For the purpose of extending the time of payment of said outstanding indebtedness, or reducing the interest charged, or when the interests of the county require it, the board may issue said bonds in exchange for bonds, theretofore issued by the county or for valid and legal warrants of the county outstanding on the second Monday of January, 1933, and may do so by resolution of the board at a regular meeting thereof, and without a vote of the people. Before any bonds shall be issued or exchanged under this section, the board of county commissioners shall ascertain that the bonds or warrants the payment of which is to be extended, or which are to be taken in exchange for the new issue of bonds, are valid and legal obligations of the county, and their findings of fact shall be entered of record on the minutes of their proceedings at least ten (10) days before any exchange is made, as herein provided. The said board shall also, before issuing any bonds under this section, deduct from the total outstanding legal indebtedness of the county at the time of the issue of said bonds, the cash on hand in the treasury of the county, that is available for the payment of said legal indebtedness, or any part thereof, and the issue of bonds as in this section provided for, shall in no case exceed the aggregate or total legal indebtedness of the county then outstanding, less the cash on hand to be applied in payment and discharge of said indebtedness.