C 66 ] 
XVIII. Remarks on the Cenfure of Mercator’s 
Chart , in a pof humous Work of Mr. Wei}, 
of Exeter : In a Letter to Thomas Birch, 
D. D. Secretary to the Royal Society , from 
Mr. Samuel Dunn. 
Rev. Sir, 
Read Nov. n, *T Should not be fo ready to trouble you 
‘7 6z * with the contents of this letter, had 
I not the higheft opinion of your readinefs to aflift 
the fcientific, in all matters wherein vou are able. 
I requeft therefore your confideration, between this 
time and the next when I have the pleafure to fee 
you, if any paper has been printed in the Philofophi- 
cal Tranfadtions, concerning a fphere being infcribed 
in a hollow cylinder, and lwelling its furface to the 
iides of the cylinder, to conftrudt thereby a more 
true and accurate chart for the purpofes of navigation, 
than that which was invented by Edward Wright, 
and hath long gone under the name of Mercator. 
The realon why I afk this is, becaufe there is late- 
ly published, a pofihumous work of one Mr. Weft 
of Exeter, revifed by J. Rowe, in which it is ftrongly 
infifted on, that the graduation of Mercator’s chart is 
erroneous, and that the fame, if rightly correfpon- 
dent with the loxodromiques or rhumbs, fhould be 
graduated as a line of natural tangents, from the 
equinoctial to the poles. 
Now this error might have paft the lefs obfcrved, 
but the Critical Review of laft month fets it forth as a 
mafterly 
