North American beaver large, webbed hind feet. The unwebbed front paws are smaller, with claws. The eyes are covered by a nictitating membrane which allows the beaver to see under water. The nostrils and ears are sealed while submerged. A thick layer of fat under its skin insulates the beaver from its coldwater environment. The beaver's fur consists of long, coarse outer hairs and short, fine inner hairs (see Double coat). The fur has a range of colors, but usually is dark brown. Scent glands near the genitals secrete an oily substance known as castoreum, which the beaver uses to waterproof its fur.
Castor oil with castor oil, however, usually requiring eventual replacement of ball bearings when the residue accumulates within the engine's bearing races. One British manufacturer of sleeve valved four-cycle model engines has stated the "varnish" created by using castor oil in small percentages can improve the pneumatic seal of the sleeve valve, improving such an engine's performance over time. Turkey red oil, also called sulphonated (or sulfated) castor oil, is made by adding sulfuric acid to vegetable oils, most notably castor oil. It was the first synthetic detergent after ordinary soap. It is used in formulating lubricants, softeners, and dyeing assistants. Castor