All bonds issued by any eligible district availing itself of the provisions of this chapter shall, before sale by the district, have attached thereto the certificate of the secretary of state, essentially in the following form:

Olympia, Washington, . . . .(Insert date). . . . .

I, . . . . . ., secretary of state of the state of Washington, do hereby certify that the above named district has been investigated and its project approved by the department of ecology of the state of Washington; that the legality of the bond issue of which this bond is one has been approved by the attorney general of the state of Washington, and that the carrying out of the purposes for which this bond was issued is under the supervision of said department, as provided by law.