1) and its maximum value of 10$^9$ [V/m]{} (state 2). Such variation therefore results in [ *positive*]{} g$_{11}$ and g$_{22}$ gyrotropy coefficients that are both equal to $0.94 \times 10^{-7}$ for a frequency of 1GHz, according to Eq. (\[eq33\]) (that reduces here to $g_{11} =g_{22}=-\frac{\omega
}{c\varepsilon_0} {\frac{dG_z }{dE}}$ in S.I. units, since there are no $x$- and $y$-components of the toroidal moment and since the field is applied along $z$ in the studied case). Interestingly, we found that the aforementioned slope of $-1.6$ e/V stays roughly constant over the entire frequency range we have investigated (up to 100GHz). As a result, Eq. (\[eq33\]) indicates that $g_{11} =g_{22}$ should be proportional to the angular frequency $\omega$ of the applied $ac$ field, and that the meaningful quantity to consider here is the ratio between $g_{11}$ and this frequency. Such ratio is presently equal to $5.9 \times 10^{-16}$ per Hz. Moreover, the rate of optical rotation is related to the product between $\omega/c$ and the gyrotropy coefficient according to Ref. [@Landau]. As a result, the rate of optical rotation depends on the [*square*]{} of the angular frequency because of Eq. (\[eq33\]), as consistent with one finding of Biot in 1812 [@Barron]. Here, the 