Dip and Variation of the Magnetic Needle. 107 
more than half the stations. When however several observations 
have been made, the result clearly should not rest solely upon the 
extreme observations. In such cases I have employed the method 
exemplified on the fourth page of this article, (p. 96.) In selecting 
the observations, I have preferred where practicable, to compare 
those which were made by the same individual. Such observa- 
tions may be presumed to be affected by a constant error, which 
will have little influence upon the annual motion. Thus at Bur- 
lington, Vt. we have (Vol. 34, page 302) a series of observations 
by Mr. Johnson, from 1818 to 1834, quite consistent with each 
other; but in 1837 another observation by Prof. Benedict, deci- 
dedly inconsistent with the former. Without stopping to enquire 
which observations represent most accurately the mean variation 
at that place, it is obvious that the former are much the best 
suited to indicate the annual motion. Like considerations have 
guided my selection at other places. 
i : Varia- No| Years Pro- | Motion 
i Lat. | Lon. | tion. |Date.jobs. embraced |motion. of lines.| ducts.|compat'd 
Burlington, Vt. |44°27'|73°10|+7°30" 1818 
8 50|1834) 6| 16 {+44 | 30.8 |135.52| +543 
Chesterfield, N.H.'42 53/72 20| 6 0 : 
. “| 7-45 |1836| 17] “16 6A | 32.3 |206.72} 5.1 
Deerfield, Mass. |42 34/72 29), 5 28 
7 57|1837| 2] 26° | ‘5.7 | 33.0°|188.10; 4.9 
Cambridge, Mass COR Arg dey @ mee 30 1810 ba 
a fee ay 9 18/1840; 4} 30 3.4 | 32.3 109.82) 5.0 
ew Haven, Ct. |41 18|72 58} 4 35 1819) mad Spite lace. taal 
: 6 10/1840, 6| = 21 4.6 | 36.7 |168.82; 4.4. 
ille, N.Y. 44°28 |73 32} 7 30]1825). | 4 | ee 
statics diaieain 40}1838, 2} 13 | 5.4 | 308 |166.32, 5.2 | 
Albany, N.Y. — 39173 451.5 4511818) | ~ : ee st Se 
cata _ | 6 47/1886 7| 18 | 3.6 | 35.2 |126.72 4.6 | 
_ |New York City, (40 43/74 1] 4 40/1824) | one 
cies oe |, & 40 |1837}. 3} 13 3.7 | 45.5 |168,35,. 3.6 
ladelphia, (39 57/75 11| 225/1813 | . 
ST a eel = pe oe yee Dat 3 52 1837 9: 24 shits 3 6 514 ’ 185. Li a2 
Milledgeville, Ga. 33 7/83 20/- 30 ai ‘ , 
wick tae ve “a1 & 4911835] 2 f° (30 f-a ret 699121883} 2.3 - 
bile, Ala. 30 40/88 11] 8 10/16 
ret, 72 2) 26 | 22/1101 24229 1.5 
O. 30/81 46) 1.30 ab 
peeveiand, ts 35 a| 33. | 45 } 367 |tes!i5} 4.4 
irsville, O. |40 10 80 52}. 3 10}. fee 
ae Cinistilles 9. 401 3 31 2| 1 | 92} 371 | sie! 4.4 
' : | 523 
een OC SON 4 51 2| 42 | 2.7 | 514 |133.78 32 
Sprin 83 47| 4 54 : 
— apg eo 3 14|1833, 2| 20. | 5.0 | 46.1 23050 3.5 
pringh¢ : 16| 5 30 
Springboro, O peters 44 2|- 18° |, 48°} 519. j249.19) 3,1 
i 81 26| 2 36 
Mariette, O. fae ~ e| 939 | 24 | 332] 9163] 43 
Cincinnati 15 
oa a ace el 4 46 2| 15 | 2.0} 529 |10580) 311 
Jetroit, Mi 3 13 
Mich. bot gaa ae 4| 18 } 4.3 | 41.1 |17673) #0 
0. : : } : 
~ a hee 745 40 2| 5 | 3.0 | 69.0 ral 24 
ae SN OT 
