SEWERAGE. 24 SEWING MACHINE. siphon, which comes into action when the water in the tank reaches a certain level. Anotiier Ivind of automatic arrangement is an irregularly shaped hucket, or tank, so arranged that when it has been filled by the supply pipe its centre of gravity is disturbed and the water discharged by tilting. Autonuvtic flush tanks should dis- charge at least once in twenty-four hours, and liberate some 200 or 250 gallons of water at each action. In the combined system of sewers all these methods of flushing are liable to be in- adequate, except on the smaller sewers. Cleaning by hand or otherwise then becomes necessary. Ventilation of Sewers is a thing which has given rise to much discussion. The simplest means are generally the best, and it is rarely the case in sewers that any improvement can be made over thoroughly good design and execution in the way of grade, "alignment, and smooth inte- riors. In some English cities ventilating shafts have been provided, but this has rarely if ever been done in America. Perforated manhole covers are about all the specific provision for ventilation made in the United States. The omission of traps at the foot of the house soil pipes will con- tribute no small amount of ventilation, and is sometimes practiced. Objection to this plan is oft'ered by some on the ground of danger to the inmates of houses if the soil pipes are converted into as many ventilating shafts, but in properly designed and constructed sewers, having such ample ventilation as is thus afforded, there is a growing belief that no reason for apprehension will follow the practice. The 'sewer gas' of which so much was said some years ago does not exist — as a specific gas. Sewers, and particularly those retaining deposits of organic matter for considerable periods, may yield various gases of decomposition, and under extreme conditions these gases may be positively and immediately dangerous. Numerous careful studies have shown that the bacterial contents of the air in sewers resemble those of the outer air above, rather than the bacteria in the sewage, and that they are comparatively few in numbers. In fact, the" air in anything approaching a model sewer is better than that in overcrowded theatres and churches. The menace of sewerage systems is the pollution of public water supplies, not the air of either streets or buildings. Xevertheless, great care should be taken to prevent the ac- cumulation of bad air in sewers and to reduce to a minimum the access of any sewer air to houses or other buildings. Pumping Works for sewage do not necessarily difi'er much from those for water, except that they generally lift the sewage but a few feet, and should be of a type not readily damaged by foreign matter. Centrifugal pumps are often used to lift sewage, as being economical, with low lifts, and having no valves likely to get out of order. Other kinds of steam pumps are used; also air displacement pumps, known as Shone ejectors, and pumps driven by the sewage itself, known as sewage lifts. In the Liernur system of sewerage the sewage is drawn or sucked to a central station through iron pipes, from which the air is exhausted by proper pumping ma- chinery. This system was introduced in Hol- land about 1880, but gained comparatively little foothold in Continental Europe and none in England or America. One of the leading features of the Liernur system was keeping the excre- ment largely free from water and manufacturing it into a fertilizer. The iron pipes and the construction and operation of the machinery re- quired for the system entailed a large outlay for fixed and current expenses. iSiBLiOGRAPiiY. Folwell, Sewerage (New York, I'JOO), a readily comprehensible discussion of the design, construction, and maintenance of sewers; Ogden, Seiver Design (New York, 1899), discusses rainfall, population, and other factors of sewer design; Staley and Pierson, Heparute Kystem, of Sewerage (3d ed,. New York, 1899) ; Goodell's translation and adaptation from the German of Baumeister's Cleaning and Sewerage of Cities (2d ed., New York, 1895), a condensed account of European and American practice; Waring, Sewerage and Land Drainage (3d ed., New York, 1891), largely but not wholly de- voted to the autlior's methods and executed works along the lines of the strictly separate system of sewerage; Jloore, Sanitary Engineering (Lon- don and New York, 1898), an extensive treatise, chiefly from the English standpoint, and devoted almost wholly to sewerage. See also list of works under Sew.age Disposal, which read in tliis connection. SEWING MACHINE (from setc, AS. seow- ian, Gotli. sin Jan. OHG. sitiwan, siwati, to sew; connected with Lat. snere. OChurch Slav, shiti, Lith. siuti, Lett, shi'it, Skt. sir, to sew). It is probable that the first sewing machine was made by an Englishman named Thomas Saint, and was patented July 17, 1790. Though made of wood, it resembled th"e later successful machines in that it had an overhanging arm, vertically recipro- cating needle, continuous thread, and automatic feed. This machine had a notch instead of an eye in the needle, for the thread to pass through, and a hole was punched by an awl for the needle to pass through. It produced a single-thread chain- stitch. In 1830 Barthglemy Thimonier pro- duced a sewing machine which was patented first in France and some time afterwards in the United States. This machine was so far successful as to be employed to make clothing for the French army, and it thereupon was de- stroyed by an ignorant and furious mob. Thi- monier's first machine was also of wood, but he afterwards constructed one of metal, driven by a cord and treadle. It had the overhanging arm, flat cloth plate, vertical post, vertical re- ciprocating needle, continuous thread, and presser-foot of the modern machine. The needle was hooked and had to be passed backward and forward through the cloth twice to complete a stitch. In 1841 Newton and Archbold patented in England a machine using an eye-pointed needle and producing a chain-stitch. About the same time that the French machine was being perfected. Walter Hunt is said to have made a sewing machine having the double thread and lock-stitch which was characteristic of the Howe machine. Hunt, however, failed to perfect or patent his invention for so many years after it was first put upon the market that when at length he applied for a patent it was denied him. In 1846 Elias Howe (q.v.) patented a sewing machine containing most of the essential fea- tures of the modern machine. The needle was curved and moved back and forth horizontally instead of vertically. The machine, crude as it was, included the grooved, eye-pointed needle and
