140 Transactions,— Miscellaneous, 
\ 
Example as before. 
poe 
uit, 
1° 18’ 337-8 
8' 19” 
4713-8 
499-9 9994 = 499-9 reversed 
2356300 
0005675 5765000 = 0005675 reversed 
Diff. of altitude = 13373 feet 
Even when a book of logarithms is available, the calculation by logs 
will be more expeditiously performed by using the logs of the above 
quantities than by using the log tangent. 
Example. 
1? 18 33° ‘8 = 4713:8 “log 8 sd 
= 499:9 log 2:6988 
Constant log -0005675 z= 6.158960 
1337:3 feet = 3:126220 
With regard to the actual results obtained by this method, I may 
mention that in the circuit of 50 miles previously referred to, the altitudes 
closed to 18 feet, and in the circuit of 60 miles, the error in closing was 
only 2 feet. 
It is thus evident that this method is quite capable of giving reliable 
results in hilly country, and is well adapted for the topographical survey of 
a new country. A line of stations might be selected in the most accessible 
positions, and each line used as a base from which to extend triangles on 
either side, and as every line is determined independently, there would be no 
accumulation of error. 
On the contrary, by observing to distant hills on either side, the distances 
found would check each other, and any erroneous result could be rejected. 
In very level country, where the refraction is too uncertain to give 
reliable results by this method, other methods may be employed, such as 
chained lines, or triangulation from a measured base, ete. 
