BETWEEN THE FREEZING AND BOILING-POINTS, 
209 
connection between the wire and mercury column, and was supplied by either one or 
two accumulators. This form of regulator works exceedingly well, and is much to 
be recommended. 
The electric heating lamp lias practically no lag, so that the effect known as 
“ hunting ” was not apparent. The bulb of the regulator was long and narrow, and 
extended the whole height of the water in the tank. For high temperatures, lamp B 
could not supply enough heat to make up for the loss from the circulating system to 
the surrounding air, so that an auxiliary gas flame was necessary, which was placed 
under the centrifugal pump, and was supplied by a large constant-pressure gas 
regulator situated in the basement of the building. The final amount of heat 
necessary to keep the apparatus at the temperatures of the experiment required, 
was supplied by the lamp B, which thus acted as a fine adjustment over and above 
the heat supplied by the gas flame. For very high points it was necessary to main¬ 
tain a second gas flame under the large copper tank, which was arranged on three 
brick supports for this purpose. 
Fig. 12. 
The water-motor which operated the pump in the circulating system ran at a very 
constant speed, on account of the very steady pressure of the water in the high- 
pressure mains. This aided very much in ensuring perfect regulation. Several 
stirrers in the apparatus were also operated by the water-motor from a pulley 
directly connected to it. One of the stirrers was placed in the tank and shown 
connected with the pulley C, in fig. 11. This helped to keep the water throughout 
the tank thoroughly mixed. It was connected to the pulley of the water-motor 
by a leather strap. Another cord was taken to the stirrer in the standardized 
resistance oil-bath, and a third to the stirrer in the cooler in the outflow end of the 
calorimeter shown in fig. 13. A general idea may be obtained of the arrangement 
of the apparatus by reference to fig. 13. 
The accompanying photographs are added to give some idea of the appearance 
and arrangement of the apparatus. Fig. 14 is a side view, and fig. 15, a bird’s-eye 
VOL. CXCIX.-A. 2 E 
