"Where plaintiffs were employed by defendants to procure for them a loan on a mortgage on land, and the loan was not made solely because the lender found insisted on a clause in the mortgage that the principal and interest should be paid in gold; the plaintiffs did not perform the contract and are not entitled to compensation, since the contract meant a loan to be paid in lawful money, and the mortgage loan could not be paid in but one kind of money. Caston v. Quimby, 178 Mass. 153, 59 N. E. 653. See also Sec. 546.