324 PROCEEDINGS OF SOCIETIES, [Monthly Microscopfeal 
curvicollis scales with the new and magnificent 1th of Powell and 
Lealand he had seen the beads mentioned by Dr. Pigott. 
He wished to make one remark about Dr. Pigott’s frequent refer- 
ence to points. A mathematical point had position without magnitude ; 
but no image, however small, was a point of this sort. Optically 
speaking, he took a point to be the smallest portion of space which 
will comprehend the waves of the smallest light-pencil we can see. 
Dr. Pigott briefly replied, explaining that he meant in his remarks 
not a mathematical point, but the smallest visible point. 
Mr. J. Beck said that his late brother, in his work on ‘ The Micro- 
scope, had given an illustration of the Lepisma scale, in which he 
showed that the appearance of dots produced at the lowest portion of 
the scale was owing to the corrugations on both sides of the scale 
crossing one another at an angle. He proved this very satisfactorily 
by putting Canada balsam on the upper or under side of the scale, and 
by so doing he obliterated the markings on that side where the balsam 
had run. He (Mr. J. Beck) therefore thought that it was shown that 
dots might be produced by lines running at an angle one to the other 
on either side of the membrane. Whether dots were always produced 
by the same cause was quite another matter. We might (reasoning 
from analogy) presume that they were formed in that way; but if we 
wanted to determine minute structures, and had been unable to do so 
by merely looking through the microscope, he apprehended the next 
best thing to do was to try experiment. Such experiment he had 
adopted so far as regarded the scale of Lepidocyrtus, and he was con- 
vinced that the appearances presented by that object were not the 
result of hemi-cylindrical tubes on the upper and under surface of 
the scale. That on one side of the scale there were gutters running 
from end to end there was no doubt. He had explained in his paper 
just published in the Journal, that this fact might be proved by 
merely breathing on the scale, and the moisture thus produced would 
run up and down on the exposed side. It was also clearly shown that 
no such gutters existed on the other surface of the scale; such being 
the case, there was the certainty that the appearances referred to were 
produced from some other cause. Did these note-of-exclamation 
markings really exist ? If they were lines, how was it they did not 
appear as lines? If anyone looked through a piece of sheet glass at, 
say, the railings of a house, the distortions caused by the rays passing 
through the sheet glass gave an appearance of the breaking up of the 
railings all over. Whether the appearance produced in Lepidocyrtus 
could be explained in a similar way, he was not prepared to say. If 
we desired to ascertain minute structure, we must not totally depend 
on what we see through the microscope, but experiments must be con- 
ducted. 
The great light that had been thrown on the structure of the 
Diatomacez was the result of experiment. The artificial deposition 
of silex had shown that the appearance visible on P. angulatum, &c., 
might be produced by hemispherical globules: that being a natural 
mode of deposition, it was fair to conclude that the structure was 
similar, unless future experiments should show that such a conclusion 
was wrong. As regarded Macrotome, there was doubtless structure on 
