292 PROCEEDINGS OF SOCIETIES. 
provements have been made in that short space of time that their 
performance is now everything that could be desired. See what 
we have gained by waiting a month longer! This strikingly ilus- 
trates the remark I made before this discussion commenced, on 
the importance of one being made acquainted with the most recent 
improvements. I have now merely to ask Mr. Browning to let 
me see Mr. Sorby’s recent letters to which he has referred. 
Mr. Beck then read a paper “On a New Form of Live-Trap 
and Parabolic Reflector.” (See ‘ Trans.,’ p. 113.) 
A paper “On New and Rare Diatoms” was read from Dr. Gre- 
ville. (See ‘ Trans.,’ p. 97.) 
Mr. Wenuam read a paper “ On the Fracture of Polished Glass 
Surfaces.” (See ‘ Trans.,’ p. 105.) t 
Mr. Brownrye asked Mr. Wenham if he had tried the effect 
of a screw on the surface of glass. The subject was an interesting 
one, and the more so because the microscope and polariscope could 
be used to detect the change effected. 
Mr. Wenuam said the polariscope afforded an excellent indica- 
tion of the condition of glass when under a strain. If it was under 
the compression of a screw, the polariscope would show colours in 
the vicinity. 
Mr. Brownine said he had tried that, and always carried a 
polariscope with him for the purpose, but he should like to know 
whether the effect was permanent. 
Mr. Wrenuam.—lIt requires this peculiar burnishing action to 
produce a permanent result. I may here mention, in reference 
to a remark just made to me by Mr. Beck, that when a glass tube 
breaks, in consequence ofa metal wire haying been passed through 
it in contact with the surface, it gives a loud sound, like the report 
of a pistol. Some imagine that if the wire is merely passed down 
without touching the tube it will have the effect I have described ; 
but I have never found this to be the case, although I have always 
found a simple touch to be sufficient. 
Mr. Becx.—I am no barometer-maker myself, but I under- 
stand that the makers never touch a tube with a piece of metal, 
as the tube would in that case certainly break. I apprehend Mr. 
Wenham could not pass a wire along a long barometer-tube with- 
out touching it in some way. 
The Cuatrman then declared the meeting adjourned to the 
1ith October. 
The following are Extracts from Mr, Sorby’s letters forwarded to 
the President, and published by his permission. _- 
June 7th, 1863.—“ TI have not attempted much work with the 
new plan, being anxious to wait until I had got all the apparatus 
finished ; but I have tried enough to see that it will be a very 
great improvement on my original method. J applied it yesterday 
to a very curious, most rare kind of erystal, ina meteorite, which 
