y of the
Horticultural Gardens, the heat from the five hundred guests, and from
an almost equal number of waiters and attendants, displaced the cold air
from the dome of the roof, and literally poured down on the assembly
(who were in evening dress) in a manner to compel many of them to put on
overcoats. If the Conservatory had been lighted with gas suspended below
the roof, this would not have been the case, because sufficient steam
would have been generated to stop these cold douches, and keep them up
in the roof. In fact, if electric lights are to be used in such a
building, it will be necessary to lay hot-water pipes in the roof, to
keep warm the upper as well as the lower stratum of air, and thus steady
the currents.

Having pointed out difficulties which arise under certain conditions of
the atmosphere in rooms built with care, to make them comfortable when
electric lighting is substituted for gas, I will lay before you some few
particulars relative to the condition of small rooms of about 12 ft. by
15 ft. by 10 ft., or any ordinary room such as may be found in the usual
run of houses in this country. The cubical contents of such a room
equals 1,700 cubic feet. If the room is heated by means of a coal fire,
we shall for the greatest part of the year have a quantity of air taken
out of it at about 2 feet from the floor by the chimney draught, varying
(according to atmospheric conditions and the state of the fire) from 600
to 2,000 or more cubic feet. This quantity of air must, therefore, be
admitted by some means or other into the room, or the chimney will, in
ordinary parlance, "smoke;" that is, the products of combustion, very
largely diluted with fresh air, will not all find their way up the flue
with sufficient velocity to overcome the pressure of the heavy cold air
at the top of the chimney. If no proper inlets for air are made, this
supply to the fire must be kept up from the crevices of the doors and
windows. In the line of these currents of cold air, or "draughts" as
they are usually called, it is impossible to experience any
comfort--quite the contrary; and colds, rheumatism, and many other
serious maladies are brought on through this abundant supply of fresh
air in the wrong way and place.

According to General Morin (one of the best authorities on ventilation),
300 cubic feet of air per hour are required for every adult person in
ordinary living rooms. Peclet says 250 cubic feet are sufficient; less
th