459 



h'gli-pressiire tubes with the boards to which they are attached were 

 fitted to a wall of the working room, which also contains the 

 standard-gauge of 60 atmospheres, in the same manner as tlie tubes 

 of the latter. Originally it was intended (comp. Comm. 106) to fit 

 np tiiis wall with similar auxiliary appa.ratus as belong (o the 

 manometer-tubes of the 60 atmospheres-gauge, such as: pressure- 

 connections to join the different manometer-tubes in series and to 

 bring np the pressure, measuring rods snspended in cardanic I'iiigs 

 beside the manometer-tubes used for measuring the height of the 

 mercury columns, etc. It was further the intenlion to set up telescopes 

 with which to take the readings on the new tubes in the same 

 manner as with the standard-gauge of 60 atmospheres and finally 

 to connect together all the tubes to one gauge of 120 atmospheres. 



Want of room in the laboratory, however, jirevented the execution 

 of this plan ; it would have been necessary to reserve the working- 

 room completely for the gauges, which it was impossible to do. 

 For this reason it was resolved in (he measuiements above 60 

 atmospheres to proceed by an indirect method. 



For measurements in the pressure-range in cpiestion a standard- 

 differential-manometer was constructed consisting of as many tubes 

 for pressures above 60 atmospheres as would be necessary to 

 supplement a pressure of about 60 atmospheres to the highest 

 pressure to be measured. To obtain this differential gauge use is 

 made of the same auxiliary apparatus, as serves for the measurements 

 below 60 atmospheres, pressure-connections, taps, measuring-rods, 

 telescopes, etc. but the tubes used for measuring pressures below 

 60 atmospheres are replaced by the desired number of high pressure 

 tubes, which are mounted in the place of the former. The high- 

 pressure tubes are joined to the system of pressure-connections and 

 connected up in series in the same manner as with the divided 

 open gauge and the pressures are regulated in such a manner, that 

 in the upper space of the first tube of the series the pressure is 

 about 60 atmospheres, and that the mercury-surface in the lower 

 space of the last tube is subjected to the pressure to be measured. 

 The pressure of about 60 atmospheres in the upper space of (he 

 first tube of the series is measured with a subsidiary manometer, 

 which only serves as a pressure-indicator, (he readings of which 

 give the pressure in absolute measure by a calibration with the 

 open standard gauge of 60 atmospheres. 



If a pressure-indicator is available of sufficient accuracy for 

 pressures of about 60 atmospheres, this method has the advantage, 

 that the number of mercury-surfaces which have to be read becomes 



30 

 Proceedings Royal Acad. Amsterdam. Vol. XVlll. 



