One pleasant September afternoon, three gentlemen were strolling along the banks of the Wissahickon, in Philadelphia's beautiful park, and stopping now and then to examine some little flower or insect with pocket lenses, when they discovered that some little boys out for a holiday were watching their proceedings with a curious and mystified interest. One of the gentlemen had a pocket microscope with three lenses of different sizes, as in Fig. 1. Calling the boys up to him he showed them a little flower magnified. They had never dreamed of such a sight, and their wonder and amazement were as great as if they suddenly beheld a new world. You will be as surprised as they were when you take your first peep, but you must learn to see such things _by yourselves_. The first thing you need is a simple microscope, that is, one with a single lens, small enough to be carried in the pocket. There are different forms and sizes of such microscopes, varying in quality and price. Those like the one just mentioned are made with from one to four lenses each, and are perhaps the most generally useful. Then there is the Coddington lens (Fig. 2) which is still more compact; and it is sometimes made in the form of Fig. 3. It has a very short focus, and is not, therefore, very easy to use. Achromatic doublets and triplets are made of two or more lenses cemented together and mounted in the same style as the Coddington lens; they are very much better than the Coddington, but are more expensive. [Illustration: FIG. 4.] [Illustration: FIG. 5.] There are several devices for mounting these simple microscopes on stands so that they can be kept steady and the objects to be examined placed behind them. One of these is illustrated in Fig. 4. An ingenious boy with a block of wood for a base, some stout wire and corks, can make one almost as useful, though not so handsome. [Illustration: FIG. 6.] A more elaborate form is shown in Fig. 5. It has a glass stage to hold transparent objects, and a brass one for opaque objects, and a mirror below to reflect light up through transparent objects. It is much better to use a good simple microscope than a poor and cheap compound one; be sure and remember this and not be enticed to buy such an one by any representations as to its great magnifying power.