INTR OD UC TOR Y. 13 



of which is trying to the eyes and irritating to the 

 temper. You should provide yourself with the fol- 

 lowing necessary accessories to the microscope, (i) 

 A number of plate-glass slides, three inches in length 

 and one in breadth; they can be bought with the 

 edges ground at about six shillings a gross. On these 

 slides are to be placed the objects you may wish to 

 examine, or to mount for preservation. (2) A quan- 

 tity of thin glass of various degrees of thickness, cut 

 in either square or circular pieces of different sizes. 

 Thin sheets of this glass, called "cylinder glass," are 

 manufactured by the well-known firm of Messrs. 

 Chance, of Birmingham, but they can be procured 

 at any optician's. The pieces should be kept in 

 a box with bran or sawdust to prevent them break- 

 ing, for they are extremely brittle. When an object 

 is placed on a glass slide for examination it should 

 always be covered with a piece of this thin glass, in 

 order to protect the object-glass from injury ; whilst 

 examining drops of water this is especially necessary. 



It would not be easy to do much work satisfactorily 

 without dissecting-needles and a pair of forceps. The 

 dissecting-needles are extremely useful instruments for 

 unravelling entangled objects and various tissues; they 

 can be readily improvised by the student taking some 

 well-tempered needles, nipping off a portion of the 

 heads, and inserting the upper part of the remainder 

 in wooden handles. The forceps may be used inde- 

 pendently, or be attached to the stage, for the pur- 

 pose of holding minute objects under the microscope ; 

 its form will suggest to you various uses to which it 

 may be applied. 



A few watch-glasses will be found convenient for 

 several purposes, and some small glass shades, about 

 five inches in diameter, are useful for protecting from 

 the dust objects you may be ''mounting." I will 



