, io Col. roy’s Experiments for 
preffion as well as of elevation were taken. When time 
would permit, the geometrical operations were repeated 
at the firft ftations ; or the angles of elevation were ob- 
ferved from fome new point connefted with the firft, 
and whofe relative height, with refpect to the others, was 
known. Small altitudes were occafionallv determined by 
levelling from one ftation to the other. 
To prove that the vertical heights, aftigned to the places 
in the preceding lift, are exceedingly near the truth, I need, 
only mention the following inllances, by way of confirma- 
tion. In 1771, with the afliftance of Dr. lind and his 
friend Mr. hoy, I meafured a bafe from the obfervatory 
of Hawk-hill weftward, whereby the height of the fum- 
mit of Arthur’s Seat, above the telefcope of the Hawk-- 
hill quadrant, in its horizontal pofition, was found to be 
685.66 feet. In 1775, thefe gentlemen levelled, three 
feveral times, from the fummit downwards to the laid- 
telefcope; and found the- vertical diftance to be, by the 
firft operation, 686.47 feet; by the fecond, 684.43; 
and by the third, 685.25. This 1 aft, which, from the 
great care that was ufed, they confidered as the beft, dif- 
fers only three-tenths of a foot from the geometrical re- 
fult. They afterwards continued the operation of level- 
ling from Hawk-hill to the pier of Leith, and having 
repeated it twice, with a difference of only two inches 
between 
