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. For the same
purpose, a light, but sufficient fender of brass wire, say 0.03 inch
diameter, might be judiciously placed around the brass tube at a little
distance, to protect it and the thermometer inside of it from shocks
from the platinum ball when hastily thrown in, as it must always be.
I have had delicate and costly thermometers broken for want of such a
fender. Thermometers cannot be too nice for this work. For accurate work
at moderate temperatures, they should be about 14 inches long, having a
"safe" bulb at the upper end, with a range of 20 deg. F.--32 deg. to 52 deg.--in a
length of 10 inches, giving half an inch to a degree F., and carefully
graduated to tenths of a degree, so that they can be read to hundredths,
corresponding to single degrees of the heat-carrier in the normal use of
the instrument.

For the determination of the highest temperatures, up closely to 2,900 deg.
F., it will be convenient to have thermometers of greater range, say 32 deg.
to 82 deg. F., 50 deg. in a length of 12.5 inches, or a quarter of an inch to
a degree F., also graduated to tenths, or at the least, to fifths of a