SCIENTIFIC SUMMARY. 
261 
In conclusion, it should be remarked that the binocular form can he 
adapted to any single microscope, so that any one possessing a good micro- 
scope of the ordinary form can, for about seven pounds ten shillings, have 
it transformed, under the workmanlike hands of Messrs. Smith and Beck, 
into the magical instrument known as“Wenham’s Binocular Microscope.” 
MINERALOGY AND METALLURGY. 
The Dissemination of Gold. — Mr. Eckfeldt, the assayer at the United 
States Mint, at Philadelphia, publishes the following curious fact : — Under- 
neath the paved city of Philadelphia there lies a deposit of clay, whose area, 
at a probable estimate, would measure over three miles square, enabling us 
to figure out the convenient sum of ten square miles. The average depth is 
believed to be not less than fifteen feet. The inquiry was started whether 
gold was diffused in this earthy bed. From a central locality, which might 
afford a fair assay of the whole, the cellar of the New Market House, near 
Eleventh Street, was dug out some clay at a depth of fourteen feet, where it 
could not have been an artificial deposit. The weight of 130 grammes was 
dried, and duly treated ; it yielded one-eighth of a milligramme of gold, a very 
decided quantity, on a fine assay balance. It is computed that there are under 
Philadelphia 4,180 millions of cubic feet of clay, and that hi it securely lies 
126 millions of dollars’ worth of gold. 
Gold in North Wales. — From time to time there has been considerable 
excitement respecting the discovery of gold fields within the British Islands. 
At one period the Lead Hills caused much stir in Scotland ; and the Wicklow 
gold washings gave rise to the appointment of a government connnission. 
Devonshire was advertised as having “ Pactolean streams,” and the “ fable 
of Colchis” was to be realized in Cornwall. The Clogan Mine, near Dolgelly, 
in Merionethshire, is however really producing considerable quantities of 
gold. In 1844, Mr. Arthur Dean read a paper before the British Associa- 
tion on the auriferous veins of this district. Since that period numerous 
triaLs have been made, but every such trial has resulted in great loss to the 
adventurous gold seekers. It is satisfactory now to know that gold is 
obtained from the Clogan Mine at a profit. Mr. Readwin gives the following 
statement as the result of the workings up to last September : — “ 207 tons 
8 cwt. of quartz gave 1,314 ounces of fine gold ; three tons of the best of this 
quartz gave no less than 976‘6 ounces of gold. If they added 56 ounces 
obtained from 5 tons in 1860, it showed a total quantity of 1,370 ounces of 
gold from 212 tons of auriferous mineral, being at the rate of six ounces and 
a half per ton.” The value of this British gold was ^£5,300. 
The Gold of Nova Scotia. — Mr. 0. C. Marsh, of Yale College, gives, in the 
last number of the American Journal of Science, an interesting account of 
this discovery. On the Atlantic coast of Nova Scotia is a belt of metam Or- 
phic rocks extending the whole length of the province, and varying hr width 
from ten to fifty miles. It is mainly composed of clay-slate and quartzite, 
