Page:The New International Encyclopædia 1st ed. v. 06.djvu/913

ELEVATION. 793 ELEVATOR. the height above the lioiizon of an object on the celestial sphere, measured by the arc of a vertical circle parsing through the object. Thus, the ele- vation of the equator is an arc of the meridian intercepted between the equator and the horizon of the place. The elevation of the pole is the meridian arc intercepted between the horizon and Uie celestial pole. It is the complement of the equator's elevation, and is always equal to the latitude of the place. The elevation of a star or any other |)oint is similarly its height above the horizon, and is a maximum when the star is on the meridian. See Altitude. The architecture and elevation is the geometri- cal representation of the exterior, or section of a building, which gives an ajipcarance as if it were viewed from such a distance that no con- vergence of lines would be seen. Technically speaking, the elevation of a building is its verti- cal righl-line projection. The elevation is one of the three drawings which are essential in de- signing any architectural structure, the others being the plan (q.v. i and tlic section (q.v.). ELEVATION AND SUBSIDENCE. Terms applied to vertical movements of the earth's crust. The great movements of the earth's crust are believed to be due to the tendency of the outer crust of the earth to contract in order to fit a more rapidly cooling and shrinking nucleus. While local areas may be elevated — that is, car- ried farther from the centre of the earth — due to the efforts of roeks to relieve themselves from great lateral stresses by bulging out. it is held by most geologists that large areas are seldom actually elevated, but that uplift is only apparent because of the subsidence of adjacent areas. In other words, it is believed that all parts of the crust are subsiding, some, however, faster than others, thus giving the impression that the ad- jacent areas are rising. If the sea-bottom should subside, the water would flow away from the continental shores, and the continents would ap- parently rise, although in reality they might re- main stationary. The great movements of up- lift and subsidence are ordinarily, considered in two great classes : (1) Epeirogenic movements, or vertical movements of large areas such as con- tinents, or large parts of continents; (2) oro- genic, or mountain-making movements — i.e. (he movements which result in the folding and cor- rugation of the earth's crust into mountainous areas. See Mnfi xtaix. ELEVATION OF THE CBOSS. The subject of two famous paintings, one by Rubens (1010), in the Antwerp Cathedral, the other by Van Dyck (1632), in Notre Dame, at Courtrai, Belgium. The former represents the bare cross being raised into position amid .i throng: in the latter the Saviour has already been crucified, and the in- clined beam is being supported and adjusted by four men. snrrovmded by the guard. ELEVATOR (Lat. elevator, raiser, from ele- vnrr. tn raise I or T.irT. A mechanical contriv- ance for transporting passengers or freight be- tween points at different levels, such as the sever- al stories of a building. The modern high-speed passenger elevator is usuallv operated by hy- draulic or electric power, and it consists (1) of a rectangular car which moves up and down be- tween guides in a shaft or well, with doors open- ing into each floor, and (2) of the mechanism necessary to give this car its up and down move- ment. Such elevators arc usually designed to run at a maxinuun speed of from tioo to 800 feet per minute, but may be run at any less spce<l the operator may desire. Safety from accident is provided for in various ways. Broadly con- sidend, modern elevator safely devices may be divided into two classes: (1) Clutch devices which are thrown into operation when the car exceeds a certain speed, and stop the car by seiz- ing hold of oi; gripping guides fastened to the walls of the elevator shaft: and (2) air-cushion devices, whose purpose is to lireak the shock of a falling car so that injury will not result to its passengers. Elevator safety grips are of various forms, and the successful ones are nearly all owned or controlled by firms which build ele- vators. The general principle upon which these devices operate is nearly the same, whatever their indi- vidual forms may be. A governor is placed on the elevator ear or on the beam which supports the sheaves, whose speed varies with the speed of the car. When a certain speed is exceeded this governor actuates a mechanism which throws the clutch into operation, as is seen in the full- jiagc illustration. The older and most commonly used form of air-cushion, invented by F. T. Elli- thorpe. consists essentially of making the lower portion of the elevator shaft tight so that the car falling into it acts as a piston in a cylinder and is brought to a slow stop by the compression of the confined air. In one of the largest in- stallations of this form of cushion, the closed shaft begins at the third story, and is 50 feet deep. The total travel of the car is 287 feet, which makes the ratio of the depth of the air- cushion to the distance of travel as 1 to .5.74. In a display test which was made with the cush- ion, a car weighing 2000 pounds was allowed ' to drop the total 287 feet, and it came to a complete stop without breaking eggs and elec- tric-light bulbs which were jdaced on the floor of the car. A more recent form of air-cushion has the air-cushion at the top of the shaft. In this arrangement the car carries two grips, the jaws of which. in normal operation, encircle but slide loosely over two steel cables provided with buttons at intervals. These cables are attached at their tops to a yoke, which is carried by a pis- ton-rod and piston working in a vertical steel cylinder placed on the roof of the shaft. Nor- mally the piston is held at the top of the cylin- der by a spring latch. When the car falls the governor first operates a clutch which opens this latch, and. secondly, it operates the grips which clo.se on the button-ropes. This throws the weight of the car into the yoke and jiiston. which, slid- ing down in the cylinder, compresses the con- tained air and brings the ear to a gradual stop. The safety device is the most important appur- tenance of the elevator car; the car itself is of simple construction, consisting usually of a rec- tangular steel framework covered inside with a grillwork of metal and provided with a solid floor and roof attachments for the hoisting cable. Eor high-s[)eed passenger elevators the operat- ing mechanism is usually hydraulic or electric. In hydraulic elevators the hoisting cables run from the top of the car to and over sheaves at the top of the shaft, and thence to the operatin!^ machinery in the ha.sement of the building. In the basement the cables pass around alternately fixed and traveling sheaves, the latter being at-