2 EXPERIMENTS ON 



tention to the effects of terrestrial refraction. After 

 him Colonel Williams and Mr. Dalby resumed 

 the investigation, as far as the service on which they 

 were employed conveniently allowed : hut as this 

 was but a secondary object with them, little addi- 

 tional information is to be gathered from their la- 

 bours. Major Mudge has, indeed, made a number 

 of experiments since that time ; but the result has 

 fallen so far short of his expectations, that he promises, 

 in his latest publication, to resume and pay particular 

 attention to the subject : and we have no doubt every 

 right to expect something very valuable from that 

 quaFter. But, may not the laws of refraction be so 

 materially affected by gravity, and other unknown 

 causes, as to varj^ in different parts of the globe, and 

 that theory which obtains in high northern latitudes 

 fail in tropical regions ? indeed, the irregularities 

 which of late have been detected in the declinations 

 of certain stars *, which, though unobserved in Eng- 

 land, are powerfully felt in these climates, sufficient- 

 ly show how much we have reason to suspect an 



* Major Lambton, in a postscript to one of his late reports to 

 jrovcrnmeni, lias this observation. " We find here, that different stars 

 " give very different httitudes after bein^ corrected for aberration, 

 " nntation, &c. At Trivandeporum, Uie latitude of that station by 

 " Aldebaran was II* 44' 52" 5£). Th.e latitude by Regulus was 

 " 1 1° 44' 47" S4, and the latitude by aOrionis, 1 1° 44' 40" ^I. I had 

 " made observations by the same three stars at PaMrf/fe station, where 

 " those by Reg^liis and aOrionis were often interrupted on account of 

 " the bad weather, and consequently left doubtful : but the differences 

 " notwithstanding were nearly the same, ike. Thougii these obscr- 

 •' vations have betn set aside, they serve sufficiently to prove thiit the 

 " declinations, as laif! <lo\vn in JEiirope, are irregular here, and this 

 " may probably arise from the uncertainty we labour under with re- 

 " spect to the laws of refraction ; and in consequence of erring in 

 " that, the difference of the corrected zenith distances of two stars 

 " observed in Europe, will not be the same as the difference which 

 " the same stars will give in this latitude. I am, however, hazarding 

 " an opinion, but as I intend, being more satisfied as to the fact, I 

 " hope I shall be able to say more ud the subject hereafter." 



