194 THE AMEEICAN MONTHLY [September, 



you are to make yourselves very much at home hei'e. Washington, as 

 the capital of the country, is, in fact, the natural and proper home of 

 all national associations, and they are beginning to discover this, for the 

 number of such gatherings here increases every year. Within the last 

 twenty years this city has become not only one of the most beautiful 

 cities in the world, but has become one of the great scientific and lit- 

 erary centres of this country . The needs of different departments of the 

 Government for accurate and precise information upon many subjects 

 connected with their work have brought together here in the different 

 bureaus many men specially trained in modern methods of investigation 

 and research, each working in some particular line, and more or less 

 of an expert upon some one particular subject, yet also interested in the 

 general progress of knowledge and the results obtained by his fellow- 

 workers. Hence it is that our local scientific societies are numerous, 

 well attended, and have an abundant supply of material to interest their 

 members, more so, probably, than the majority of local societies in other 

 and larger cities. Among these associations we number an active and 

 flourishing microscopical society, for although the Government has no 

 department or bureau exclusively devoted to this subject, yet in almost 

 every department and in many of the bureaus there are and must be 

 men who are familiar with the use of the microscope or they could not 

 answer the questions which are liable to come before them at any mo- 

 ment. You may be sure, therefore, that the American Microscopical 

 Society will always find an appreciative and interested audience for its 

 papers and discussions here. Of the numei'ous bureaus of the Govern- 

 ment which make use of and are interested in the microscope and mi- 

 croscopic technique, there is none which makes more constant use of 

 this method of investigation, and none which in times past has done 

 more to stimulate improvements in microscopy, than the medical de- 

 partment of the army, including the Army Medical Museum. The 

 improvements in microscopic objectives 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 photo-mi- 

 crography to the testing of such objectives as to resolving power and 

 flatness of field under different conditions of illumination. 



Photo-micrography, with high powers, became a practicable and 

 useful process when the use of direct sunlight as a means of illumina- . 

 tion was introduced. This was first done in this country by Prof O. 

 N. Rood, of Columbia College, N. Y., in i86o-'6i. It was first sug- 

 gested and applied in this country to histological preparations in the 

 spring of 1864 in a military hospital here, in Washington, by two as- 

 sistant surgeons in the army, Jas. 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. W^oodward, of the army, who was engaged in the collection of 

 materials for the preparation 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 espe- 

 cially the optical combinations and technique of illumination adapted 



