Mr. Prideaux's Table of Atomic Weights, fyc. 423 



of observation and the angles y and y' (the zenith distances 

 of the bodies) ; that P and Q likewise involve d and «, and that 

 u and v contain these angles instead of D and A. It is there- 

 fore not necessary to give particular methods for the calcu- 

 lation of eclipses, be they either eclipses of the sun or transits 

 of the inferior planets over the disc of the sun, as all these 

 phsenomena may be treated after the method which I have 

 developed for the occultations of stars. 



From the formulae [14] results * 



G 2 =s sin 7T 2 — 2 sin 7r . sin n' . cos <r + sin ir' 2 



. . , sin «■' cos§ sin (a— A) 



tang (A — a) = - - r— V — ? ; — tt - 



° v ' sin w . cos D — sin it' cos a cos [a. — A; 



where <r stands for the geocentric distance of the two bodies. 

 For a solar eclipse we may put 



G = sin 7r — sin n 



. sin vr , A v 



a = A — -7 (a. - A) 



sin sr v ' 



d = D t—^- (5 — D) without causing in the cal- 



sin 5T x ° 



culation any perceptible deviation from the truth. The quan- 

 tities whose introduction has so much contracted the formulas 

 will then be found almost without calculation, and the calcula- 

 tion of solar eclipses will in point of ease present only insignifi- 

 cant differences from those of occultations of stars. We have 

 here another confirmation of the remark which one has so 

 often occasion to make, — that the rigorous mathematical so- 

 lution of astronomical problems ceases to require more diffi- 

 cult calculations than the approximately correct ones, as soon 

 as one has succeeded in representing the former in its true 



sha P e - F. W. Bessel. 



LX V. Continuation of the Table of Atomic Weights, and 

 Notice of a new Scale of Equivalents. By Mr. John Pri- 

 deaux, Member of the Plymouth Institution. 



To the Editors of the Philosophical Magazine and Annals. 

 Gentlemen, Plymouth, Aug. 8th, 1830. 



BEG leave now to send you the Table of acids and bases, 

 and a description of the scale, which has already intruded 

 on so many of your pages. 



I 



Table 



