NOTES AND QUEiaES. 
193 
diamond ; but this process must be seen to be perfectly understood. The 
franjments and dust crushed otF fall into a metal sieve, which separates the 
smaller from the larger particles ; both are used for cutting and pohshing 
purposes, — the larger, under the name of splint, for engraving stone seals, 
drilling, and slitting ; the finer particles, after being beaten in a steel 
mortar of the required fineness, for the cutting of diamonds. Diamond 
hoart, which is the massive opaque variety, is also used for the same pur- 
poses as splint. The impure crystals having sharp cutting angles are 
used by glaziers : these are of no value as gems. 
Witii regard to cutting, it is generally stated that the diamond is first 
imbedded in fusible metal, the reason why is not given ; but it is as fol- 
lows : — In cutting diamonds the soft iron wheel, which is charged with 
diamond powder and oil, revolves with such amazing rapidity, either by 
steam or some other power, that if the diamond were merely attached to 
cement, as rubies, sapphires, and all other stones are, to be cut, the heat 
• caused by the friction would melt or soften the cement so that it would 
be impossible to cut it ; but the heat generated by the wheel revolving is 
not sufficient to melt the metal. The smallest rose diamonds, even of 800 
to the carat, or 200th of a grain weight each, have thus to be placed 
in fusible metal. Of these, as also small brilliants, three or more are cut 
at onetime. The wheels for cutting other stones than diamonds revolve 
at the rate of from 100 to 300 times in a minute. 
Another peculiarity in the process of cutting diamonds is the polishing. 
This is effected on the same wheel and almost at the same time as the 
cutting, and with the same material — crushed diamond. No other stone 
is so cut and polished at the same time. Some have two or three polish- 
ing materials, which are always much softer than the stone to be cut. 
These few remarks on cutting diamonds will be, I think, understood, 
although it is a process that ought to be seen to enable any one completely 
to appreciate the difference in the respective physical characters and 
mineralogical peculiarities of the diamond in respect to other stones. — 
James R. Geegoey, 25, Golden Square, London. 
Separation of the Isle of Wight. — Sir, — You are of course w^ell 
aware of the famous passage in Diodorus Siculus (lib. v. cap. 22), which 
is now interpreted by Sir G. C. Lewis and the latest German philologists 
as referring, not to St. Michael's Mount, but the Isle of Wight. There 
the writer expressly says that in his time the passage at low w ater was 
dry. 
Now we have in this neighbourhood, of which you may not be aware, 
various traditions to the same eflect, such as that the Cistercian monas- 
tery of Beaulieu was built of Binstead stone, brought across from the 
Isle of Wight in carts at low tides. 
I. I should be glad to know if these assertions have any truth in them, 
and to what period you date the separation of the Isle of Wight, between 
Calshot Point and Hurst Castle, from the mainland ? 
II. Can you refer me to any good book or article on the subject ? 
Your constant reader, 
Lymington, Hants. W. B. H. 
Geological Tables. — The Synoptical Tables of British Geology in use 
by Professor King, of Galway, having been highly thought of by teachers 
of our science, w^e are happy to be able, through the Professor's kindness, 
to present our readers with a new edition, which he has revised and cor- 
rected up to the present time, expressly for this magazine. — Ed. Geol. 
YOL. Y. 2 C 
