404 Of! ihfi aliiKisplier'/cdl Refraction. 



Reply nf the Regent's Cnnal Company to the Joregoiiig Appli- 

 cation. 

 Regent's Canal Office, 108, Great Russell-street, Oct. 26, 1820. 

 Sir, — I am directed to acknowledge tlie receipt of your letter 

 of the lOtli instant, stating that the locks on the Regent's Canal 

 had been constructed according to the design sent in by you, in 

 the year 1812, and claiiiiing the premium of 100 guineas offered 

 for the best design for a lock; and in reply I am desired to ac- 

 quaint you, that the engineers to whom the several designs were 

 referred, did not adjudge the design sent in by you to be entitled 

 to the premium above mentioned ; and that no reference was had 

 to your plans, on the adoption of the lock which the Company 

 determined to construct upon the Regent's Canal. 

 I am, sir, 



Your obedient servant, 



Ed.m. L. Snee. 

 P. S. — The plan which accompanied your letter, will be de- 

 livered to any person bringing a note from you desiring the re- 

 turn of the same. 



LXXI. On the atmospherical Refraction. By James Ivory, 

 M.A. F.R.S. 



To the Editor. 



Sir, — 1 HAVE to acknowledge the favonr done me bv vour in- 

 serting in vour la?t publication, my formula for tl;e astronomical 

 Refractions ; and I shall now add some more observations on the 

 same subject. In examining the hypothesis relating to the con- 

 stitution of the atmosphere, on which is founded the solution of 

 the problem of refractions published in the MCcanicjue Celeste, 

 I was naturally leil to take the calculation, given in that work 

 itself, of the depression of the thermometer for the great height 

 of 3817 fathoms ascended by Gay-Lussac in a balloon; which 

 comes out at the rate of 82 fathoms to a centesimal degree. But 

 the gradation of heat in this supposed atmosphere ought to agree 

 with observation not only at great elevations, but likewise at the 

 surface of the earth. Now, if the calculation be actually made, 

 the height at the earth's surface necessary to depress the ther- 

 mometer one degree, will be found no more than 61 fathoms, 

 about two-thirds of the observed quantity, and considerably less 

 than in my formula. 



We are indebted for the most correct Table of Refractions that 

 has yet been produced, to the science of Laplace, and the skill 

 and diligence of the able men who assisted his labours by fur- 

 nishing 



