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PROCEEDINGS OF SOCIETIES. 
see would be two series of circles, tbe one well defined and the other 
ill defined, and crossed by a series of hyperbolas. He thought there 
were often very erroneous appearances produced by seeing two series 
of markings one behind the other. 
Mr. Beck said that it was for that very reason that they had such 
difficulty in making out the nature of such fine structural markings as 
those on the diatoms, which were probably not simple structures, for 
nature did not deal in simple structures ; so that when looking at the 
structure of the Podura scale, it was not easy to say what it was they 
really did see ; and he thought it was not so much by examining 
these objects themselves as by taking similar structures . of a simple 
kind and arguing from analogies, that they would be able to form a 
correct idea of what really existed. The reference to a wire-gauze 
blind reminded him that if light were passed through it upon a sheet 
of white paper, by varying the distance they could get the effects of 
all the markings of the Diatomaceae, but it was clear that none of 
them really existed. He must express his dissent from the statement 
that they did not learn anything from oblique light. He should quite 
agree with the opinion that if they were to settle questions of structure 
merely from what they could make out by means of oblique light, 
they would fall into a series of errors ; but oblique light was of great 
value in many respects, particularly when sections had to be examined. 
They had not been told the size of the globules of mercury employed 
by Dr. Pigott ; this was, however, not of great importance, as the real 
object in view was to produce an artificial star, the most minute point 
of light with which they were acquainted. 
Dr. Pigott said that Mr. Beck had very properly remarked that he 
had not said anything about the size of the globules. His practice 
was to pour out a small quantity of the metal, and then to keep 
sweeping the globules away until he got them sufficiently small for 
the purpose. Globules about -^th of an inch were small enough to 
form a miniature, to be reduced by the objective employed. 
The thanks of the Society were voted to Dr. Pigott for his paper. 
Mr. Wenham then explained to the meeting a new method of 
viewing objects at extreme angles, and illustrated the manner of 
mounting and observing them by means of drawings on the black- 
board. Several mounted specimens were also placed in the hands of 
the Fellows for inspection. (Mr. Wenham’s observations will be 
found printed at p. 156). 
The thanks of the meeting were unanimously voted to Mr. Wenham 
for his communication. 
The President remarked that all observers were well aware that 
illumination was half the battle in microscopy. In many cases he had 
no doubt but that Mr. Wenham’s method would be a very valuable 
aid to investigation. 
Mr. Browning suggested that as the glass must be ground to a 
perfect knife-edge, the greatest care must be taken of the edges, as 
they would certainly break if touched. 
Mr. Wenham said he did not think there was much difficulty 
about that ; the edges could be butted together, and would be pretty 
