Frazer.] 



646 



[April 6, 



ular variation in the rate of magnetic declination at any place within the 

 limits of the stations named in the discussion. 



By the tables thus framed the average error in the computed declinations 

 is rb 0.0063. 



He adds that the small table extracted from the Phil. Trans. Royal Soc. 

 Vol. XI, abridged, from IToS to ITOo, which Ilausteen used in the con- 

 etruction of the isogonic curves in his Erdmagnetismus, and which here fol- 

 low are erroneous, inasmuch as we know that the Western declination had 

 been decreasing from 1700 to about 17!)7, while the last two lines of this 

 table make it seem to increase. It may be remarked that the first two lines 

 virtually show increase of Westerly, because they show decrease of Easterly 

 declination. 



OBSKUVATION.S 



BY P. F. Jr. 



30 miles E. of Rodriguez 

 Key, Fla 



76 miles E. 8° N. of St. Au- 

 gustine, Fla 



32 miles K. S. E. of Cape 

 Hatteras 



365 miles E, of Sandy Hook. 



Declinations in 



Lat. Long. 1700. 



250 



8O0 43 E. 



30O I BOO I 2i E. 



I 



350 i 750 j 2i W. 



400 I 70O I 7 W. 



1730. 



9 W. 



1744. 



3J E. 



i E. 

 6^ W. 



Hi w. 



1756. 



3 E. 







7 W. 



12f W. 



Mr. Schott's contribution to our knowledge concludes with the following 

 remark : 



" Before closing the appendix it will be seen that a look out for a time 

 of inflexion to be expected about 1867 it 15 years was not premature and 

 indeed we find from the following comparison of the computed, and my last 

 observed declinations that the latter always fall short of the former — a plain 

 indication that the curve commenced turning its concave side towards the 

 axis of abscissae ; or in other words that in 1855.5 the maximum annual 

 increase had already been passed." 



The annual variation of 1850 is recommended as a constant for some years 

 till a new series clears up the point. He adds : * " Thus for example the 

 declination in Boston in 1870 will be found by computing the increase for 

 twenty years (the difierence of 1870 and 1850) prior to 1850, and adding 

 the same to the declination for 1880 ; the declination at Boston for 1870 

 becomes + 90.8I + 1° .48 ^ 11^ 18' W." f 



Referring to Mr Scholt's admirable iriniioircd tiibles to accompany the C. 

 S.- Report for 1874 we find the Declination at Boston for 1870 given at 10^.90 

 (see table of decennial values). This varies from his prophecy by 0O.28 

 or 16'. 8 (or with the correction suggested below by 0*^.39 or 23'. 4). 



•Written In \m^. 



t Should this not be 11°.29 7 



