Hour Glasses

All the Tear Round gives the followmg account of theae primitiva devices tor taking note of time : ' Sand, when very fine and dry, flows through an orifica with regular speed, wbether th& quantity be great or sinall. In this property it is unlike water, which as we havo seen, descends more swii'tly the greater the weight of it there isabove the oritioe. Supposing sucb sand filled a tiili glass cylinder with h, small oritice at t ie bottom ; supposing there wils undern ath this another cylinder, graduated at e-jual intervals of an inch or half iuch ; then the saud would aocumulate in this graduated cylinder, after entering it through the oritice, by equal quantities in equal times ; and the latter cylinder would becoiue a true measure or nieter ot hour or half-hour portions of time. Nay, more than this. Not ouly is the flow of saud uniform whatever be the quantity which is above the orifice, but it cannot bo mude more rapid hy any ainount of pressuro. We may use a piston, plug, or plunger, and press it down forcibly on the sand in the tube, and yet the _sand wül flow out as befcre, neither more nor less quickly. The pressuie is not obliterated ; it dues some work ; but that work is exerted against the sides of the tube- a fact soon made manifest by the rupture of the tube unless it be made of stiong material. This singular property of sand becomes of a high value in mining and quarrying. When a hole is bored in a hard rook, partly filled with gunpowder, and exploded by means of a tuse or an electric wire, the products of combustión are blown out ot the hole and scarcoly any useful effect is produced in blasting the rock. When a plug of wood is driv en in after the powder, this also is blown out, and the blast is nearly as inpffective as before. But wheu the charge is plugged with sand, this refuses to be driven out ; tutt force of the explosión expends itself laterally, and the rock is riven into fragments. A time-glass might be made of a vertical cylindrical tube, so far as the principal of action is concerned ; but the wellknown forin has inany conveniences Two oonioal vessels, or two paar-shaped vessels, joined together at their pointud ends, and an orifice piercing the place of junction - this sufHciently denotes the usual loria. In making tho hour, or minute, or three-minute glasses sold in the shops, the sand is placed in one bulb beforo the other is jomed to it. Connnon sand is used for cheiip glasses ; but the best is white silver sand, thoroughly dried and sifted. The two bulbs ure fix.d together by tbe heat of a blowpipe, with dut; attentiou. to the maintainence of the bore or orifice. The French have an ingenious mode of making and filling saudglasses by blowing four bulbs on one tube or glass ; two to form the time measuriug part of the apparatus one to bo opened and made to serve as a hopper, through which tho sand is poured in, and the other to be opened aud serve as a stand. Egg-shell, baked and finely pounded, is found to be a good substitute for sand. No one knows at what period these time-measures were introduced. In a bassorelievo at the Mattei Palace, representing the marriage of Thetis and Pelesus, Morpheus appears holding an hourglass in bis hand. This shows, at any rate, that such iinpleinents were known in the mythological days of' Greece. The Atheniarïs, we are told, carried hourglasses about with them, somewhat as we do our pocket watches. But the most interestiug feature connected with the subject is the use of the hour-glass to regúlate the lengthof sermons. This was especially the cat,e after thn Reformation, when long sermons came into fashiou. Tho medteval and pre-Keformation di vines contented themselves with ahomily varyiugfrom ten to 30 minutes in lengtii; but the Hugue-Waldeness, Puritans, Covenanters, Independents, and other protecting bodies, conceiving it their duty to assert and maintain these relating to doctrine and discipline, made their seruions argumentative, and sometimes span out the argument to an inordinate length. The hour-glass littrally corresponded with its name, for it ran tor one hour before the sand had all passed through and the preiicher claimed his full 60 minutes. Sometimes he was provided with a halihour glasá, which he used when a shorler sermón was to be preached. It was ftbout the uiiddle of tha seventeenth century when Puritan sermons oocasionaly reached the enorinous length of two hours thal the hour-glass limit was apphed. Many pulpits were furnished with an iron stand tor the reception of the hour-glass. One such is stiü existing at Compton Bassett Chuich, Wilts, with a fleur-de-lis handle tor turning the glass when the sand had run out. Another at Hurst, in Berkshire has a fanciful wrought iron frame, with foliages of oak and ivy, and an inscription " As this glass runneth, so man's life passeth." At Cliffe, in Kent, is a stand tor an hour-silss on a bracket affixed to the pulpit. The parish accounts of 8t Katharine, Aldgate contains an old entry " Paid for an hour-glass that hangeth by the pulpit where the preacher doth makt a sermón that he inay know how the hour passeth away, one shilling "; and anothei relates to a bequest of " an hour glass with a frame to stand in." Many old stories relating to pulpil hour glasses have a dash of humor aboul them which would seem a little out oi place in our own days. One preacher had exhausted his sand-glass, turned it, and gone through three-fourths of another running; the congregation had nearly all ï-f-tired, and the clerk, tired out, audibly asked his reverend superior to lock np the church and put the key under the door, when the sermón was done.