Si8 
Journal of Agricultural Research 
Vol. V, No. 8 
bottle filled with pieces of pumice as large as will pass through the narrow 
neck. In this reservoir the water is mixed so that any change in the tem¬ 
perature of that entering the bottle, due, for instance, to fluctuations in 
the voltage of the current in the preheater, will be dissipated through 
the mass to such extent that there will be no rapid fluctuations in the 
temperature of the water leaving the bottle. From this reservoir the 
water enters the final heater which completes the heating necessary to 
bring the water to the desired temperature. This device functions 
automatically and varies the amount of heating it does to accord with 
the fluctuations in temperature of the water coming from the mixing 
bottle. From the final heater the water flows into a smaller mixing 
bottle, from which it passes to the heat absorber. 
WATER COOLER 
To cool it, the water from the pressure tank is passed through a coil 
of pipe submerged in cold water, in a tank nearly i meter in length by 30 
cm. in width and depth and containing 80 to 90 liters of water. The 
coil consists of nearly 6 meters of iron pipe, of 15 mm. bore, in six parallel 
rows running from end to end near the bottom of the tank. The water 
in the tank is chilled by cold brine flowing through a second coil, immersed 
in the water above the former coi^| A small ethyl-chlorid refrigerating 
machine keeps the temperature of the circulating brine quite uniform. 
In this manner the temperature of the water leaving the cooling coil is 
readily kept below that at which it may be needed at any time during an 
experiment, and fairly uniform, but it can not be regulated by cooling 
alone as closely as needed for use in the heat absorber. 
WATER HEATER ADJUSTED BY HAND 
The preheater consists of several coils of electric-resistance wire of 
different sizes wound upon a thin-walled brass tube about 16 mm. in 
diameter, from which they are insulated with mica. Outside of this is a 
similar tube about 26 mm. in diameter, and the annular space between 
the two and surrounding the resistance coils is filled with sand, so that 
the heat generated by the electric current in the resistance wire is trans¬ 
mitted rapidly to both tubes. This heater is mounted inside a brass 
tube 3 7 mm. in diameter, in such manner that the chilled water, entering 
the large brass tube, flows in one direction along the outside of the heater 
and returns along the inside, absorbing all the heat generated in it. By 
means of plug switches on the base supporting the heater various combi¬ 
nations of the coils may be put into service, as desired, to vary the 
heating. By the use of this device the temperature of water flowing at a 
rate of about 1 liter a minute may be increased nearly 10 degrees, if 
desired, in increments of about 0.25 of a degree. 
