Mr. mountaine’s Letter to Mr. maskelyne, x 9 
whole feems written by the fame hand ; fo that both of 
them (containing 1719 obfervations each) may be Riled 
originals: I have lent mine herewith for your infpec- 
tion. To your fecond queRion, I anfwer, that I could 
not make any ufe of them in the conftrudtion of either 
of my charts, as the firR was formed from actual obfer- 
vations made about the year 1744, and douglass's 
conclude in the year 1735; but as many of them as 
fuited the periodic times were taken in, and compared 
with many thoufands of others, according to the order of 
their refpe£tive date^, in forming the fix periodic reviews, 
as published in the Philofophical Tranfadtions, vol. L. 
part I. for 1757. To the third queflion ; viz. whether 
they are worth a public record ? I rather think they are ; 
and have fometimes thought to prefent them to the Royal 
Society for their approbation : for, notwithstanding they 
have been thus made ufe of, yet they are mixed and 
moulded up with others, and thofe only to every five 
degrees of latitude and longitude; fo that the variations 
refpedling the leveral latitudes and longitudes do not 
fingly appear. And as the true theory of this arcanum 
in nature is yet fo little known, every thing that ferves to 
illuRrate it, deferves attention. And as thefe tables, for a 
fingle fet, are extenfive, and may be efleemed authentic, 
they may very well ferve for comparatives in future 
times; for if the change of the variation be regulated 
by any conRant law, which I Rill continue to doubt, the 
difcovery of that law muR greatly depend upon fuch 
comparifons made from multitudes of good obfervations 
D 2 taken 
