82 The Microscope. 



dow, many preferring the stand so arranged that the mirror shall 

 face the window and the sky ; others place it so that the 

 window shall be at the side of the instrument. This is en- 

 tirely a personal preference, nothing, so far as I know, being 

 gained or lost in either position. If, however, day-light is used 

 with a substage condenser, the plane mirror should be turned 

 toward the sky. If no substage condenser is employed, then 

 the concave surface should be directed upward. 



The use of lamp light has already been referred to, and 

 the employment of some special form of microscopical lamp 

 recommended. Its position in relation to the mirror may, if 

 desired, be ascertained by the formulae given in a preceding 

 chapter, but I think most microscopists, for ordinary work, do not 

 enter into the niceties of such an arrangement, reserving these 

 refinements for some very special and delicate investigations. 

 The reader will find, however,that any attention paid to these 

 points, even for everyday observations, will result in good. 

 Usually the lamp is placed somewhat in advance of the micro- 

 scope and always on the left hand side. This gives plenty of 

 room on the table, so that the lamp is in no danger of being 

 overturned. If the observer should be left-handed the converse 

 arrangement would of course be necessary. 



EDrroR;s^ 



DEPARTMENT 



^^*s 



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