Intelligence and Miscellaneous Articles. 315 



nations previous to the present. Newton, from observations of the 

 fourth satellite made by Pound, determined the mass to be^Vy-a- of 

 the Sun's mass ; Laplace, from the same observations, found nearly 

 the same value; and Bouvard obtained nearly the same from the 

 perturbations of Saturn ; Nicolai, from the perturbations of Juno, 

 found -nrr-nr (a value generally adopted by the German astrono- 

 mers) ; Encke, in examining whether the absolute attraction of Ju- 

 piter on the Sun and on Vesta were the same, found -rxri-rr-T, re- 

 marking at the same time that Nicolai's value would satisfy his 

 observations nearly as well. Professor Airy's observations were 

 made on the elongation of the fourth satellite in right ascension. 

 Thirteen sets of observations were made, in each of which the planet 

 and satellite were observed upon twenty-four or thirty-six wires. 

 The first set was never calculated. The second and third were 

 rejected, because the axis of the declination circle of the equatorial 

 employed in these observations, was not strictly perpendicular to the 

 polar axis (all the other adjustments being tolerably exact). It ap- 

 peared in the sequel, that in these two observations the instrument 

 had been in opposite positions, and the mean of the determinations 

 might therefore have been retained. The effect of such a want of 

 adjustment was guarded against in the other observations, by re- 

 versing the instrument in the middle of the series. For calculation 

 of the mass, the place of the satellite was computed from Laplace's 

 theory, leaving only the mean distance indeterminate. In the course 

 of these calculations, some remarkable numerical errors were disco- 

 vered in the Mecanique Celeste: in particular the mean longitude of 

 the satellite is in error by nearly one third of the circumference. On 

 comparing the different results, it appeared that all the observations 

 in which the satellite followed the planet indicated a greater mass than 

 those in which it preceded the planet; this is attributed by Professor 

 Airy to a constant difference in the mode of observing a satellite 

 and a planet. The value of the mass which from these observations 

 is most probable, is -r-^-g-.^-; Encke's value, however, would satisfy the 

 observations nearly as well. The value assigned by Nicolai is by 

 no means so probable, as it makes the sum of the squares of errors 

 nearly four times as great ; and Laplace's mass, which makes the 

 sum of the squares about thirty-four times as great, is exceedingly 

 improbable. 



LI. Intelligence and Miscellaneous Articles. 



ACCOUNT OF AN AURORA BOREALIS, SEEN AT CAMBRIDGE ON 

 THE 13TH OF MARCH. BY PROFESSOR AIRY. 



A WELL marked specimen of Aurora Borealis was seen at Cam- 

 bridge on the evening of Wednesday, March 13th. It was first 

 noticed at about half-past eight (nothing remarkable having been 

 visible a few minutes before that time), when its appearance was that 

 of a dark cloud, with abroad bright upper edge ; the boundary line of 

 the upper edge passing a little below Polaris and below Venus. The 

 impression upon three persons who saw it at this time was, that the 



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