430 Screntifie Intelligence. 
three plates; GEORGE “Davipson, collection of some magnetic 
variations off the coast of California and Mexico, observed by 
Spanish Navigators in the last quarter of the 18th century ; Wm. 
FERREL, on the harmonic analysis of the tides at Governor’s 
Island, New York Harbor; Lieut. J. E. Prrtspury, U.S. N., on 
deep-sea current work in the Gulf Stream; C. 8. Peirce, on the 
influence of a noddy on the period of a pendulum, and on the 
effect of unequal temperature upon a reversible pendulum. 
Magnetic dip in North America.—My. Schott, in Part II of his 
paper, mentions Prof. Loomis’s deduction as to the diminution of 
magnetic dip based on observations from 1819 to 1839, making it 
1°5' per year; and again, “comparing the dips in N. York by Sir 
E. Sabine and Sir J. Franklin (1822 to 1825) with his own and 
others about the epoch 1835, deducing the rate of 2°1’ per year, 
and thence, including also the earlier observations, a rate of 1°8' 
as the annual diminution of dip in the Eastern United States. 
Mr. Schott then observes that in 1856 he showed that in the 
northeastern part of the country the dip continued to decrease 
till about the year 1843, when it became stationary, 1842°72-0°7, 
being deduced as the period of the minimum; that from that 
date to 1856, the increase had been 2-7’. But unexpectedly the 
increasing of the dip stopped about 1859 in the Eastern United 
States, and that since about 1860, a decrease has been in progress 
“thus suggesting the idea of a secondary motion or wave of com- 
paratively short duration, and of a character opposite to the 
general motion in the variation of the dip as it existed before and 
after this temporary interruption.” The time was the same at 
Toronto and Washington, but much later on the Pacific in South- 
ern California. After a further discussion of the subject, Mr. 
Schott gives as the annual decrease in seconds for Cambridge and 
Boston, 7°5 ; New Haven, 5:6; Albany and Greenwich, 6°6; New 
York, 5:4; Philadelphia, 5°5; Baltimore, 4-8; Washington, 3°5; 
Toronto, 2°5; Cleveland, 3°6; Detroit 2-8; Saint Louis, 5-0, “ which 
values, in the absence of any additional observations, may be used 
for a few years to come.” 
At Rio de Janeiro there has been a steady increase of north 
dip between La Caille’s observation in 1751 (dip =—20° 0’) and 
Harkness’s observation in 1866 (—11° 47’). The same is noted 
in Valparaiso, between the observations of Malaspina in 1793 
(dip=—44° 58’), and Harkness’s observation in 1866 (—35° 23’). 
In contrast with this, at Havana the present annual change is 
probably less than +0°8’: at Acapulco about +1:0'; at Mexico 
and San Blas, perhaps, +1°5’ to +2°0’. “At Magdalena Bay, 
Lower California, the annual change seems to have become zero 
at present.” 
In British N. America, North of Dakota over the Lake Winni- 
peg region to Hudson’s Bay, it is not now very different from 
what it was forty years ago; farther west at Fort Chipewyan, 
Fort Edmonton, it may be about —0°5’; at Nootka Sound, Van- 
couver Island, about —0-7’; at Port Simpson, —1°5’; in Alaska, 
