Page:The New International Encyclopædia 1st ed. v. 12.djvu/187

LEVEL. with the strike. In some regions, such as the anthracite region of Pennsylvania, tlie term gangway is used instead of level, and the main gangway is called the entry. Chambers and drifts are usually run oH' from the levels. LEVELERS. An ultra-reform party which aro^e in the army of the Long Parliament, when the army overawed that body, and sent Charles I. to Hampton Court in 1647. They determined to level all ranks and establish an equality of titles and estates throughout the Kingdom. Several of the officers belonging to this party were cash- iered in 1649; and on the departure of Cromwell for Ireland, at the close of that year, they raised mutinies in various quarters, which were sup- pressed by Fairfax with bloodshed. One of their works. The Leveler, or the Principles and Max- ims Concerning Government and Religion of Those Commonly Culled Levelers, shows that in politics their fundamental principles included : (1 ) The impartial authority of the law; (2) the legislative power of Parliament; (3) absolute equality before the law; (4) the arming of the people for securing the enforcement of the laws, and the protection of their liberties. In religion they claimed: (1) Absolute liberty of conscience; ( 2 ) freedom for every one to act according to his knowledge, even if this knowledge should be false; (3) religion to be considered in two aspects — one as the correct understanding of revelation, which is a private affair, the other as its effects manifested in actions, which are subject to the authorities; (4) they condemned all strife on matters of faith and forms of wor- ship. This sect disappeared at the time of the Restoration. LEVELING. In surveying, the operation of ascertaining the different elevations of objects on the surface of the earth. Leveling is employed to find the relative elevation of points a con- siderable distance apart, to obtain the profile of a line, or to establish a grade. These objects may be more or less intermingled in any piece of work. For convenience of discussion, leveling operations may be broadly classed into common spirit-leveling, trigonometrical leveling, and pre- cise spirit-leveling. The difference between the first and the third classes lies chiefly in the de- gree of accuracy with which the work is per- form<^d. Spirit-leveling operations are essentially the same whatever their object may be. For ex- ample, suppose it is required to determine the difference in elevation between two distant points. The instruments are the level and the level- rod, forms of which are illustrated on the Plate of Engi.neerino IN.STRIMENTS. The rod is set up on the starting-point and the level is set up a convenient ilistance away in the direction of the otlier point, and where a plain view is had of the level-rod. When the level is adjusted, the levelman takes a reading on the graduated level- rod and records it in his note-book. The rodman then moves his rod to a point ahead of the level, and the levelman takes another reading, which he likewise records. This reading is called a fore- sight, in contradistinction to the first reading, which is called a backsight. The levelman then removes his level to a point ahead of the second position of the rod. sets it up. adjusts it, and takes a backsight reading on the rod. This being recorded, the rodman moves to a new position ahead of the level, where he sets up the rod on which the levelman takes a foresight reading, and then moves again to a new position ahead of the rodman. By means of sufficient repetitions of these operations the distance between the two points whose dilTerences in elevation are to be determined is traversed, the last reading being taken with the rod set up on the finishing-point. When the final reading has been taken a simple calculation in addition and subtraction per- formed on the recorded readings gives the level- man the result he desires, which is the difference in elevation between the starting and the finish- ing points. In conducting such a series of read- ings as has been described, the attempt is always made to make the lengths of the backsight and foresight for each setting of the level as nearly equal as possible, and also to make them as long as possible consistent with clearness of sight. It is in this way that the profile of the route of a railway line or highway is determined. Having obtained the natural profile, the engineer in railway or road building has to cut down the irregularities by means of one or more uni- form gradients. These he determines first on paper, figuring out the rate of ascent or descent. Supposing that he has determined a grade of one foot in a hundred feet, then each succeeding inteivening point is one foot higher or lower, according to direction, than the preceding point. The levelman then re-runs his line of levels according to this adopted gradient, and marks on the stake at each intervening point the eleva- tion at which its top is above or below the adopted grade-line. Precise spirit-leveling is performed in exactly the same way, except that larger and more per- fect instruments are employed and more care is taken in making the readings and performing other necessary operations. In trigonometric leveling the difference of ele- vation between two different points is determined by measuring the vertical angle, the horizontal distance between the two points having been pre- viously measured by triangulation. ( See Slr- VEYING.) This distance and the vertical angle give the necessary data for the calculation of the difference in elevation by the familiar rules of trigonometry. This method of leveling is liable to error from refraction, and is far less precise than spirit-leveling when the latter method is practicable. Elevations of different points, as the tops of mountains, are often measured by barom- eter or by noting the temperature at which water boils. These are not exact methods, and are used only in exploration work. See Hypsoiietry. LEVEN, le'v'n. Loch. A picturesque lake in the east of Kinross-shire, Scotland (ilap: Scotland, E 3). It is oval in shape, about four miles long and two wide. It is celebrated for its trout. Loch Leven Castle, in which, in 1.567, Queen Mary was imprisoned and forced formally to abdicate the throne, and whence she escaped in 15CS. is one of the islets in the lake. LEVENSHTJLME, le'v'nz-hulm. A manufac- turing town in Lancashire, England, three and one-half miles southeast of Jfanchester (Jlap: England. D 3). Population, in 1891, 5500; in ion I. 11. .500. LEV^QUE, IS'vak'. .lE.>r Cii.irles (1818- 1900). A French philosopher, born at Bordeaux. He was a pupil of the Normal School, taught at Besancon, and studied in Athens (1847-48)'