[ 45 3 
*Tis with futh ah Inftrument that Mr.' Bradley, a 
celebrated Englifo Aftronomer, has difcover’d, in the. 
Meridian Altitudes of fome fixt Stars, certain conftant 
and annual Variation's, which do not proceed either 
from the Variation of the Refra&ions, or from the Pa- 
rallax of thefe Stars, or, in fine, from any Nutation or 
W avering of the Earth's Axis 5 but which he accounts 
for by the fucceflive Motion of Light. v 
Whatever be the Caufe of thefe Variations, (which 
Caufe, as well as its Effeft, are not as yet, perhaps, 
entirely cleared up), as they may poffibly happen in 
the Space of Time requifite to be fpent in making 
the Obfervations for the Meridian, or in paffing from 
one End of the Meridian to the others it is necefiary, 
with the fame Inftrument, or fuch another, that is 
of pretty near the fame Exaftnefs, to examine the 
Variations of the Stars made ufe of: Wherefore it 
would be of confiderable Advantage, not only for 
the Obfervations of the Meafurement of the Earth, 
but alfo for all the other principal Refearches in Aftro- 
nomy, to have Orders given for procuring two mural 
Quadrants of Mr. Grahams Make, and of the fame 
Conftrudion, as I have already fpecified 5 for which 
there are Walls already raifed at the Imperial Obfer- 
vatory, in the Plane of the Meridian. 
With thefe two Quadrants, which might be of 
feven Feet Radius, and the moveable Telefcope nine 
or ten Feet long, we fhould be in a Condition to make 
Obfervations of the utmoft Accuracy, fuch as the pre- 
fent State of Aftronomy requires. 
Beftdes thefe Inftruments now mention'd, which, 
are of abfolute Neceility to a folid Eftablifhment of 
Aftronomy and Geography in this Country, there are 
