128 
CELESTIAL DAY OBSERVATIONS. 
Observations when it is once found, the exact vaiiation of the movement is 
nr°VenniFin ascertained, by comparing the calculations which were 
the day-time, previously necessary, vviih the time pointed out by the nonius 
on the equatorial circle- All this may be accomplished in five 
or six minutes. The equatorial, too, is, perhaps, the best in- 
strument for teaching a learner the names and positions of the 
principal stars. For when the right ascension and declination 
' of any star is known, the telescope may be immediately ad- 
justed to point to it, which will infallibly prevent his mistaking 
one star for another. In this way, also, the precise position of 
the planet Mercury, the Georgium Sidus, a small comet, or any 
other body not easily distinguished by the naked eye, may bo 
readily pointed out- But to enter minutely into these and 
other particulars, would protract this paper to an inconvenient 
length. 
In conclusion, I cannot but express my surprise, that the 
equatoiial telescope is so little known, even by many of the 
lovers of astronomical science. In several respectable acade- 
mies in this part of Britain, and, if I am not mistaken, in some 
universities, this instrument is entirely unknown- This is the 
more unaccountable, as a small equatorial can be purchased 
tor a moderate sum ; and as there is no one instrument so 
well adapted for illustrating all the operations of practical as- 
troru-ni)’- Where very great accuracy is not required, it may 
occasionally be made to serve the general purposes of a transit 
instrument, a quadrant, an equal altitude instrument, a theodo- 
lite, an azimuth instrument, a level, and an accurate universal 
sun dial. It is to be hoped, the members of the Edinburgh 
Astronomical Institution, w'ho are just now erecting an observa- 
tory, will not not omit an equatorial instrument as part of the 
apparatus they are now furnishing for astronomical observa- 
tions. 
Should the above communication be acceptable, several 
other observations and remarks on kindred subjects may after- 
wards be communicated. Mean time I am your’s, &c. 
THOMAS DICK. 
An 
Methven, near Perth, N. B, 
lAlh Sep. 1813. 
