THREAD-WORMS. 254 THRESHING. long, has been found living in man ; allied species occur in the brain or brain-cavity of birds. Among the most formidable human, parasites of this group are the Trichina (q.v.), the guinea- worm (q.v. ), and the species of Filaria. FUaria saiigiiinis-houiims, a microscopic thread-worm found living in the blood of the mosquito in In- dia and Cliina. is thought to occasion the disease known as elephantiasis. The formidable disease called heri-ben' is supposed to be due to a nema- tode worm, whose eggs and embryos swarm by millions in the soil and dirty puddles around the villages. In certain species of the family Anguil- lulidae there is an alternation of generations (see Parthexogexesis), from an hermaphroditic internal parasitic to a free dioecious generation. Thus Rhahditis [ Rhabdonema) nigrovenosa lives in nnul, and gives rise to a second form living in the lungs of frogs. THREATS. See such titles as Blackmail; False Imprisonment: Conspibact; Intimida- tion ; and consult the authorities referred to under Criminal L.w and Con.spikacy. THREE CHAPTER CONTROVERSY. See CHAPTER.S, The Three. THREE CHOIRS FESTIVAL. An English musical festival which had its first regular or- ganization in 1724, when the three cathedral clioirs of Gloucester. Worcester, and Hereford joined for the performance of a cathedral serv- ice, and an oratorio performance given in the Shire Hall. The proceeds have always been de- voted to a fund for the relief of the widows and orphans of the poorer clergy of the three dio- ceses. In 1753 the festival was extended to three days, and in 1830 to four days, the period which still prevails. The festivals are held al- ternately in each of the three cities, and the conductor is always the organist of the cathedral of the city in which the festival is held. THREE-COLOR PROCESS. A photome- chanical process of reproducing in color appli- cable either to stone or metal. The general pro- cess consists in first making three photograph negatives of the same subject through three dif- ferent color screens representing the three pri- mary colors, red. yellow, and blue. From these three negatives printing blocks are made and the result is obtained by making three printings, one from each block, Avith three different pig- ments, each pigment representing as nearly as possible the color originally used in the color screen. The accuracy of the finished picture de- pends, therefore, to' a great extent, upon the correctness of the pigments selected. The process is largely mechanical and the re- sult is only approximately correct, though increased care is being taken in the ma- nipulation and better results are constant- ly obtained. The Colored Plate shown in the article on Lithography (q.v.) was prepared in this manner. Reference should also be made to the article Color Photography, where the un- derlying principles are explained. The method of making the metal 'half-tone' plates is dis- cussed under PnCTO-ENGEAVixG. THREE KINGS OF COLOGNE. The three ■wise men of the East or Jlagi who followed the star to the birthplace of the infant Jesus. Their names are usually given as Caspar, Jlelchior, and Balthazar. Their bones are supposed to be pre- served in Cologne Cathedral. THREE MUSKETEERS. See Trois Mous- quetaires. THREE RIVERS. A port of entry and the capital of Saint ilaurice County, Quebec, Canada, at the Junction of the Saint Lawrence and Saint Maurice rivers, and on the Grand Trunk and the Canadian Pacific railroads, midway between Mon- treal and Quebec (Map: Quebec, D 4). It was founded in 1034 by Champlain, and is within a short distance from the famous falls of Shawa- negan. It has a cathedral, a college, saw mills, iron foundries, machine shops, and a shoe factory, and the water power of the falls has been utilized for the manufacture of wood pulp. Here on .June 8, 177C, an American force of about 2000 men under General Thompson attacked a British force of about 6000 men, and was disastrously defeated, both Gieneral Tliompson and Colonel Irvine, his second in command, being captured. Population, in 1891, 8334: in 1901, 9981. THRESHER-SHARK, or Swingletall. An extraordinary shark (Alopias vidi)es) abounding in all warm seas, especially in the Mediterranean and the Atlantic, and distinguished by its long tail. (See Plate of CtRE.4^t Sharks under Shark.) This is an extension of the upper lobe of the lietei'ocercal tail to a length equal or exceeding that of the body, and is used in obtaining the food. This shark follows the herring, menhaden, and other gregarious fishes in their migrations, and, rushing into their schools, threshes about with its tail, killing or stunning many. It is reported to attack whales, but there is no scientific evi- dence of this. It is about 15 feet long, lead color above, and whitish beneath, and contains some oil, but not enough to compensate for the trouble its capture causes. THRESHING (from thresh, AS. ]>erscan, pwrscan, Goth, priskan, OHG. drescan, Ger. dreschen, to thresh; connected with Lith. trasz- kcti, to rattle, OChurch Slav, ihryeshiiti, to strike) and Threshing Machines, Thresh- ing is the separating of the grain or seeds of plants from the straw or haulm, a process which has been accomplished in various ages and coun- tries by sundry means more or less effective. The first method known to have been practiced was the beating out of the grain from the ears with a stick. An improvement on this method was the practice of the ancient Egyptians and Israelites of spreading out the loosened sheaves of grain on a circular piece of hard ground and driving oxen over it, so as to tread the grain out ; but as this mode was found to damage a portion of the grain, it was partially super.seded in later times by the threshing-sledge, a heavy frame mounted on three rollers, which was dragged over the heaps of sheaves. The method of treading out the grain or seed, however, is still used to a limited extent on small farms in the United States, especially in case of buckwheat, c4over, beans, etc. Similar methods of threshing were employed by the Greeks and Romans, the stick {fiistis, bacuhim, pertica ) , the treading by men or horses, and the threshing-sledge (tribtihim) being found in com- mon use among them : but their threshing-sledge, which is still to be seen in operation in Greece, Asia Minor. Georgia, and Syria, differed from the Eastern one by having pieces of iron or sharp
