136 Mr. Wollaston's Description 
purpose ; though I am growing too old to expect to make 
many more observations, I gave orders for one of a size and 
form which I thought most convenient to myself. Observers 
know best what it is they want ; and an instrument-maker 
who will condescend to listen to them, is a treasure. In this, 
as well as other respects, it is but justice to Mr. Cary to say, 
that he has answered the character which was given of him. 
He has shewn himself, during the whole time, very diligent 
and attentive ; comprehending readily my directions ; giving 
freely his opinion, and his reasons for dissent, if he disap- 
proved of what was proposed ; yet being willing to follow 
mine, if I still continued in the same mind ; improving upon 
some of my hints ; and executing in a masterly way every 
part of it. 
The drawing accompanying this paper (Tab. XV.) will 
shew the general form of the instrument ; and need very 
little explanation. 
The whole stands on three feet, adjustable by screws. The 
bottom plate (of 21^ inches diameter) turns in azimuth ; not 
on a long axis, but on a center ; and rides on a bell-metal 
circle, truly turned, and to which the bottom plate itself is 
ground. In this way it moves very smooth by hand ; but it 
is capable of being turned by a winch, with tooth and 
pinion. The intent of its turning thus, is merely for the 
convenience of reversing the instrument : for, though it 
might be used out of the meridian, and for azimuths ; yet, 
since it is designed principally for meridian passages, when it 
is in its place the whole is clamped firmly to the bottom 
frame by four clamps, which confine it to the circle on which 
it rides : and this method of turning proves itself to be 
