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WHAT IS TRUE TACONIC? 197 
The photograph was taken without an eyepiece, the magnify- 
ing power being obtained by distance; owing to the moderate 
angle of the objective the picture was freer from diffraction fringes 
and consequently handsomer than any Amphipleura picture I had 
previously obtained, for this reason only it was selected for repro- 
duction. Since it has been in the hands of the printer, however, 
it is only fair to say that I have obtained equally beautiful 
pictures with the same power by an objective made by Tolles of 
40° angle, as well as by an objective of Powell and Lealand, 
both used without eyepieces. Copies of these pictures I have sent 
to the Editor of the department of microscopy of this journal for 
exhibition. I suspect each maker would claim that the picture 
by his objective was the best. For myself I regard them as 
nearly equally good, and think that to discriminate slight shades 
of excellence between objectives of this high grade, it is necessary 
either to give a much higher power, by distance or eyepiece, or 
else to use some more subtile test, such for example as the finer 
bands of the Nobert’s plate. 
My present object is not to advocate one maker or another, 
but to present an. image of what the best glasses of several 
excellent makers will do with ease if properly handled, and to 
those who are influenced by more partisan feelings I need only 
Suggest that less than two years ago no American microscopist 
had been able to see any striz on this well marked diatom, and 
that those who had made the attempt were disposed to regard 
the observations of the Hull naturalists, made over ten years 
fore, as quite fictitious. 
In conclusion I need only mention that the illustrative print 
Was reproduced from my negative by “The American Photo- 
relief Printing Company” No. 1002 Arch Steet, Philadelphia, Pa. 
WHAT IS TRUE TACONIC? 
BY PROF. JAMES D. DANA. 
‘Tue true use of the term Taconic should be learned from Prof. 
Emmons’s first application of it when he made his formal an- 
nouncement of the “ Taconic system.” In his final New York 
