( f)36 ) 



Besides being connected through the safety valve case and tlie 

 above mentioned connection, the compression tube and the exhaust 

 tube are also connected (comp. again the diagrammatic fig. 4, as an 

 explanation of figs. 1, 2, 3) by the cocks )\, )\, i\, i\ and may be 

 connected with an airpump /, an indicator i and a vacuummano- 

 meter in. The use made of this auxiliary apparatus in regular working 

 or in preparing, mounting, testing, drying and exhausting the pump, 

 requires no further explanation. As a matter of course, the pump 

 is not introduced into a circulation unless it has worked for a long 

 time with the exhaust- and compression sides closed and no change 

 has been found in the vacuum. 



I further remark that the principle of an oilconnection as illustrated 

 by fig. 5 may be profital)ly ai)plied wlien wide tubes have to be 

 connected, which have neither tlanges nor nuts and joints or in cases 

 where it is not advisable to make these contrivances. The method then 

 to be followed is illustrated by fig. 8 where K\, K\ and K\ are 

 loose pieces slid on the tubes h^ and/;,, ^vhicii we want to connect 

 A good fit is obtained by means of the India rubber rings K\i, 

 K',^, K\, K' ., K\, under brass tightening bands. K\^ and K\^ 

 serve to admit and lo run oul the oil. In this way one always suc- 

 ceeds in making Avithin a short time an airtight fit. For the connec- 

 tion of the pumj) tubes to llie conduit at f\ and /., (comp fig, 1) 

 this method has been used in a manner which will be clear from 

 the figure. 



Physics. — Connnunication n". 84 from the Physical Laboratory at 

 Leiden "Isothernu- of diatomic ynses and their Jnnanj mivtuves. 

 V. An accurate vohunenometer and mixiny apparatus" (By 

 H. Kamerlingh Onxes and H. H. F. Hyndman). 



§ 'J 9. ^1 conipression tube of laryer dimensiouö-. In § (5 of Conim. 

 n". 69 March 'Oi we have explained that the apparatus described in 

 ^ 3 and 4 hardly gave the accuracy required in the determinations of 

 density, if the total quantity of compressed gas was smaller than 

 5 cc. Since, however, at most 600 cc. of gas under normal condi- 

 tions is available in this apparatus it is not suitable for densities 

 of more than 120 times the normal. 



On PI. 1 a compression tul)e is shown a\ Inch has about three 

 liters capacity and hence which is suitable for measurements up to 

 densities of some 500 times the normal and with at least the same 

 accuracv as the above. The drawing is, as usual, schematic in 



