Dent's new Compensation Balance for Chronometers. 83 
would reduce the temperature to 32°, in a climate where the 
mean temperature is but 52° or 53°.* 
In endeavoring to explain the low temperature of the Ice Moun- 
tain, the effect resulting from the bad conducting nature of the 
mass, and its protection by similar materials on all sides except 
the N. W., have alone been considered. ‘The nature of the rocks 
as absorbents of heat should also be estimated, as from their dull 
white color, most of the heat would be reflected, leaving but a 
small portion to be absorbed. It should also be borne in mind, 
that the air immediately in contact with the ice would be, from 
its lower temperature, specifically heavier than the external at- 
mosphere, except in midwinter, and could only be replaced by 
an atmosphere heavier than itself, and therefore colder. It hence 
follows that the ice could only be affected by the hot air of sum- 
mer, so far as its heat is conducted by the surrounding rocks, 
which, as will appear from the foregoing explanations, must be 
very inconsiderable. 
Arr. X.—On the E’rrors of Chronometers, and explanation of a 
new construction of the Compensation-balance ; by BK. J. Denr.+ 
Ir must, doubtless, be interesting to the public in general to 
have the opportunity afforded them of noticing the various state- 
ments of reported improvements in chronometers, that are, from 
time to time, set forth by their respective inventors. Such ac- 
counts moreover answer the desirable and double purpose of 
registering the several ingenious contrivances, as well as of ex- 
hibiting in a clear light the nature of the difficulties usually 
encountered in this important branch of the mechanical arts. By 
such a work, too, the public obtain a more distinct knowledge of 
the subject, and at the same time receive a more attractive idea 
of human ingenuity striving to attain mechanical perfection. It 
must be confessed, however, that the result of the skill, labor, 
and expense which have been bestowed within the last fifty 
years on the improvement of chronometers, affords but little 
room for congratulation, and must convince every one acquainted 
* Deduced from observations on the temperature of the springs of that region. 
t Communicated by the author. 
