1 80 Mr. J. Farey on the Encke Planet, on Satellitula, Sfc. 



On comparing the pressures at Madras with the velocities, 

 a principal minimum of pressure appears in May, and an in- 

 ferior one in December ; also two almost equal maxima in No- 

 vember and January, instead of one least velocity in Decem- 

 ber and one greatest in July, as above mentioned. Also, in 

 the Table given in p. 1 78, between 35° and 45° of Temperature, 

 the pressure decreases '32 inches, whilst the observed velo- 

 city increases 5*7 feet; all which show the velocities, not to be 

 in the direct sub-duplicate ratios of the pressures, although 

 Mr. Ivory appears, in p. 426, to consider that this assumption 

 " agrees sufficiently well with experiment :" — perhaps this 

 able mathematician, whose communications do so much ho- 

 nour to the pages of your Magazine, will oblige me and others 

 of your Readers, by detailing the Experiments to which he 

 alludes, or otherwise illustrating the subject. 



I consider it very fortunate for Astronomical Science, that 

 the discovery has been made by M. Encke, of a Comet, 

 moving in an orbit with so small a major axis, as in my hum- 

 ble opinion, well to entitle it to be designated the Encke Planet ; 

 and I am particularly pleased that its sensibly decreasing pe- 

 riods of revolution, has drawn the attention of M. Massotti 

 (see p. 457 of your last volume) to consider the effects of a pe- 

 culiar and very rare atmosphere of the Sun, as most probably 

 occasioning, by its resistance to this planet, when in perihelio, 

 the obvious loss of part of its motion on each return. 



I think it extremely probable, that there are several other 

 small planets, having rather excentric, although not large or- 

 bits, yet undiscovered, but with which the laudable vigilance 

 of astronomers will ere long make us acquainted; and that 

 the different degrees of approach of these to the Sun, when in 

 perdielio, considered in connection with their periodic decrease 

 of orbit, respectively, will fully demonstrate the existence and 

 the law of density and resistance of the solar atmosphere. 



I am sanguine also in thinking, that the multitudes of Sa- 

 tcllitulce which revolve round our planet *, in orbits which 

 though considerably excentric, do not probably carry them 

 beyond the orbit of the Moon, will ere long receive attention 

 from astronomers ; by the united labours of two or three of 

 whom, the periodic return of some of these Satellitulce might be 

 ascertained, and the length of course which each one periodically 

 makes through the higher part of our atmosphere, whilst ex- 

 hibiting the appearance of a shooting Star, might be deter- 

 mined ; and its accelerated periods of return to perigeo, might, 

 on similar principles of calculation to those lately applied to 

 * See vol. lvii. p. 346, vol. lviii. p. 183, &c. 



the 



