79 



i inch. The fluid will then always be free from dust 

 and by withdrawing the cork the stick will always 

 carry a drop of fluid with it. 



In fixing an immersion objective to the stand, the 

 latter should first be put in an upright position ; the 

 fluid should now be attached to the front lens, but 

 care should be taken not to put on too much ; it 

 should be merely enough to cover the surface. If 

 too much, a portion of it should be removed by allow- 

 ing it to adhere to the finger. The objective may 

 then be attached to the stand and brought down until 

 the fluid is in contact with the cover ; the stand is 

 now inclined and the objective focused ; if this 

 method is followed there is no danger of flooding the 

 entire cover with fluid, which sometimes may be the 

 means of destroying the object ; neither can the fluid 

 run out from between the two surfaces. 



Extreme cleanliness should be observed in all work 

 connected with the microscope, and particularly in 

 the use of immersion objectives. The use of immer- 

 sion fluid in itself involves a certain amount of incon- 

 venience, but as in many cases it is absolutely neces- 

 sary, the observance of fixed rules will materially help 

 to overcome some of the disagreeable features. After 

 the work with an immersion objective has been com- 

 pleted, the objective should be removed from the 

 stand, and its front, as well as the slide, should invar- 

 iably be cleaned ; the fluid may be removed by a moist 

 piece of soft linen and then cleaned with a dry piece; 

 chamois skin is not suitable, as it does not absorb the 

 fluid. 



