This mystifies me every time. My 1990 Telford, Geldart, and Sheriff

says on p. 64, "Magnetic susceptibility in emu differs from that in SI

units by the factor 4pi, that is

  k(SI) = 4pi k'(emu)

Now, since

  M = k H

where M is the magnetization and H is the magnetizing field (both

in the SI unit ampere-meter squared/meter cubed = ampere/meter),

then k must be a unitless constant of proportionality.

On p. 74 Telford gives the average value of k for Basalts in a table

as the number "70", in a column labeled "Susceptibility x 10^3 (SI)".

On p. 73 they say "k ranging from 10^-3 to 1 SI unit as the volume

percentage of Fe3O4 increases from 0.05% to 35%." So I think the real

value for basalt is k = 0.070 (SI), and the column label means they

took the real value and multiplied it by 10^3 to get the number in the

table. So you take the number in the table and DIVIDE by 10^3 to get

the real value (trying to save ink, I guess!).

So if we take the 14,300 in Dobrin and divide by 10^6 we get 0.014 .

This all sounds consistent to me since Telford's range for basalt

is 0.0002 to 0.175 SI.

Values in "cgs" should be the same as in SI, since k is dimensionless.