THE VICTORIAN ERA 
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due to changes in local attraction. A method was 
eventually devised by the English physicist, Barlow, for 
getting rid of this source of error by compensating 
masses of iron suitably arranged near the compasses, and 
the observations were thus improved in scientific value. 
The instruments were rough and the methods crude until 
the beginning of the nineteenth century, when terrestrial 
magnetism assumed an importance never before attained. 
Humboldt on his unparalleled scientific journey in 
South America had paid special attention to magnetic 
work, though he neglected no branch of human knowl- 
edge — being as he was the last man who could grasp 
the whole of the rapidly widening sheaf of natural 
science. The observatories he subsequently established 
in Europe showed that the minor perturbations of the 
magnetic needle were simultaneous over vast areas of 
the Earth’s surface, and suggested the magnificent con- 
ception that their origin was not local but cosmical, due 
to some influence outside the Earth altogether, to the 
variations of which all parts of the globe responded at 
the same moment. On his geological expedition to 
Siberia in 1829 Humboldt, with the permission and indeed 
the active assistance of the Russian Emperor, established 
a chain of magnetic observing stations from Moscow 
throughout Siberia to Peking and across the Pacific in 
Sitka. Distinguished physicists in* the United States, 
amongst whom Bache deserves to be specially mentioned, 
carried similar observations across America. 
The great Norwegian physicist Hansteen, and the 
Russian explorer Erman, had conducted magnetic sur- 
veys throughout Siberia, north into the Arctic circle, and 
round the world through the Pacific and Atlantic 
Oceans, bringing together an immense amount of new 
