§ 15. The sinking funds provided for the payment of interest and the
extinguishment of the principal of the debts of the state heretofore
contracted shall be continued; they shall be separately kept and safely
invested, and neither of them shall be appropriated or used in any
manner other than for such payment and extinguishment as hereinafter
provided. The comptroller shall each year appraise the securities held
for investment in each of such funds at their fair market value not
exceeding par. The comptroller shall then determine and certify to the
legislature the amount of each of such funds and the amounts which, if
thereafter annually contributed to each such fund, would, with the fund
and with the accumulations thereon and upon the contributions thereto,
computed at the rate of three per centum per annum, produce at the date
of maturity the amount of the debt to retire which such fund was
created, and the legislature shall thereupon appropriate as the
contribution to each such fund for such year at least the amount thus
certified.

If the income of any such fund in any year is more than a sum which,
if annually added to such fund would, with the fund and its
accumulations as aforesaid, retire the debt at maturity, the excess
income may be applied to the interest on the debt for which the fund was
created.

After any sinking fund shall equal in amount the debt for which it was
created no further contribution shall be made thereto except to make
good any losses ascertained at the annual appraisals above mentioned,
and the income thereof shall be applied to the payment of the interest
on such debt. Any excess in such income not required for the payment of
interest may be applied to the general fund of the state.