382 Mr. E. B. H. Wade. On a new Method of 



of the drum at v. If the three-way taps t x t 2 (Plate 1, not seen 

 Plate 2) are closed, any liquid in the G-tubes " finds its own level " 

 on the burettes, and then by means of the same three-way taps the 

 level in question maybe adjusted to any desired mark on the burette. 



If a current of steam from the boiler is now caused to pass 

 through the G-tubes, the liquid is dragged out of the burette into 

 the G-tubes.* The current of steam used in practice was never 

 sufficiently rapid to empty the burettes. Suppose, now, that conden- 

 sation proceeds more rapidly in one G-tube than in the other. 

 Owing to the increased hydrostatic pressures, the velocity of steam 

 on that side automatically diminishes, and in consequence some liquid 

 slips out of the G-tube and back into the burette, till the former 

 velocity is reproduced. It is not claimed that this device entirely 

 equalized the levels of the liquids, but it certainly tended in a very 

 marked way to do so. This is best demonstrated by closing the 

 burette taps. On doing this the readings become unsteady at once. 



One more appliance has to be described affecting the adjustment 

 of the pressure in the drum. It was necessary that any fluctuations 

 in pressure (not necessarily the result of leaks) should at once be 

 detected and smoothed down. Neither mercurial thermometers nor 

 manometers are sufficiently rapid in their indications for this purpose, 

 and manometers consisting entirely of light liquids are very cum- 

 brous. The following combination proved to be what was wanted 

 (Plate 1). The bottle M is more than half full of mercury, the 

 remainder being occupied by water coloured red by fuchsin. A 

 rubber cork, having two holes, fills the mouth of the bottle, leaving 

 no air-space between itself and the surface of the red water. The tall 

 tube T passes through one hole of the cork and below the level of 

 the mercury. T is connected by a rubber tube to the Woulfe's bottle 

 V, so that when the latter is exhausted the mercury rises in T. 



Through the other hole in the cork passes a capillary tube whose 

 lower end terminates in the coloured liquid without reaching down 

 so far as the surface of the mercury. The upper end of this capil- 

 lary tube is open to the air. About midway up it communicates 

 through a side tube with the funnel F, which is also open to the air. 

 The coloured liquid in the bottle M extends up the capillary tube 

 and half way up F. The usefulness of the apparatus turns on the 

 fact that if t 7 is open any fall in pressure in the Woulfe's bottle will 

 show itself mainly by a small rise of the mercury surface in T, but if 

 t-i is closed, by a fall, about tenfold greater, of the light liquid in the 

 capillary. This is due to the fact that the cross-section of T is great 

 compared to that of the capillary. The apparatus can therefore be 



* Compare the action of Giffard's injector. It should be added that, when in 

 use, the whole system, p, q, r, s } was packed with canvas, except near the meniscus 

 in s. 



