- ( 44 9 ) 
had other Affairs of more Importance to me : And 
it was owing to an Accident which gave me fome Un- 
eafinefs, viz. his attempting to pubiifn fome Ac« 
count of it in Print here, that I did it at that Time, 
viz . in May 1732, when I tranfmitted it to Dr, 
Halley j to whom I made not theleaft Doubt but the 
Invention would appear -entirely New. This, on my 
part, was all the Merit I had to claim, nor did I then, or 
now affume any other, in either ofthefe Inftruments. I 
only wifhthat the ingenious Inventor himfelf might by 
fome means be taken Notice cf, in a Manner that 
might be of real Advantage to him. 
There needs not, I fuppofe, much more of a De- 
feription of the Iuftrument than has been given : I 
(hall only fay, the Bow had bell be an Arch of a- 
bout iooDegrees, well graduated, and numbered both 
ways j the Radius of zo or 24 Inches ; the Curve at 
the Center to be Ath of the Radius on each Side, that 
is, Ath of it in the whole; the Radius of that Curve 
As Parts of the Radius of the Inftrument ;-Cat the 
Glafs for the Solar Vane fhould not be Jels, but ra- 
ther larger, than a filver Shilling, with its Vertex 
moft exadlly fer. And that the utmoft Care be ta- 
ken to place the Middle of the Curve at the Centre 
exa&Jy perpendicular to the Line or Radius of 45* 
Degrees. As the Obferver muft alio take Care that 
the two Vanes on the Limb be kept nearly equi- 
diftant fromjthat Degree ; to which I fhall only add, 
that it may be bell to give the horizontal Vane only 
one Aperture, and not two. The reft I fuppofe 
may be left to the Workmen. Thus doubting I 
have already been too prolix on the Subjecft, to 
which nothing but a.fincere Inclination to promote 
O o o any 
