Himaxiava Mounrains. 
ND 
do 
yr 
An account of the meusurement of a Base Line of 21,7548 feet. 
By Lizvrenant J. D. HERBERT, 8ru Recor. N. L 
Captian Hopason having in what precedes, referred to me for an 
‘account of the manner in which the task that devolved on me, (in conse- 
quence of his bad state of health) of measuring a base, has been execu- 
ted; I propose in what I have to say, first, to give a brief description of the 
instruments and methods of using them; and to subjoin a table containing 
the particulars of the measurement, with the resulting length as properly re- 
duced. These are to be followed by details of a small triangulation, founded 
on the base; with the length of one of the great lines determined therefrom. 
In the execution of this measurement, I had to contend with great diffi- 
culties; owing, to the want of assistance. Iam of opinion however that 
the error of the measurement, does not exceed two feet; an uncertainty 
which will only affect the distances of the most remote peaks, by about 
sixty or seventy feet. As the fruit of my experience, I may mention; that 
¥ would not attempt a similar operation with wooden rods, withgut such 
metallic additions, as should detect and register the alteration in their 
length, arising from atmospheric changes. 
Ir may be thought that witha chain such as has been described in Cap- 
tain Hopason’s account of the instruments, there was required little con- 
sideration, as to the mode to be f~lewed—all that was necessary, being to 
