46 Mr, SmeatonJs Obfervatiom on the 
den, to life circles inftead of quadrants, or other portions of 
circles, will bid much the faireft for perfection in actual prac- 
tice; and that his ingenious method of making them both ftiff 
and light, by the ufe of hollow conical tubes by way of fpokes, 
in the manner of a common wheel, will enable him to mount 
them of five feet diameter, upon hollow axes, in the nature of 
a tranjit . By this means we fhall have all the good properties 
of both the quadrant and tranfit united in one inftrument ; and 
obfervations both of right afcenfion and declination, through the 
very fame telefcope, as long fince attempted by M. Roemer ; 
and to a degree of perfection and certainty, in point of decli- 
nation, hitherto unattainable by the largeft inftruments that 
have yet been made. 
N. B. In matters of very nice determination, fmall circum- 
ftances often come to be of confequence ; and it is in this view 
that I mention what follows. It was a practice of Hindley’s 
of many years {landing, and fince followed by myfelf and 
others, wherever he made any ufe of the vernier , to lay the 
vernier plate in the fame plane, or cylindrical fur face conti- 
nued, whereon the principal divifions are cut. It is of equal 
utility, though the vernier be rejeCled, to lay the index ftroke 
in the plane of the divifions. In this way the divifions being 
by convenience upon the external border of the limb *, two 
fets of divifions are thereby rendered incommodious ; but thofe 
* It has been objected, that laying the divifions upon the extreme edge of the 
limb of the inftrument fubjeCts it to injury : but, to obviate this, in an Hadley's 
quadrant made forme, by my direction, by the late Mr. Morgan, in the year 
1756, wherein the vernier is laid even with the divifions, thofe are protected by a 
projection of the folid part of the limb, beyond the divifions ; a Rabbet being funk 
in the edge of the limb, to clear the vernier. 
that 
