423 Microscope Teachings. 



•achromatic, that is, without those fringes of 'rainbow colours 

 always seen surrounding objects in inferior microscopes. It 

 should also be constructed to lean backward, as being far less 

 fatiguing to the observer than the upright positiou. It should 

 have at least two different degrees of magnifying, and one of them 

 should be of low power, with large field of view, for the purpose 

 of showing as much as possible of an object at once. These, with 

 the condensing lens, and mirror to throw light on or through 

 objects, are things indispensable." A reference to our adver- 

 tising pages will show how cheaply these necessaries can be 

 obtained, and although those who have money to spare will be 

 sure to want a superior instrument if they continue the pursuit, 

 a comparatively simple one, judiciously selected, will serve all 

 ordinary purposes of investigation or display. After giving 

 information and advice, which every beginner will be glad of 

 in learning to use a microscope, Mrs. Ward describes the 

 methods of collecting and mounting objects, and then, in the 

 fourth chapter, begins her list of objects with the structure of 

 insects' wings. This chapter is illustrated by many, exquisitely- 

 drawn, and coloured, figures from her own pencil, and is appro- 

 priately followed by another chapter on " the scales of insects 

 and fish," which likewise supply beautiful plates. The objects 

 described in these and other chapters are for the most part 

 easily obtainable, and this is important, because, although it is 

 both useful and pleasant to have a collection of slides prepared 

 by professional mounters, the most substantial knowledge will be 

 gained by collecting and mounting for ourselves. Every one 

 ought to do this to a certain extent with reference to every 

 class of object, even if the cost of prepared slides is of no im- 

 portance; and those which are bought or given will be. much 

 better understood if the student has prepared something of the 

 same kind for himself. 



As a specimen of Mrs. Ward's directions we will cite her ac- 

 count of how to obtain the scales of the eel — a beautiful struc- 

 ture, which few who are in the habit of eating the creature take 

 the trouble to behold. Our author says, "When I first began 

 to prepare objects for the microscope, I road in some old book 

 that these were worth looking at, so I procured a dry piece of 

 eel skin, but it was long before I could find what I was in 

 search of. I scraped and scraped with a knife, and examined 

 the scrapings with a microscope, magnifying them twenty 

 times — forty times — perhaps 100; but no scales appeared. 1 

 forget how I contrived t<> make bhem out at last; but, if I take 

 ;; little pieco of eel skin, and view it as a transparent object, 

 magnified rather more than four diameters, the first thing I see 

 is that the skin is covered with star-like spots, and next I ob- 

 serve the scales lying close together. And this is the way to 



