• OF ARTS AND SCIENCES: MARCH 8, 1864. 245 



I am not confident that I have incUuled all the results which might 

 be collected, although I have made a diligent search for them. But 

 there are results from seventeen different observatories, some of them, 

 as Greenwich, Paris, Dorpat, under several directors ; and it is to be 

 noticed that each one of the results in Table I. is derived from more 

 than forty complete transits ; in many cases, the number exceeds three 

 hundred. No results have been excluded on account of discrepancy 

 in the final combination of all. 



In order to compress Table I. into smaller compass, I have combined 

 several years' work of one observatory, in a somewhat similar man- 

 ner to that used in §§ 2, 3. In many cases this has been already done 

 by the astronomers themselves. The numbers given above for Cam- 

 bridge in England, Greenwich, and Paris do not appear in Table 

 I., as the corresponding observations are differently combined. 



So far as I conveniently could, I have kept separate the work of 

 different observers. This is not always practicable with the Green- 

 wich, Paris, etc, observations. The names of astronomers in Roman 

 in Table I. are those of the actual observers ; those italicized are those 

 of the directors, in cases where several observers employed the same 

 instrument at about the same time. 



The notes to Table I. give various details. 



I have corrected the results reduced by the nutation-coefficient 

 8".977 to Peters's value 9".223, so far as the lunar nutation is concerned. 

 The variation of the coeflacients of aberration and solar nutation is 

 so mixed with the errors arising from the effect of temperature on the 

 instrument, that the precautions which eliminate the latter will also 

 cause the former to disappear. 



Table II. contains the corrections to be added to observations already 

 reduced with the lunar nutation 8".977, to make the results accord with 

 the value 9".223. The part of the correction common to all stars is 

 omitted. The corrections for aberration and solar nutation have not 

 been applied. These, it will be seen at once, are of different signs 

 in different seasons. 



The most conspicuous result of the comparison between Bessel's 

 theory and observation is, that the former does, in fact, require a slight 

 correction. This is not remarkable, as it was published about 

 thirty-eight years ago. At that time the great majority of the obser- 

 vations here employed to correct it were not made, and Bessel adopted 

 the wisest course then possible. He devoted a considerable portion of 

 VOL. VI. 24 



