86 Scientific Intelligence. 



tions are represented in the discussion, and over 400 observations. 

 t ormulae are given for each station, with decennial tables com- 

 puted therefrom. Mr. Schott says : 



"A cursory examination of the column containing the epochs 

 of greatest easterly excursion, the deflecting force prodi 

 secular change attaining then an easterly 'maximum, shows that 

 the needle became stationary hi direction, and then reversed its 

 secular motion, m the New England States toward the end of the 

 past century, in the Atlantic coast States to the west and south 

 early in the present, and in Mexico about the close of the first 

 l»v-e„t -entnrv. In California. Oregon ,,nd Wa<h- 

 rntory, it has not yet reached this condition. We thus 

 have the following epochs for comparison: Halifax about 1711- 

 Portland, Portsmouth, Newburyport, Salem, Boston, Cambridge, 

 n.i Providence, about 1779; Hartford, New Haven, 

 Isew York, Hatborough, Philadelphia, Washington and Cape 

 Henry, about 1800; Charleston, Suva n i, I, Is',, -,\ . , 

 about 1800; New Orleans, about 1831 ; Vera Cruz Mexico \ca- 

 pulco and San Bias, about 1837; San Diego, Monterey and San 

 Francisco, expected about 1907 (yet very uncertain ) 



We are thus directed to the extreme northeastern States for 

 probable indications of what may be expected to follow on the 

 seaboard in more southern and western States. Kespcctii... the 

 ovement of the needle, apparently a little more than a 

 century pass, .,.,. which produced the turmng f 



the north end of the needle westward in Maine (increasing there 

 the western declination), was felt in Lower California (diminishing 

 there the eastern declination). In California, Oregon, and Wash- 

 ington Territory, the eastern declination is at present stil 

 iy, but with a losing rate. By the time the western elongation 

 of the secular change is reached in Maine, we may expect to see 

 the needle in the opjMsite phase, or at its eastern elono-ation in 

 California. We cannot as yet full 



the interior of the United States for want of early observations; 

 the westernmost interior stations for which an epoch could be 

 made out were Buffalo, Erie, Cleveland and Detroit- these give 

 the average turning epoch 1794. It may be quite practicable 

 hereafter to trace out curves uniting all stations where the needle 

 was stationary at a given epoch, and again at other epochs for 

 regular intervals of time, say of ten or twenty-five years. 



Keturning to the first table, the constant in each formula would 

 represent the normal direction of the needle about which the mo- 



average cycle 



of 



al.on 



t two hu, 



ndred and sei 



rcsnty yet 

 d to the 



US 1 





•tio 





a either s 



ide of it equi 



coefficient of 



the periodic te 





, all 



under the 



su /l; „, .•,;/;,,„ 



that the 



hi- 



«r of the 











■ rested. It is 



lotibt n. 



uch more 



complex, and 



he- 



-id,- 



may fail 







s f; 





present expert 

 trustworthy." 



s 



- 



aches, and within the ii 



itervai w 



he, 



is found 



