«35 
of a Transit Circle. 
transit at the end of the axis itself (which appear to me es- 
sential to a due performance) ; and at the same time with the 
opposite readings, and all the adjustments of the circles now 
in use. 
On this idea the following instrument was constructed: 
and since there are some particular contrivances in it, which 
are new, I take the liberty of laying a general description of 
it before this Society ; not by way of setting forth the praises 
of any one instrument; but that this may be known in all its 
parts, with the advantages and disadvantages of each, as far as 
I have discovered any ; and that such of them as are judged 
useful, (if the Committee shall think proper to honour this 
paper with a place in our Transactions) may be adopted by 
others. 
My first design was, not to have given orders for one my- 
self, but merely to communicate the thought to those who 
might improve upon it. Accordingly, I mentioned it first to 
Mr. Ramsden, in 1788 : but the multiplicity of his engage- 
ments, and the fertility of his own imagination, (at that time 
particularly turned towards contriving to make instruments 
move freely in azimuth) rendered him disinclined to listen to 
a scheme for one on another plan. The same was the case 
with Mr. Troughton. I mentioned it likewise to several of 
my acquaintance: but (perhaps the trouble and expense at- 
tending the construction of a first instrument, seldom so com- 
plete as a second or a third of the kind, might be the cause) 
no one was set about. After three years waiting, and be- 
coming, in the mean time, more and more convinced of the 
advantages of such an instrument to astronomy ; and Mr. 
Cary being recommended to me, as fully qualified for the 
T 2 
