of bonds in 1896. One series, issued pursuant to a mortgage and paying four percent interest, will mature on January 1, 1997 ("Prior Lien Bonds"). The second series, issued pursuant to a second mortgage on the same properties and paying three percent interest, will mature on January 1, 2047 ("General Lien Bonds"). Both series are secured by two types of collateral: railroad properties that Northern Pacific owned as of November 10, 1986; and "Resource Properties," or property interests granted to Northern Pacific's predecessor in interest by Congress. The Resource Properties comprised of mineral rights as well as lands held in fee simple  have become far more valuable than the bonds that they secure. Par value for the outstanding bonds is $117,700,000. The Resource Properties may be worththat on April 19, 1985, the Prior Lien Bonds traded on the New York Stock Exchange ("NYSE") at three percent above their value as debt obligations; on the same day, the General Lien Bonds traded at 66 percent above that value.
Northern Pacific's first recorded attempt to release the Resource Properties from the mortgage liens took place in 1959. Plaintiffs' Exhibits 28 and 29.[2] That aborted effort did not survive the trustees' vigorous opposition. Id. In 1973, Burlington sought the advice of two law firms regarding modification of the mortgages; both concluded that the mortgages barred all means of substituting collateral. Plaintiffs' Exhibit 63.
The third attempt to release the Resource Properties from the mortgage liens brought Burlington to this court. On April 19, 1985, Burlington signed two agreements *170