The Groundwork of the Univerfie, &c. 59 



this were so great that it was generally assumed to be an 

 impossible task ; Init Sir William Ramsay and Dr. Whytlaw-Gray 

 were not deterred by this idea : and they proceeded to construct 

 a microbalance " capable of weighing the extremely small 

 quantity of niton available. This balance, when eventually con- 

 structed (from quartz fibres) was so delicate that it turned with 

 the weight of 0-000,000,04 ounces. Its construction marks the 

 high-water mark of accuracy in weighing ever successfully per- 

 formed. Of course, no weights could be prepaied of sufficient 

 refinement to use on a lialance of this accuracy ; but Sir William 

 Ramsay overcame this difficulty by utilising as his weight a glass 

 tube filled with air at oi'dinary pressure, and by making his 

 balance-case air-tight and capable of evacuation. When the air 

 in the balance-case was at ordinary pressure, obviously the air in 

 the "weight" had no effect ; but when the air was pumped out 

 of the balance-case then the "weight" depressed the beam, 

 because the air inside the glass " weight " was no longer equi- 

 poised with the air outside the "weight." Thus by measuring 

 the pressure of the air in the balance-case, it was possible to 

 calculate the exact " weight " of the glass tube, plus the air inside 

 it By means of this balance the exact weight of the tiny 

 quantity of available niton was ascertained ; and when its atomic 

 weight was calculated from this it was found that the atom of 

 niton was 222 times heavier than a hydrogen atom — a figure 

 which brings niton into the bottom of the inert gas column of the 

 Periodic Table. 



It will be noticed that the word Niton has the same ter- 

 mination as most of the other elements of the group. The name 

 was given to it because of its luminosity. In the dark a tube of 

 niton glows with a greenish-white lustre ; and on this account 

 Ramsay called it Niton — the shining one. It was originally 

 termed " radium emanation." 



The decay of the element niton is extremely rapid. In 

 ninety-four hours half of it disintegrates, no matter what quantity 

 >ve start with at first. In the next ninety-four hours it falls again 



