lowered half a de- 

 gree, the windows and doors should again be closed, leaving the ven- 

 tilators open, and the temperature will rise again. Those who have 

 Venetian blinds to the windows, should open the windows to allow the 

 air to enter. Persons who attend silkworms should breathe as freely 

 in the great laboratory as in the open air; they should feel no differ- 

 ence but that in the heat of the interior temperature, and the latter 

 in temperature, not in the closeness. Therefore, should the air ap- 

 pear heavy, the fire of straw or shavings ought to be lighted, to renew 

 the air, which is done in a moment. In the laboratories described, 

 the interior air is more pleasant than the exterior air, from the delight- 

 ful smell of the mulberry leaves. 



In proceeding in the manner detailed, the silkworms will breathe 

 continually a pure and dry atmosphere, which makes them healthy, 



CHAPTEH IX. 



piF THE RI:ARING OF THE SILKWORMS IX THE FIRST PERIOD OP THE 

 FIFTH AGE, OR UNTIL THE MOMENT Vv'HEN THEY PREPARE TO RISE 

 ON THE HEDGES. 



The fifth age of the silkworm is the longest, and most decisive. 

 Previously, therefore, to resuming the description of the daily pro- 

 gress of the silkworms, a few practical observations will be given. 



Should the worms die in the first age, the loss is trifling, because 

 expense is not prolonged; while, on the contrary, should the worms 

 perish in the fifth age, the loss is considerable, leaves having been 

 consumed, labor paid fqr, and other expenses incurred; besides 

 seeing the hopes of all that profit vanish, which had been reckoned 

 upon. 



It is then very needful to know the condition of the worms in the 

 fifth age, to learn how to manage, so as to ensure their health and 

 strength against the cfiects of a bad atmosphere, or other evils that 

 assail them. 



As the silkworms grov/ in the fifth age, they are liable to three 

 evils, which attack them according to their strength, and to their dis- 

 tribution in the laboratory, and may weaken them so as to cause their 

 t^peedy destruction. These are, 1st. the great quantity of fluid dis- 

 engaged from the insects, their dung, leaves and litter. 2. The damp 

 hot atmosphere of the laboratory. These causes of disease, and the 

 means of preventing them, shall be treated of in the chapter on the 

 diseases of silkworm?. 



