354 OBSERVATIONS ON THE MAGNETIC DIP AND DECLINATION. 
é 
Dip, by sixty-four observations on needles Nos. 1 BE is oi ne GS, Se 
Weather clear and fine. Almost calm. 
Notx.—The dip was observed at this station by Professor A. D. Bache, of Philadelphia, on the 27th of 
August, 1840, to be 71° 34’.4. See proceedings of Am. Phil. Soe., vol. i. p. 295. 
The following magnetic bearings were observed from this tree, in order still farther to identify the position of 
this station, viz.; 
From the tree, the Washington monument bears 8. 45° W. 
_ * the steeple of St. Paul’s Church bears 8, 13° W. 
«the dome of the Exchange bears 8. 14° HE. 
Ke «“ the most western shot-tower bears 8. 18° E. 
“ the most eastern shot-tower bears 8. 33° E. 
= “ the white steeple of a distant church bears N. 82° E. 
The bearings are given as observed with a good prismatic compass. 
L now felt curious to ascertain what would be the change of dip at positions intermediate of stations one and 
iwo, and also if the needles would be affected at those two stations by a line of iron pipes, which f was informed 
lay at a depth of four feet under ground, along the margin of an intermediate drain or valley, for conducting the 
water from a neighbouring spring-house. 
I accordingly chose two intermediate points between stations one and two, which are called the third and fourth 
Baltimore stations. 
The following observations and measurements were made to show the relative positions of these four stations 
with respect to one another. The bearings are magnetic and were observed with a prismatic compass. The 
distances were measured with a surveyor’s chain. 
From the centre of the Washington Monument to station one is N. 5° E., and distance 1089 feet. 
From station one to station three is S$. 35° E., and distance 212 feet. 
From station three to station four is S, 8° E., and distance 181 feet. 
From station four to station two is N. 78° E., and distance 449 feet. 
Station No. 3 is forty-three feet north of the line of iron pipes. 
Station No. 4 is one hundred and thirty-seven feet south of the line of iron pipes. 
XV. Baltimore—third station.—June 10th, 1841. 
Neepie No. 1. 
Starked pee we Meutie. Boeditegs: Gosceration. Temperature, Dip obgerved. ° 
N 8 3h. 52m., P.M., 87°.5 71° 41'.05 
Ss 8 4 62 Mh 87 71° 54’.85 
Dip, by 16 observations on needle No. 1, first set,. . . . . . 71° 47.9 
The observations were repeated with needle No. 1 at this station, and the readings of 
the needle were made by Mr. James Green, of Baltimore, as follows, viz.: 
Ss 8 5h. 27m., P.M. 85° 71° 57.25 
N 9 5 49 “ 86 71° 39''75 
Dip, by sixteen observations on needle No. 1, second set, . . . 71° 48'.5 
Dip, by thirty-two observations on needle No. 1, being a mean of two 
sets of observatton®.:  ¢ (meio oh wee BE be i. TA. 2 
XVI. Baltimore—fourth station —June 10th, 1841. 
NeeEpiE No. 1. 
N fe) 6h. 467., P.M. 80° 71° 45/.6 
Ss 8 7 02 a 78 71° 55'.85 
Dip, by sixteen observations on needle No.1, . . ... . + « 71° 55/85 
