49 



Room. If possible a room should be selected fac- 

 ing the north, as the light in this direction is most 

 constant. It will prove a great saving of time if all 

 or a portion of it can be permanently arranged to 

 receive the entire working outfit. It should also be 

 chosen with a view to its being free from disturbance. 



Light As stated, the light from the northern sky 

 is most desirable, and that from a white cloud is pre- 

 ferable to that from a blue sky. On account of its 

 intensity, direct sunlight should seldom be used ; but 

 if modified by a white curtain or reflected from a 

 white wall it is excellent. 



For lamp light an ordinary flat wick kerosene or 

 student lamp is well adapted. The Hitchcock lamp, 

 from its better combustion is still better, as its color 

 more nearly approaches white. The ideal artificial 

 light is that from an electric light. Gas light is not 

 desirable as it is seldom sufficiently steady. 



Position of Light. The relation of the micro- 

 scope to the source of light is principally a matter of 

 personal convenience. With daylight it makes little 

 difference whether it is at the front or side of the 

 instrument, although the writer prefers it at the front, 

 as the manipulation of the object does not obstruct 

 it ; but the lamp should be placed at the right or left 

 side within, easy reach of the hand for the purpose of 

 controlling it. The writer suggests that the beginner 

 make it a habit at the outset to place it on the side of 

 the instrument opposite to the unoccupied eye, as the 

 tube then places the latter in the shadow. 



