Units unrationalized

A minor variant of the SI system, called MKS by experimentalists in nonlinear optics, is called SI here and defined below. Alas, there are also other systems "rationalized" or "unrationalized", Heaviside-Lorentz, "atomic" (where me = c = h = 1), and so on. The "rationalized" and "unrationalized" versions differ in how they apportion the pesky factor An (surface area of a sphere with unit radius that is involved in surface integrals) between the various electrical and the magnetic variables. 

In Eq. D.l a factor l/(4ir) is inserted, somewhat arbitrarily, for ease in solution of many electrical theorems (e.g., Gauss ). Units which are defined as rationalized electrical units include this factor of l/(4ir) unrationalized units would omit it. 

The basic electrostatic units (esu), however, are the unrationalized cgs units. Hence, to convert from unrationalized cgs units to the rationalized mks system of units, start with the relationship... 

However, it may be noted in passing that Chestnut ° has given a powerful argument for the retention of the unrationalized cgs-Gaussian system of units— where, specifically, electromagnetic quantities are involved. 

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