205 



A horizontal glass t-ibe n passes on tlio let'thand side into a 

 vertical tube c \ ia an emergency reservoir h. The tnbe c can be 

 fastened to the Gaedepnmp by nneans of a glass spring and a gronud 



Fiff. 12. 



joint piece. In the middle of the tube a is a three-way-cock A, 

 which gives access to a vertical tnbe d. A tnbe e is fnsed on to 

 d, the former being pro\ ided with a cathode and an anode, which 

 are connected with the secondary wire of a Rnhmkorff bobbin. The 

 primary wire is simply connected with the electric light behind an 

 incandescent lamp. The purpose of this tid)e will be mentioned 

 presently. Attached to d is a branch tnl)e ƒ, bent downward, which 

 may be considered as one of the limbs of a siphon barometer. Tlie 

 01 her leg ƒ/ of the barometer is fastened to the righthand part of 

 the tnbe a. In this there is another three- way-cock i> with a branch 

 tube Ji. To suck the mercury easily into the barometer tnbes, resp. 

 to expel it from them, a vertical tube with cock C is adjusted into 

 the transition from ƒ to //. On the t(d)es ƒ and g, Avhich are filled 

 halfway with mercury, millimeter ilivisions have been etched to a 

 height of 1 m. To make the mercury mirrors visible at a great 

 distance care has been taken that a lamp can be slid up and down 

 behind these tubes, a strip of ground glass between the lamp and 

 the tubes intercepting the heat and making the light more diffuse. 

 To the right of the place where the tube g opens into (t, the latter 

 is bent downward, and passes into a wider tube k. This tnbe is 



