ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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cally upwards on to the third mirror, also placed horizontally, which 
reflects them again downwards on to the fourth mirror, placed at an 
angle of 4°, and this turns them finally into a horizontal direction to the 
eye-piece. 
A telescope of 10 ft. focus thus constructed would, when its axis is 
horizontal, have a vertical height of about ft., the distance between 
the eye-lens and the object-glass being about 1 ft. The object-glass 
and the eye-lens are in a line with one another, and are placed in the 
middle of the telescope. 
