May :?, 1895.] 



SCIENCE. 



479 



1884-85, using a novel form of astronomical 

 instrument of his own invention. These 

 observations, continued uninterruptedly for 

 tliirteen mouths, revealed a progressive 

 change of a pronounced periodical character 

 in the instrumental values of the latitude. 

 In publishing these results in 1885 he an- 

 nounced his intention to continue the re- 

 search throughout the remainder of that 

 year. Yet cu'cumstances prevented him 

 from carrying out his intention at that time, 

 and he did not resume his examination of 

 the subject until six years later. Mean- 

 while Dr. Kiistner, at the Observatory of 

 Berlin, in 1888, published a memoir on the 

 Constant of Aberration, as deduced by him 

 from a series of observations also made in 

 1884-85, simultaneously with Chandler's 

 series, which brought to light anomalies of 

 an entirely analogous character. Kiistner's 

 series was not continuous enough to show 

 the periodic nature of the phenomenon ; 

 but, by an exhaustive examination of the 

 possible subjective sources of error, he 

 clearly demonstrated that it was no longer 

 permissible to retain the hypothesis of an 

 invariable position of the pole, and he 

 recommended that properlj' organized ob- 

 servations at various places be instituted 

 to settle the question definitely. It was 

 doubtless this work of Kiistner's which 

 compelled the attention of astronomers to 

 the subject. As a result, by the coopera- 

 tion of three German observatories, under 

 the auspices of the International Geodetic 

 Association, and the independent action of 

 that at Pulkowa, the fact of the variability 

 of terrestrial latitude was placed beyond 

 question, and, by a corresponding series 

 made at the Sandwich Islands, the further 

 fact was established that the variable ele- 

 ment is the position of the axis of rotation 

 with respect to the earth's body, and not 

 its jx)sition in space. 



It was just before this point that a re- 

 newal of Chandler's connection with the 



problem began. The results are published 

 in a series of eighteen papei-s in the Astro- 

 nomical Journal (18111-04). exclusive of a 

 series of five papers upon a topic closely re- 

 lated thereto, and involving it ; namely, 

 the abberation-constaut, which will be 

 separately spoken of lat«r. 



The keynote of these investigations, and 

 the undoul)ted cause of the success which 

 has attended them, lies in the fact that at 

 the outset he first recognized the necessity 

 of deliljerately disi-egarding all teachings 

 of the adopted theory, which had misled 

 previous investigators, and of examining 

 the facts bj- a purely inductive process, 

 taking nothing for granted, and basing all 

 conclusions strictly upon the observations 

 themselves. 



It is impossible to give here more than a 

 bare statement of the principal results thus 

 established, which we arrange in their nat- 

 ural order, and not in the historical order 

 of their derivation. 



1. The phenomenon is not a local or a 

 regional, but a terrestrial one ; also it is a 

 displacement of the earth's axial rotation 

 with reference to the principal axis of in- 

 ertia, and not of the direction of the former 

 in space. 



2. The axis of rotation, although fixed 

 as regards its direction in space, performs 

 a relative revolution about that of inertia 

 in a period of 428 days. This motion is 

 circular, with an average radius of about 

 fourteen feet, and its direction is from west 

 to east. 



3. Sinuiltaneously with the above motion, 

 the actual position of the principal axis of 

 inertia on the eai-th's surface is in motion 

 .about a mean position, in a period of a year. 

 Its direction is also from west to east, but 

 is in an ellipse, thi-ee or four times as long 

 as bi-oad, the major and minor axes being 

 about twenty-five feet and eight feet re- 

 spectively. The major axis is inclined at 

 present, by about 45° to the Greenwich 



