652 SAW SAW FISH fected by making the blade thinner toward the back, but the most effectual mode is in the " set " given to the teeth. In- finishing the saw the last process is to bend half the teeth a little out on one side, and the other half on the other side. In eastern countries a group of a dozen teeth or thereabout are bent to one side, and the next group to the other. The operation is performed with a small hammer, the saw being held with the teeth resting on the rounded edge of a small anvil. The same may be done with the saw set, which is a bit of steel with slits suited to the different thick- nesses of saw blades. The amount of set va- ries with the sort of service the saw is in- tended for. The more likely the material is to clog, the wider must be the spread of the teeth ; but if it is an object to avoid the waste of the wood or the greater labor involved in a wide cut, the set should be as little as pos- sible. Circular saws were in use in 1790, and some forms have been employed for cutting the teeth of clock wheels ever since the time of Dr. Hooke. For cutting wood they were first brought into important service in the machines invented by M. I. Brunei for making ships 1 blocks, and adopted by the British ad- miralty board in Portsmouth in 1804. From that time they have continued in constant use and in various forms for different applica- tions. Saws of this kind commonly run in a slit through a table, upon which the board or other material to be sawed is placed and pushed on against the descending teeth. They are made to revolve with great rapidity, and the teeth for those intended to work in soft wood and with the grain are made well apart and inclined and curved even to the fish-hook form. For harder wood the teeth are made smaller and more upright. Insertable teeth, now much used, are placed in notches in the periphery of the saw plate, and when worn down can be replaced. This contrivance is a great saving, and at the same time allows the dimensions of the saw to be preserved. The oldest factory for large saws in the United States is probably that founded by William Rowland in Philadelphia in 1802. The largest saws in the world for sawing boards and plank are probably those made expressly for the Cali- fornia market, where they are wanted for the gigantic timber of that region. At the saw fac- tory of Messrs. R. Iloe and co., in New York, circular saws are made of 80 in. diameter and a fourth of an inch thick, and mill and cross- cut saws 10 ft. long and upward. At this establishment are produced nearly all the va- rieties of saws in use, from circular saws of 4 in. diameter up, and from the common wood saw to the largest mill saws. Some of the articles are peculiar to the United States, as also the processes employed. The steel plates are almost entirely imported from England; some are received also from Philadelphia. Chain saws, made of solid links with sernitod edges, the links being connected by rivets, are in common use by surgeons for sawing bones when they are so situated that they cannot be operated upon with the common surgeon's saw. They are also sometimes used by mechanics under similar circumstances of position. Band saws, made by serrating and setting the edge of a flexible steel band, are now largely used in shops for the working and carving of wood, making patterns, &c. They may be of almost any size, from that adapted to the sawing of scrolls in the thinnest boards to the sawing of lumber from logs, and they have the advantage of continuous motion in one direction. The band is moved by means of two rollers covered Avith leather or vulcan- ized caoutchouc, one of which is connected with the motor shafting. The earliest notice of saws being run by power is contained in a manuscript of the 13th century in Paris, in which is a representation of the saw mill with a self action turned by a water wheel. Beck- mann finds evidence of saw mills worked by water power in Augsburg, Germany, as far back as 1322. In the island of Madeira one is said to have been in operation in 1420, and the first one in Norway was built in 1530. In Holland they were in use more than 100 years soon- er than in England ; and the Dutch furnished the English with lumber. The operation of one at Lyons in 1565 is described by the bish- op of Ely, then British ambassador at Rome. The first recorded attempt to establish a saw mill in Great Britain was made near London in 1663 by a Dutchman; but the enterprise was abandoned on account of the opposition of the hand sawyers. In 1700 the advantages offered by this improvement were set before the public by one Houghton ; but no one ven- tured, to introduce it till 1767 or 1768, when by the desire of the society of arts a saw mill was built at Limehouse by James Stansfield. It was soon destroyed by the mob. In the American colonies the importance of this ex- peditious means of obtaining sawed lumber was generally felt, and efforts were early made to obtain the necessary machinery, such as was used in Holland. In 1634 a saw mill was put in operation at the falls of the Piscataqua, be- tween Berwick and the Cocheco branch of that river, and this is supposed to have been the first mill of the kind in New England. In New York as many as three mills were con- structed by the Dutch West India company about 1633, to run by water power or by wind. One of them was on Nut or Gover- nor's island, which was leased in 1639 for 500 merchantable boards yearly, half oak and half pine. Another was on Saw Mill creek, a small stream which flowed into the East river from the pond known as the Collect. On the Dela- ware saw mills were erected by the Dutch and Swedes before the arrival of Penn. SAW FISH, a cartilaginous fish of the genus pristu (Lath.), the type of a family interme- diate in position between the sharks and rays, though generally ranked with the latter. It
