MR. RITCHIE ON THE ELASTICITY OF THREADS OF GLASS. 
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fineness, having small brass tubes cemented on their ends for the purpose of 
attaching them to the fulcrum and torsion key. 
The method now described may appear somewhat tedious, but it is only so 
in appearance, as the oscillations do not continue so long as in a delicate 
balance without the torsion thread. In some delicate experiments with this 
balance, I have used threads of glass about ten feet long, so that in raising a 
weight of one grain, the glass thread suffered a torsion of at least 5000 degrees. 
Hence a very small fraction of a grain may be determined with an extraordi- 
nary degree of accuracy. From the perfect elasticity of torsion which glass 
possesses, and from the ease with which threads of any length and fineness 
may be procured, I am fully convinced that, for all delicate investigations 
connected with torsion balances, threads of this substance will be found to 
possess decided advantages. 
