THE VICTORIAN ERA 
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tion in every place, and that the direction varies in any 
one place from time to time. Some of these variations 
are temporary and irregular, partaking of the nature 
of storms, others are steady and uniform, admitting of 
ready calculation and prediction when a sufficient number 
of data is known. 
The difference between sciences based on observation 
and those based on experiment, is that in the former no 
short cut is possible to arrive at the theory binding 
together all that has been discovered, and pointing the 
way to all that remains to be found out. The toil of 
hundreds, or it may be thousands of observers is neces- 
sary for scores of years, or it may be for centuries before 
the raw material has been accumulated in sufficient quan- 
tity for the theoretical mathematician to deduce and prove 
his simplifying theory. It was so in the case of astron- 
omy, and it has been so in the case of terrestrial magnet- 
ism, and it is so in the case of meteorology. 
The scientific study of magnetism began in the 
spacious days of Queen Elizabeth, when Dr. Gilbert of 
Colchester proved the properties of the lodestone and 
stated many fundamental facts as to the dip of a freely 
suspended needle toward the horizon and its deviation 
horizontally from the meridian or north and south line. 
Observers in all parts of the world had kept records for 
longer or shorter times which showed that the compass 
needle pointed to the east or west of north in almost 
every place, and that the amount of its deviation from 
the true north was progressively changing. Thus Gil- 
bert had found in 1576 that the compass needle pointed 
eleven degrees east of north in London and year by year 
this easterly declination diminished until in 1652 the 
needle pointed due north — the poets of the middle of the 
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