156 Mr. Wood house on the derangement of certain 
from mine : but it cannot be that circumstance that confers 
inflexibility on Mr. South’s transit instrument ; for, were it 
so, the Greenwich instrument, which is similarly constructed, 
and by the same excellent artist, ought to possess the same 
rigid character. This, however, is not the case. Soon after 
the publication of my first Paper, the Assistants at Greenwich 
held in their hands the diagonal braces, and, by examining 
the meridional mark, detected a considerable deviation in the 
telescope. But in order to be more sure of the nature of the 
result arising from the partial heating of the braces, I re- 
quested the Astronomer Royal to try, with the Greenwich 
transit, the first experiment mentioned in this Paper. Mr. 
Pond immediately, with his usual kindness, complied with my 
request, and the following are the details of the experiment. 
Experiments on the braces of the transit at the Royal 
Observatory (Oct. 25, 1826.) 
With warm flannel applied to one brace, the interval of the 
Pole star passing from centre to 4th wire 
The true interval by observation 
Star accelerated - 
With warm flannel applied to two opposite braces, from 
the 4th to 5th wire - 
The true time by observation - 
| 9 m 4U.5 
zo 49.7 
j 8 .2 
] 9” i 5 \c 
10 47.5 
Acceleration - - - - - - -132 .5 
Total acceleration from the centre to the 5th wire - - 2 40 .7 
(Signed) Thomas Tavlor. 
The peculiarity of construction then, which the excellent 
artist who made the Greenwich transit, has used in joining 
together the tubes composing the telescope and axis, does not 
prevent the braces from deranging the instrument ; nor was 
