A438 Miscellaneous Intelligence. 
time : so that after the speculum had been a certain number of hours 
under the action of the polisher, he was well assured that the proper 
figure had been attained. Prof. Stevelly briefly described these motions 
and adjustments ; and stated that the actual result was, an enormous 
circular disc of six-feet aperture, without crack or flaw, and of a splen- 
did uniform polish, and reflecting light from objects of a perfectly 
natural tint—-Mr. Varey said he had found that the use of a little zinc 
in the composition of the speculum metal took from it the liability to 
tarnish which he had found so annoying. He expressed regret that 
struction of his speculum ; his own experiments had led him to hope 
they might be avoided.—_Mr. LassEtt said, if he had heard Mr. Sollitt 
o the proper proportion. of tin to be used with the 
copper, he believed it to be impossible to give an unvarying rule, as the 
copper of commerce was very irregular in its quality and purity. 
found the best mode to be to add nearly the quantity of tin known to be 
required,—which generally was from 14 to 15 parts tin, to 32 copper ; 
and then weighing a small portion of that alloy, add to it by slow de- 
grees known weights of tin,—and, assaying it from time to time by the 
simple test of dropping it into water as soon as it acquired a certain 
brittleness and briliiancy of fracture, easily to be recognized by practice, 
the North 
Atlantic and Northern Oceans ; by the Rev. Dr. Scoressy, (Proc. Brit. 
