Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 3, 1802).djvu/109

91&#93; LEV of level. — Instead of cups, how- ever, two short glass cylinders, tliiee or four inches in length, may be hxed to both extremes of the pipe, with wax or mastic. Some water, either p.ain or coloured, is now poured into the pipe, when the liquor appears through the cylinders, and thus the horizontal line IS determined. This contri- va.ice is very simple, and of great service for taking the level of small distances. . There are various other kinds of ^yater levels, which have been de- signed with a view to ascertain de- clivities, for the purpose of irrigat- ing land : as these, however, are either too complicated, or other- wise defective, we refer the reader to p. 31, of t';<=; present volume, where he will hnd an account of a- more simple contnv"ance, illus- trated with a cut, by Dr. Ander- son ; and which is calculated to jcniove these difficulties. — Lastly, though we have several other in- struments tor taking levels In par- ticular .situations, yet, as their ap- plication requires a previous know- ledge of mathematics, and is not strittly conne6ted with domestic econoni), our limits do not admit of farther descriptions. LEVER, a bar made of iron or wood, one part of which is sup- ported by a fulcrum or prop, so that all l!;e others turn upon it as tlicir common centre of motion. Levers are of various kmds, ac- cording to the purposes for which they are designed; and, being emi- nently serviceable for the lihin; of weights, we have subjoined the follow ing representation of a Cross- bar -lever, which is particularly calculated for raising earth that aboiuids with great quantities of sjpnesj though this raachiae is [91 likewise applicable to other objefts. ■ — It was invented by Mrs.WvND- HAM, of Petworth, in Sussex, on whom the Society for the Encou- ragement of Arts, Stc. in i.79^> conferred their silver medal. A, is the level*. B, an upright piece of wood, to be atHxed to the lever ; care being taken to place the side marked with this letter opposite to that marked A on the lever ; by which means it inclines backwards, and thus in- creases the power. C, is a cross-bar, being the hand by which the workmen exert their strength. D, is another cross-bar, to be placed at the bottom, behind the upright piece of w ood, on which the labourers are to stand, and throtigh which the end of the lever passes. These additions iire so construded, that they may be oc- casionally fixed and removed ; be- cause tJiey are to be employed only.