Dr. M. C. White, Diffraction in Microscopie Vision. 377 
Wy #8: 
Arr. XXXVIII.-—Jnfluence of Diffraction upon Microscopie 
‘ Vision; by Dr. M. C. WHITE. 
[Read before the Connnecticut Academy of Arts and Sciences, Jan. 15th, 1862.} 
era Serene 
scenes 
in diameter. These objects it appears were reduced images 
dimensions of these images were calculated, but not directly 
Measured. It will be shown hereafter that the calculation of 
these dimensions are probably liable to considerable errors. 
Mr. W. S. Sullivant of Columbus, 0., has kindly supplied me 
_ With a single experiment of the same kind, made with the best 
_ American objectives. A microscope was adjusted with a ;'; inch 
ject glass, and a 7 inch objective to act as an achromatic con- 
denser, A globule of mercury z;'55 of an inch in diameter, was 
Placed about 3 inches from the ,'; condenser, in which position it 
| Was determined by previous experiment that an image, reduc 
5 diameters, would be formed in the common focus of the con- 
: denser and the zs objective by which the reduced image was to 
viewed. The reduced image of the globule of mereury was 
therefore calculated to be only zs}ss Of an inch in diameter. 
is image was clearly seen in the compound mic ith 
the ,!, objective with a light (by no means the best) from a north- 
| a window and an overcast sky. It will be understood that the 
see that prevents the resolution of a series of lines like the 
ds 
* This Journal, [2] xxxii, 9. $ This Journal, [2], xxxi, 14. 
$ This Journal, et xxxi, 14. 
Au. Jour. Sc1.—Seconp Series, Vou. XXXIII, No. 99.—Mar, 1863. 
