OBSEKVATIONS AND OKBIT-ELEMENTS OF COMET GALE. 133 



was a pretty good one. The three fundamental places are thus 

 represented in the sense of observation minus calculation : — 

 Date. A A cos A/3 



April 2 



+ 0-2 



— 0-5 



„ 21 



+ 132 



—16-1 



May 10 



—0-4 



—o-i 



By redetermining the values of the comet's radii vectores and 



anomalies from these elements and substituting them in Watson's 



expression for M before referred to, this value becomes 1-15804 



instead of 1*15808 as previously obtained. The improvement by 



this substitution is really so small that it becomes hardly necessary 



to redetermine the elements ; the residuals for the middle place 



would not, I think, be materially reduced. It is quite possible 



that the magnitude of these residuals is due partly to errors of 



observation and partly to a small departure of the real orbit from 



the assumed parabolic form. It will be vain to attempt the 



determination of elliptic elements till the northern observations 



are completed and published. In order further to test the elements 



thus derived, I have compared the theoretical places for April 12th 



and May 2nd W.M.T. with the observed places for those dates 



duly corrected for aberration and parallax with the following as 



he residuals in the same sense as before : 



Date. A A. cos /3 A/3 



April 12 +9-8 —19-8 



May 2 +21*6 —9*3 



I believe Messrs. Innes and Merfield and the Rev. Dr. Roseby 

 are at present engaged in a redetermination of the orbit from 

 the Windsor positions for April 3rd and 21st and the Melbourne 

 meridian observation on May 17th. The method adopted is that 

 known as the varying of the geocentric distance, and I hardly 

 need say I shall await the result with interest. I shall also look 

 out with equal interest for the determinations we shall receive 

 from Europe in the course of two or three weeks. 



It will now be interesting to note a few particulars based on 

 the orbit which I have computed. Previous to June 1st, 1891, 



