Life, Researches , and Discoveries of F. W. Bessel. 309 



few, No. 310) the effect produced on a comet's orbit by the reac- 

 tion of the matter of these jets, so projected forth from the nucleus 

 into space, a subject of mathematical calculation. And it may 

 not be irrelevant here to notice that other phenomena, of a totally 

 different nature, exhibited by the same comet subsequent to its 

 perihelion passage, as observed in the southern hemisphere, appear 

 to authorize conclusions, which, though not precisely identical 

 with those of Bessel, have yet so much in common with them, 

 that the assumption of repulsive forces as a means of accounting 

 for cometary phenomena, must henceforward take its place among 

 hypotheses which cannot be lightly rejected, but must come to 

 be tested by the combined aid of rigorous mathematical deduc- 

 tion and increased refinement of observation. 



In a note appended to one of the numbers of the Astronomische 

 Nachrichten (No. 175), the following remarkable expression of 

 Schumacher occurs: — "It may almost be said that one exact 

 and able calculator is capable of doing better service to astronom- 

 ical science than two new observatories. 57 It was in the capacity 

 of such a calculator (taking the word in that enlarged and emi 



writer 



a calcu- 



lator thoroughly master of every resource of theory, and capable of 

 bringing them all to bear on the subject of discussion) that Bessel 

 undertook and completed, while yet young as an astronomer, his 

 great work, the Fundamenta Astronomic, a work which it is 

 difficult for any astronomer, and least of all an English one, to 

 speak of m measured terms. It affords the first example of the 

 complete and thorough reduction of a great series of observations, 

 grounded, in the first instance, on a rigorous investigation, from 

 the observations themselves, of all the instrumental errors, and 

 carried out on a uniform plan, neglecting no minutiae which a re- 

 fined analysis and a perfect system of computation could afford, 

 and resulting in a model catalogue, such as (without disparage- 

 ment to the far more extensive catalogue of Piazzi, published 

 J*» years antecedently) the world had not before imagined. As 

 Englishmen, we cannot but be proud to have furnished from our 

 national observatory, in the twelve years' work of a single British 

 ^ronomer, that "one entire and perfect" mass of precious mate- 

 naL from which has been sculptured forth in so masterly a man- 

 n «, and in all its classical proportions, the fair form of modern 

 Sl dereal astronomy. Independent of the deduction of the places 

 °* the stars, of the instrumental reductions, and of the local data, 

 the disquisitions which this work contains on the several urano- 

 ^phical corrections are, and ever must remain, models of deli- 

 ? at * and powerful research, monographs of their respective sub- 

 lets, embodying in a succinct and perspicuous point of view, so 

 tar as their complexity will admit, the totality of our knowledge 

 01 their theory brought into the most practical forms for applica- 



