On the New Astronomical Circle at Greenwich. 
cy 
Li) 
reservoir C *), to throw back, by contact, the whole con- 
tents of the stnaller ¢ upon the sowrce; converting the in- 
strument, by this process, into a species of doubler. These 
latter parts of the instrument, N and OOO, must how- 
ever be considered as mere objects of curiosity: all 
doubling operations (no matter what number of revolutions 
are employed) being subject to equivocal results. 
* C may be said, in this instance, not to appertain to the instryment. 
—— 
VII. On the New Astronomical Circle at Greenwich. 
To Mr. Tilloch. 
Sir, — On referring to the article “ Transit Circle,” in Dr. 
Rees’s new Cyclopedia, I found the following observations re- 
Jative to the new astronomical circle which was, a few years ago, 
fitted up by Mr. Troughton for the Royal Observatory at Green- 
wich. ‘ Mr. Pond has already published one volume of Obser- 
vations taken with this instrument, and has therein given a plan 
and section of the circle, which is six feet two inches in diame- 
ter. But, as Mr. Troughton intends to give a complete descrip- 
tion thereof, himself, as a paper suitable for the Philosophical 
Transactions, which, to be published therein, must be an ori- 
ginal communication, Mr. Pond was not at liberty to describe 
the drawing which he has given as a frontispiece to his first 
volume.” And the writer goes on to state (what may be readily 
anticipated by any onc), that as Mr. Pond had not thought pro- 
per to describe the circle, he (the writer) of course was pre- 
vented altogether from giving any description of it. 
Why Mr. Pond was not at liberty to give a description of am 
instrument which was in his own possession, and which in fact 
belonged to him, in his official capacity, does not appear; but 
I should conceive it was merely a matter of courtesy between 
him and Mr. Troughton. As several years however have now 
elapsed, and Mr. Troughton has not given the promised descrip- 
tion, it is presumed that the same reserve is not now necessary. 
Indeed, I have been informed that Mr. Pond has recently fur- 
nished the French with @ complete drawing and description of 
this instrument ; and that this circumstance had great weight in 
the distribution of the medals with which the astronomer royal 
has been lately honoured. ‘This, if true, surely requires some 
explanation; and, if not true, ought to be.formally contradicted. 
The instruments at the Royal Observatory at Greenwich are 
furnished at the public expense ; and the Government have, with 
a munificence unequalled in former times, provided that esta- - 
blishment 
