12 Chapters in Modern Botany CHAP. 



and how one combination of these is brought near the eye 

 ("eye-piece"), so as to multiply still further the image 

 already magnified by another held nearer the object (and 

 hence naturally termed object-glass), is of course the ele- 

 mentary common sense of that exquisite marvel of detailed 

 perfection, the compound microscope. The further develop- 

 ments, as that of shutting off side light above the object- 

 glass by the microscope tube, and below it by the stage- 

 diaphragm, of placing the object upon a transparent stage, 

 and this upon a perforated one, or of getting the instrument 

 when we wish to examine a transparent object out of the 

 inconvenient horizontal position at first necessary into the 

 more convenient vertical or sloping one by the simple 

 device of reflecting the window light through the tube to 

 the eye by means of a mirror fixed below the stage, are 

 again no less obvious. This elementary instrument once 

 constructed, a new set of considerations would naturally 

 arise, among which the necessity of focussing and the diffi- 

 culty of getting rid of the prismatic colours which would as 

 yet enhalo our magnified image may be cited as specially 

 important. These have to be met by mechanical and 

 optical devices respectively, which are familiar enough ; and 

 so we might work on, a whole volume being needed to do 

 justice to the history of the instrument, as, indeed, are 

 special journals to its unending developments. The bare 

 outline given above is but to emphasise the idea, con- 

 mo nplace in phrase but too little habitual in practice, that 

 the scientific study of anything, be it a natural or social 

 product, ought always to proceed from the known towards 

 the unknown, and rationally from its beginnings onwards 

 wherever possible. 



Given, then, the compound microscope, we may first 

 attempt to examine the epidermis more in detail, beginning 

 with the attractive surface of the lid by shaving off thin 



