, C 412 ] 
it is fnfpencled by a i'mooth even catgut, by U’hich 
that end is let down to the altitude required. This 
catgut bears conltantly againd: a deep angular 
groove that is cut round the end of the Icrew 
marked A ; by which means that end hangs al- 
' u'ays from the fame point at all ’altitudes ; from 
whence, the centre of gravity of the tclefcope 
keeps it conftantly in the fame plane. This ferew 
runs eart; and weft j and therefore, when the te- 
ielcope is drawn up to a horizontal pofition, ferves 
to adjuft it to the meridian, by direding the wires 
to a diftant mark. The fettling of that meridian 
mark is certainly the fame in this as in other tranfit- 
inftruments ; and perhaps mine is not exadly right. 
But I fufped my inftrument errs in another particu- 
lar ; that the line of collimation does not run par- 
allel to the interfedion of crofs axes and the center 
of gravity ; which it ought to do. This is owing 
to Jbad workmanfhip, which a fkilful operator could 
eafily let right j and, when adjufted, I fhould think 
would not be apt to vary, but would always con- 
tinue to deferibe a true vertical, as indeed it has 
proved upon trial ; having always, in this rude 
form, kept to the fame errors at the fame alti- 
tudes. 
The reft of the drawing, I believe, explains it-' 
felf : excepting the two curved pieces of pafte- 
board between which the telefcope is direded ; 
which are defigned to keep off the air that would 
make it vibrate j and do in effed take off alfo a 
great deal of falfe light in the day time, and an- 
iwer the purpofe of an illuminator at night. 
