10^ <SVr George Shuckburgh’s Account 
of the planets, higher powers may be put on ; and of these, 
that of 400 seems to be near the maximum that this glass will 
bear ; with 500 the image is not so well defined ; with 200 
or 300, it is beautifully distinct and bright ; but this inquiry 
demands more experiments than I have hitherto made, hav- 
ing been able to procure these high powers only within a few 
weeks. 
(23.) Having now given, as I apprehend, a very satisfac- 
tory idea of the accuracy of the parts of this instrument, I 
shall proceed to the method of adjusting them. This ma- 
chine, not being capable of having its polar axis laid horizon- 
tal, its adjustments, in some respects, will be different from 
those of small instruments of the same name. (See the me- 
thods proposed by Mr. Ramsden, in his Description, and by 
Mr. Vince, in his Practical Astronomy.) It may be proper 
to premise, that the principal points required are, 1st. to ad- 
just the level P, k, parallel to the declination axis U, V. 
2dly, to adjust this axis at right angles to the line of collima- 
tion of the telescope ; and, gdly, to make this axis at right 
angles to the polar axis. 
Probably others may be devised, but the inode I have 
adopted is as follows.* 
The polar axis is placed nearly in the meridian, by means 
of a meridian mark, previously verified, and elevated pretty 
nearly to the latitude of the place. This is to be done more 
accurately afterwards, by the sliding plates, and screws, at the 
bottom of the polar axis. 
* Whoever is desirous of seeing some very ingenious disquisitions of the errors and 
adjustment of this instrument, will do well to consult the Abbe Boscovich’s Opera 
pertinentia ad Astronomiam el Opticam, quarto, Bassani, 1785. Tomi 4ti Opuscu- 
lum i4tum. 
