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October 9th, 1871. 
The President in the chair. Twenty-four persons present. 
Pror. A. M. Epwarps presented, in the name of Lt. Col. 
J. J. Woodward, three Photo-Micrographs of Microscopic Test- 
Objects, and read the following paper. 
Note accompanying three Photographs of Degeeria Domestica as 
seen with Black Ground Illuminations. 
By Lr. Cou. J. J. Woopwarp, M. D., Asst. Surg. U.S. Army. 
The scale represented in these photographs, was selected 
from a slide presented to the Army Medical Museum, by Mr. 
S. J. McIntire of London. 
The photograph was made by mono-chromatic sunlight, 
obtained by passing a parallel pencil of sunlight reflected 
from a heliostat and plane mirror, through a cell containing a 
solution of the Ammonio Sulphate of Copper. 
The illumination was managed by the parabola of Mr. 
Wenham, aided by a small pace lens fixed with oil of 
cloves to the bottom of the slide, as described in Mr. 
Wenham’s paper in the monthly microscopical journal for 
July, 1871. The small truncated lens was presented to the 
museum by Mr. Wenham. 
The magnifying power is one thousand diameters, obtained 
by the immersion 7s in. of Powell & Lealand without an eye- 
piece. 
Photographs No. 1 and 2 are favorable to Mr. Wenbama's 
well-known views of the nature of the markings. 
The first is slightly out of focus, but shows the high-light 
on the knob of each exclamation mark. 
The second shows the exclamation marks, with cross bars 
between as Mr. Wenham describes them. 
The third shows double rows of corrugated ribs precisely 
