ARTICLE. PAGE. 1 I.-On the Cornus florida of the United States. By George S. Blackie, A.M., M.D.,......... By Bernard II. A popular Treatise on the Fur-bearing Animals of 5 36 III.-Addenda to the Natural History of the Valley of the River Rouge. By W. S. M. D'Urban, ...... IV. On the occurrence of Freshwater Shells in some of our Post Tertiary Deposits. By Robert Bell,... 42 V.-Professor Guyot on the Physical Geography of the Appalachian Mountain System, Natural History of Canada, Reviews and Notices of Books. Contributions to the Natural History of the United States. The Romance of Natural History. By Philip Henry Narrative of the Canadian Red-River Exploring Expedi tion of 1857,....... 51 Geological Gossip, or Story Chapters on Earth and Ocean. Coins, Medals, and Seals. The Academy of Natural Science of Philadelphia,.......... 70 The Natural History Society of Boston, The Essex Institute,....... Miscellaneous. Professor Lawson on Botany, and on the Chemistry of Plants...... The Ancient Vegetation of North America,... Stereoscopic Phototographs of the Moon on Glass, from negatives taken by Warren De la Rue, Esq., F. R. S., $6.50 Extract from the "Athenæum," 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, .$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. |