The corrections of the errors of the instrument by means of little screws are given up, and the errors which are known to exist are corrected in the computations.
"Professor Smyth finds that although the two pillars upon which the instrument rests were cut from the same quarry, they are unequally affected by changes of temperature; so that the variation of the azimuth error, though slight, is irregular.
"The collimation plate they correct with the micrometer, so that they consider some position-reading of the micrometer-head the zero point, and correct that for the error, which they determine by reflection in a trough of mercury.

With this instrument they observe on certain stars of the British Catalogue, whose places are not very well determined, and with a mural circle of smaller power they determine declinations.
"The observatory possesses an equatorial telescope, but it is of mixed composition.

The object glass was given by Dr.Lee, the eye-pieces by some one else, and the two are put together in a case, and used by Professor Smyth for looking at the craters in the moon; of these he has made fine drawings, and has published them in color prints.
"The whole staff of the observatory consists of Professor Smyth, Mr.
Wallace, an old man, and Mr.Williamson, a young man.
"The city of Edinboro' has no amateur astronomers, and there are two only, of note, in Scotland: Sir William Bisbane and Sir William Keith Murray.
"From the observatory, the view of Edinboro' is lovely.

'Auld Reekie,' as the Scotch call it, always looks her best through a mist, and a Scotch mist is not a rare event--so we saw the city under its most becoming veil.
"October, 1857.

I stopped in Glasgow a few hours, and went to the observatory, which is also the private residence of Professor Nichol.
Miss Nichol received me, and was a very pleasant, blue-eyed young lady.
"I found that the observatory boasts of two good instruments: a meridian circle, which must be good, from its appearance, and a Newtonian telescope, differently mounted from any I had seen; cased in a composition tube which is painted bright blue--rather a striking object.
The iron mounting seemed to me good.