24 PREPABATIOX AND MOUNTING 



CHAPTER II. 



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 

 bv unpleasant experience that we fully learn what "cleanli- 

 ness is. 



An object which is to be viewed under the microscope 

 must, of course, be supported in some way this is now 

 usually done bv 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 objei/t 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 visually made of " sheet" glass; 

 but is seldom found in those of the quality know.i 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 



