1824.] Thirty-Seven Principal Stars. 141 



As to the comparative ease with which it would enable astro- 

 nomers employed on scientific missions, to obtain accurate 

 astronomical observations ; — greatly to the credit of the British 

 government, it has of late years transmitted to distant parts of 

 the globe, several distinguished men, for various scientific pur- 

 poses ; the period which from some cause or other, they can 

 remain at the same station being generally short, any thing 

 which would enable them to multiply observations, or to confer 

 accuracy on those made, would prove highly valuable. At home, 

 surrounded by all the paraphernalia for reducing observations, 

 we have shown that the drudgery is hardly tolerable ; how much 

 more severely then must it be felt by the travelling astronomer, 

 whose situation denies him these advantages : his observations 

 are purely differential, having the Greenwich stars as points of 

 departure : grant him, therefore, the daily corrections of them, 

 and his labours, instead of being protracted, would terminate, 

 almost as soon, as the observations are completed. 



As to the facilities which it would afford to the examination 

 of published observations ; — on this head I would dilate a little ; 

 and much as I respect the Greenwich observations, I would with 

 becoming deference suggest, that some alterations be made in 

 the printed copies ; whereby the invaluable data which they 

 furnish, may more readily be converted to immediate use. For 

 the right ascension observations, I would propose the insertion 

 of a column immediately after that which contains the mean 

 transit, in which should be presented the clock's error by each 

 observed zero star; so would the position of the instrument, with 

 regard to the meridian, be instantly seen, although superior and 

 inferior transits, of the same circumpolar stars, through unpro- 

 pitious weather, may not have been procured. Were also the 

 clock's daily rate computed from consecutive clock's errors, by 

 the same stars in lieu of consecutive transits of the same stars, 

 increased accuracy would be the result. For the observations 

 of polar distance, two additional columns would be desirable; 

 one appropriated to the correction for barometer and thermome- 

 ter, the other wherein the index error, as found by each star, 

 might be entered in the same manner as was hinted at for the 

 clock's error; and at the end of each day's work, the mean 

 index error should be inserted, so that a person, wanting the 

 polar distance of any comet, or planet, might easily arrive at it 

 by applying to its observed place corrected for refraction, the 

 necessary equation for index error. If also the apparent diame- 

 ter of the planet, as observed with the micrometer were sub- 

 joined, it would, I think, be an improvement. Observations 

 thus published woidd, with the assistance of the daily corrections, 

 be readily examined, and occasional errors, however trivial, 

 would promptly be discovered ; but without such an arrange- 

 ment, or such an aid, the labour of wading through a mass of 

 observations of zero stars alone, is such that few individuals 



