24, PREPARATION AND MOUNTING 
CHAPTER wt. 
APPARATUS. 
BEFORE entering into the subject of the setting of Objects 
for the Microscope, the student must be convinced of the 
necessity of cleanliness in everything relating to the use of 
that instrument. In no branch is this more apparent than 
in the preparation of objects; because a slide which would 
be considered perfectly clean when viewed in the ordinary 
way is seen to be far otherwise when magnified some hun- 
dreds of diameters; those constant enemies, the floating 
particles of dust, are everywhere present, and it is only 
by unpleasant experience that we fully learn what cleanli 
Ness 78. 
An object which is to be viewed under the microscope 
must, of course, be supported in some way—this is now 
usually done by placing it upon a glass slide, which on 
account of its transparency has a great advantage over 
other substances. These “slides” are almost always made 
of one size, viz., three inches long by one broad, generally 
having the edges ground so as to remove all danger of 
scratching or cutting any object with which they may come 
in contact. The glass must be very good, else the surface 
will always present the appearance of uncleanliness and dust. 
This dusty look is very common amongst the cheaper kinds 
of slides, because they are usually made of “sheet” glass ; 
but is seldom found in those of the quality known amongst 
dealers by the name of “ patent plate.” This latter is.more 
expensive at first, but in the end there is little difference in 
the cost, as so many of the cheaper slides cannot be used 
for delicate work if the mounted object is to be seen in per- 
fection. These slides vary considerably in thickness ; care 
