822 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
which have been made during the last thirty years, have been, to a 
considerable extent, stimulated, suggested, and given definite direction 
by the application of photomicrography to the testing of such objectives 
as to resolving power and flatuess of field under different conditions of 
illumination. Photomicrography with high powers became a practical 
and useful process when the use of direct sunlight as a means of illumi- 
nation was introduced. This was first done in this country by Prof. 
O. N. Rood, of Columbia College, New York, in 1860-1. It was first 
suggested and applied in this country to histological preparations in the 
spring of 1864 in a military hospital here, in Washington, by two 
assistant-surgeons in the army, James William Thomas and William R. 
Norris, both now well-known ophthalmologists in Philadelphia. These 
gentlemen brought the results obtained by them to the attention of 
Dr. J. J. Woodward, of the army, who was engaged in the collection of 
materials for the preparations of the medical history of the war and the 
formation of an army medical museum, and by his direction the process 
was taken up, extended, and improved by Dr. Edward Curtis, now of 
New York, who was then engaged in making microscopic preparations 
to illustrate the pathological histology of certain camp diseases. Sub- 
sequently Dr. Woodward himself took the matter up, studying especially 
the optical combinations and technique of illumination adapted to secure 
the best results, and applying these methods as a means of minutely and 
accurately comparing the powers and performances of different objectives, 
and of making of such performances records whose accuracy could 
not be questioned, and which could readily be compared with each 
other. 
When Dr. Woodward was doing the greater part of his testing work 
homogeneous immersion objectives were unknown, and with high powers 
the proper adjustment of the cover correction was a matter of the greatest 
importance to secure the best results, and was also often a matter of 
considerable difficulty. Dr. Woodward’s skill and patience in making 
these adjustments and in regulation of the illumination were unrivalled. 
He often spent half an hour and more in securing a single cover correc- 
tion, and the makers of microscopic objectives, both in this country and 
abroad, came to recognize the fact that he was not only absolutely 
impartial to his tests, but would get from each lens the very best work 
of which it was capable. The result was that they were glad to send him 
lenses for trial and to obtain his suggestions as to the possible means of 
improvement, which in this way was strongly stimulated. Since his 
death, microscopic and photomicrographic work have been carried on 
steadily in the museum, but on somew'hat different lines, consisting 
mainly in the practical application of these methods to pathological 
research and to bacteriology. We shall be very glad to have you spend 
as much time at the Museum as you can spare, and to show you what we 
are doing there. In connection with this I wish to invite your attention 
to two cases at the south end of the main Museum hall which contain a 
number of Microscopes illustrating the development of and changes in 
this instrument and its accessories, from the time of the first known 
compound Microscope of Janssen, in 1685, down to the present time. 
In bringing together this collection during the last ten years, I have 
been greatly aided bv [the late] Mr. John Mayall [Jun.] of London, who 
