made separation difficult. Langstroth later used this discovery to make the frames themselves easily removable. If a small space was left (less than 1/4 inch or 6.4 mm), the bees filled it with propolis; conversely, when a larger space was left (more than 3/8 inch or 9.5 mm), the bees filled it with comb. Innovations to beehive design On 5 October 1852, Langstroth received a patent on the first movable frame beehive in America. A Philadelphia cabinetmaker and fellow bee enthusiast, Henry Bourquin, made Langstroth's first hives for him. By 1852, Langstroth had more than a hundred of these hives, and began selling them where he could. Langstroth spent many years attempting to defend his patent without success. He never earned any royalties, because the patent was easily and widely infringed. Langstroth hives are still in common use today. He wrote that “... the chief peculiarity in my hive was the facility with which they could be removed without enraging the bees .... I could dispense with natural swarming, and yet multiply colonies with greater rapidity and certainty than by the common methods .... feeble colonies could be strengthened, and those which had lost their queen furnished with the means of obtaining another. .... If I suspected that anything was wrong with a hive, I could quickly ascertain its true condition and apply the proper remedies.” Langstroth also found that several communicating hive boxes can be stacked one above another, and that the queen can be confined to the lowest (or brood) chamber, by means of a queen excluder. In this way, the upper chambers can be reached only by the workers, and therefore contain only honey-comb. This made hive inspection and many other management practices possible, and turned the art of beekeeping into a full-scale industry. At the time of Langstroth's contributions, honey was the chief sweetener in American diets, so Langstroth's new beekeeping techniques were of great importance. His discoveries and inventions allowed beekeeping to be done more cost-effectively on a large scale. Since four to twelve pounds of honey—in addition to many hours of bee time—are consumed by bees in the production of one pound of beeswax, honey production was increased from reuse of the comb. The Hive and the Honey-Bee In 1853, Langstroth had moved back to Greenfield, Massachusetts from Philadelphia, and published The Hive and the Honey-Bee (Northampton (Massachusetts): Hopkins, Bridgman, 1853), which provided practical