106 On a new Transit Instrument. 
that never could answer the purposes for which it was intended. 
Not content with this rejection zz foto, without any particular 
fault being pointed out, and seeing Mr. B. so prejudiced against 
it, | determined to attempt the constructing of it myself; and, 
rude as my instrument was, its performance convinced me that 
it had not merited the unqualified censure that had been passed — 
upon it. Since that time, I have been procuring glasses, &c. for 
a more perfect essay on a larger scale ; and it is something ex* 
traordinary that Mr. T. Jones himself, about a month ago, fur- 
nished me with the apparatus for adjusting the wires, but with- 
out my mentionmg to him the instrument it was intended for. 
That Sir H. C. Englefield was one among the scientific gentle- 
men to whom my plan was shown by Mr. Banks, or that he got 
the hint from it in any other way, I cannot for a moment sup- 
pose, since he has mentioned the source from whence he derived 
his idea. It must however be considered as a very extraordinary 
instance of the same thought occurring to two individuals at 
nearly the same time ; and certainly Sir Henry, in meeting with 
a person so competent to realise his idea, has been more fortunate 
than I. From the little experience I have had with the home- 
made instrument above mentioned, I am convinced that, when 
properly constructed, it is capable of the greatest possible accu- 
racy. By having two marks, one to the north or south, and the 
other to the east or west, the position of the instrument may at 
all times be ascertained, as nearly as it is possible to place those 
marks at right angles to each other; and if the northern or 
southern mark be bisected by the central wire at the instant of 
observation (as it always ought to be), such observation must be 
as perfect as the power of vision in the instrument to distinguish 
when the object and wires are in contact. Nor will it be found 
impossible, when the object-glass is pretty large, to observe stars 
in the day-time. I had at first intended to subjoin a few 
observations, to show how far it was capable of being used 
by day; but as I have sent the glasses, &c. to Mr. Jones to be 
fitted up by hini in a rather more accurate manner than I had 
been capable of doing, and as I expect to find it much improved 
thereby, I shall defer it to a future opportunity. 
I am, gentiemen, 
Your obedient servant, 
JamEs GROOBY,. 
Messrs. Nicholson and Tilloch. 
XXIII. Solutions 
