Where a contract authorizes an agent to sell land for "$15,000, about one-half cash," but is silent as to a sale for any larger sum, or as to receiving more than one-half cash, or as to the form in which that part of the price which is not cash should be put, a sale for $15,000 cash on delivery of the deed is in accordance with the contract. Witherell v. Murphy, 147 Mass. 417, 18 N. E. 215; Pope v. Peeples, 121 S. E. 303, - Ga. App. - . Compare Sec. 410a.