24 On the Optical Advantages Konthir ae 
But it will be seen hereafter that the water itself introduces a 
new compensation for spherical aberration. To avoid the analytic 
calculations the fact will be geometrically displayed in the drawing 
accompanying the second part of this paper, where every refracted 
line has been laid down by calculation, and the angles assiduously 
protracted by scale. 
The course of each ray is given by the following table for re- 
fraction from plate glass into air, and the mode of calculating the 
tables is indicated by two examples in the appendix. 
TABLE I. 
REFRACTIONS BETWEEN AIR AND REFRACTIONS FOR IMMERSION. 
Guass. (Air.) Obliquity > of (Water.) 
Ray entering 
¢' Deviation. sees Deviation. ¢' 
fe] ' °o ' fe} (eo) ! fo} Uj 
0 40 0 20 1 Oo F 0 53 
1 20 0 40 2 0 14 1 46 
2 00 1 00 3 0 20 2 40 
2 43 1 ee Wy 4 0 26 3 34 
3 20 2 40 5 0 33 4 27 
6 41 3) Uy) 10 t 6 8 54 
9 56 5 4 15 1 40 13 20 
NG 27 / 6 53 20 2 16 17 44 
16 22 8 38 25 2 53 ieee | 
19 45 10 15 30 3 33 26 27 
25 25 14 35 40 a 4 34 56 
30 43 21 54 50 GiiDg 43 1 
35 16 24 44 60 oi 50 29 
38 47 Syl 2 70 13 15 56 45 
41 2 38 58 80 22 20 57 40 
41 37 43 23 85 23 42 61 18 
41 48 48 12 90 2h. ask 62 57 
Angle of Refraction. Deviation. Inclination of Deviation, Angle of Refraction. 
Ray to Axis. 
The practical importance of “ Tables of Deviation” for compound 
refractions will be acknowledged at once by persons accustomed to 
original research in optical science. Their calculation, as will be 
seen in the appendix, involves considerable expenditure of time ; 
but if these tables should in any way advance microscopical per- 
fection, and enable us to clear away the errors still easily detected 
in most of the objectives now in use, the writer will be amply 
rewarded for his pains. 
Apparently deviations for every degree up to 5’, and then for 
increments of 5° and 10° are sufficiently close for practical use. The 
refractions are in each case actually taken to the nearest minute. 
By these tables the ingenious amateur and optician will at once 
be able to delineate the course of a pencil of rays through a variety 
of compound refracting media with precision and confidence. 
