43G 
MR, E. H. GRIFFITHS ON THE VALUE OF 
about twenty-six revolutions per second, it was found that when the lid was removed, 
the water was thrown many inches above the top of the cylinder, while the stirring- 
shaft remained dry. A small window at E caused a stream of water to be continuaDv 
thrown on to the top of the thermometer bulb. 
The bearings at the top of this shaft ultimately assumed the form shown at H. A 
small block of steel was fastened by a screw to the shaft, and the lower end of this 
steel terminated in a projecting ring, which revolved in a brass bearing of the form 
shown at H. This brass bearing was, as already mentioned, fixed to the top of the 
central glass tube. A drop of oil placed in the channel, on the top of the brass, 
rendered this bearing practically air-tight, at all events, sufficiently so to prevent 
any possibility of evaporation.* The shaft from TI to the top of the calorimeter was 
about 8 inches long, and made of ebonite; the conduction of heat along this shaft 
was, therefore, very small. The heat generated in the bearing at H passed almost 
entirely into the water of the outer tank, for the brass tube which terminated there 
was continued downwards to the steel lid, and thus the lower three inches were 
immersed in the water. 
The portion at D was at first shaped like a horizontal paddle-wheel. It was, how¬ 
ever, found that although it would work excellently for a time, a gradual accumu¬ 
lation of air at the centre of the paddle-wheel greatly diminished its efficiency. 
Many attempts were made to surmount this difficulty, and it was only by the con¬ 
version of the upper portion into the form of an inverted cone that it wms finally 
overcome. 
To adjust the stirrer, the screw in S was loosened and the shaft lowmred until the 
end of the agate touched the base of the calorimeter. The stirrer was then raised 
about 1 millim., and fixed in that position by means of the screw at S. When 
investigating the action of these stirrers, the lid of the calorimeter was replaced by a 
sheet of glass which prevented the contents from being ejected. As far as it was 
possible to see the interior through the shower of water that poured against the glass, 
the water without the cylinder assumed a slow circular movement only. At the same 
time, there can be but little doubt that the entire contents passed from the bottom to 
the top within the space of a second or two. As long as the volume of the contained 
water exceeded 130 cub. centims., the throw appeared to be the same, whatever the 
quantity, and, as the figures will show, the work done altered only slightly. 
Our first series of experiments was performed with the object of ascertaining (l) If, 
under the same conditions, the work done by the stirrer was constant; (2) In what 
respect the work done varied, if at all, with the mass of water; (3) If there was any 
constant relation between the heat developed and the rate of revolution. 
The results of our preliminary series are given in the following table, the rise in 
temperature being expressed in millimeters of thermometer E,,,, since our object at 
this time was not to determine the actual quantity of heat developed, but to investi¬ 
gate the points mentioned in the above headings. 
* It was found tliat this “ join ” would support a pressure of 7 or S inches of water without leakage. 
