THE MICROSCOPE. V 



and moving objects, especially when they live in 

 water. 



In the use of the cage and the slide, care must 

 be taken not to break them, by turning the object- 

 glass down upon them. The tube is provided with 

 rack-work and a handle, by which it moves ; so that 

 the object-glass may be adjusted to any distance 

 from the object. It is sometimes a difficult thing, 

 when the object-glass has a focus of not more than 

 a quarter or eighth of an inch, to adjust it to 

 exactly the point at which the object is best seen, 

 by means of the coarse handles on the rack- work ; 

 and the Microscope is often provided with what is 

 called a fine adjustment, by means of which the 

 object-glass is moved down on the object in a much 

 slower and more gradual manner. Care, however, 

 must always be taken lest the object-glass is brought 

 down on to the object or slide, so as to break them. 

 In some cases the lens of the object-glass itself has 

 been broken in this way. Your incautious friends 

 who have never seen a Microscope before, and have 

 sufficient confidence in themselves to attempt to 

 command a man-of-war, though they were in one 

 for the first time, will frequently turn your Micro- 

 scope up and down with a force sufficient to crack 

 your lens. Such friends should, if possible, be 

 kept from the table till the instrument is ready 

 for them to take a peep, and then it is best to 

 request that they will keep their hands behind 

 them. 



The picture of the object brought to the eye in 

 the Compound Microscope is always the wrong end 

 upwards. That is, the picture is always the reverse 

 in the Microscope to what it is with the naked eye. 

 You need constantly to be aware of this, especially 

 if you are going to dissect an object under the 

 Microscope, as your right hand becomes left, and 



