The writer believes he was the first person in the United States, aided by a director of the New England Glass Company, to build a lead furnace. This was in 1818. His only guide was a volume of "Cooper's Emporium of Arts and Sciences," which furnished a plan on a very limited scale. The furnace proved successful, and enabled the Company to continue their manufacture of glass at a period when no foreign red lead was to be procured. They enlarged their works, until they have become the most important in the country; while for over thirty years they monopolized the business in all its branches, from the highest qualities of pure Galena and painter's red lead to common pig lead. In manufacturing metallic lead, its weight is materially increased by the absorption of oxygen gas. In 1847 the writer made many test experiments, one as follows: 660 pigs of blue lead, weighing 45,540 pounds, turned out from the ovens 48,750 pounds of litharge,--an increase in weight of 3210 pounds. The cost of labor was $65.50; fuel, $86.50; engine power, $17.50; total, $169.50; and the market value of the excess in weight of the lead was $250, showing a satisfactory profit to the company for their outlay in this branch of their business. Chemistry gives the increase in course of manufacture: In protoxide state, 7 per cent.; in deutoxide state, 11 per cent.; in tritoxide, 15 per cent. Muriatic acid will detect iron in lead, on dissolving a small piece of lead in the acid. If colorless, it is good. Nitric acid will detect if there is cobalt in the lead, by adding to the acid half the quantity of high-proof alcohol. If present, the evidence is soon seen. Some use the following as more direct:--In a small evaporating glass dish place say one ounce of lead; cover it with muriatic acid; dissolve the lead over a spirit lamp, add a little water, and let it settle; draw it off into another glass vessel, and add five or six drops of the solution of potash. If the lead is suitable for glass-makers, the solution will be of a light, clear, greenish color; if of a blue or purple shade, it is not suitable for flint-glass. SAND, OR SILEX. In the manufacture of glass it is essential that the silex should be perfectly pure, as the slightest mineral taint affects the color.