NEW FORM OF BOMB CALORIMETER. rai, 
The cross bar at the top of the stirrer, shown in figure 2, has in 
the center a small ring. To this is attached a cord which con- 
nects with a wheel above. By the slow revolution of the latter 
the stirrer is raised and then allowed to fall by its own weight. 
The wheel is moved by a motor at nearly uniform rate so 
that the amount of motion of the stirrer in a given time is 
always nearly the same. The cross bar is held to the upright 
rods by nuts and is easily removed when the covers of N and O 
are taken off and put on. 
The temperature of the water is measured by the thermometer 
P. We have several thermometers for this purpose. All are 
graduated to hundredths of a degree. One, which we employ 
as a standard thermometer for correcting the others and which is 
also very convenient for regular use, was made by Fuess and 
calibrated by the Physikalischtechnische Reichsanstalt in Berlin. 
The scale, which is 25 centimeters long, covers six degrees 
marked from o to 6. Each degree is divided into hundredths, 
and the divisions are of such length as to permit of easy estimates 
of thousandths by the aid of a magnifying glass. We are per- 
suaded that, in this way, measurement of the temperature of the 
water to thousandths of a degree can be made with as close an 
approach to accuracy as the weighings to the tenths of a milli- 
gram with an ordinary laboratory balance. This especial ther- 
mometer.is provided with a Boeckmann reservoir at the top into 
which a part of the mercury can be driven at will. The readings, 
therefore, as marked from o to 6 on the thermometer, may indi- 
cate actual temperatures from the freezing to the boiling point 
of water according as little or much mercury is driven into the 
reservoir. The thermometer'is calibrated for measurements at 
any of these temperatures. The cost of the thermometer in 
Berlin was 37.50 marks, the charge for calibrating was 21 marks, 
making total cost in Berlin about $17. We have found it very 
satisfactory. 
The accessory apparatus consists of a screw press of the kind 
used by Hempel* for compressing the substance to be burned 
into a firm cylindrical cake, vise, vise-grip, lever for screwing the 
cap, a cylinder of compressed oxygen with tubes and manometer 
for filling the bomb, an electrical apparatus to furnish a cur- 
rent for igniting the substance (we connect directly with an 
electric lighting circuit, using a resistance coil to reduce the 

* Gas Analysis, page 356. 
