1. Previous negotiations are merged in a subsequent written contract, and additional obligations can not be grafted thereon by parol testimony, unless made subsequently to the contract and upon a valuable consideration. Smith v. Newton, 59 Ga. 113. The trial judge did not *537err in his ruling upon the admissibility of evidence, nor in his remarks complained of in the fourth ground of the amendment to the motion for a new trial, nor in his charge in reference to the clearly opinionative statements, alleged to have been made by the plaintiff, as to the probable volume of sales of the defendant’s patented device. Terhune v. Coker, 107 Ga. 352 (33 S. E. 394); Dortic v. Dugas, 55 Ga. 484, 495; Angier v. Equitable Association, 109 Ga. 625 (3), 627 (35 S. E. 64); Baldwin v. Daniel, 69 Ga. 782.

2. The evidence fully authorized the verdict; no error of law appears, and the court did not err in overruling the motion for a new trial.

Judgment affirmed.