8 Lieutenant Foster's account of 
additional solidity was given to the supports, by attaching 
to the hindmost leg of each, a mass of lead, weighing from 
40 to 50 lbs. The clock was now fixed to its support ; but 
the pendulum of experiment remained on board the Hecla, 
until all the necessary preparations were completed. The 
small telescope containing the diaphragm, and used to observe 
the coincidences, was placed at the proper distance (9J feet) 
from the pendulum, on its stand outside of the room, in a 
porch originally erected for the use of the repeating circle : 
this stand was sunk so far into the ground, as to bring the 
object-end of the telescope, on a level with the bob of the pen- 
dulum of the clock. An aperture of a foot square was found 
sufficiently large for observing the coincidences, as well as 
the face of the clock, when sitting at the telescope, which was 
sheltered by a screen of canvas from any rush of air into the 
room, on opening the door of the porch. 
A transit instrument made by Dollond, of thirty inches 
focal length, and two inches aperture, was cemented to the 
pedestal already described, with plaister of Paris, at the latter 
end of October, and brought accurately into the meridian by 
the transits of high and low stars. A mark was then set up 
at the distance of 50 6 feet, to which it was afterwards always 
adjusted before making an observation : towards the end of 
March, the sun's rays caused such an apparent wavering 
of the meridian mark, as to render its removal neces- 
sary, and it was accordingly transferred from the exposed 
situation where it stood at first, to the opposite side of the 
harbour, a distance of 6697 feet, where, being fixed in a 
hollow part of the rock, and completely shaded from the 
sun, it ever afterwards afforded the means of adjusting the 
