Notwithstanding they are under seal, they are clothed with all the attributes of negotiable or commercial paper, pass by delivery or indorsement, and are not subject to prior equities (where the power to issue them exists) in the hands of holders for value, who took before maturity and without no- tice. Payment of interest on such bonds for a number of years will estop the cor- poration from setting up a mere irregularity in their issue, as against bona fide holders for value; 80 Fed. Rep. 672. The coupons usually attached to such bonds are like- wise negotiable, and may be detached and held separately from the bond, and may be sued on by the holder in his own name without his being the owner of the bonds to which they were originally attached ; 1 Dill. Mun. Corp. § 486; 3 Wall. 327; 1 Dill. 338; whether he has given consideration for them or not; 80 Fed. Rep. 672. Coupons when severed from the bonds cease to be incidents of the bonds, and be- come independent claims, and do not lose their validity, if for any cause the bonds are cancelled or paid before maturity; 20 Wall. 583. See as to coupons as distinct and separate instruments, 6 L. R. A 562, n.: COUPONS. The fact that such bonds are payable out of a special fund, known as a "sinking fund," does not prevent the holder from suing at law to enforce collection; 75 Fed. Rep. 967. A very important principle with respect to municipal bonds was settled by the lead- ing case of Gelpcke v. Dubuque, 1 Wall. 175, in which it was held that bonds which were valid under the decisions of the state court of Iowa at the time they were issued, will be sustained by the federal court, al- though the state court had subsequently overruled its earlier decisions and held that they were issued without authority. See 3 id. 294; 7 id. 181. See also an article sus- taining this doctrine in 4 Harv. L. Rev. 311, by Prof. J. B. Thayer, in a preliminary note to which are cited a number of adverse criticisms of it. Purchasers of the bonds of a municipality issued to aid the building of a railway, which recite a compliance with the law authorizing their issue, are not required to ascertain conditions imposed by the pro- position voted on, which do not appear in the bonds; 82 Fed. Rep. 873; they have a right to assume that the conditions have been complied with; 73 id. 966. See 5 Am. & Eng. R. R. Cas. 241; 36 Cent. L. J. 133; and as to power to subscribe; 18 Am. & Eng. R. R. Cas. 689; 15 id. 621, 655; ratification; 12 Am. & Eng. R. R. Cas. 651; effect of recitals; 12 id. 524; 15 id. 584, 675; 2 Am. & Eng. Corp. Cas. 291, 320; 35 Corp. L. T. 438, 460. See also an extended dís- cussion of cases on municipal bonds in aid of railroads, in the supreme court of the United States; 17 Am. L. Reg. N. S. 209, 609. See, generally, as to municipal bonds for public purposes, Coler; Burhans, Mun.. Bonds; Burroughs, Pub. Sec. in America; Dillon, Mun. Corp.; Jones, Railroad Se- curities, ch. 7; Report Mo. Bar Ass'n, 1891, 221; 1 L. R. A. 787, note; 15 Am. & Eng. Corp. Cas. 356; 86 Fed. Rep. 594, 263; as to election for issue; 40 id. 543; negotiability; 5 id. 593; over issue; 40 id. 535; limit of indebtedness; id. 584; 26 id. 473; fraudulent circulation; 2 id. 263; estoppel to deny validity; 2 Am. Ry. Corp. Cas. 525; power to issue; 5 L. R. A. 726; bona fide holder; 23 Am. L. Reg. N. s. 310; 29 id. N. S. 390; mandamus, to enforce sub- scription; 12 Am. & Eng. Ry. Cas. 609; to enforce payment; 15 id. 629.