Burstall's measurements for the Gas Engine Research Com-
mittee in 1895 gave the suction temperature as lying between
84° C. and 99° C, depending upon the compression ratio em-
ployed.
The results obtained by this method can only be regarded as
approximate, as the exhaust gas temperature within the cylinder
cannot be accurately inferred from measurements within the
exhaust pipe, although in modem gas engines where the com-
pression pressures are high and the combustion chamber volume
small the error introduced by wrong estimation of the exhaust
temperature is email.
This more or less unsatisfactory method has led to attempts at
direct measurement of the temperature, the earhest being made
by BurstaU,* with the engine running upon weak charges under
light load and at low speeds, since the temperature attained
during explosion, under normal conditions of running, melted the
platinum wire of his electrical thermometers. He was able to obtain
a few temperature values under the above-mentioned conditions,
from which he concluded that the highest explosion temperature
was at least 1,250° C. In some later experiments made for the
Gas Engine Research Committee, temperatures as high as 1,570° C.
were observed.
The suction and compression stroke temperatures have been
measured accurately by Profs. Callendar and Dalby f by means
of the platinum resistance thermometer, by the " jack-in-the-box "
method.
This method consisted in introduciag a fine platinum loop of
To OS inch diameter (to take up the temperature quickly) into the
cylinder by an arrangement shown diagrammaticaUy in Fig. 89.
