SILK-WORMS. 
295 
When fires are not needed, nor the chimneys 
wanted as ventilators, they may be closed with 
chimney-boards . 
By the sliding panels on the ventilators that 
are under the windows, should there be too much 
draught, they may be closed, so as to regulate 
the air as it is required. The same is applicable 
to the high ventilators, with this advantage, that 
as they can have a glazed -window panel, they 
may be closed and yet give light. Both may be 
opened occasionally. 
The stove is only used when the air of the 
laboratory wants warming, and the temperature 
raising. 
In which case, when the stove warms the la- 
boratory, a column of external air enters con- 
tinually into a portion of the body of the stove, 
which is separated from that part in which the 
fire burns, and from that through which the 
smoke issues ; in this receptacle, when the 
air is heated, it escapes, through holes per- 
forated on purpose, into the laboratory, and 
augments both the quantity of heat and fresh 
air. 
In different parts of the laboratory I have 
placed four barometers, six thermometers, and 
two tliermometro graphs, to shew what is to be 
done in case of any accumulation of moisture, 
