368 Mr. Barlow on the effects produced in the rates of 
These experiments were made with a small steel bar or mag- 
netic needle, finely suspended with untwisted silk in a glass 
vessel, and some care was taken to get the time as accurately 
as seemed desirable for the purpose ; but as the only intention 
of the experiments was to have some general ideas of those 
situations near the ball, where a compass needle would be 
the most affected in its vibrations, and where also, according 
to my ideas, the chronometer would be most affected in its 
rate, I did not conceive it necessary to carry these observa- 
tions to the utmost degree of precision. 
Every thing being thus prepared, I applied to my friend 
the Reverend Mr. Evans, to allow the experiments to be 
conducted at his observatory, in which was an excellent 
transit instrument by Troughton, and every thing requisite 
for conducting them with the greatest accuracy. To this 
request he very readily assented ; and he superintended the 
observations with the utmost attention, from March 11 to 
April 30, when, being about to remove to another part of 
the country, he was obliged to dismantle his observatory, 
and the experiments, during the rest of the period, were 
carried on in the same way by myself, in the Observatory of 
the Royal Military Academy. 
'Explanation of the table of experiments. 
In the first column is given the day of the month, and in 
the second, the state of the thermometer for each day at ten 
o’clock A. M. 
The third column shows the rate of the observatory clock, 
as deduced from each two consecutive transit observations : 
it is of no other use than that of showing the degree of con- 
