CAPTAIN NOBLE AND ME. E. A. ABEL ON EIEED GUNPOWDER 
63 
3. Measurement of the Volume of the Permanent Gases. 
The apparatus used for the measurement of the permanent gases is shown in Plate 
15. figs. 1 & 2. A is a vessel the annular space (B) of which is filled with water ; on 
the surface of this a thin film of oil is floated, to prevent any slight absorption of the 
gas which might otherwise take place. 
Immediately after the explosion of a charge, the gas from which it is desired to 
measure, the cylinder (C) containing the products is placed on the table (D), and the 
gasometer (E) is placed over the cylinder ; the height of the water on the glass scale (F) 
being then registered, the escape-screw (G) of the cylinder is turned, by means of a 
turncock passing through the stuffing-box (M). 
When the gas has all escaped, the height indicated on the glass scale being again 
registered, the cubic contents are known, and the thermometer (H) and height of 
barometer being noted, the necessary data are available for reducing the volume of 
the gas to a temperature of 0°C. and a barometric pressure of 760 millims. 
4. Measurement of Heat. 
To determine the heat generated by explosion, a charge of powder was weighed and 
placed in one of the smaller cylinders described, which was kept for some hours in a 
room of very uniform temperature. When the apparatus was throughout of the same 
temperature, the thermometer was read, the cylinder closed, and the charge exploded. 
Immediately after explosion the cylinder was placed in a calorimeter containing a 
given weight of water at a measured temperature, the vessel being carefully protected 
from radiation, and its calorific value in water having been previously determined. 
The uniform transmission of heat through the entire volume of water was maintained 
by agitation of the liquid, and the thermometer was read every five minutes until the 
maximum was reached. The observations were then continued for an equal time to 
determine the loss of heat in the calorimeter due to radiation, &c. ; the amount so 
determined was added to the maximum temperature. 
In this method there is a possible source of error ; the walls of the cylinder being of 
very considerable thickness, it is obvious that, although the outer surface of the cylinder 
must be of the same temperature as the water, it by no means follows that this is true 
of the internal surface ; consequently the loss of heat due to radiation, &c. may be in 
some degree compensated by a flow of heat from the interior. 
We had reason, from some experiments we made, to believe that the error due to this 
cause was very small ; and our views were confirmed by finding no appreciable rise of 
temperature on placing some water from the calorimeter into the chamber of the 
cylinder immediately after an experiment. 
5. Collection of Gaseous Products. 
To collect the gases for analysis, a small pipe was screwed into the escape-passage (H^ 
of the cylinder (Plate 14. figs. 2..&.3), and an india-rubber tube, terminating in a glass 
