( ) 
Numb. If 5 
V. J Letter from Dr Wallis to Dr. Sloan, Se- 
cretary to the Royal Society., concefmng fame 
fuppojed Alteration ef the Meridian Line ; 
Tphich may affeB the DecUnation of the Mag- 
nctical Needle, and the Poles Elcvacion. 
Oxford, 7«»^ 21. 1699. 
SIR, 
I Received (two days fince) a Letter (to me direfted} 
from an unknown Perfon (without any name Sub- 
fcribed, or mention of the Place from whence,) con 
taining a Suggeftion about ^omt Variation of the Z^^- 
ridian Line, (which, if fo, ma yconfequently afFe<3r the 
variation of the Magnetick Needle, and the Elevation 
of the Pole,) which he defires may be Communicated ; 
and is Verlatim, as folioweth, 
For the Reverend Dr. John Wallit Geometry Pro- 
" fefFor in Oxford^ thefe, June 12, 99. Sir, This comes 
v*^ from one who is noftranger to your Abilities, though . 
unknown to your Perfon; however I prefume on a 
" Minute of your Leifure, without any further Apo- 
" logy, than that I hope it may tend to promote a 
Point of Learning. Upon Reading the Phtlofophkal 
Tranfaclton, Num, 241. Agd as I was wondering how 
" an ordinary Mathematician could mils faeafy a thing 
" as the drawing a true Meridian, \ hit upon a Thought, 
^[ that; Meridians mufl: needi vary ; but whether in fuch 
manner, and proportion, as appears in the Inftance 
of chat tranfatlion^ I am not able to determine : 
Having contented my Rlf with (uch skill in Aftrono- 
my as ftrvesoniy to contemplite the wonderful Fa- 
brick of the vifible Heavens, wir ■lout adding fb muc!/i 
Geome- 
