( 6 } 7 ) 
Hence it appears, that the Hypothefis correfponds 
with the Obfervations of this Star through all Parts of 
the Year} for the fmall Differences between them feem 
to arife from the Uncertainty of the Obfervations, 
which is occafioned (as I imagine) chiefly by the tre- 
mulous or undulating Motion of the Air, and of the 
Vapours in it $ which caufes the Stars fometimes to 
dance to and fro, fo much that it is difficult to judge 
when they are exadly on the Middle of the Wire that 
is fixed in the common Focus of the Glaffes of the 
Telefcope. 
I ffluft confefs to you, that the Agreement of the 
Obfervations with each other, as well as with the Hy- 
pothefis, is much greater than I expeded to find, be- 
fore I had compared them ; and it may poflibly be 
thought to be too great, by thofe who have been ufed to 
Agronomical Obfervations, and know how difficult it 
is to makefuch as are in all refpeds exad. But if it 
would be any Satisfadion to fuch Perfons (till I have 
an Opportunity of defcribing my Inftrument and the 
manner of ufmg it) I could allure them, that in above 
70 Obfervations which I made of this Star in a Year, 
there is but one (and that is noted as very dubious on 
account of Clouds) which differs from the foregoing 
Hypothefis more than z", and this does not differ 3". & 
This therefore being the Fad. I cannot but think* it 
very probable, that the Thanomena proceed from the 
Caufe l have affigned, fince the foregoing Obfervations 
make it fufficiently evident, that the Effed of the real 
Caufe, whatever it is, varies in this Star, in the fame 
Proportion that it ought according to the Hypothefis. 
But lead y Tiracoms may be thought not fo proper 
to fhew the Proportion, in which the apparent Altera- 
S f f f tion 
