AND THE INTENSITY OF MAGNETICAL FORCE. 317 
Cumberland, Maryland, Latitude 39° 56’, N.; Longitude 78° 47’, W.; March 26, 1844. 
Calculated 
duration 
at 60°. 
Duration 
of 500 
Dip. , 
Vibrations. 
No. of 
Epoch of commencing 
Needle 
Vibrations. 
Square of the 
Tempe- 
preceding. 
rature. 
Horizontal 
Total intensity, 
intensity. 
Hor. being 1000. 
71° 36’ 4 3h.56m.01s.6 P}1144.8 | 69°0/1143.8 |1809033.4569) 941.95 
5 4 22 04 4 /1895.2 | 70 0/1894.22)1943849.4084| 938.82 
6 4 50 04 0 {1389.2 | 70 0/1888.65)1928348.8225) 939.24 
Mean,| 939.03} 996.75 
Ina ravine. Substratum, sandstone and shale of the coal measures, not horizontal but 
more or less disturbed by the contiguous up-heaved ridge of the Alleghenies. 
Washington, Latitude 38° 53’, N.; Longitude 77° 01’, W.; April 6, 1844; at the Magnetical Observatory, United 
States Naval Observatory. 
71°39'20"| 4 1h.22m,028.0 P)1142.4 | 58°0/1142.92|1806266.1264 |943.05 
5 1 52 00 0 {1391.6 | 52 0)1392.38)1938722.10644/941.30 
6 | 2 26 59 6 {1386.0 | 52 0)1886.97)1923685.7809 1941.51 
Mean,|941.41} 1002.58 
In the above the reduction of the horizontal intensity by No. 4, by the deduced constant, 
would give 941.26, quite consistent with the other two needles; still, we have relied on the 
two Nos. 5 and 6, Geology, drifted gravel and sand, superimposed on gneiss rock in place. 
It seems that this locality is almost identical with Cincinnati in its total intensity. 
Washington, at the old “ Depot of Charts and Instruments,’’ near Georgetown, and say one-third of a mile north 
and a little west of the last station; April 8, 1844. 
71°384'48"/ 4 |[104.23m.00s.0 A}1145.60] 70°0|1144.86/1810704.4196/939.65 
5 {10 52 O1 6 {1394.80} 72 0/1893.60/1943120.9600/941.99 
6 |11 26 00 0 {1389.20) 80 0/1888.'76/1923103.29761940.75 
Mean,|940.72 | 997.76 
Geology, probably identical with that of the preceding. 
Washington, at the Capitol Hill, west side of the Capitol, and in a range with the southern end, distant about two 
hundred feet; April 9, 1844. 
71°13'23"| 4 | 7h.86m.028.4 1138.00 62°0/1138.00 1295044.0000|952.67 
5 8 04 O1 6 1387.60, 66 0)1366.97/1923685.7809 948.86 
6 | 8 34 05 0 {1383.60 71 0/1339.30)1910753.2900/ 947.88 
| Mean,|948.28 | 988.22 
Washington, Capitol Hill, east side, near the south part of the grounds; April 9, 1844. 
71°138'27"| 4 | 6h.35m.02.0 P/1138.8 | 63° 0[1138.58]1296364.4164 
951.16 
—2.71 
948.45 (987.72 
It is presumed, from the situations selected, that they were sufficiently removed from the 
iron pipes conducting the water through the grounds. 
Washington, near the Patent Office, April 10, 1844. 
71°14'58"| 4 7h.21m,59s.6 Aj1141.20| 58° |1141.35]1302679.8225/946.55 
5 7 48 59 6 {1390.40) 60 |1390.40)1933212.1600/943.98 
6 6 53 O1 6 {1384.80} 56 |1885.30/1919056.0900/943.77 
Mean,|943.88 984.21 
In the grounds of the Patent Office, north of its western end. 
