appearing in Eq. 1 of the letter, is directly given by the measurement of the third harmonics of the polarisation. We briefly summarize here what can be expected for the third harmonics in the case of a liquid without any glassy correlations. We use the work of D´ ejardin and Kalmykov [2] which studies the nonlinear dielectric relaxation of an assembly of rigid polar symmetric particles. The particles are assumed to be diluted enough in a non polar solvent, so that any interaction between them can be safely neglected. A strong electric field is applied to the system, which biases the (noninertial) rotational Brownian motion of the polar particles and yields a net dielectric response. This response is expressed by expanding the relaxation functions as a Fourier series in the time domain. Then the infinite hierarchy of recurrence equations for the Fourier components is obtained in terms of a matrix continued fraction. We focus on the case where the field is purely ac, namely E ( t ) = E cos ωt . In the following equations, the subscript “D” refers to the calculation of D´ ejardin and Kalmykov. By using their Eq. (21), one gets : where τ$_{D}$ is the usual Debye time since one finds χ ′′ 1 ,D ∝ ωτ$_{D}$ 1+ ω $^{2}$τ 2 $_{D}$, i.e. χ ′′ 1 is maximum for the frequency f$_{D}$ = 1 / (2 πτ$_{D}$ ). By using Eqs. (7) and (19) of D´ ejardin and Kalmykov, one can calculate all the prefactors and obtain χ$_{3}$$_{,D}$ ( ω = 0): where N$_{0}$ is the volumic concentration of polar particles, and where, as in the letter, Δ χ$_{1}$ = χ ′ 1 $_{,D}$(0) − χ ′ 1 $_{,D}$( ∞ ). To get a benchmark for the behavior of χ$_{3}$$_{,trivial}$ for the ‘no glassy correlations’ case, we set f$_{D}$ = f$_{α}$ as well as N$_{0}$ = 1 /a 3 with a 3 the molecular volume in glycerol. We thus obtain from the above equations: 14 χ$_{3}$$_{,trivial}$ ( ω ) = ϵ$_{0}$ (Δ χ$_{1}$ ) $^{2}$a3 k$_{B}$T ( 1 5 χ$_{3}$$_{,D}$ ( ω ) χ$_{3}$$_{,D}$ ( ω = 0) ) . (10) χ$_{3}$$_{,D}$ ( ω = 0) = ϵ$_{0}$ (Δ χ$_{1}$ ) 2 k$_{B}$T N$_{0}$ 1 5 , (9) χ$_{3}$$_{,D}$ ( ω ) χ$_{3}$$_{,D}$ ( ω = 0) = − 3 3 − 17 ω $^{2}$τ2 D + iωτ$_{D}$ (14 − 6 ω $^{2}$τ2 $_{D}$) (1 + ω $^{2}$τ 2 $_{D}$)(9 + 4 ω $^{2}$τ 2 $_{D}$)(1 + 9 ω $^{2}$τ 2 $_{D}$) , (8) II) THIRD HARMONICS FOR A LIQUID WITHOUT GLASSY CORRELATIONS.