Van Nostrand's eclectic engineering magazine (1869)
[New York : D. Van Nostrand] · leaf 186
be expressed by 3d. The relative intensity of the magnetic force resident in the rocks under considera- saying that magnetic force is as the square of the number of vibrations made by tion, was approximately measured, as has the needle in the unit of time. Therefore been explained, by the number of… … actually exists. Under the influence of the came to the surface, sometimes there were cosmical force alone, the needle vibrated but several fe^t and perhaps yards of drift be- tween ; it is therefore an important practical six times in the unit of time, which was taken at a quarter of a minute.…
Engineering
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