C 844; 
VIII. A Fropofal concerning the Parallax of the 
Fixed Stars, in Reference to the Earths An- 
nual Orb. In fever al Letters of May the 2d, 
June 29, and]\i\y 20. from Dr. John 
Wallis to William Molineux Efe 
SIR, 
IAm obliged to you for two Books which you have 
been pleafed to (end me , that of your Sciothericum 
Telefcopicum^nd that of Dioptricks ; which you havener- 
formed Co well, that I have not been better fatisfied with 
any that I have feen of that Subjedi. I ftiould not fo 
long have negle&ed to return my Thanks for them, but 
that I thought a Letter of bare Thanks to be too emp- 
ty, unlefs I had tbmewhat dfe to lend with it. 
You will, I hop^ give me leave (though I have not 
had the opportunity cf being perfonaiiy known to you) 
tofuggeft a Speculation, which hath been in my Thoughts 
thefe Forty Years cr more,- but I havi not had the op- 
portunity of reducing it to Practice, as being no* fbweli 
ftored with neceiTary Inftruments of that kind, nor 
much exercifed to Telefcopick Obfervations. And 
though I have many Years fmce tuggefted it to others, 
yet neither have they had leiiure or convenience of put- 
ting it in Pra&ice. 
it is concerning the Parallax of the fixed Stars, as to 
the Earths Annual Orb. 
Galileo complains of it a great while firrce fin his Sy- 
iema Cefmicum) as a thing not attempted to be obfer- 
ved 
