Another simple weather-gauge may be made by stretching whip-cord or catgut over five pulleys. To the lower end of the string a small weight is attached, and this rises and falls by the side of a graduated scale as the moisture or dryness of the air shortens or lengthens the string. Again, whip-cord, well-dried, may be hung against a wainscot, a small plummet affixed to it, and a line drawn at the precise spot it falls to. The plummet will be found to rise before rain, and fall when the prospect brightens. Another device is to take a clean, unpainted strip of pine--say, twenty inches long, one wide, and a quarter of an inch thick--cut _across the grain_; then have a piece of cedar of the same size, but cut _along the grain_. Let these be glued together and set upright in a stand. Before a rain-fall the pores of the pine will absorb moisture, and swell until the whole forms a bow; this will gradually straighten on the approach of fine weather. There are two forms in which a balance is used that are interesting from the natural laws that govern their motions. In one a dry sponge that has been saturated in salt and water is nicely balanced against a small weight at the opposite end. The sponge becomes heavier or lighter according to the presence or absence of moisture, and any variation in this respect may be noted on the gauge above, to which the index finger on a dial points. The simplest plan of all, and as good as any, is to place in an accurate pair of scales on one side a one-pound weight; on the other, one pound of well-dried salt. This swells and grows heavier on the approach of rain; when brighter skies return, the one-pound weight asserts itself once more. [Illustration: VACATION DAYS--THE REASON WHY BOB COULD NOT GO A-FISHING.] [Illustration: OUR POST-OFFICE BOX.] So many of our correspondents are collecting birds' eggs and nests that we wish to call their attention to some important points. Never take all the eggs in a nest, because if you do you will leave the poor mother bird very desolate. You can always take some from each nest, and still leave enough to make a pretty little brood of young birdlings. In some nests you will find eight or ten eggs, and then you may take three or four. But if there are but three eggs, you must take only one. Always be sure to leave more than half. Be careful to gather them before the mother bird begins to set, because when her brooding-time has begun she is very jealous of her nest, and is easily frightened away; and then if the eggs have begun to harden and form young birds, they are useless to you, for you can not blow them, and they will soon change color and become worthless. Never take a nest until the mother has flown away with her little ones and left it empty; for to disturb the pretty home the bird has built with so much care for her babies is a wanton cruelty we trust no reader of YOUNG PEOPLE would be guilty of. * * * * *