J 4-8 Notices respecting New Books. 



fact, it is only in the case of stars which really are nearly equal that 

 doubts on such points ever arise. Push observation and reasoning 

 to what extent we will, there will always be shades of difference too 

 slight for certain discrimination ; and practically speaking, I am dis- 

 posed (from my experience in these reductions) to consider a misar- 

 rangement to the extent of a tenth of a magnitude in one of our cor- 

 rected sequences, arising from such causes of uncertainty, as a very 

 unlikely occurrence." — P. 327. 



The different steps of the process of arrangement are explained at 

 considerable length ; the author treating, — 1st, " of the formation of 

 corrected sequences by the collation of several observed sequences, 

 and of the elimination of discordant and contradictory observations ; " 

 2nd, "of the consilience of sequences, or the formation of normal 

 sequences by the partial or entire combination of several corrected 

 ones, and of the assignment of a series of provisional magnitudes to 

 serve as a basis for those to be finally adopted ; " and 3rd, " of the 

 complete interpolation of the observed sequences, the conclusion of an 

 independent numerical result from each observation of each star, and 

 the assemblage of their results for the final determination of its mag- 

 nitude." The whole number of stars included in the final arrange- 

 ment, and to which magnitudes have now for the first time been 

 assigned upon a systematic plan, is 452, — a number sufficiently 

 considerable to serve as a fair specimen of the practical application 

 of the method. The following intimation will be received with in- 

 terest : — " Since my return to England I have been, and still am, 

 engaged in extending its application to the northern stars with some 

 perseverance, and I venture to hope not without some corresponding 

 degree of success. Sixty-one sequences, in addition to those above 

 recorded, have been observed and partially reduced, and where com- 

 pletely so, and brought into comparability with the southern se- 

 quences by means of the intertropical stars common to both series, 

 will afford a uniform system of astrometrical nomenclature, on which 

 I have every reason to believe considerable reliance may be placed. 

 This work, however, besides that it is as yet incomplete, cannot pro- 

 perly find its place in a volume of Southern Observations." — P. 340. 



A comparison of the magnitudes finally deduced by this process 

 with those which were provisionally assumed, gives the following 

 results: — out of 118 stars, the cases of exact agreement are 22 ; of 

 disagreement under one-twentieth of a magnitude, 64 ; of disagree- 

 ment above a twentieth but under a tenth, 26 ; of a tenth but under 

 an eighth, 6. These results completely bear out the statement made 

 above as to the precision with which the relative brightness of stars 

 can be determined by the judgement of the naked eye. 



One of the principal uses of the determination of relative magni- 

 tudes, as has been already stated, is the means it gives of ascertain- 

 ing the existence of variable stars, — a class of objects probably more 

 numerous than has been suspected. Several of those included in 

 the sequences are marked as variable, or possibly so, and a Hydrse 

 and j3 Ursse Minoris are instanced as two of the most remarkable. 

 Sir John concludes some interesting remarks on this subject with 



