Contract Entered Into Betweenfrancisoc S.Llas, Secretary Of Agriculture And Fomento, Repreaenting The Executive Of The Union By Express Authorization, And Dr. I. N. Thaeker, Attorney In Faet Of The Compania .Idroelectrica Potosina, S.A., Amending The Thrid Clause And Supplementing The Contract Of November 27, 1928, Relating To The Utillzation Of The Watersof The Los Naran Jo. River, In The Municipality Of The City Of Maiz, S.N Luls Potoal,For The Production Of Motive Power Designed For Sale.