116 THE NEW KNOWLEDGE. 



acts like one in continuously diffusing into the surrounding 

 air and that, moreover, by passing a current of air over the 

 radium it may be carried away like an ordinary gas, and 

 that the air so permeated by it continues to give off rays 

 long after its passage over the radium. Next it became ob- 

 vious that the amount of emanation given off by it in the solid 

 cold state was insignificant compared to the veritable rush 

 emitted on heating the radium salt or on dissolving it in 

 water. This also is quite in accord with the supposition 

 that it is a gas of some kind occluded or hidden away in the 

 radium. This latter method, that of solution, is the best 

 method of obtaining the emanation for purposes of study. 

 A small quantity of radium chloride is dissolved in water 

 and the rush of emanation is collected by bubbling air 

 through the solution and carrying off the air so permeated 

 with the emanation into an ordinary gas-holder, where it will 

 li^ht up a screen of phosphorescent zinc sulphide for days 

 and will show some radio-activity even after the lapse of a 

 month. On passing this ray-emitting air containing the 

 emanation from the gas-holder over platinum, palladium, 

 zinc, magnesium and lead chromate, all at an intense red 

 heat, it was found impossible to alter the ray-emitting power 

 to any sensible degree. The ray-emitting power of the 

 emanated air is absolutely conserved. No ordinary gas 

 could withstand the action of the powerful reagents speci- 

 fied above and hence we are obliged to assume that if it is 

 a gas, and it seems to be, the emanation must belong to 

 that interesting family of inert gases discovered by Raybigh 

 and Ramsay in the atmosphere, which are known as helium, 

 neon, argon, krypton and xenon and which the reader will 

 find tabulated in the zero group of the periodic law and 

 discussed in Part II. The probability that the emanation 

 is an actual gas is greatly emphasized by the fact that it 



