202 



NATURE 



\yune 26, 1879 



at times, with a large current, carmine, as in the capillary 

 part of a spectrum-analysis hydrogen-tube, the strata in 

 the large tube being much fainter and pink. The appear- 

 ance when the point was positive is shown in the diagram, 

 Fig. 17, 62(J, and when negative in 62^, copied from photo- 

 graphs obtained, the former in 15 seconds, the latter in 10 

 seconds. Another example is shown in Fig. 12 in the Plate. 



Tube 160, Hydrogen. — This tube was constructed with 

 the object of sending the analogue of a smoke ring 

 through a tube in which a steady stratification had been 

 procured and sustained ; Fig. 18 shows the arrangement. 



The tube is 40 inches long and i'875 inch in diameter, 

 and has a stop cock at each end ; near one of the ends is 

 a small tube, 075 inch in diameter, sealed to the main 



TUBE 160 



« m m {\\ mm\ mm 





Fig. 18. 



tube at right angles, and fitted with a glass stopper, in 

 which two stout platinum wires, o"043 inch diameter, are 

 melted ; there is soldered, with gold, to the two platinum 

 wires a spiral of palladium made of wire 12 inches long 

 and o'oi25 inch diameter, 'Pd, in the diagram. The 

 palladium coil was charged to saturation with hydrogen, 

 by immersing it in dilute sulphuric acid and making it 

 the negative pole of a bichromate battery of six elements ; 



4,800 cells without external resistance : — 

 Pressure 0*9965 mm., before the discharge of the condenser, 

 „ l'038i „ after ,, „ 



Fig. 19- 



after it had been washed in distilled water it was dried 

 and inserted in the tube. The two stout wires of platinum, 

 to which the palladium coil is attached, are connected to 

 a condenser of 10-9 m.f., charged with 3,240 cells. One 

 of the wires leads to the key K', so that no current can 

 pass from the condenser until this key is pressed down ; 

 when this is done the charge passes, and by suddenly 

 uniting the wire drives off the hydrogen. 



Difference o'04i6 ,, SSM, 



strata were produced from the positive up to the palla- 

 dium coil which was on the negative side. On liberat- 

 ing hydrogen by the discharge of the condenser these 

 were driven back 14 inches 

 towards the positive, and sub- 

 sequently only a confused dis- 

 charge was produced. 



When the terminal near the 

 coil was positive the same phe- 

 nomena were not produced on 

 the discharge of the condenser. 



In /srder to test whether it 

 would be possible to render 

 evident pulsations in the current 

 when perfectly steady strata are 

 ■s MEcoHM 2 produced in tubes containing 



^~A. "A residual gases, we arranged the 



detector apparatus as shown in 

 Fig. 19. 



A Z is the battery ; A being 

 connected through the fluid re- 

 sistances F R, F r' (which can be 

 plugged out of circuit by means 

 of P and P'), the megohm wire 

 resistance, and the primary of 

 Apps' induction-coil No. 819, 

 to the terminal T' of the tube ; 

 the terminal A is also connected 

 direct to one plate of the con- 

 denser C. Z is connected through 

 the key K to the fluid resistance 

 F R* (which can be plugged out by pressing down the key 

 K'), thence to the other plate of the condenser, and through 

 the safety-wire to the other terminal t of the tube. The 

 secondary wire of coil 819 is connected to a delicate 

 Thomson galvanometer T. 



Many observations were made with coil No. 819, which 

 we had taken to pieces several times during the course of 

 our trials, on account of suspected leakage from the 



