November 25, 1898.] 



SCIENCE. 



731 



experiments in psychological laboratories, 

 viz. : that the time of reaction, like that of 

 chrouographic registration, is lengthened 

 Vfhen the impression on the sense is faint. 

 But for eye-and-ear transits the experiments 

 with screens are so far few and somewhat 

 indecisive, and the phenomenon detected 

 by Argelander, viz.: an anticipation of the 

 transit of a star faint enough to be a little 

 difficult of observation, has been noticed by 

 several observers and tested in various 

 ways. 



The suspicion is expressed in Number 

 369 of the Astronomical Journal that the 

 variation of personal equations with the 

 magnitude of the star observed affects 

 equally eye-and-ear observations and those 

 made with the chronograph. 



But on reading over the article in ques- 

 tion it is at once noticed that there is great 

 lack of detail in the result quoted, and that 

 the direct determination by Becker shows 

 an anomaly which the author of the article 

 in Astronomical Journal No. 369 is con- 

 fessedly unable to account for. A care- 

 ful reading of Becker's investigation in his 

 Berlin zone shows that the observations 

 were made with Professor Becker's well- 

 known skill and care, and whatever diffi- 

 culty there may be in reconciling these 

 results with other observations is probably 

 due to the treatment of the latter, and 

 hence that the lacking details in Astronom- 

 ical Journal No. 369 would, if supplied, per- 

 haps account for the discrepancy. 



The author of the article quoted has not, 

 so far as it appears, used his conclusions in 

 his later important investigations. Even 

 his rather hasty decision in favor of such a 

 variability of eye-and-ear personal equation 

 with magnitude deserves careful study as 

 to the facts involved. 



I venture to suggest a line of observation 

 which I desire to see carried out, and which 

 will add to the certainty of these conclu- 

 sions. 



The Christiana zone 64° 50' to 70° 10' of 

 the A. G. C. has been long completed by 

 the late Professor Fearnley, by whom the 

 transit observations were made by eye 

 and ear, and his successor, Professor Geel- 

 muyden, who made the observations for 

 declination and most of the reductions. 

 The observations for right ascension are 

 liable to but small casual errors, and have, 

 I believe, been shown to be nearly free 

 from constant error due to the faint- 

 ness of the stars below the magnitude 

 at which they are easily observable. The 

 stars of this zone below a certain mag- 

 nitude, for which I may assume 8.2 of the 

 B. D. scale, might be reobserved to some 

 advantage in connection with a similar re- 

 observation of Groombridge's stars, which 

 is now going on at Greenwich. In order to 

 conduct such reobservation to the best ad- 

 vantage, all things considered, I should 

 confine it to those stars in Groombridge's 

 catalogue which are within 25° of the pole 

 for the epoch 1875, as the meridian circle in 

 my charge has an aperture of four and one- 

 half Paris inches, and there are verj' few of 

 Groombi'idge's stars which it cannot easily 

 reach, as I know by long experience with 

 it. The few Groombridge stars, if there are 

 any such, which would give any trouble with 

 the Williams College circle to reobserve, are 

 those which Groombi-idge picked up on ex- 

 ceptionally clear nights, but they are in 

 eluded in the Eadcliffe Catalogue, whose 

 right ascensions were observed with an 

 aperture of considerably less diameter. 

 The cases will be very few in which Groom- 

 bridge's stars will not be easily observed on 

 any good night with the aperture of 122 

 mm., and in which the observer would be 

 liable to the ' Argelander phenomenon ' or 

 reversal of the ordinary order of sensations 

 as shown in the cases of Argelander him- 

 self, Copeland, Borgen, Bauschinger and 

 other good observers. 



The difficulty of separating this form of 



