During the cold weather it is not pleasant to make excursions into the country and search for objects for the microscope; so you will look about and see what you can find at home; and if you live in Boston, Cochituate water will invite your inspection. The best way to get at the minute objects in this or any water that is supplied through pipes, is to make a bag of cotton cloth, not too fine, well washed in water without soap, about a foot long, large enough at the top to slip over a faucet that has a screw on it (like the common kitchen faucet adapted for a filter), so that it can be tied with a string, and small enough at the bottom to be tied on to the neck of a small bottle such as is used for homoeopathic pills. This bag should taper gradually in size from the top to the bottom. (_Fig. 1._) [Illustration: The Water Flea FIG. 2. CYCLOPS QUADRICORNIS. MAGNIFIED 20 DIAMETERS.] [Illustration: FIG. 3. CANTHOCAMPTUS MINUTUS. 40 DIAMETERS.] If there is a strong head of water where your faucet is, you must reduce the pressure by opening other faucets on the same floor, such as those in the laundry, otherwise many of the small creatures will be crushed in the interstices of the bag. Now let the water run. The bag will swell out and the water ooze through its sides, and all objects too small to pass through it will fall down and settle in the little bottle at the bottom. When you see that there is a considerable amount of sediment in the bottle, shut off the water and gently squeeze the bag between your thumb and forefinger, beginning at the top and moving your hand down towards the bottle. This movement will cause much of the sediment that has adhered to the sides of the bag to fall down. Now untie your bottle and set it aside and let the water run through the bag to clean it. If you have a filter attached to your kitchen faucet you can get a very good idea of the solid contents of the water by unscrewing it, or turning it over if it is made so as to reverse, and letting the sediment that has collected on it drip into a tumbler, but the bag gives much better results, as many of the delicate forms that live in the water are crushed to death on the filter. [Illustration: FIG. 4. CHYDORUS SPHOERICUS. 50 DIAMETERS.] Having got the sediment in either a tumbler or a bottle, you must make your first observation on it with the naked eye by holding it up to the light and looking through it. You will find it of a brown color, because a large part of it consists of particles of earth and decayed vegetable matter, but you will presently see many little white specks moving about with a jumping or hopping movement. These are commonly called "water-fleas," on account of their peculiar movements, but the name is misleading, as they belong to the crustacea (animals having a shell or crust like the lobster), and not to the insects.