716 IMJOGREbS OF ASTRONOMY I'oK 1X!H AND 1SII2. 



indicate it I'otutioii (»!' the l»uU' in little iiiori' than a ycaf and witli a 

 lar.Qer ladius tliaii that of ISGO-ISSO, the ran,-;e beinj;- about 1". In tlie 

 same paper Mr. Cliandler states that Biinkley's observations at Dub- 

 lin (1808-1813 and lS18-bS22) are found to indieate a rotation in about 

 a year, with range more than l'\ ''wherein lies tlie solution of the hith- 

 erto unsolved enigma of Brinkley's singular lesults which led to the 

 spirited and almost acrimonious dispute between Brinkley and Pond 

 Avith regard to stellar parallaxes." The details were promised in a 

 later paper, but have not yet been given, owing doubtless to the ne- 

 cessity of attending to a vitally important point which will presently 

 appear. 



In papers 5 and t! are i^resented the results of an enormous mass of 

 reductions extending from 1837 to 1891, made at no fewer than seven- 

 teen observatories. The w^hole is broken up into forty-live series, or 

 short groups, for the purposes of this particular discussion; and the 

 result of this minute inquiry, contirmcd (or ])erlia])s suggested) by the 

 observations of Bradley and Brinkley above mentioned, seenu'd clear, 

 viz, that the " instantaneous rate of angular motion of the pole has 

 been diminishing during the last half century at a sensibly uniform 

 rate, by its one-hundred-thousaudth i^art." 



Mr. Chandler was led to modify this statement in a remaikable 

 manner and within a few weeks. 



Astronomers had hesitated to accept the 427-day period, even in face 

 of the very strong evidence of the 18G0-1880 observations, owing to the 

 difticulty in accounting for it theoretically. It had been iiointed out by 

 Euler that, treating the earth as a rigid body, the pei'iod of rotation 

 of the }>ole must be 300 days. Prof. Newcomb, however, happily 

 X)ointed out that a (lualitied rigidity (either actual viscosity or the 

 composite character due to the ocean) atibrded an ex])]anation of this 

 longer period ; and after this suggestion Mr. Chandler's 427-day 

 period was well and even warmly received. But the further elaboi-a- 

 tion of this hypothesis by a changing period was a new difficulty. 



Prof. Xewcomb, who had reconciled the tirst article of the hyi)othesis 

 with theory, was not slow to declare that the second was irreconcilable. 

 Mr. Chandler's reply, in i)aper 6, is a model of controversial courtesy 

 and skill. He says: ''It should first be said that in beginning these 

 investigations I deliberately i)ut aside all teachings of theory, because 

 it seemed to nu^ high time that the facts should be examined by a 

 purely inductive ]>rocess: that the nugatory results of all attempts to 

 detect the existence of the I<'.ulerian period probably arose from a 

 defect of the theory itself; and that the entangled condition of the 

 whole subject rc(piired that it should l)e examined afresh by i»rocesses 

 unfettered by any precom-ei\'ed notions whatever. . . . The ap- 

 peal to observation, treated irrespectixe of theory in the present 

 series of papers, shows that a rotation of the i)oIe really exists, but 

 {(() at a daily rate of but 00.85 (for 1875), and (/>) that this velocity is 



