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NOTES AND MEMORANDA. 
Microscopical Vision.—In the present aspect of this important 
question, which is being inquired into by Abbe, Sorby, and others, 
the following remarks are of interest. They are made by the Presi- 
dent of the Dunkirk Microscopical Society (U.S.A.), Mr. G. E. Black- 
ham, in a letter—part of which is private—to the Editor. He says, 
speaking of one of the reports of his Society :—“I am well aware 
that some of the work done by Professor Smith at this meeting will 
not meet with ready credence, especially among those who have on 
a priori grounds set the limit of microscopical vision at 80,000 lines 
to the inch ; the facts are, however, just as stated in the report, and 
I may say that, in the quiet of my own parlour, Professor Smith 
showed me the lines of the 19th band on one of Nobert’s recent 19th- 
band plates, clearly resolved, with my own ‘ duplex’ 4th objective, 
‘ A’—2-inch—eye-piece, on Zentmayer’s army hospital stand, fitted 
with thin revolving stage—the illumination being lamp—bull’s-eye 
and concave mirror, without achromatic condenser, or other light 
modifier whatever.” 
Dr. J. E. Smith on Wenham’s Reflex Iluminator.—This Ame- 
rican microscopist gives an opinion of Wenham’s illuminator as 
follows :—“ My first attempt with the illuminator in the histological 
line was over a balsam slide of pavement epithelium from my own 
mouth. The first field, as given by the illuminator, reminded me of a 
painting depicting the Arctic regions in a gale of wind! I saw 
scores of icebergs projecting their long black shadows over the field in 
inextricable confusion—any attempt to correct the objective at that 
stage of my experience would have been folly. I was very far from 
being discouraged, for it was palpable that the very power that caused 
the havoc in my field, would, when properly harnessed into the traces, 
do yeoman service. Removing the illuminator, I selected the smallest 
nucleated scale, and one which was far distant from the larger 
organisms, bringing it to the centre of the field and clamping the 
object carrier. Again, trying the effect of the illuminator, the result 
was similar to that of the initiatory trial. But now, knowing the 
exact locality of the scale beyond a doubt, I soon managed to identify 
it, and, after correcting the objective, was rewarded by a display of 
surface markings that amply repaid all costs. The details of this and 
similar investigations with the Wenham illuminator I hope before 
long to submit. Those who use the illuminator have noticed the 
ease with which blue, red, green, and the intermediate tints are 
obtained in the field. Some ten days ago it occurred to me to try 
unmodified sunlight with the instrument, presuming that the blue field 
due to the reflex might have the same effect as the intervening pane 
of blue glass which I had before used and recommended in the ‘ News.’ 
The experiment was a perfect success, and I saw No. 20 of the 
Moller plate, not exactly as coarse ‘as the pickets on a fence,’ but 
more like the teeth of a fine-toothed comb. The }th inch solid eye- 
