NOVK.MHKIi 16, 1883.] 



SCIENCE. 



655 



rigorous, ant] are liable to aouiileiital I'lror^ of o lo or 

 two secoiiils. 



C - 0. 



Hill.-, 



Green wicli 

 > time. 



'tin . Obscrvalory. 



Harvard 

 Harvard 

 Harvard 

 Harvard 

 Kiel . . 

 Albany . 

 Harvard 

 AVien 

 Albany . 

 Ciuciuuali 

 J^eiden . 

 Kunigeberi 

 Dun KclU 

 Harvard 

 Albany . 

 Albany . 

 Harvard 

 Cincinnati 

 Harvard 

 Wion . 

 Kiel . . 

 Harvard 

 Leiden . 

 Dun Ecbt 

 I'ulliowa 



Kiel . . 

 .Strashury 

 Albany . 

 Harvard 

 I'uikowa 

 Kiel . . 

 Dun Kchl 

 Strasburg 

 Cincinnati 

 Kiel . . 

 Dun Koht 

 Pulliowa 

 Albany . 



Strnsburg 

 Albanv . 

 Albany . 

 Ivonigaberg 

 Wien . 



Kiel . . 

 Leiden . 

 Albany . 

 Albanv . 

 Albany . 

 Cincinnati 

 Albany . 

 Albanv . 

 AlbanV . 

 Albany . 

 Albany , 

 Albany . 

 Albany . 

 Albany . 

 Albany . 

 Albany . 

 .Vlbany . 

 Albany . 

 Albany . 

 Albany . 

 Albany . 



I + 21" 



+ 9 



I +23 



[ +22 



-10 



- 3 

 [ + 12 



— 3 







[+12 



- 4 



- 3"] 



- 6 



+ 4 ] 



* ] 



» ] 



Tlie observations enclosed in brackets were not 

 used as exhibiting large systematic or accidental 

 «rrors. 



A few observations were made with ring-inicronie- 

 ters, but it is not possible to determine how many. 



At Albany the ring was used until Sept. 21, after- 

 wards the tilar micrometer. 



The following table shows the constant dift'eience 

 for each observer when there are three or luore 

 observations given, and includes nothing later than 

 Sept. 26: — 



These constant errors, though founded on rather 

 slender material, probably represent fairly what is to 

 be expected from modern observations of comets. 

 Following are the heliocentric co-oidinates : — 

 X = r (9.5S0340) sin (ir)3° 14' 15.1" + t) 

 y = r (0.996200) sin ( S2 04 40.0 + ») 

 z - r (9.970401) sin (174 59 17.4 + v) 



H. V. Egbert. 



Rapid geological changes in Alaska. 

 Mr. Dall kindly calls my attention to an error in 

 the note of my le'marics, given in ;Scibxce of Oct. 19. 

 Hood's Bay is nearly a degree south of the locality 

 of the submerged forest described. Looking at my 

 diary, I find the entry ' Iloona,' which is, 1 believe, 

 synonymous with ' Bartlett Bay' of some charts. 

 While making my verbal remarks at the academy, I 

 mistook my pencilling of ' lloona' for ' Hood.' The 

 exact location of the forest is latitude 5S° 27', longi- 

 tude 135° 40 '. I am very much pleased to find from 

 Mr. Dall's letter that my view of the modern changes, 

 drawn from botanical "facts chiefly, derives support 

 from some geographical evidence within his reach. 



Thomas Meehan. 



The mechanism of direction. 



I read with interest Professor Newcomb's article 

 on the sense of direction (Science, Oct. 20). Profes- 

 sor Newcomb says nothing about the behavior of the 

 subjective co-ordinates under a slight change of angle. 

 My experience in this respect I give below, and I 

 have reason to believe the experience to be quite 

 general. 



The street A B tunis into B C. Walking from A 

 to B, my co-ordinates begin to change when about a 

 hundred yards from B. 'By the time I get to B, or 

 rather just after B, they have changed by the angle 

 ABC, no matter how large or how small A B C is. 

 The same takes place in going from K to 

 B to A. While close to B on either c^ 

 side, I can by an effort imagine myself 

 under the old co-ordinates; but the new 

 ones are much more natural. In the 

 dark, I think the turn is not seen so far 

 ahead, and the change takes less time. 

 If I go from A to B, with my eyes turned 

 towards A, I have a different experience. 

 I have never tried it by iralking backwards; 

 but I have observed "my sensations while riding on 

 the back platform of a street-car. As the car turns 

 at B towards C, and I am looking towards A, my co- 



