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Art. XIII. — A’ Method of determining the Height of Cliffs 
or Mountains, hy measuring the Depression of the Horizori. 
By William Scoresby, Esq. jWwor, F. B. S. E. &c. Com- 
municated by the Author. 
The determination of the height of cliffs and mountains, is 
an object of importance and interest to the geologist, meteoro- 
logist, hydrographer, and land-surveyor : hence, any practical 
mode of performing this operation in an easier or more familiar 
manner, either as to the mode of observation or calculation, 
than the methods now in use, may not be unworthy of atten- 
tion. 
Trigonometrical operations, and barometrical observations, 
are the principal means at present practised for the mensuration 
of heights. The former can be applied in very few situations, 
without considerable labour, the use of several instruments, and 
the employment of several assistants ; and, after the necessary 
observations are made, a troublesome series of calculations is 
requisite, before the elevation of the situation can be determined, 
The latter, though easy as to the nature of the observations, re- 
quires a delicate, portable, and expensive barometer,* and the 
use of at least two thermometers, and then does not afford any 
accurate result, without the application, to the observations, of 
a troublesome formula. 
In the proposed method of measuring heights, the use only 
of a small sextant and an artificial horizon are necessary, with 
which instruments, after observations that may be made in five 
minutes are obtained, the height of the station above the level 
of the sea is found at once, by the simple inspection of a table, 
This method is, however, limited in its application, and is only 
calculated for situations from whence the sea, on the horizon, 
can be seen, and at such times (unless other instruments are 
used) as the sun, or other heavenly body, appears either within 
thirty degrees of the zenith, or in azimuth over the sea. 
The necessary operation merely consists in finding the depres-? 
sion of the horizon from the point whose elevation is required. 
This may be effected, either by measuring the angle between a 
horizontal plane and the visible horizon by a dip-sector, (in 
