APPENDIX. 351 



NOTES ON THE USE OP THE MICROSCOPE. 



See that the tube of the microscope moves easily, but 

 not too easily, up and down. It should occasion- 

 ally be rubbed round with a little olive-oil, and 

 the oil then wiped off with a dry cloth. 



With a piece of soft chamois leather or silk, remove 

 any dust that may be on the lenses of the eye-piece 

 or on the lower lens of the objective. If by accident 

 the objective has been smeared with glycerine, 

 stream it with water from a wash-bottle, and wipe it 

 dry with chamois leather: if with Canada balsam, 

 place on it a drop of chloroform or strong spirit, and 

 rub gently, repeating till the balsam is quite re- 

 moved : this must be done very cautiously, since the 

 lenses are sometimes fixed in with Canada balsam. 



All unnecessary rubbing of lenses however should be 

 avoided; hence take care to put them away after 

 they have been used. 



It is advisable for the student not to unscrew the 

 separate lenses of a high objective; when however 

 the dimness of an object under observation renders 

 it necessary to do so, care must be taken not to 

 remove the black coating on the inside of the tube 

 in cleaning the lenses, and when cleaned to restore 

 them, in proper order, to their previous positions. 



"With a low power (cp. foot-note, p. 35), twist down 

 the microscope-tube till it is rather less than a 

 quarter of an inch from the object; then looking 

 through the eye-piece, twist the tube upwards till 

 the specimen is in focus. 



