222 THE CULTURE 



property of the air, that when pureft, it 

 is always moil heavy; and when mixed 

 with vapour, either putrid, aromatick, or 

 watery, or indeed with almoft any thing 

 that afFe6ls the fenfe of fmelling, it is 

 lightefl. a 



Now, in any room where filkworms are 

 fed, if an aperture, about nine inches fquare, 

 be made in that angle of the cieling which 

 is farthefb from the door, and this aper- 

 ture continued by a funnel of board, till 

 it communicates with the open air, then 

 will the putrid vapours, occafioned by the 

 litter and the multitude of worms, con- 

 ftantly afcend thro' this funnel, and the 

 pure hea\7 air will fucceed by the door in its 

 place ; or rather, if an aperture is made 

 towards the bottom of the door, of the 

 fame fize with that in the cieling, with a 

 fmall fhutter to open and clofe as occafion 

 requires ; then will the frefli heavy air 

 come into the room with greater advan- 

 tage, by railing up, and carrying of the 

 foul air which is above it : or if two of 

 thefe apertures are made in the oppofite 

 walls of a room, near to the floor, and 

 opening into the air abroad, they will have 

 this convenience that you can take the ad- 

 vantage 



