1897.] and the formation of Clouds in Changed Oases. 249 



current of about 12 or 14 amperes is sent through them. They 

 have also been found to be electrified when so small a current as 

 two amperes is sent through them, but the rate of evolution is so 

 small that the larger currents have been generally used. 



10. When these charged gases are bubbled through water, they 

 become clouded. The cloud which is thus formed can be com- 

 pletely removed by bubbling the gases through sulphuric acid or 

 sending them through a U tube of CaCL, but when they get 

 into the atmosphere of the room they condense the moisture and 

 form a stable cloud in an unsaturated atmosphere. The process of 

 forming the cloud in positive or negative oxygen by bubbling 

 through water, and removing it again by bubbling through sul- 

 phuric acid, can be gone through without losing more than 20 or 

 25 per cent, of the original charge on the gas. Clouds having 

 similar properties are formed by the hydrogen coming off a 

 rapidly dissolving metal. 



11. Fig. 2 represents a convenient form of apparatus for 

 examining the electrical properties of these gases. The electrolyte 

 is contained in the beaker F, and the gas which is given off from 



Fig. 2. 

 (The dotted lines indicate insulators.) 



the platinum electrode E rises into the cup C and is brought by 

 glass tubing to the paraffin tunnel P inside a large screen S, 

 which contains all the apparatus which it is desirable to connect 

 to the electrometer in order to measure charges. Between the 

 two tunnels P and Q can be put any apparatus D whose discharging 



