[ 175 ] 130 



When the liygioineter indicates a very damp state of the atmos- 

 phere, wood shavings or stravir should be burnt in the fire-places, to 

 absorb the humidity, and replace it by the external air which is dried 

 by this same blaze. Blaze is preferable to mere fire, for two reasons; 

 the first is, that, for instance, with two pounds of shavings, or of dry 

 straw, there can be attracted, from all points, towards the chimney, a 

 large body of air, which issues at the flue of the chimney. While, in 

 the meantime, this air is replaced by another quantity of exterior air, 

 which spreads over the wicker hurdles, and revives the exhausted silk- 

 worms. This change of air may take place without effecting any ma- 

 terial variation in the degree of heat in the laboratory. If, on the 

 contrary, thick wood were employed, it would require more time to 

 move the interior air; ten times more fuel might be consumed, and 

 Ihe laboratory would be too much heated. The motion of air, all cir- 

 cumstances being equal, is in proportion to the quantity of blaze of 

 the substances that burn quickly. When wood shavings or dry straw 

 cannot be procured, small sticks of dry and light wood may answer. 

 As soon as the flame rises, the hygrometer shows that the air has be- 

 come drier, and the degrees of it can be seen distinctly. 



The second motive which should lead us to prefer the blaze, is the 

 light it diffuses. It cannot well be imagined how beneficial this light 

 is, which penetrates every where, nor how much it influences the health 

 und growth of the silkworms. 



IV. Diseases from want of room. 



When silkworms lie so thick on the wickers, or feeding frames, that 

 ihey cannot feed with ease, a difference in their development will re- 

 sult, and large healthy worms will be found mixed with small and sick- 

 ly worms. This mixture affects the periods of their transition; some 

 will be lively, some torpid, and others still requiring food previously" 

 to their transition: this confusion kills great numbers, or causes them 

 to drag on a sickly existence. 



Silkworms, as stated in their anatomical description, do not breathe 

 by the mouth, but by small apertures, which are placed near their 

 legs, and called stigmata, or spiracles. These breathing holes are al- 

 most all stopped when the worms are heaped together; hence their 

 breathing becomes difficult, their transpiration ceases, and sickness 

 takes place.'-' 



V. Diseases from the quality or quantity of food, 



Rem.'irks and cautions on this head, will be found in the course of 

 instructions for rearing the silkworm; but it is proper to notice the^ 

 mode in Avhich the food affects them. 



• Several IhousanJ worms were killed in one case last summer, from the above 

 cause, near Philadelphia. See the account of the disease called tripes. 



