98 PROCEEDINGS OF THE AMERICAN ACADEMY 



the reception of vapor, leading it in at one end and suitably with- 

 drawing it at the other. Low temperatures are obtained by a jacket 

 of circulating water. 



10. Method of Filling. — When the screw is in good adjustment, 

 fresh supplies of oil are not frequently necessary. The method of 

 filling is indicated in Figure 4. The steel rod 00, threaded and 

 tinned at one end, and provided with a strong cross handle at the 

 other, is enveloped by a brass tube, P, surmounted by a funnel-shaj)ed 

 inlet, Q. Both Q and P are kept full of oil, and there is an ordinary 

 stuffing box at pp. A spring clamp (not shown), keeps the end of P 

 pressed against the side of the barrel BB, a suitable leather washer 

 being interposed. To fill the barrel, take off the pressure and screw 

 out 00, without removing it from P. The oil will then follow the 

 retreating screw ST. One of the screws il/may finally be removed, 

 until the oil exudes ; for it is clearly advisable to expel air, which 

 must be considerably reduced in volume before it will sustain high 

 pressure. 



Ordinary sperm oil or machine oil of a thickish quality is available 

 for filling the barrel. It has an advantage over water in protecting 

 the screw against rust, and perhaps in keeping the moving parts oiled. 

 Mercury is not available, since it would dissolve the tin coatings on 

 the bolts. 



11. Case for Protection. — Working as far as 2,000 atmospheres 

 explosions are not infrequent. They occur with slight detonation, 

 scattering thin mists of oil ; but there has been nothing of a serious 

 nature. It is well to surround the barrel with a case of two-inch 

 plank, and to provide a barricade beyond the end of the piezometer 

 tube. A suitable tin pan placed underneath the bedplate of the 

 screw is of use in catching oil. After filtering, it may be used over 

 again. 



The whole apparatus usually works better after some use than 

 immediately after packing. Indeed, it often happens that a ten- 

 dency to leak shown at 500 atmospheres quite disappears at 2,000 

 atmospheres, for the packing is compressed and solidified, and the 

 moving parts oiled. 



1 2. Vertical Piezometer. — An adjustment similar to CC UU, but 

 smaller in dimensions and ending below in a finely perforated screw, 

 may be attached at M. The piezometer is thus fixed in vertical posi- 

 tion, and is easily adjusted or withdrawn, while the end of the barrel 

 is available for other purposes. § 23. 



