( 215 ) 



Another defect of the Reichsanstalt-apparatus is that both tlie 

 weaker and the gi'eater pressures are indiscriminately measured in 

 tubes of such a size of bore as is required to resist the greatest pressure 

 that those pressures whether great or small are deduced from the and 

 equilibrium of one and the same number of columns of liquid of 

 the same length, and adjustments on one and the same number of 

 mercurv-menisci. And so in the case of low pressures the uncertainty 

 resultirg from the correction for capillary depressions and for the 

 temperature and the reading error are unnecessarily great. For the 

 purpose mentioned in the beginning, this apparatus which for the 

 rest serves to test metal-manometers is of no value. 



When I reflected for the first time upon the problem how to 

 measure regularly with an absolute manometer pressures, even greater 

 than those determined by Regxault on the tower of the College 

 de France, at the Leiden laboratory where I could not dispose of 

 a great height, the shoi'tened manometers mentioned above were 

 unknown to me. I have considered the transference of pressure by 

 means of a liquid which allowed of contact with steel and mercury, 

 yet after all I did not make use of this means. At first sight it 

 seems that tlie division of the manometer into separate manometers, 

 in which the pressure is transferred from the one to the other by 

 means of compressed gas offers more difficulties than the transference 

 of the pressure by water so simple in its principle. Yet it seemed 

 to me that these difficulties, at least there where the experimentalists 

 are accustomed to work with gases under high pressure, could be 

 easily surmounted. Especially the ordinary steel bottles filled with 

 gas under high-pressure may bo utilized to bring the required tension 

 into the space between the two succeeding columns of mercury, by ad- 

 mitting gas into the counecting-tube of the manometers and this with 

 great accuracy with the aid of finely-regulating high pressure-cocks. 



By adhering to this idea I have already succeeded so far that in 

 a room of the laboratory pressures to 60 atmospheres can be deter- 

 mined by one direct measurement with an apparatus constructed 

 according to this principle and consisting of 15 partial manometers 

 connected together. Seven of the partial manometers connected 

 together may be used as a differential manometer of 28 atmospheres 

 under a pressure of 100 atmospheres, so that after having deter- 

 mined at once directly the pressure of 60 atm. one can, with this 

 pressure as a basis by means of a second determination with a 

 column of mercury of 28 atm. attain a pressure of 88 atm. and 

 again proceeding from this pressure attain 100 atm. by means of a third 

 determination. This apparatus (represented in fig. 1) is constructed 



15 



Prooeediu's Rovjtl Acad. Amsterdam. Vul. 1. 



