ON THE MECHANICAL EQUIVALENT OF HEAT. 325 
^Yas more than sufficient to maintain the pressure, so that it was continually allowed 
to escape. 
The Stufjinrj-hox and Cap to prevent Leahage. 
24. The thing that was revealed by the experiments at high temperatures was that 
the leakage of water at the coned bushes of the brake was so much increased by the 
pressure within the brake that even when these bushes were adjusted to run, as close 
as was practicable, on the cones of the shaft, this leakage was very considerable, so 
that some other method of controlling this escape became necessary. 
This matter threatened to present great difficulties. It was apparently impossible 
to close in the bushes with stuffing-boxes and stop the leakage altogether, as that 
would prevent the lubrication of the shaft, and, apart from this, would cause the 
temperature on the shaft side of the brake to rise to the temperature of the brake, 
212° Fahr., wdrich would cause a large escape of heat along the shaft. Besides this, 
the adaptation of stuffing-boxes to the existing brake presented such difficulties that 
it almost seemed as though it would be necessary to have a new brake, which, besides 
the delay, would entail an addition of some T200 to tlie expenses, which wmre other¬ 
wise very considerable. 
Fig. 9. 
To avoid this I determined to try a stuffing-box on the shaft side, constructed in 
halves to be bolted together on the shaft, and then sweated into one, this stuffing-box 
to screw on to the exposed screw of the bush, and make a joint against the lock ring ; 
then to open a passage through the box inside the packing-ring, with a tap to control 
the escape of water, and o,t the other end to screw a cap on to the bush, entirely 
inclosing the end of the shaft, with an aperture and a tap to regulate the water, also 
