PROCEEDINGS OF SOCIETIES. 
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difficulty and trouble, viz. by using tbe parabola and truncated lens. 
He (Mr. S.) bad tried the new plan on several objects, and he had 
succeeded in obtaining some very striking appearances with butterfly 
scales lying flat on the glass and not on the cover. He had been able 
to get a beautiful definition of several diatoms. In one of the insect 
scales he noticed a striking exhibition of a complicated fracture 
running in a zigzag line. The fracture ran exactly between the 
spherical dots, which is the course cracks always take in diatoms. He 
could find not that any dot had been broken through either on the 
upper or lower surface. This mode of illumination did not, in his 
hands, succeed when the light passed through objects of considerable 
thickness, and possessing high refractive and reflexive powers. Such 
objects gave rise to internal reflexion, and a considerable amount of 
distortion ensued. He thought the instrument, nevertheless, to be a 
very valuable one, though it might not be applicable universally, for 
it gave information which could be obtained in no other way.” 
Mr. Mclntire said he had tried the instrument (Mr. Wenham’s 
illuminator) with considerable success and satisfaction. It could 
hardly be expected that the best effects should be obtained at the first 
trial, yet those he had obtained were very good, and practice had 
enabled him to acquire further skill in getting beautiful results. He 
had resolved, without much difficulty, N. cuspidata, N. rliomboides, 
Surirella gemma, and the Podura scales, all on a field more or less 
dark. The markings of the Podura scales came out with a distinctness 
which left nothing to be desired — a convincing proof of the accuracy 
of Mr. Beck’s view as to their structure. The delicate cross-striae on 
the test-scale which gave rise to Dr. Pigott’s beads also occasionally 
came clearly in sight. A great deal of care was necessary in adjusting 
the object-glass and manipulating the illumination in order to ensure 
the best effects and to reduce the flare caused by too much light. With 
such objects as Arachnoidiscus and Heliopelta this was especially the 
case. It would be found also that objects mounted in balsam and 
illuminated by this apparatus could only be examined satisfactorily 
with dry lenses. He was altogether much pleased with the invention, 
and considered it an important addition to the limited resources at 
present at the disposal of microscopists in using high powers, whether 
for display or investigation. 
Mr. Wenham said he wished to make some remarks relative to 
objects having bulk. These ought to have some extent of surface in 
contact with the glass. If in examining objects such as Gorgonia any 
means could be applied for increasing the surface of contact, the 
object would be displayed beautifully, but taken alone on account of 
its irregularities there must be only a few minute points in contact 
with the glass which abstract light partially, and in a way that might 
give false appearances. But if a fluid be introduced beneath the 
object, the light would be generally admitted and diffused throughout 
its structure. He would recommend that experiments be tried with 
hairs of animals or insects ; for instance, a mouse’s hair, which is 
a difficult object to show up well. If this object be laid on a total 
reflecting surface alone, without any intimate contact therewith, it 
