J. J. Woodward on Photo-micrography. 191 
crown lens should be combined with a flint which will pro- 
duce a combined focal length about one-tenth shorter than would 
be required to satisfy the conditions of achromatism for the eye, 
and in this condition the objective is entirely worthless for vis- 
ion.” With a telescopic objective constructed on this principle, 
Mr. Rutherfurd obtained telescopic photographs of such satisfac- 
tory quality that he concludes his paper as follows: 
“The success of this telescopic objective has encouraged me 
to hope that an almost equal improvement may be made for 
photography in the microscope, which instrument is more favor- 
ably situated for definition than the telescope, since it is inde- 
pendent of atmospheric conditions, Its achromatic status is 
easily examined by the spectroscope, using as a star the solar 
image reflected from a minute globule of mercury. Mr. Wales 
is now constructing for me a one-tenth objective, which, upon 
his new plan, is to be provided with a tube so arranged as to ad- 
mit the removal of the rear combination, and in place of the one 
ordinarily used, one is to be substituted at will which shall 
bring to one focus the actinic rays.” 
This objective was satisfactorily constructed by Mr. Wales (of 
Fort Lee, N. J.) and Mr. Rutherfurd made with it a number of 
experiments, full of promise, though his other pursuits prevented 
him from following out the new plan to its ultimate results, 
Such was the condition of photo-micrography in America 
when it occurred to me to resort to this method of illustration 
in preparin proper representations of the histological studies 
of camp diseases which have been made by me or under m 
se ese for the Official Medical History of the War of the Re- 
lion. 
done in this direction. This is also the opinion of Dr. lox, 
whose judgment is of the greater value as he is one of the most 
successful laborers in this direction in Europe, ; 
