Page:Cyclopaedia, Chambers - Volume 2.djvu/743

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3. To meafure a Rhombus. Suppofe the Side 12 Feet, and the Length of a Perpendicular let fall from one of the obtufe Angles, to the oppofire Side, 9 Feet : Set 1, on the Line B, to 1 2, the Length of the Side, on the Line A 5 then againft 9, the Length of the Perpendicular on the Line B, is ic8 Feet, the Content.

4. To meafure a Triangle. Suppofe the Baft Seven Feet, and the Length of the Perpendicular let fall from the op- polite Angle to the Bale, 4 Feet : Set 1 on the Line B, to

I on the Line A; then againft half the Fetpendicular, which is 2, on the Line B, is 14 on the Line A, for the Content of the Triangle.

5. To find the Content of a Circle, its Diameter being given. Suppole the Diameter 3.5 Feet: Set 11 on the Girt-Line D, to 1)5 on the Line C; then againft 3.5 Feet on D is 9.6 on C, which is the Content of the Circle in Feet.

6. To find the Content of an Oval or Elliffs. Suppofe the longeft Diameter 9 Feet, and the fhorteft 4. Find a mean Proportional between the two, by Jetting the greater 9 on the Girt-Line, to 9 on the Line; then, againft the left Number 4, on the Line C, is 6; the mean Proportional fought. This done, find the Content of a Circle, whole Diameter is 6 Feet; this, when found, by the laft Article, will be equal to the Content of the Ellipfis fought.

Ufe of Coggefhal's Sliding-Rule, in the Meafuring of Ttmber.

1". To meafure Timber the nfttal Way. Take the Length in Feet, Half- Feet, and, if required, Quarters; Then mea- sure half way back again; there girt the Tree with a lmall Cord or Line; double this Line twice, very evenly, and mea- fiire this fourth Part of the Girt or Perimeter, in Inches, Halves, and Quarters. The Dimenfions thus taken, the Timber is to be meafiired as if Square, and the Fourth of the Girt taken for the Side of the Square, thus; Set 12 on the Girt-Line D, to the Length in Feet on the Line C, then againft the Side of the Square, on the Girt-Line D, taken in Inches, you have, on the Line C, the Content of the Tree in Feet.

For anlnftance: Suppofe the Girt of a Tree, in the Middle, be 60 Inches, and the Length 30 Feet, to find the Content, fet 12 on the Girt Line D, and 30 Feet on the Line C; then againft 15, one Fourth of 60, on the Girt-Line D, is 46.8 Feet; the Content on the Line C. If the Length .mould be 9 Inches, and the Quarter of the Girt 35 Inches; here, as the Length is beneath a Foot, meafure it on the Line of Foot-mealure, and fee what decimal Part of a Foot it makes, which you will find 75. Set 12, therefore, on the Girt Line to 75 on the firlt Radius of the Line C, and againft 35 on the Girt Line is 64 Feet on C, for the Content.

2 To meafure round Timber the true Way. The former Method, though that generally in Ufe, is not quite juft. To mealiire Timber accurately, inftead of the Point 12 on the Gift Line, ule anorher, viz. 10.635; at which there fhould be placed a Centre-pin. This 10.635 is the Side of a Square equal to a Circle, whofe Diameteris 12 Inches. For an Inftance : Suppole the Length 15 Feet, and -i of the Gift 42 Inches : Set the Point 10635 to 15 the Length; then againft 42 on the Girt Line is 233 Feet for the Content fought; whereas by the common Way, there arifes only 184 Feet. In effect, the common Meafure is only to the rruo Meafure, as 1 1 to 14. See Timber.

3 To meaftire a Cube ■ Suppofe the Sides to be 6 Feet each; fet 12 on the Girt Line D, to 6 on C; then againft

II Inches (the Inches in 6 Feet) on the Girt Line, is 216 Feet on C, which is the Content required.

4 To meafure ttnequally-fquared Timber; that is, where the Breadth and Depth are not equal. Meafure the Length of the Piece, and the Breadth and Depth (at the End) in Inches : Then find a mean Proportional between the Breadth and Depth of the Piece. This mean Proportional is the Side of a Square, equal to the End of the Piece; which found, the Piece may be meafur'd as Square Timber. For an Inftance : Let the Length of the Piece of Timber be 13 Feet; the Breadth 23 Inches, and the Depth 13 Inches: Set 23 on the Girt Line D, to 23 on C; then againft 13 on C is 17.35 on the Girt Line D, for the mean Proportional. Again, letting 12 on the Girt Line D, to 13 Feet, the Length on the Line C; againft 17.35 on the Gift Line, is «7 Feet, the Content.

5° To meafure taper Timber : The Length being meafured iri Feet, Note, one third of it; which is found thus : Set 3 on the Line A, to the Length on the Line B; then againft I O" A, is the third Part on B : Then if the Solid be round, meafure the Diameter at each End in Inches, and fubtract ■he l e f s Diameter from the greater; add half the dif- ference to the leffer Diameter; the Sum is the Diameter in 'he middle of the Piece. Then fet 13.54 on t ' le Girt t0

the Length of the Line C, and againft the Diameter in the middle, on the Girt Line, is a Fourth Number on the Line V r A S ain > fct ,»3-J4 on the Girt Line to the third Part of the Length on the Line C; then againft half the Difference on the Girt Line, is another fourth Number on the Line Cj thefe two fourth Numbers added together, give the Content For an Inftance; Let the Length be 27 Feet (one Third' whereof is 9) the greater Diameter 22 Inches, and the leffer 18; the Sum of the Two will be 40, their Difference j„ and half the Difference 2, which added to the lefs Diameter, gives 20 Inches for the Diameter in the middle of the Piece. Now fet 13.54 on the Girt Line, to 27 on the Line C, and againft 20 on D, is 58.9 Feet. Again, fee 13.54 of tllc Girt Line to 9 on the Line C; and againft 2 on the Girt Line (reprefented by 20) is 196 Parts; there- fore, by adding s9. 9 Feet to 126 Feet, the Sum is 59 05 S Feet the Content.

If the Timber be Square, and have the fame Dimenfions 5 that is, the Length 27 Feet, the Side of the greater End 22 Inches, and that of the leffer 18 Inches, to find the Con- tent : Set 12 on the Girt Line to 27 the Length on the Line C, and againft 20 Inches, the Side of the mean Square orl the Girt Line, is 75.4 Feet. Again, fet 12 on the Girt Line to 9 Feet, one Third of the Length, on the Line Q and againft 2 Inches, half the Difference of the Squares of the Ends on the Girt Line, is 25 Pans of a Foot, both to- gether make 75.65 Feet, the Content of the Solid.

The Girt or Circumference of a Tree, or round Viece of Timber given; to find the Side of a Square within, or tin Number of Inches of a Side, when the round Timber isSquar\h Set 10 on A to 9 on B, then againft the Girt on A, are the Inches for the Side of the Square on the Line B.

SLING, Fundus, a String-Inftrument,fervir.g for the calling Stones with the greater Violence. — fiiny, L. 7. C. 56. attri- butes the Invention of the Sling to the 'Phoenicians. VegetiuS attributes it to the Inhabitants of the Balearic Wands; who were famous in Antiquity, for the dextrous Management thereof. Fkrlls and Strati fay they had three Kinds of Sluigs; Tome longer, others fhorter, which they ufed ac- cording as their Enemies were nearer or more remote. 2)iodo- rus adds, that the firft lerved them for a Head-band, the fecond for a Girdle, and that the Third they conftantly car- ried with them in the Hand.

SLINGING, is ufed varioufly at Sea; but chiefly for the hoifting up Casks or other heavy Things, with Slings or Contrivances of Ropes, fpliced into them lei ves at cither End, with an Eye big enough to hold the Thins to be Slung.

SLIPPING (among Gardeners) is the pulling off a Sprig from a Branch, or a Branch from an Arm of the Tree; and lo a Slit may have its Rents double and treble Slipped, or its Stalk ragged.

SLOOP, is a floating Veffel of the Shailop-kind, See Floating Vessel.

In our Navy, they are Attenders on the Men of War 5 and are ufually about 60 Ton, and carry about 30 Men. See Navy.

SLOUGH, a deep and muddy Place; alfo the caft Skin of a Snake, the Damp of a Coal-pit, and the Scar ofa Wound, arefo called. The Slough ofa Wild Boar is the Bed, Soil, or Mire, wherein he wallows, or in which he lies in the Day- time : Slough (in Hunting) is ufed for a Company of fome Sorts of Wild-Beafts.

SLUICE, a Frame of Timber, Stone, or other Matte?, ferving to retain and raife the Water ofa River, He. and on Occafion, to let it pafs: Such is the Sluice of a Mill, which flops and collefts the Water of a Rivulet, He. to let it fall, at length, in the greater Plenty upon the Mill-wheel : fiich alfo are thole ufed as Vents or Drains to difcharge Water off Land : And fuch are the Sluices of Flanders, He. which ferve to prevent the Waters of the Sea overflowing the lower Lands, except when there is Occafion to dtown them.

Sometimes there is a kind of Canal inclofed between two Gates or Sluices, in artificial Navigations, to five the Water and render the Paffage of Boats equally eafy.and fafe, upwards and downwards; as in the Sluices of Sriare in France, which are a kind of maflive Walls, built Parallel to each other at the Diftance of 20 or 24 Fecr, clofed with ftrong Gates t at each End, between which is a kind of Canal or Chamber, confiderably longer than broad, wherein a Veffel being in- clofed, the Water is let out at the firft Gate, by which the Veffel is railed 15 or 16 Foot, and pafs'd out of this Canal into another much higher. By luch means a Boat is convey'd out of the Louvre into thcSeyne, though the Ground between them be raifed above 150 Feet higher than either of thofe Rivers. — The Word isform'd of the French, Efhlufe, which Menage derives from the Zatiti, Exclufa, found in the Salic Law in the fame Senft. But this is to be reftrained to the Sluices of Mills, ^c. for as to thofe ferving to raife Veffels they were unknown to the Ancients,

SMACK,