238 The Microscopic Compass. 
of brass, three inches in diameter and very light, weighing fifty grains. 
Although the word “card” is inappropriate, yet as it has been “coin- 
ed” by use for that part of a compass when it moves with the needle, 
I shall use it in the subsequent part of this paper. Se 
ask nh 
i ; ‘ ¢ ‘ 
eee e etm ew ed aneneanenewemsnaewennne 
K 
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I 
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This card is suspended in a brass box three and a quarter inches 
in the inside diameter and half an inch deep, (TV Fig. 2.) ‘The Z 
sights (KS and V J Fig. 2.) arise from opposite sides of the box as io 
the surveyor’s compass, but are not carried out on arms, the distance — 
between them being the exact diameter of the box. Indeed these 
