CHAIN. 457 CHAIN-SNAKE. the open ends. The welding is done link by link as in the case of hand-uiade chains. These small sizes of luachine-welded chains are often made with twisted links, but are never made in the form of stud chains. Weldless niachinemade chains are manufactured by auto- matic machinery which takes the rolled iron, cuts it into lengths, forms these lengths into links, and connects or couples the links into com- pleted chains. In weldless chains the links are formed by twisting or locking the unconnected ends of the short lengths of rod. There are numerous forms of such connections and certain advantages are claimed for each form. Chains of this construction are made only in the small sizes which are used for horse-halters, cow-ties, dog-chains, fence-chains, sash-chains, curtain- ehains. picture-chains, harness-chains, and simi- lar purposes. For many of those purposes brass, bronze, and composition metals are used instead of iron, but the process of manufacturing the chain is otherwise unchanged. With the single exception of the stud chain, the chains so far de- scribed have each link composed of a single piece of metal bent to form and welded, twisted into a closed ring. Chains for transmitting power are of an en- tirely different construction. In these each link is made of several pieces of metal connected by rivets, bolts, or stud screws, and is so formed as to engage with the teeth of a sprocket wheel. The bicycle chain is an excellent example of this variety of chains, but there are several forms in use which are even more perfect. Chains of this kind are made by assembling by hand the several parts composing each link and connecting them together; the separate parts are themselves cut, stamped, turned, threaded or otherwise formed by machinery designed especially for the pur- pose. Watch-chains, neck-chains, and other chains made of precious metal for ornament form a class by themselves. Some of the larger and heavier chains of this class, which are made in the ' simple forms common to the chains of brass and iron which have been described, are made by methods closely corresponding to those used in making iron and brass chains. The smaller sizes of wire chains are made by machinery with twisted and locked links, others are formed by methods analogous to that adopted in producing machine-made welded chains of iron, the links being closed by brazing instead of by welding. In still other forms the links are stamped and cut from metal plate and are assembled and brazed together by hand. The strength of chains is a very itpportant matter in certain uses to which chains are put. For cxamjile. the safety of an anchored ship and the lives of its crew may often depend upon the strength of its chain cable. For this reason the British Admiralty and the organizations corre- sponding to this body which exist in other coun- tries require all chain cable to undergo severe tests before it is used on shipboard. Similar tests are required by railways, 'builders of cranes and dredges, and other large users of chain. The size of chains is defined by the diameter of the bar of which the links are made; thus, a one-inch chain is one whose links are made by bars one inch in diameter. According to tests made by the X,'nited States Testing IJoard. "with proper material and construction the ultimate resistance of chains may be expected to vary from 155 per cent, to 170 i)er cent, of that of the bar used in making the links and to show an average of about 1U3 per cent." This conclusion refers only to hand-welded chain cable. The Pennsylvania Railrotul recjuires its IVi-inch crane- chain to stand without giving way a pull of 70,000 i)ounds. and not to break under a load of 110,000 pounds. The British Admiralty re- quires a 2-inch stud chain cable to withstand a proof load of 72 tons before it is used. These figures are selected at random for the purpose of illustration. For a statement of the test re- quirements of the Pennsylvania Railroad, the British Admiralty, and the United States Test- ing Board, see Kent, ilechanical Engineer's Pocket Book (Xew York, 1901). Special litera- ture on the manufacture of chains is very scarce, and such as there is will be found scattered through the engineering papers and the proceed- ings of the various engineering societies. CHAIN, AxcnoR. See Cable; Axchob. CHAIN, Exgtxeeb's, or Subvetob's. See KxGIXEElilXG IXSTRUMEXTS. CHAIN BKIDGE. See Bridge. CHAIN CABLE. See Cables. CHAIN CORAL. See Halysites. CHAIN CEEEPEK. See P.ArnixiA. CHAIN MAIL, or CHAIN ARMOR. A coat of hammered iron links, interwoven into the form of a garment. It was much more flexible and convenient than either the bymie (q.v. ) or ]ilatc armor, but was not so good a protection as the latter. It was much used from the Twelfth to the Fourteenth Century. See Abmob. CHAIN-SHOT. A projectile composed of two shot fastened together by a short chain, and used chiefly at sea to cut or destroy the enemy's rigging. They have long been obsolete. CHAIN-SNAKE. A Xorth American harm- less snake {Ophiholus gctulus), found from the Hudson River and Great Lakes to Jlexico. and subject to great variation in color and markings. CHA1X-8NAEE — TOP AND PBOFU.E TTEWS. The typical form of the East and South is lus- trous black, crossed by about thirty yellow lines which unite along the sides, forming a chain- like pattern; the belly is yellowish, blotched with black ; head-plates black, with yellow spots. The lighter and larger variety west of the Mississippi is sai/i, and that of the Pacific Coast Boi/lii. In the last the markings are ivory-white, and in the form of bands encircling the body, and broaden- ing, but not coalescing along the sides, so that it has been described as '■cream-colored, sharply marked by rings of black," instead of the re- verse. Everv'where these snakes are large (4 to 5 feet), strong, active, and mainly nocturnal. They do not take to water nor climb trees, and feed mainly iijicm small mammals, amphibians, and reptiles, including other snakes; and they are protected by the country people of the South and West, as one of the 'king* snakes (q. v.), be- cause they constantly destroy venomous reptiles.
