[ 36 . ]. 
XXV. On the effects produced in the rates of Chronometers by 
the proximity of masses of iron. By Peter Barlow, Esq. 
of the Royal Military Academy . Communicated by John 
Barrow, Esq. F.R.S. 
Read June 28, 1821. 
Jt having been ascertained during the voyage made by 
Captain Buchan to the Arctic regions, in the year 1818, that 
the rates of the chronometers were considerably different on 
board and on shore, and this change having been attributed 
to the iron of the vessel,* I felt very desirous, first, of ascer- 
taining whether the proximity of a mass of iron had actually 
any effect in changing the rate ; and, secondly, supposing this 
to be the case, to determine, if possible, the laws and prin- 
ciples by which that action was governed. 
I accordingly, through the kindness of some of my friends, 
procured the loan of six excellent chronometers, besides one 
or two others, which upon trial were found to have too wide 
and irregular rates for my purpose. Having procured these, 
and made the requisite preparations, I began my series of 
observations on them on the 11th of March of the present 
year, and continued them daily till the 25th of May ; when, 
having obtained a considerable number of results, they were 
discontinued .-f It will however be proper, before I proceed 
• See a Memoir by Mr. Fisher, who accompanied Captain Euchan, in the 
Philosophical Transactions for 1820, Part 11 . 
f 1 ought not to omit this opportunity of returning my best thanks to those 
