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THE ART OF REARING 
half of these hurdles may thus he fed and at- 
tended to, while those on the other side may be 
reached by means of portable steps. 
There are only two passages down this labo- 
ratory, because I do not reckon the narrow sepa- 
ration between the hurdles of only the width of 
the posts. 
There are four ventilators in the ceiling, above 
the passages, that the exterior air may not strike 
directly on the hurdles. There are eight venti- 
lators on a level with the floor, placed at regular 
distances, four fire-places in the four angles, a 
stove in the middle of the laboratory, the pipes of 
which may be carried along the walls, and another 
in the centre of the end wall facing the door. 
There are two barometers and four thermo- 
meters. In the night it is lighted by two Argand 
lamps that yield as little smoke as possible. 
This laboratory, like the large one, is detached 
on three sides : there are four large windows r 
without blinds or shutters, because the whole 
change of air is made perpendicularly from top 
to bottom, and bottom to top. It is not neces- 
sary there should be ventilators in the floor corre- 
sponding to those in the ceiling. However calm 
the air may be, it may have as much motion as is 
desired imparted to it, by burning blazes in the 
fire-places, and opening the ventilators. 
I have also small laboratories, that only contain 
