470 THIRD REPORT — 1833. 



Desiderata noticed in Professor Airy s Report, p. 187. 



1. Directions for placing a thermometer so as to indicate cor- 

 rectly the Temperature of the Air at the place of observation, 

 for Refraction-corrections, the external and internal tempera- 

 tures being supposed as nearly as possible equal. 



2. Experimental Data for the Theory of Refraction — 



What is the law of the decrease of temperature, or of 

 density, in ascending ? 



How does this vary at different times ? 



Can any means be contrived for indicating practically at 

 different times the modulus of variation? 



Does the refractive power of air depend simply on its 

 density, without regard to its temperature ? 



Is it well established that the effects of moisture are al- 

 most insensible ? 



Can any rule be given for estimating the effect of the 

 difference of refraction in different azimuths, accord- 

 ing to the form of the ground ? 



When the atmospheric dispersion is considerable, what 

 part of the spectrum is it best that astronomers should 

 agree to observe ? 

 o. An investigation of the coefficient of Nutation from the 

 Greenwich circle-observations. 



4. The reduction of Bradley's and Maskelyne's Observations 

 of the Sun and Planets, on a unifoi'm plan. 



5. Remeasurement * of the elongation of Jupiter's Satellites, 

 to correct the estimate of the mass of Jupiter. 



6. Separate investigations, from observations, of the diminu- 

 tion of the aphelion distance and perihelion distance of Encke's 

 Comet, for the purpose of testing the truth of Encke's assumed 

 law of density of the resisting medium. 



7. Calculations of the perturbations of Biela's Comet for the 

 interval between 1773 and 1806, and of those of the node and 

 inclination from 1806 to 1826, for the purpose of ascertaining 

 the identity of the comet of 1772, and examining whether this 

 comet gives any indication of a resisting medium. 



8. Verification of Burckhardt's formulae in the Memoires 

 de VInstitut for 1808, and extension of them to terms depend- 

 ing on the inclination. 



9. Theory of the perturbations of Pallas, and of Encke's 

 Comet. 



1 Professor Airy himself has since made the required measurements, and 

 given a determination of the mass of Jupiter. 



! 



