Aquatic Microscopy for Beginners. 



CHAPTER I. 



THE MICROSCOPE AND ITS PARTS. 



Simple and Compound Microscopes. — Pocket-lens. — "Craig Micro- 

 scope." — "Excelsior Microscope." — Watchmaker's Glass. — Cod- 

 ding Lens. — How to Focus a Simple L,ens.^Parts of the Com- 

 pound Microscope. — Draw -tube. — rEye-pieces. — Society-screw. — 

 French Triplets. — Objectives. — Selecting Objectives for the Be- 

 ginner. — Coarse Adjustment. — Focusing. — Fine Adjustment. — 

 The Stage. — Diaphragm. — Mirror and BuU's-Eye Condensing- 

 lens. — Preparing the Object. — Thin Cover-Glass. — Cells. — Cement. 

 — Dry Mounting. — Needles. — Dipping-tube. — Bunsen Burner. — 

 Evaporation from beneath the Cover. — Life-slide. — Growing-cell. 

 Air-bubbles. — Drawing. — Camera Lucida and Glass Reflector. — 

 Micrometer. — Measuring the Object. — To ascertain the Magnify- 

 ing Power. — Collecting-bottles. — Books and Magazines for Refer- 



' ence. 



Microscopes are compound or simple: compound 

 when they consist of two or more glasses, one or more 

 being near the object to be examined, and one or more 

 near the eye of the observer; simple when they con- 

 -sist of but one double-convex lens to be held near the 

 object, or of two or more lenses which can be used 

 singly or all at the same time. When thus used in 

 combination, the two or three simple lenses are not 

 only placed close to each other, but close to the ob- 

 ject, the combination acting as if it were a single lens, 

 the magnifying power being much greater than that of 



