4 36 Mr. South on the discordances between the 
braces being 14 degrees, but without any evidence of in- 
creased displacement. 
On the 24th of August, the western half of the instrument 
was exposed 65 minutes before noon, still without any ma- 
terial difference ; indeed, if the observations could be relied 
upon (which they certainly cannot ), to 7-hundredths of a 
second of time, the result of this day’s exposure of the instru- 
ment, would militate against the hypothesis, that the sun’s 
rays have any thing to do with the matter, seeing that the 
difference is in the negative sense. 
On September 2nd, all the coverings were removed from 
the instrument, and it was defended from the solar rays, till 
the sun’s first limb had nearly reached the first wire. On Sep- 
tember 3rd, the instrument* without its coverings, was ex- 
posed to the sun’s rays, 59 minutes before his centre came to 
the meridian ; the difference between the thermometers on the 
western axis and brace, and those on the eastern, being nearly 
14 degrees, yet the discordance between the results of the two 
days transits, is absolutely insensible. 
On September the 4th, the instrument was entirely defended 
from the sun’s rays. On the 5th, the western braces and 
axis, also the western half of the centre piece being covered 
with black cloth, whilst those on the eastern half were enve- 
loped in white, the instrument was exposed 65 minutes before 
noon, to the sun’s rays ; thermometers placed under the covers 
of the western axis, and western brace, stood 13°.5 higher, than 
those placed under the covers of the eastern axis and brace ; 
yet the discordance between the observed and computed right 
* Previously to the shutter being opened, for the experiments of exposure, the 
instrument was always elevated to the sun’s altitude ; and it remained so, until the 
transit was observed : during the experiments, the windows and door of the obser- 
vatory were closed; the thermometers employed, were made by Mr. Troughtoit. 
