Quantity of Radium in Rocks and Minerals, Sfc. 137 



risk of the moisture, which at first condenses in the asbestos, 

 impeding the free escape of the gases. 



Fig-. 1. 



Connexion with the platinum resistance wire is made by 

 two binding-screws placed beneath the silica shade, one of 

 which is shown in the figure. This one is insulated from 

 the iron base by a luting of fire-clay. The second binding- 

 screw is screwed into the iron. A binding- screw screwed 

 into the outer rim of the base makes connexion with it through 

 the iron. 



At the conclusion of an experiment it is desirable to wash 

 out the interior of the shade by means of a stream of air 

 directed into the crucible. The tube t enables this to be 

 effected. It is closed without, until the conclusion of the 

 experiment, when it is opened and air allowed to enter and 

 flow through the furnace on its way to complete the filling 

 of the electroscope. 



The platinum resistance wire used in heating the crucible 

 is about one metre in length and 1*2 mm. in diameter. It 

 is folded in vertical folds, some folds being longer than 

 others and some being partly bent in under the crucible. 

 It is easy to giye the right form to the wire. It is first 



