66 SABINE’S EXPERIMENTS. 
It has been already stated that the mean temperature of the experiments, 
with the attached pendulums at New-York, having béen estimated from a 
mean between the extremes in 24 hours, when the progress of natural tem- 
perature was uninfluenced by artificial heat, might be considered to exceed 
the true mean temperature by a small amount; the corresponding experi- 
ments in London were made in Mr. Browne’s Library, where a fire is always 
kept during the day, and where, consequently, the temperature of the apart- 
ment approaches the maximum of the registry at an earlier hour, and con- 
tinues in proportion higher to a Jater hour than where the sun is the only 
source of heat; in such circumstances, therefore, the registered mean may 
‘rather be below than, as in the former case, above, the true mean ; and being 
in opposite directions, the acceleration will be affected by the sum of the dif- 
ferences between the true and registered temperatures : now it will be per- 
ceived that a difference of half a degree, or more precisely 0. 53 or 433, of a 
degree of Fahrenheit at each station, in the directions which were certainly 
anticipated as probable in both instances, before the observations were exa- 
mined, would make the results of the two methods of experiment identical. 
To have caused the results of the attached Pendulums to have been com- 
parable, in point of minute accuracy, with those of the detached pendulums, 
would have required not merely a more frequent registry of temperature, but 
that the experiments with the former should have been continued through a 
much longer period than it was expedient to employ; there are many per- 
sons who are of opinion that a detached pendulum needs no confirmation, and 
others that it can receive none, from a pendulum applied to a clock; but 
those whose opinions are not so decided, will probably consider the present 
approximation as satisfactory evidence of the agreement which more time, 
and an equal attention to both methods, might have been expected to have 
produced. 
