Rare patent model for Eli Slater's Hot-Air Furnace c. 1860s. Eli Slater, of Philadelphia, Pennsylvania submitted a patent application for his cage-like Smoke & Gas Consuming Furnace in 1869, as presented in his 12-inch tall miniature handmade tin model. Burning coal-powered American industrialization in the nineteenth century, and it showed: the skies of American cities were choked with smoke and noxious fumes, creating serious health problems and coating the landscape with soot. The smoke problem ran up against business leaders who often equated smoke with progress or simply denied the problem existed at all. Slater's invention was one of hundreds of design attempts to mitigate smoke; its efficacy apparently predicated on the idea that smoke itself could be burned under the right conditions. Slater was granted patent number 99,015 for his invention on January 18, 1870. A decade later, some three hundred patents had been issued for smoke-consuming technology. Largely ineffective, none were deemed worthy of widespread adoption. Condition: Good antique condition with a couple of small dents and one missing pipe in the cage. Measurements 5 " wide, 6 " deep,11.75 " tall US Shipping $25 insured. Courtesy Old As Adam Antiques oldasadam.com