Mr. L.H. Landy then exhibited, by means of the gas microscope, several beautiful rock sections, both American and German. The same gentleman also showed the effect of passing polarized light through certain crystal sections, the black cross and rainbow-hued rings revolving like so many wheels as the polarizer was turned.
At the conclusion of this brilliant exhibition, Dr. P.T. Austen made some remarks on
LABORATORY MANIPULATIONS.
The points referred to were the apparently unimportant details which often contribute so much to the ease and pleasure of working. First, the use of square pieces of felt, such as are used under beer glasses in saloons, for setting hot beakers and flasks on to prevent chilling and consequent cracking. Second, in crystallizing substances for examination under the microscope; one watch glass is placed upon another with the substance between them, and the upper glass filled with ether, the cold produced by its evaporation hastening the crystallization. Third, removing precipitates and solid matter from flasks, by heating to boiling, and inverting in a vessel of water. Fourth, crystallization by gradual dilution. Fifth, filter paper without ash. In German laboratories it is customary to dissolve out the mineral matter from white filtering paper by washing in dilute hydrochloric and hydrofluoric acids. Sixth, the use of infusorial silica for drying purposes. Being very porous, it will absorb five times its own volume of water. If a filter paper, holding a wet precipitate, be placed upon a layer of this earth, it will become quite dry in a very short space of time. Mr. Austen also remarked that substances retain their heat for several days when placed in cork boxes. To keep a substance air-tight, it may be placed in a flask, the neck painted with a solution of india rubber in chloroform, and a plate of glass laid upon it. The solvent quickly evaporates, leaving a delicate film of rubber, which holds the glass tightly in place.
The next meeting of the Chemical Section will be held February 12; of the Mineralogical Section, February 19.
ANNUAL REPORT OF THE PATENT OFFICE.
The annual report to Congress of the Commissioner of Patents, for the year 1876, has made its appearance.
The amount received on applications for patents, reissues, designs, extensions, caveats, disclaimers, appeals, trade marks, labels, copies, etc., was $757,987.65. The amount paid for salaries was $425,930; other expenses, $226,612. Total payments, $652,542.
| Number of applications for patents during the year 1876 | 21,425 |
| Number of patents issued, including reissues and designs | 15,595 |
| Number of applications for extension of patents | 2 |
| Number of patents extended | 3 |
| Number of caveats filed during the year | 2,697 |
| Number of patents expired during the year | 814 |
| Number of patents allowed but not issued for want of final fee | 3,353 |
| Number of applications for registering of trade marks | 1,081 |
| Number of trade marks registered | 959 |
| Number of applications for registering of labels | 650 |
| Number of labels registered | 402 |
| Of the patents granted there were to— | |
| Citizens of the United States | 16,239 |
| Subjects of Great Britain | 511 |
| Subjects of France | 104 |
| Subjects of other foreign governments | 172 |
| ——— | |
| Total | 17,026 |