EXPLANATION OF THE TABLES. 
223 
every yard from 402 to 1500 feet. To use the table, search column for 
the angle measured, and opposite to this will be found the distance in feet. 
In that part of the table, where the distances are only given for every 
second or third foot, intermediate distances can be found by interpolation. 
Table XXIY. contains useful constants. 
Table XXY. Logarithms of Numbers .—The Table contains the logs, of 
numbers from 1 to 9999, to six places, with differences and proportional 
parts. 
The diff. D. is the mean of the diffs. between each log. and the suc¬ 
ceeding one in the same line; and is near enough for most cases. 
I. Direct process ; to find the logarithm of a given number. 
1. To find the logarithm to any number consisting of two or three 
figures. Look for the number at the side, and take out the log. against 
it. Thus, the log. of 717 is 855519.* 
2. To find the logarithm of a number consisting of four figures. Look 
for the three first figures at the side, and the fourth at the top; thus, the 
log. of 7176 is 855882. 
3. To find the logarithm of a number consisting of more than four 
figures. Find the log. of the first four figures; find the diff. D. in the 
lower part of the Table, in column D, and against it, under the 5th figure 
(or 6th, if required), are the parts, which add. 
Example 1 .—(Five figs.) Find the log. of 26574. 
2657 log.424392 D. 164 
Against D. 164, under 4.. .. .. 66 
Log. req .. .. .. . . .. . . 424458 
Example 2 .—(Six figs.) Find the log. of 265748. 
2567 log.424392 D. 164 
4 (parts 66). 66 
f 8 (parts 131 -f-10) . 13 
Log. req. .. 424471 
The arithmetical complement of a logarithm (Ar-co-log) is found by 
taking the logarithm from 10*000000, thus the Ar-co-log of 2*564782 is 
7*435218. 
* This, however, is only part of the complete logarithm, as adapted for 
purposes of computation, and requires the index. 
t Observe to set down the parts correctly, carrying those for the 6th figure one 
place to the right of the parts above them, as a mistake frequently occurs here. 
