Mr. J. A. Wanklyn on the Movements of Gases. 211 



deflected in the original direction, and both needles will very 

 gradually resume the perpendicular." 



" There is a most marked difference between the effect produced 

 between a coiled and a straight cable. The return current ap- 

 pears obliterated, or rather it is overpowered by the effects of the 

 inductive action which takes place from coil to coil. The deflec- 

 tion thus produced is much greater than that produced by the 

 return current. I have had perhaps peculiar facilities for obser- 

 ving this striking phenomenon. Whilst picking up a cable at 

 sea, I frequently test the length I am operating on for return 

 current ; and as the cable becomes coiled into the ship the deflection 

 of the needle, when testing for return current, becomes reversed. 



" It is also my practice to cut the cable at certain distances 

 as it is picked up, and then test such sections separately. On 

 these occasions, sections which, when one end is insulated, will 

 give a charge and discharge of 5°, will when that end is to earth, 

 give a current at the battery end, after contact, of 90°, but in the 

 reverse direction to that in which the discharge or return current 

 would be if the cable were laid out straight." 



XXVI. On the Movements of Gases. By J. A. Wanklyn, De- 

 monstrator of Chemistry in the University of Edinburgh*. 



WHEN a gas heavier than air is placed in a cylindrical 

 vessel closed at the top and open at the bottom, it does 

 not descend rapidly. In like manner, a gas lighter than air con- 

 tained in a cylinder closed below, but freely communicating with 

 the atmosphere above, does not move upwards with rapidity. 



By simply placing a gas in a vertical cylinder shut at one end, 

 the ordinary course of gravitation is disturbed — to how great an 

 extent few people would anticipate. 



The following experiments show how remarkably the fall of 

 is retarded by such an arrangement. 



A tubef filled with carbonic acid was allowed to remain with 

 its mouth open and directed downwards for the space of five 

 seconds. After the lapse of that time, the gaseous contents of 

 the tube were analysed in order to ascertain how much carbonic 

 acid had made its escape. 



The composition of the gas was — 



Air 26-3 



Carbonic acid . . . 73 7 

 100-0 



* Communicated by the Author. 



t Dimensions of the tube :— Diameter, 14*5 millims. ; Length, 232 mil- 



lims. ; capacity, 37 cubic eentims. 



