384 Scientific Proceedings, Royal Dublin Society. 
forming minerals. When Dr. Joly? and Mr. Ralph Cusack* made 
accurate determinations of the melting points of the minerals, the 
incompatibility of the two sets of facts in no sense disappeared. 
Here, then, was just the sort of material which demanded a theory 
to endow the facts with an intelligible meaning. 
As an experimental foundation for his “theory,” Dr. Joly 
took what Professor C. V. Boys? had named a “ quartz fibre,” 
and stretched it by a force amounting toa little less than two tons 
per square inch.* This fibre was surrounded by a platinum trough 
which was mounted as the ribbon of a meldometer, so that its 
temperature could be raised to a known degree. The elongation 
of the fibre was observed by means of two micrometer microscopes. 
Under these conditions the fibre was found to stretch at a tem- 
perature estimated at about 800° C. 
Now, i venture to submit the following remarks on this 
experiment for consideration :— 
1. In the first place, as was pointed out by Professor Grenville 
Cole at the March meeting of this Society, the so-called ‘“ quartz 
fibres’ experimented upon by Professor Joly are not quartz at 
all, but amorphous silica, as was proved by their optical inactivity 
between crossed nicols. In fact, so far as I am aware, quartz once 
fused alone at atmospheric pressure has never been found to re- 
crystallize as quartz. If rapidly cooled after fusion the density of 
the resulting silica is 2°2. If maintained for long at a high 
temperature its density increases to 2°3.° The conditions under 
which quartz fibres are produced (/.e. by shooting an arrow the tail 
of which has been dipped in fused silica) are evidently such as to 
insure rapid cooling. In fact, the elasticity and strength of the 
1J. Joly, ‘‘On the Determination of the Melting Points of Minerals,’’ Proc. Roy. 
Trish Acad., Ser. 111-, vol. 11. (1891), p. 38. 
2 R. Cusack, ‘‘On the Melting Points of Minerals,’’ Proc. Roy. Tish Acad., 3rd 
Ser., vol. iv. (1896), p. 399. 
3C. V. Boys, ‘‘On the Production, Properties, and some suggested Uses of the 
Finest Threads,’’ Proc. Phys. Soc., 9 (1887-88), p. 8. 
It may be well to point out an obvious misprint in Dr. Joly’s paper (p. 299, 
1, 28):— 
‘ For “‘Stress . d - 293 x 10° kilogrames per sqr. cm,’’ 
read “‘ Stress . : - °293 x 10% kilogrammes per sqr. cm.” 
5 Frémy, Encyclopédie Chimique, T. 11., Sect. 3°, 6, p. 142. Paris, 1884. 
