Poole — Mechanical Device for Sealing off Radium Emanation Tubes. 339 



used for holding it, and gripped in such a position that the ink-spot, marking 

 the point where it is desired to effect a division, is midway between the chucks. 

 A tube is seen in position in tig. 1, and the division marks on it are just visible. 

 The fingers are then unlocked, and the chucks, which are geared up in the ratio 

 3 : 1, are rotated at some 400 to 500 r.p.m. The gas flame is then applied to the 

 desired point on the capillary, which is very quickly drawn out and sealed off. 

 The flame is then moved slightly along the axis of the capillary, so as to apply 

 it to each separate sealed end in turn, in order to strengthen the seals. A 

 short finished tube is most readily removed from an unscrewed chuck by tilting 



Fio. 3. 



the entire appliance over a sheet of white blotting paper, when a slight shake 

 usually causes the tube to slip out. Longer tubes may be handled with forceps. 

 Every tube is then tested by slipping it into a standard needle. If, as occasionally 

 happens, a seal is too unsjTnmetrical or too large to enter the needle, the tube 

 is again inserted in the sealing apparatus for rectification. Want of symmetry 

 can generally be corrected by careful heating of a stationary tube. An enlarged 

 seal must be treated by fusing on another piece of capillary tube, and redrawuig 

 out just at the seal. This operation can quite easily be carried out in the 

 apparatus. 



