It shall be lawful for the Company, if they think fit, to receive from any of the Shareholders willing to advance the same all or any Part of the Monies due upon their respective Shares beyond the Sums actually called for ; and upon the Principal Monies so paid in advance, or so much thereof as from Time to Time shall exceed the Amount of the Calls then made upon the Shares in respect of which such Advance shall be made, the Company may pay Interest at such Rate, not exceeding the legal Rate of Interest for the Time being, as the Shareholder paying such Sum in advance and the Company shall agree upon.