Page:Collier's New Encyclopedia v. 07.djvu/457

LEFT PTJLKOWA 381 PULMOTOR gressman. In 1878 he assumed control of the St. Louis "Post-Dispatch," and in 1883 purchased the New York "World." He endowed a School of Journalism at Columbia University (1903) and gave large sums for educational and philan- thropic purposes. He died in 1911. PTJLKOWA, a village of Russia, 10 miles S. of the site of a magnificent ob- servatory (lat. 59° 46' 18" N. and Ion. 30° 19' 40" E.), the "St. Petersburg ob- servatory," built by the Czar Nicholas in 1838-1839. In 1882 one of the largest telescopes in the world was erected here. Besides being one of the largest institu- tions for original research in the world, it is also a school for the training of as- tronomers and geodesists. It contains the largest refracting telescope in the world, except the 36-inch Lick glass, and the Yerkes telescope at the University of Chicago, 111., its objective being 30 inches in diameter. It was made by the firm of Alvan Clark & Sons, of Cam- bridgeport, Mass., the makers (since then) of the glass for the Lick telescope. ^ PULLEY, in mechanics, one of the six simple machines or mechanical pow- ers. It consists of a small circular plate or wheel which can turn round an axis passing through the centers of its faces, and having its ends supported by a framework which is called the block. The circular plate has a groove cut in its edge to prevent a string from slipping off when it is put round the pulley. With a single fixed pulley (that is one in which the block in which the pulley turns is fixed), there is neither gain nor loss of power; for, as the tension in every part of the cord is the same, if a weight be suspended at one extremity, an equal weight must be applied at the other to maintain equilibrium. Hence, the effect of a fixed pulley is simply to change the direction of a force. By means of movable pulleys one can gain mechanical advantage, greater or less, according to the number and mode of combination of the pulleys. Fast pulley, a pulley firmly attached to the shaft from which it receives or to which it communicates motion. Loose pulley, a pulley running free on the shaft, to receive the belt and allow it still to traverse without being affected by, or affecting the motion of, the shaft- ing. Sliding pulley, a kind of coupling in which the band-pulley is slipped into or out of engagement with an arm freely attached to the shaft and rotating there- with. PULLMAN, GEORGE MORTIMER, an American inventor; born in Chautau- qua CO., N. Y., March 3, 1831; learned Vol. VII— Cyc the cabinetmaker's trade; settled in Chi- cago; studied for many years the prob- lem of making journeys by rail more comfortable; and as a result invented the Pullman palace car. In 1863 he started building these cars, and in 1867 organized the Pullman Palace Car Com- pany. He also invented the vestibule train and founded the town of Pullman, 111., in 1880. He died in Chicago, Oct. 19, 1897. PULMOBRANCHIATA, an order of gastropod mollusks (also called by some naturalists Pulmonata), in which the respiratory organ is a cavity formed by the adhesion of the mantle by its mar- gin to the neck of the animal. The greater part of them are terrestrial, among these being the snails and slugs. PULMOTOR, a device used for pro- ducing artificial respiration. It is used in cases of drowning, asphyxiation by noxious gases and electric shock. There are several types of pulmotor on the market such as the lung motor, the Brat apparatus and the pulmotor. The pul- motor which automatically makes the respiratory changes is the most common of the various devices. The air used in the pulmotor is a mixture of atmospheric air and pure oxygen, while in the Brat apparatus pure oxygen is used. The pulmotor consists of a tank of com- pressed oxygen, a reducing valve which connects with an injector, from which a n^ixture of air and oxygen pass through a hose to a face mask. Although the oxygen in the tank approximates chemi- cal purity, the mixture which is injected into the lungs averages only about 30 per cent, oxygen, an increase of about 9 per cent, over the amount contained in pure air. A valve mechanism causes al- ternate pressure and suction to be ap- plied at the face mask. The lung motor consists of a pair of pumps so connected that each one alternately pumps fresh air to the face mask or exhausts the air injected by the other pump. Connec- tion may be made to an oxygen tank and the air enriched. It was felt by some people that the backers of the pulmotor had been somewhat extravagant in the claims which they made for their ap- paratus and a committee was appointed to make a scientific study of its actual worth. The committee which was head- ed by Professor Yandell Henderson of Yale University acting under the direc- tion of the United States Bureau of Mines, made a series of experiments on various animals, but the results obtained were not conclusive. It was found by the investigation that expiration was caused by suction, the extreme strength of which often caused complete collapse 25