MEMORANDA, 227 
0 
upper and lower figures (as a0 as representing the lower 
30 
BO mks : : 20. 
90? OF im other words, that 30 8 
not the same as on but is synonymous with a or rather 
side of the square of 
a and indicates that the object lies in the upper half of 
the square ae Here the line converts the upper figures 
from longitude into latitude, and the lower ones from latitude 
into longitude. So far as I know, this mode is adopted by 
very few, and it has no doubt arisen from using a high power 
(as a 3-inch objective), in place of a 2-inch or l-inch, when 
registering the objects ; the field of view then consisting of the 
half of two adjacent squares, when the object lies near the 
bottom of a square, or below the top of the adjacent one 
below. 
The other method is to consider the line as a mere 
vinculum, or bond of connection, between the upper and 
lower figures, and which may or may not be used without 
altering the meaning of the numbers registered. Here, also, 
are three very slight variations. ‘The one is, when the object 
hes on the right hand or the lower edge of the square, or half 
way to the next square, either on the right or below, to draw 
a line there, with an ink-dot on it to denote as nearly as 
possible the position of the object. The second variation is to 
express this, not by a line, but by the decimal ‘5, thus :— 
= or ee as the case may be; and if at the lower right- 
90:5 
hand angle of the square, it would be noted by ae 
third variation is to apply two lines at a right angle, at the 
angle of that quarter of the square at which the angle lies 
By the first method mentioned this position would be indica- 
ted by a and by the second either by mi or 2 
If great accuracy were required, the first of these methods 
is, no doubt, the best; but as the difference between the 
finders as made by the same optician amounts often to half 
a square, and if by others to sometimes more than a whole 
square, such minuteness seems quite unnecessary— of course, 
I mean when one correspondent sends a slide to another; 
but even for one’s own cabinet, if the finders used be broken, 
the minute subdivisions may be of no value when a new ona 
