The platinum heat carrier, sometimes at a temperature of
2,500 deg. to 2,800 deg. F., is thereby brought into more rapid and forcible
contact with the water, steam or water in the spherical condition is
washed away from its surface, and by cooling it more rapidly, the
duration of the observation is lessened, and errors due to transmission
of heat through the walls of the instrument are diminished. The upper
part of the agitator stem is of hard rubber, and the brass portion,
which terminates at the under side of the cover when the agitator is in
its lowest position, suspended by the shoulder at the upper end, need
never be lifted for the purpose of mixing out of the hard rubber tube at
the cover, so that loss of heat from this cause must be very slight.
The brass tube is very freely perforated with holes to admit water,
streaming radially through the holes in the agitator, to contact with
the thermometer. The hole in the stem at the top is flared, to receive
a cork, through which the thermometer is to be passed. The bulb of the
thermometer should be elongated, and very slightly smaller in diameter
than the stem. After passing it through the cork, a very slight band--a
mere thread--of elastic rubber should be put around the bulb, near its
lower end, or a thin, narrow shaving of cork may be wound around and
tied on, to keep it from contact with the brass tube, for safety; and a
little tuft of wool, curled hair, or hard rubber shavings should be
put in the bottom of the brass tube to avoid accidents.
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