40 THE MICROSCOPE AND ITS LESSONS. 



use will vary from what is called a four-inch objective to 

 a sixth inch : these are terms used by the makers to denote 

 the focal distance of the field-glass from the object. My 

 lowest power, the four-inch, with the "A," that is the 

 lowest eye-piece, magnifies only ten diameters that is, one 

 hundred superficial times. True, it is only a "magnifying 

 glass," but it may be greatly increased at the upper end 

 with other eye-pieces, till, with the fourth eye-piece, it 

 may be brought up to thirty-two diameters, or 1024 super- 

 ficial times. This glass is invaluable to the lover of flowers. 

 If I show you a blossom of mignonette you will never 

 forget it ; while, looking into the indescribable beauty of 

 a heartsease will astonish you. I have found the most 

 useful of all the glasses to be a good three-inch with the 

 use of the drawer- tube and the deeper eye-pieces ; but we 

 shall need all our object glasses in the delightful work 

 before us, and I must not stop to weary you with figures, 

 for which probably you' have no interest. Our lowest 

 magnifying power, I have told you, costing thirty shillings, 

 will only magnify at the most 1024 superficial times; our 

 highest, a so-called sixth, that is nominally a sixth of an 

 inch from the field-glass to the object, with the deepest 

 eye-piece and the draw-tube extended, will give us fully 

 nine hundred diameters that is, about a million of super- 

 ficial times. " Good eyes see light through the smallest 

 chinks," but your eyes would require to be educated that 

 you might know how to appreciate these wonderfully 

 perfect specimens of magnifying glasses. I have found 

 the lower powers and the draw-tube to be the most useful, 

 I repeat, for educating the eye. I have frequently been 

 told that I could see more with my one eye than others 

 could with their two ; but everything depends upon the 

 right management of light, in which we shall find our 

 first " lesson." 



