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Art. XX. Corrections in Right Ascension of Thirty-Six 

 principal Fixed Stars to every Day of the Year, together 

 with some Observations on the Use of the Transit Instru- 

 mentf S^x. By James South, F. L. S., Honorary 

 Member of the Cambridge Philosophical Society, and 

 Member of the Astronomical Society of London, 



To the practical Astronomer there is nothing more important, 

 than an accurate knowledge of his Time, and when his situation 

 will allow of its use, there is no Instrument so well able to 

 afford it, as a Transit ; accordingly, in well-appointed Observa- 

 tories, it is considered an Instrument, which is absolutely in- 

 dispensable. 



As there found, however, it is, from its bulk, but little 

 adapted to the purposes of the Amateur, and still less, to the 

 convenience of the Traveller; but its peculiar aptitude to the 

 object, for which it is designed, has occasioned the construction 

 of the portable Instrument. 



But whether the one, or the other, be the subject of our em- 

 ployment, if we are desirous of arriving at the greatest ac- 

 curacy, which the instrument is capable of affording, (and 

 without this, either becomes a mere toy,) we must carefully 

 guard against every source of error ; thus, the Collimation of the 

 Instrument, the Horizontality of its axis, and the Meridionality 

 of the Telescope, should claim our attention ; the former of these, 

 viz., the collimation, not being easy of derangement, requires 

 only occasional examination ; but the two latter, demand all our 

 solicitude, as often as the Instrument is employed. 



The usual mode of detecting the error of collimation, as 

 also of correcting it, is too well known to require comment ; it 

 will however, be advisable, never to allow the milled heads 

 which are applied to the collimating screws, to remain on 



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