478 



to introduce tliis complicalioii and we have therefore preferred to 

 cali'ulate the corrections for air. 



For this purpose Amagat's') isotherinals are available which have 

 been represented in different ways by equations by Brinkman') and 

 by Kamkrungh Onnks'): from these equations tables of correction 

 were drawn up. The corrections calculated by the two methods 

 a(>,ree lo 0.5 mm. even at 100 atmospheres. As will appear further 

 down the results prove, that in this manner the correction is ap- 

 proximated with sufficient accuracy. 



The correction for the compression of the mercury renuiins small, 

 it is true, even at 100 atmospheres, but sliU comes into account. 

 For this correction we have also calculated a table, based on the 

 compressibility of 0.00000392 according to Amagat. 



There was no need for a connection for the flow of the mercury 

 through the tubes, fully discussed l)y Schalkwijk, as the mercury 

 did not move al all. Thanks to the steel connecting tubes being 

 soldered to the glass tubes, to the fibre-washei's and to all the 

 couplings being immersed in oil'; we succeeded in obtaining the 

 open manometer completely free of leakages even at 100 atmospheres, 

 while at the same time the room-lempei'aiure was kept constant so 

 successfully (owing to steam-heating, improved illumination iiy metal- 

 wire lamps, which give very little heat etc.) that even with the 

 very lengthy readings at the higher pressures there was hardly any 

 sign of flow in the tubes. 



The corrections for capillary depression have not been applied. 

 A discussion showed, that the algebraic sum of these corrections 

 would have no influence on the accuracy aimed at, especially if 

 by tapping the tubes care was taken to obtain well-shaped convex 

 menisci*). As a matter of fact the correction would have been very 

 difficult, seeing that with the illumimxtion used the height of the 

 menisci could not be determined with the telescopes which served 

 for reading the mercury-surfaces. 



The further corrections do not require any special mention. The 

 method of reducing the indications of the manometers J/^, and J/,,» 

 do not call for any remarks either. As regards the load on the 



1) E. H. Amagat, Ann de cliim. et de phys. (6) 29, Juni and Augustus 1S93. 



2) G. H. UrIiNKMan, Dissertatiün. Amsteidam, 1!I04. 



3) Zie J. P. Dalton, These Proceedings 11, p. 87 i, 1P09 § 2 Gomm N'\ lOQc 

 ■*) The oil-vessels in question are not shown in the somewhat diagrammatic 



figure. For some of the improvements mentioned here compare H. Kameelingh 

 Onnes, These Proceedings 8, p. 75, 1905, Gomm. N". 946. 



S) Here again the results prove the reasoning to have been correct. 



