Page:Cyclopaedia, Chambers - Volume 1.djvu/565

 DIA

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DiA

Diatonic, Enharmonic, or Chromatic. See Genera, j^rATONic, Vc. j±s the Lyre was improv'd, and more Chords added to it ■

will only fliew the Hour during the Spring, and <?u Seafon.

And a train, as the Sun only illumines the I«i™. o r fcwas .k»*'« •• Byfuchmeans it came from 4 of an Equinoftial Plane, while^e is in ,hfs uthe n " Chords to 7, then 8, then 10, then 14, and at laft 18. See fp hm> or on the other Side the Equator ,C^*

l»»', ,,, , „ , «, , , r '° a '"l Dial will only ihew the Hour in Autumn S

To each of thefe Chords, or Sounds, they gave a particu- Winter. Jar Name, taken from its Situation in the Diagramma, or the Lyre. Their Names, and Order, commencing from the imvefl, are as follows : •Projiambanomenos, Hypate-Hypa- ton, 'Parhypate-Hypaton, Lyohanos-Hypaton, Hypate- •Mefon, 'Parhypate-Mefon, Lycbanos-Mejon, Mefe, Trite- Synem,T'rite-Synemmenon,'Psranete-Synem-menoii,Nete- Syimn-rnenon, Para-Mefe, T'rite-Diczeugmenon, 'Para- tiete-diezeugmenon, Nete-Diezeugmenon, Trite-Hyperbo- Uo", Paranete-Hyperbolneon, Nete-Hyperbolieon.

Guide Aretine improved this Scale, or Diagram, very greatly. Finding it of too fmall Extent, he added five more Chords, or Notes to it; lay'd them all down on a Staff of 5 Lines 5 and in/lead of the long Greek Names abovemen- tioned, named all his Notes by Gregory's feven Letters. See Note, and Gammut.

The firft, or lowe/t Note of his Scale, he marked f and call'd Gamma; whence the whole Scale came to be deno- minated Gamnmt.

DIAGRAM, in Geometry, Z5c. a Scheme, for the Ex- planation, or Dcmcnftration of any Figure, or the Properties thereto belonging. See Figure.

DIAGRYD1UM, in Pharmacy, is prcpar'd Scammony. See Scammony.

The Preparation is ordinarily perform'd by boiling the Scammony in a Quince. Omers make it receive the Fumes of lighted Sulphur, whence it is call'd, Sulphurated, Diagrydium fulphiiratiim. Some incorporate it with a Quantity of Spirit oi Vitriol rofat. fufficient to make a Sort otXiquid pall, which is afterwards fet to dry in the Sun, or by a gentle Fire. And this Preparation they call Diagry- dium Rofatum. The End of all thefe Preparations is to correct the Scammony; But many more are ofOpinion, it has nothing that needs Correction, and that it may be ufed in its natural State. See Scammony.

The Word Diagrydium is form'd, by Corruption, from ^ctupiMVop, little 'Tear.

DIAHEXAPTA, orDIAHEXAPTE, among Farriers, a Drink made for Horfes, denominated from the lix In- gredients it confi/iscf; viz. Birthwort, and Gentian Roots, Juniper Berries, Bayberries, Drops of Myrrh, and Ivory Shavings, mix'd together. It is an excellent Counter-Poifon, cures Bites of venomous Beafts, Colds, Confumptions, c5c.

DIAL, or .SVtfz-Di al, anlnftrument ferving to meafure Time, by means of the Shadow of the Sun. See Time, and Shadow.

The Word is form'd from the Latin Dies, Day, becaufe indicating the Hour of the Day. See Hour.

The Greeks call it Sciatericum, from its doing it by the Shadow. See Sciatericum.

TJial is more accurately defin'd, a Draught, or De- fcription of certain Lines on a Plane, or Surface of a Body given, fo contriv'd, as that the Shadow of a Style, or a Gnomon, or a Ray of the Sun pafs'd through a Hole there- in, /hall touch certain Points at certain Hours. See Style.

The Diverfity of Sim-Dials arifes from the different Si- tuation of the Planes, and the different Figure of the Sur- faces whereon they are defcribed; whence they become denominated Equinoctial, Horizontal, Vertical, 'Polar, TJiretl, Eretl, Declining, Inclining, Reclining, Cylin- drical, ckc. See Dialling.

'Dials are fometimes diftingui/h'd into 'Primary, and Se-

Primary Dials, are thofe, either drawn on the Plane of the Horizon, call'd Horizontal Dials; or perpendicular thereto, on the Planes either of the Meridian, or Prime Ver- tical, call'd Vertical Dials; to which Number are ufually added thofe drawn on the Polar, and Equinoctial Planes, tho' neither Horizontal, nor Vertical. See Plane.

Equinoctial Dial, is that defcrib'd on the Equinoctial Plane, or a Plane reprefenting that of theEquinoctial. See Iqjinoctial.

A Plane oblique to the Horizon, either hangs over to- wards it, and makes an acute Angle with the Plane of the Horizon; or it falls off backwards from it, and makes an obttife Angle therewith. This latter is call'd a Reclining iPlane; which, if it recline back equal to the Complement of the Latitude of the Place, it lies in the Plane of the •Equinoctial; and a Dial drawn thereon, is denominated an EqninoBial Dial.

&Piino8iai TJials are ufually diftingui/h'd into Upper, which look towards the Zenith; and Lower, which refpeft me Nadir.

Now ) as the g un on jy;ii um; nes the U pp er Surface of an tqumoftial Plane, while he is in our Hemifphere, or on the Northern Side of the Equator, an Upper Equinoctial Dial

utumn, and

To have an Equinotlial Dial, therefore, that /hall ferve all the Year round, the Upper and Lower mufl be joyned together; that is, it mufl be drawn on each Side of the Plane.

And fince the Sun mines. on one Side or other of art Equinoctial Plane the whole Day; fuch a Dial will /hew all the Hours of an Artificial Day.

To defcribe an Equinoctial Dial Geometrically. „Th? Equinotlial is the firft, eafieft, and moft natural of all Mials: But the Necefltty of drawing it double, pre- vents its being much in Ufe. However, as its Strucfuro /hews the rea/on of the other Kinds; and as it even furni flics a good Mechanical Method of drawing all the other Kinds of Dials, it /hall be here laid down.

Firft, then, to defcribe an Upper Equinoftial Dial: , r0r?T?r^ nKr, C (' rab - X) >'<Ili„g,Fig.ii,.) defcribe a Cir- cle ABDE, and by two Diameters AD, and BE, imerfeft- ing each other at right Angles, divide it into Quadrants AB, BD, DE, and ER. Subdivide each Quadrant into fix equal Parts by their right Lines C I, C 1, C 3 (Sc' which Lines will be Hour-Lines. Through the Centre C drive a Style, or Pin, perpendicular to the Dane ABDE.

The Dial thus defcrib'd, being raifed fo as to be in the Plane of the Equator, the Line C 12, in the Plane of the Meridian, and the Point A looking towards the South - the Shadow of the Style will /hew the Houts both of the Fore-noon and After-noon.

For, Horary Circles include Arches of the Equator of fifteen Degrees each. (See Horary Circle.) Confc- quently the Plane of ABDE being fuppofed in the Plane of the Equator, the Horary Circle will likewife include Arches of 15 Degrees of the Circle ABDE. Where- fore, fince the Angles 12 C 11, 11 C 10, 10 C o, £?<•. are each here fuppofed 15 Degrees, theLineCu, Cn, C 10 C 9, £Sc. are Interferons of Horary Circles, with the Plane of the Equinocfial.

Again, fince the Style paffing through the Centre C,. is the Axis of the World; its Diitance from the Centre of the Earth being inconfidetable, and it being the common Diameter of the Horary Circles; its Shadow "will cover the Hour C 12, when the Sun is in the Meridian, or Circle of 12 a-Clock; C 11, when in the Circle of 11 a-Clock - C 10, when in the Circle of 10 a-Clock, &c.

Secondly, To defcribe a Lower Equinoffial Dial; The Method is the fame as that for the Upper Dial already defcribed; except that no Hour-Lines are to be drawn beyond that of 6 a-Clock.

Thirdly, To defcribe an Univerfal Equinoctial Dial t Joyn two Metal, or Ivory Planes ABCD, and CDEFj {Fig. 5.) fo as to be moveable at the Joynt. On the upper Surface of the Piane ABCD, defcribe an Upper Equi- noSial Dial, and upon the lower a Lower, as already di- rected; and through the Center I drive a Style. In the Plane DEFC cut a Box, and put a Magnetical Needle G therein; fit on the fame Plane a Brafs Quadrant nicely graduated, and paffing through a Hole cut in the Plane ABCD. Now, fince this may be fo plac'd, by means of the Needle, as that the Line 1 12, /hall be in the Plane of the Meridian : And, by means of the Quadrant, may be fo raifed, as that the Angle BCE /hall be equal to the Ele- vation of the Equator; it will ferve as a Dial in any Part of the World.

Horizontal Dial, is that defcribed on a Horizontal Plane, or a Plane Parallel to the Horizon. See Horizon.

Since the Sun may illumine a Florizontal Plane at all Times of the Year, while he is above the Horizon; a Ho- rizontal Dial may Iliew all the Hours of the Artificial Day* throughout the Year : So that a more perfect Dial cannot: be requir'd.

T"o defcribe an Horizontal Dial Geometrically.

Draw a Meridian Line B, {Fig. 6.) on the given immo- veable Plane; or affume it, at Pieafure, on a moveable one; See Meridian Line.

From a Point taken at Pieafure, as C, ereft a Perpendi- cular CD, and make the Angle CAD equal to the Eleva- tion of the Pole. In D make another Angle CDE equal likewife to the Elevation of the Pole, and draw the right Line DC meeting AB in E. Then make EB equal to ED, and from the Centre B with the Radius EB, defcriba a Quadrant fcBF, which divide into 6 equal Parts. Through E draw the right Line GH, cutting AB at right Angles, From the Centre B through the feveral Divifions of the Quadrant EI draw right Lines B a, B b, Be, B d, BH y