DIAGBAH. 196 DIAL. direction of the dnui^'lit. Kix a pencil to the index, and let its point rest upon a sheet of paper on a plane or a cylinder which moves at a uniform velocity in a direction perpendicular to the mo- tion of the index. The conil)iiied movements of the pencil and |)apcr beneath it will trace a more or less irrc;;ular line. If tlic ixvvv of drau^'hl is constant, the pencil will remain at a constant distance from the edge of the pai)er, and the trace will be parallel to the edge. If the paper does not move while the pencil varies, the line will be perpendicular to the edge. If both move, and the pencil is subject to a diminishing force, the trace will be oblique, approaching one edge; while if the force increases, the oblique trace will diverge from the same edge. Such mechanism is often arranged for instruments which indicate meteorological, physiological, or other changes, as the force and direction of winds, or the pulsa- tion of the arteries ( see Spiiycmogr.pii ) , or the novements of a clock combined with the observa- tions of an astronomer. (See CiinoNOGB.i'n.) An important applicafion of the same principle is found in the indicator diagram, by which the pressure of the steam in the steam-engine and the work done by each stroke of the piston be- come matters of record. The paper moves with the movement of the piston, both in ita excursion and return; the pencil moves at risht angles to the direction of the motion of the paper, under the influence of the steam pressure, and the dia- gram drawn shows for each instant of the stroke the volume and pressure of the steam, while the total area of the diagram indicates the amount of work done. A me<hanical device to illustrate the luminosity of various colors was invented by Xswton, and is known as yetclon's diariram. In mechanics {he .stresses on the various parts of a frame or bridge are graphically exhibited by a form known as a stress or funicular dia- gram. The seismometer, seismograph, or scismo- scope is an instrument to record the velocity, di- rection, and magnitude of seismic waves. See HOIIOGRAPII. DIAKOVA, d.'a-k'i'va. A town of European Turkey, situated, in the Vilayet of Kosovo, on a tributary of the Wliite Drin, 20 miles northwest of Prisrend. Population, about 2.5,000, mostly Mohammedan Albanians. DIAL (ML. dialis, daily, from Lat. dies, day). The. A wellknown American magitzine. found- ed at Boston, Mass., in 1840, as the official organ of the .so-called 'Transcendental' school of thought. As early as IS.S.d the idea was conceived by members of that school of idealists of .start- ing a paper to be called The Transecndcntalist, and Emerson, the same year, went so far as to suggest that Carlyle should be invited to come to America to assume the editorship of it. The scheme was not in that form realized, and the paper which finally appeared. The Dial, was not issued till .July. IStO, with Margaret Fuller (see Filler, S.raii Maroaret) (is editor. At the end of two years she was succeeded by Emerson. The pap<>r, through laik of funds, came to an end with the A|>ril number of 1S44. after a career marked by unusual brilliance in its ma- terial and exirnordinarj- fame on (he part of its contributors. Tn it had been published, among others, Fmerson's pr<i«e essays entitled "The Transeendentalist," "The Conservative." and some of his best -known poems, as "The Sphinx;" 'Woodnotes;" "The Problem;" and "Fate." Con- stant contributors were Margaret Fuller, Anio- Uronson Alcott, George lUpley, .lames Freeman (,'Iarke, Theodore Parker, W. H. (.'banning, W . E. (^banning, and Henry David Thorcau. who wrote for nearly every number. A reissue of The Dial has been published by (lie Rowfant Club. Consult Cooke, IJislorical and liioffraphical In- troduction to the Rowfant reissue (London, 1902). SIAXi AND DIALING. A sundial is an in- strument for measuring time by means of the motion of the sun's shadow. It is an instrument of very great antiquity, the earliest mention of it being in Isa. xx.xviii. 8: and before clocks and watdies became common it was in general use as a tinu'keeper. The art of constructing dials to suit any place and situation was then an im- portant branch of mathematical study: now the subject is more an object of curiosity than utility. A dial consists of two parts — the stile, or gno- mon, usually the edge of a plate of metal, nuide parallel to the earth's axis, and pointing toward the pole: and the dial plane, which may be of anv hard substance, and cm which are marked the directions of the shadow for the several hours of the day, their halves, quarters, etc. Dials re- ceive various names, according, mostly, to the positions which they arc constructed to occupy. When the dial plane is on the plane of the horizon, the dial is called a horiz<mtal dial : when perpendicular to that plane, a vertical dial. An equinoctial dial is one whose plane is parallel to the equator. Besides these names, there are others, such as the south dial, north dial, east dial, west dial, polar dial, declining dial, of which it is useless to write at length. These names all depend on the position of the dial plane. The cylindrical dial is a dial drawn on the cur-ed surface of a cylinder. The ring dial is an ingenious small portal>le dial, but rather a curious toy than a scientific instrument. A nifjht or nocturnal dial is an instrument for showing the hour of the night by the shadow of the moon or jdanels. .Moonilials may be am- structed relative to the moon's motion: or the hour may be found by the moon's shadow on a sun-dial by computation. DtALiXG. The stile of a dial being parallel to the earth's axis, those familiar with spherical trigonometry will readily see that the problem of constructing a dial resolves itself into that of ascertaining where the hour-lines cut a ;;ivcn circle, with a view to the graduation of the dial |)lane. Rut even without a knowledge of trigo- nometry the principle may be readily understood from the following illustrations. Suppose a hol- low and transparent sphere, as of glass, to repre- sent the earth: and suppose its equator divided into twenty-four equal parts by the meridians, one of them passing through a given place — .say London. (See Horizon.) If the hour of twelve 1* marked at the equator, both on the latter meridian and that opposite it. and all the rest of the hours in order on the other meridians, those meridians will be the hour-circles of Lon- don, because, as the .sun appears to move round the earth in twenty-four hours, he will pass from one meridian to another in one hour. Tlicn, if the sphere has an opaque axis, terminating in the poles, the shadow of this axis would fall, in the eiuirse of the day. on every particular merid- ian and hour, as the sun came to the plane of
