In selecting "situations for gardens' and also for planting trees for shelter, the length to which their shadows will reach during winter deserves consideration, as also does that of the shade caused by halls and other buildings; for no screen should be planted so close as to shade any part of the ground, nor any glass roof be erected on which the sun may not shine every day in the year.

Several rules are given for determining this. The relation between the height of a tree and the length of its shadow depends on the latitude of the place and the sun's declination, which latter will be found by consulting an almanack, and the former by the sun-dial - at least, most sun-dials have the latitude engraved on them; if not, the map of the county will give it. The height of the tree, wall, or building, and the triangle, the hypothenuse of which angle is represented by that of the sun's rays from the top of the tree to the ground. This hypothenuse, or direction of the sun's rays at noon, always forms, with the ground line, an angle equal to the amount of the latitude and the sun's declination added together, from. the 20 th of March till the 22d of September; but from the 22d of September till the 20th of March, the sun's declination is to be subtracted from the amount of the latitude. This angle being found and the height of the wall, house, or tree taken, all the rest will be found by the rules of trig-onometry.

The following simple rule may be of use to such as do not understand geometry or trigonometry, and will give the shadow near enough for practical purposes: -

Multiply the height of the wall, tree, or buildirg -

 In latitude 51½ by 8.719. • • • • 62° .. 3.852. • • • • 68° .. 4.149. 54° .. 4.402. • • • • 55° .. 4.895. • . . • 56° .. 5.869. • ■ • • 67° .. 5.944. • • • • 58° .. 6.651.

The product will give the length of the shadow at noon on the shortest day.