NEW

Achromatic Stereoscope.

Price in Walnut Wood,

Do. Mahogany do.,

$23.00

$21.00

Stereoscopic Phototographs of the Moon on Glass, from negatives taken by Warren De la Rue, Esq., F. R. S.,

$6.50

Extract from the "Athenaeum," Aug. 28, 1858, page 269.

"The adoption by Mr. CHAPPUIS of the principle of the daylight reflector to the stereoscope was noticed by us in the Athenæum for Nov. 7th, 1857. We there made some suggestions for further improvements, with a recommendation to Mr. CHAPPUIS to try them.' That gentleman has not done so; but Messrs. SMITH & BECK have not only carried out, they have gone beyond our suggestions,-and from a toy the stereoscope has progressed to an object belonging to science. A few words will enable our readers to understand the improvements that have been made in this justly popular instrument. 1st. By the introduction of achromatic lenses the optical part is greatly improved, thereby increasing the definition and correcting the colour which single lenses invariably show on the margin of the objects. These errors in the unachromatic stereoscope frequently destroy the delicacy of the image altogether.-2nd. By the application of lenses of such a focal length, and placed at such a distance apart as that all shall see without fatigue, which is not the case with those hitherto contrived. But with these improvements in the optical part of the instrument arose the need of greater delicacy in the mechanical contrivances for observing to the best advantage; this led-3rd. To an arrangement whereby any one having the sight of both eyes could see the effect.-4th. A thoroughly steady and substantial stand adapted for a person seated at a table, and allowing of any alteration of position. 5th. A method for holding the slides so that they can be placed and replaced easily and without danger.-6th. Means have been adopted for varying the illumination at pleasure, causing a great variety of very beautiful effects of light and shade, from the cool tints of moonlight to the ruddy glow of the morning sun. And, lastly, a compact case to keep the whole from dust, injury, or exposure. The result is a perfection beyond which it is hardly possible to carry the stereoscope. This perfection is admirably exhibited in the stereoscopic views of the Moon, taken on glass by Mr. HOWLETT, from the negatives obtained by Mr. WARREN DE LA RUE with his equatoreal reflecting telescope of 13 inches aperture and 10 feet focal length. The stereoscopic effect is obtained by combining two views of the moon, taken at different epochs nearly in the same phase, but when the disc is in two different conditions of libration."

SMITH, BECK & BECK'S IMPROVED MICROSCOPES. Price of the Educational Microscope,

แ Student's

from..

.$65.00 and $96.00 $96.00 to $200.00

Apparatus, &c., Instruments used in preparing and materials in mounting Microscopic objects, or any other article of their manufacture can be supplied by

FRANCIS CUNDILL, AGENT, 6 Commercial Chambers, St. Sacrament Street, MONTREAL

Catalogues forwarded.

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VOLUME VI.-NEW SERIES.

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The SCIENTIFIC AMERICAN is indispensable to every inventor, as it not only contains illustrated descriptions of nearly all the best inventions as they come out but each number contains an Official List of the claims of all the Patents issued from the United States Patent Office during the week previous; thus giving a correct history of the progress of inventions in this country. We are also receiving, every week, the best scientific journals of Great Britain, France, and Germany; thus placing in our possession all that is transpiring in mechanical science and art in these old countries. We shall continue to transfer to our columns copious extracts from these journals of whatever we may deem of interest to our readers.

Chemists, Architects, Millwrights, and Farmers.

The SCIENTIFIC AMERICAN will be found a most useful journal to them. All the new discoveries in the science of chemistry are given in its columns, and the interests of the architect and carpenter are not overlooked; all the new inventions and discoveries appertaining to these pursuits being published from week to week. Useful and practical information pertaining to the interests of millwrights and mill-owners will be found published in the SCIENTIFIC AMERICAN, which information they can not possibly obtain from any other source. Subjects in which planters and farmers are interested will be found discussed in the SCIENTIFIC AMERICAN; most of the improvements in agricultural implements being illustrated in its columns.

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ARTICLE XXX.-On the recent discoveries of Gold in Nova Scotia. By J. W. DAWSON, LL.D., F.G.S., &c.

(Read before the Natural History Society.)

The discoveries of gold recently made in Nova Scotia, are of much interest both in a geological and commercial point of view; and should they exercise an influence on the destinies of that Province, comparable with that which similar discoveries have produced in California and Australia, they will not be without importance to Canada, and will probably contribute to attract attention to other mineral resources of the Lower Provinces heretofore neglected. In the present paper, I propose to record the leading geological facts connected with these discoveries, using materials collected in my former geological researches in Nova Scotia, and the facts communicated to me by friends who have visited the localities.

In a paper on the Silurian and Devonian rocks of Nova Scotia, published in Vol. V of the Canadian Naturalist, p. 132, et seq., I referred very shortly to a series of metamorphic rocks extending along the Atlantic coast of the Province. I stated that it has afforded no fossils; but from its apparent relation to the fossiliferous Silurian rocks further inland, and to the older slate series of CAN. NAT. VOL. VI. No. 6.

Newfoundland, it may be inferred to belong to the lower part of the Lower Silurian system. The map attached to that paper and here reproduced, shews the geographical position of the beds, which extend along the whole Atlantic coast, from Cape Canso to Cape Sable.

(1) Secondary Trap.

(2) New Red Sandstone (Permian or Triassic.)

(3) Carboniferous. (In eastern part of Nova Scotia proper.) (4) Devonian.

(5) Middle and Upper Silurian.

(6) Metamorphosed Lower Silurian. (Auriferous region.)
(7) Granite.

The numbers refer to the section and to the corresponding shades of the map.

In my "Acadian Geology," (1855) a more full description is given of this "Atlantic Coast Metamorphic District," extending from p. 346 to 365, and including some remarks on the probabilities of the discovery of gold and other metals in this formation. From this description I may condense the following notice of the rocks occurring in the district, and their distribution.

The prevailing stratified rocks are clay slate and quartz rock, the former of various degrees of coarseness, and usually of grey and black tints, and the latter in thick massive beds of a grey colour, locally named "whin." In some localities these are replaced by mica slate and gneiss, perhaps consisting of the same material in a farther state of metamorphism, and they are penetrated by veins and masses of intrusive granite, which from its relations elsewhere, would seem to be of Devonian age.