CORK, ITS MANUFACTURE AND PROPERTIES. 649 



this way is a tangent to the inner surface of all the strips, and presents 

 in section a circumference inscribed within a polygon. In the second 

 method, No. 2, thin strips of cork, glued to cloth, by a kind of India- 

 rubber cement, are wrapped spirally round the pipe. The third 

 method consists in employing two hollowed half-cylinders (No. 3) ex- 

 actly fitting the surface of the pipe. These cylinders, which can be 



Fig. 9. Pipes Covered with Non-conducting Cork. No. 1, bands laid side by side, 

 band cf cork pasted ou cloth and rolled in spiral shape. No. 3, artificial cork. 



No. 2, 



made of any length, are composed of cork-powder mixed with starch, 

 and are covered with strips of cotton cloth rolled spirally over them, 

 which can be painted with coal-tar or any other suitable paint. Either 

 of the methods will effect a great economy of fuel. 



Cork, being also a very poor conductor of sound, is employed 

 successfully in finishing the interior of telephone-cells. It may be 

 put over the doors of consulting-offices ; floors made of it are very ac- 

 ceptable in cure-houses and sick-chambers ; and it has been adopted 

 in some stringed musical instruments to prevent waste of sound. 



Cork has superior buoyant qualities, which are sufficient not only 

 to keep it on the surface, but also to enable it to support tolerably 

 heavy bodies. It is thus employed as a float for night-lamps, for bath- 

 thermometers, and for fish-lines. It is excellently adapted to use in 

 swimming-jackets and life-saving apparatus, in the construction of 

 which inventors have exercised their genius industriously. Many 

 ships carry cork mattresses, which have proved of great service in 

 cases of shipwreck. Life-saving buoys are composed of pieces of cork, 

 are usually in the form of rings, and are furnished with knotted pieces 

 of rope, permitting them to be easily taken hold of. They are also 

 usually covered with painted sail-cloth, to insure their preservation. 



