BECK, ON ILLUSIVE APPEARANCES. 5 
surfaces obliterated in different parts ; this is seldom the case, 
and generally it is only the outer surface of the scale that is 
in such a condition. 
Fig. 1V shows parts of a small 
scale in a dry and natural state ; 
at the upper part the interrupted 
appearance is not much unlike that 
seen at the sides of the larger 
scales, but lower down, where lines 
of equal strength cross nearly at 
right angles;* the lines are en- 
tirely lost in a series of dots, and 
exactly the same appearance is 
shown in fig. V, to be produced 
by two scales at a part where 
they overlie each other, although 
each one separately shows only 
parallel vertical lines. 
Considerable disturbances pro- 
duced by the passing of light 
through transparent bo- 
dies are very common in 
microscopic objects, and 
when such is the case 
ire, PY: 
great care is required in \ Y 
the true interpretation 
of structure. 
In many cases I be- 
lieve it may be almost 
impossible to arrive at 
the truth, yet some kind 
of analysis, that which I 
have alluded to being 
only one of many, should 
I think be employed 
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before so many hasty and speculative theories are started 
upon the structure of many microscopic objects. 
* The faint lines in this figure merely show the direction and not the 
character of the lines. 
