305 



but is not required for the simple continuance of life when no action 

 is going on ; and illustrates this opinion by the instance of the com- 

 mon garden snail. 



Remarks on a Correction of the Solar Tables required by Mr. South's 

 Observations. By G. B. Airy, Esq. M.A. Fellow of Trinity Col- 

 lege, Cambridge, and Lucasian Professor of Mathematics in the 

 University of Cambridge. Communicated by Dr. Young, F.R.S., 

 8sc. Read February 15, 1827. [Phil. Trans. 1827, p. 65.] 



The discordancies observed by Mr. South between the sun's right 

 ascension, as deduced from observation, and those given in the Nau- 

 tical Almanac, follow a law so simple as not to allow of their being 

 regarded as errors of observation, or arising from any casual cause, 

 but justify us in attributing them to imperfections in the solar tables, 

 with the exception of three days, in which there seems to be some 

 ground to suspect error of computation. 



A single inspection of these discrepancies, Mr. Airy observes, suf- 

 fices to show that they arise almost entirely from an error in the epoch, 

 and an error in the place of the perigee. From the peculiar form of 

 the tables in Vince's Astronomy, which give great facility to the in- 

 troduction of an error in the excentricity, he was induced at first to 

 suspect that one might exist ; but on calculation found the error in 

 the equation of the centre so small as to be entirely insensible. He 

 then proceeds to detail the process by which, from Mr. South's ob- 

 servations, he has deduced the amount of the several errors, which 

 consist in regarding the epoch, the mean anomaly, and the equation 

 of the centre, as erroneous by three very small unknown quantities, 

 and forming as many equations of condition for determining them as 

 there are observations. These combined and resolved, so as to give 

 the most probable result, lead to the conclusions, first, that the cor- 

 rection of the equation of the centre is evanescent ; secondly, that 

 the epochs of the sun must all be increased by 9", and the epochs of 

 the perigee each by 1' 48". 



On the mutual Action of the Particles of Magnetic Bodies, and on the 

 Law of Variation of the Magnetic Forces generated at different 

 Distances during Rotation. By S. H. Christie, Esq. M.A. F.R.S. 

 Read February 15 and 22, 1826. [Phil. Trans. 1827, p. 71.] 



The results obtained by the author, described in a former commu- 

 nication, when a copper disc was made to revolve under a magnetized 

 needle, appearing to him not likely to lead to an accurate knowledge 

 of the law of magnetic attraction, developed during rotation, from the 

 effect of lateral attraction ; he was induced to resume the inquiry, 

 substituting a ring for a disc, expecting that, as no lateral forces 

 would here be called into action, the results would be more uni- 

 form, and in this expectation he was not disappointed. One of the 

 first phenomena encountered by him in this research, was a very 



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