20 Reynolds and Moorby, Equivalent of Heat. 



for a time the success of the research seemed doubtful. It 

 necessitated the reconsideration of the whole scheme of 

 working. This revealed to the author that it would be 

 possible to reverse the course of the lubricating water, 

 make it flow in at the bushes instead of out, and so not only 

 maintain lubrication, but also cool the bushes and shaft. 

 That this would be the result of forcing the water in at the 

 bushes was tolerably obvious, but what was not obvious 

 at first, was that there was already provision in the form 

 of excess of pressure in the inflow pipe, between the cooler 

 and the supply-regulating valve, to maintain this flow, by 

 merely admitting a portion of the cooled water into the 

 bushes by by-pipes with regulators, without passing it 

 into the thermometer chamber. This water being taken 

 from the inflow pipe before the rest passed into the 

 thermometer chamber would be nearer 32^^, but would be 

 warmed by the radiation into the by-pipe, so that it would 

 enter at a slightly uncertain temperature, but this would 

 be a radiation effect, and would be eliminated with the 

 other radiation effects. As soon as this became clear, the 

 success of the research became assured. The work was 

 executed by Mr. Foster, and, when complete, rendered it 

 possible to keep the bushes at any required temperature. 



In the preliminary trials this temperature was ascer- 

 tamed by touch, and regulated to that of the laboratory 

 as nearly as possible, the cocks being set to a definite 

 opening, and the excess of pressure maintained as nearly 

 constant as possible. This plan was found to give con- 

 sistent results. But it appeared that, in order to maintain 

 the same temperature in the stuffing-box with the heavy 

 as with the light trials, the pressures in the pipe being the 

 same, it was necessary to open the branch cock 

 wider in the heavy trials, on account of the greater 

 vortex pressure in these trials. In commencing the 

 final trials, the same setting of the cocks was maintained 



