Manchester Memou^s, Vol. xlii. (1898), No. 6. 19 



the tower, to drive a i^'in. quintuple centrifugal pump in 

 the circuit of the water between the service tank and the 

 cooler, and in this way the requisite steady head was 

 obtained. 



These preliminary investigations and the construction 

 of the appliances, so far described, were not completed till 

 May, 1895. It then became possible to make experi- 

 ments as to the working of the brake under pressure and 

 at high temperatures, so as to obtain guidance as to the 

 artificial atmosphere and means of controlling leakage at 

 the bushes. These showed that the artificial atmosphere 

 would be a simple matter. A strong vessel, made of tin 

 plate, with a capacity of three gallons, was connected with 

 the air passage on the top of the brake by a flexible tube. 

 The vessel had two openings at the top besides that con- 

 nected with the brake — one with a cock, to admit of air 

 being forced in ; the other with a fine screw stop, to allow 

 of a definite escape of air. There was also a cock at the 

 bottom, to drain water which might accidentally get 

 in. A syringe was used for pumping in air at starting, 

 while, during the trials, the small amount of air released 

 from the water was more than sufficient to maintain the 

 pressure. 



On the other hand, these experiments showed that the 

 increased leakage at the bushes was a very serious matter, 

 and must be controlled. 



The first step was to enclose the open end of the shaft 

 byl^a cap screwed on to the bush, and the side on which 

 the shaft was continuous by a stuffing-box, having small 

 apertures controlled by cocks to regulate the outflow of 

 water for lubrication. {^Fig. 5.) The result was, however, 

 far from satisfactory, as the lubricating water flowing out 

 from'the brake not only raised the shaft to a high tem- 

 perature, but was itself of uncertain temperature. It 

 was in July, 1895, that this experience was obtained, and 



