. Schott on Magnetic Declination. 339 
Py : Ss ¢ 2 
poe fee : E - Te g = 4 
prehy e ee teed bale ie 
Bz | Se E oe S = tan os i 
. a yet Bedi IRs z e s™ g fe er 
o °o ° 3° ° ° 
1680|.,...3 feulScclgei dl, cite lebemod gcd. 244 Ag. Paes 
| Se OP lirhiw ces $3 ol iiavathic> och +48) 
85 | +88 1% Vy ciceeiie es, +48 
PSs vss 8-0 8-4 ig eee ae Se ee ee 
eres 76 79 ve Daa geet, Srkioe: a. Bar Cream 
Pl... ks 7-0 V1 OB tines ix toasts: 
ENS SS eee 6:4 6:3 ee Sp Pg ee 
ye dy Dp ey Meme 58 53 re aes eters CEES Sy eee 
1760 | +61 5:2 44 $8 |... aie Oe 
1770) 55 47 35 ae Un aphte +12 
7 Ss aaea’ Paeee 44 2°8 eg Bs eee +07 
} af Phe +:3-0 4-2 22 PO et ia ee +02 
Sara e 3-0 42 20 Che oo. +04 | =02 
1810) 47 | 454) 31 43 1-9 21 | +06 05 | -04 
1820} 5-0 58 | 34 4°T 22 26 0:8 os | -04 
1830 5421 63 382] 616) 270; 820; 12 11 | -02 
18 598! 70 | 4483] 8738) 341] 389 17 15 | +01 
1850; 671) 77 | 5:15| 687| 425 o4 | 90 | +06 
1860/4746 | +83 |+5-95| +701! 45:19) +5321 +29 | +26 | +1°9 | 
Note—aAt Cambridge, Mass., the observations after 1855 require farther examin- 
ation, At Williamsburg, the values between 1700 and 1770 were not considered 
raed reliable for insertion. The expression for ce depends for length 
; e ws 
The total number of observations upon which the tabular 
Values and the formuls are based is 180, the average number 
of any one station is 10, and the average probable error of any 
ee representation is +11’. ' 
We arrange the stations geographically, we find that at the 
eastern stations the minimum (west) declination occurred earlier 
_‘han at the more western and southern stations; thus, six 
Stations between Portland and Providence it occurred about the 
year 1777; in the Connecticut and Hudson valleys and along 
€ sea-coast as far south as Washington, the year of the mini- 
Mum does not differ much from 1797 ; Miengrg’: in Virginia 
j iti Ww ew England 
States is somewhat abrupt, but too well marked to be accidental. 
the inimum 1769; going farther west we 
find that at fonceee gee have occurred before the year oe, 
and at York Fort, Hudson Bay, I find the year 1842 (as ly 
pertained by General Sabine, after the receipt of Capt. B a 
ton’s observations of 1857). This latter station 1s nearly half- 
Way across the continent, and if we proceed to the western 
. ini but 
a its maxi uivalent to 4 western minimum), 
itis highly probable that it will reach it before the close of the 
