E. B. Hunt on the Dynamics of Ocean Currents. 169 
Observations of the Magnetic Variation at Hudson. 
Dave. | Hour, |. Yauevigt |Correction| corrected: 
hm i ' 
1839 April 15. | 330r.m. | 5196E. | +402 | 55°98 E. 
1840 April 13. 940 a. M. 53°87 —1°88 51°99 
1841 May 18 651 P.M. 48°80 +0:18 48-98 
1842 May 12 243 r.M 49-23 4:60 53°83 
10 57 a. M. 43° +2°76 46-11 
1843 June 17 423 P.M. 38°87 3-04 4y91 
“ — Sept. 19 2a.M. 47°65 —4-:29 43 
1844 June 8. 4 lem. 38°20 +361 41°81 
1849 July 24. 14 P.M. 30:04 1-93 31/97 
1858 July 22. 11 40 a. M. +3-03 12:40 
« July 26. 12 P. M. 11-47 +0-91 12:38 
July 28. 4 1Pp.Mm. 56 +3°59: 9°20 
“ Aug. 4. 0 6Pr.M. 30 +573 15-03 
= Bue. 2. 610 P.M. 10°58 +0-43 1101 
“ Aug. 16, | 1137 a.m. 425 +4:52 8°77 
“ Aug, 17. 5 55 P. M, 9-50. +061 10-11 
* ‘Sept. 1. 2 32 P.M. 9-52 +404 13°56 
In order to deduce from these observations the most probable 
result, let us put @ for the mean variation Jan. 1, 1839, and 4 
for the annual motion. Then if we regard the observations of 
any one year as forming a single observation, we shall have the 
following eight equations of conditio 
é O285 A= 55°98 oe 4586 A= 4263 
é 12799 A= 51°99 || Oo 54338 A= 41°81 
d+. 2375 A= 48°98 | 8+ 105584—= 81-07 © 
6+ 3538 A= 49°97 5+ 19598 A= 11°56 - 
Solvin A uations by the method of least squares, we 
obtain § 55! 13. which te mean value of the isin for 
Jan. 1, 1839; fe A=—2! 2416; that is, the easter] Set is 
diminishing : at the rate of 24 minutes in a year. also con- 
clude that the line of no variation will pass Bini Hudson 
etime during the year 1863. 
Arr. XIX.—On the Dynamics of Ocean Ourrents; by Lieut. 
E. B. Hunt, Corps of Engineers, U. 5. A. 
(Read before the American Association, at the Baltimore Meeting, May, 1857.) 
— ean scarcely be denied that the state of our knowledge of 
currents is any thing but satisfactory. ot only are we to 
a very great extent ignorant of the precise state of the facts, but 
We are also deficient in the theoretical ck of of those already 
