34 C. A. Schott—Magnetic Declination in the United States, 
Washington Territory the eastern declination is at present still 
increasing, but with a losing rate. By the time the western 
elongation of the secular change i is reached in Maine we may 
expect to see the needle in the opposite phase, or at its eastern 
elongation, in California. We cannot as yet follow this influ- 
ence directly over the interior of the United States for want of 
early observations ; the westernmost interior stations for which 
an epoch could be made out were Buffalo. Erie, Cleveland and 
Detroit ; tisde give the average turning epoch 1794. It may be 
quite practicable hereafter to trace out curves uniting all sta- 
tions where the needle was stationary at a given epoch and 
a at other sieaktil for regular intervals of time, say of 10 or 
25 y 
- facets to the first table, the constant in each formula 
would represent the normal direction of the needle, about which 
the secular change would be performed in an average cycle of 
about 270 years, and with extreme deflections on either side of 
it, equal to the co-efficient of the periodic term—all under the 
con ae ae that the law of the secular movement was truly ex- 
pees It is no doubt much more complex, and besides, may 
il Ry any time; yet as far as our present experience rea aches, 
and within the interval when the first reliable observations 
were made to the present time, it is found trustworthy. 
Table of Decennial values of the a apni pigperan computed 
Srom m preceding equation 
hese tables have been constructed to ges. the reduc- 
tion of eledhek declinations from one epoch to another; they 
will be found specially useful, when old lines run by compass 
have to be retraced and for the construction of i isogonic charts 
for a given epoc 
s occurring in the table indicate either no or doubtful 
values for the corresponding times ; values given to the nearest 
tenth of a degree are less reliable than those given to hun- 
dredths. + sign indicates west, a — sign east declination. 
