(after stating the facts). The view we have reached renders it unnecessary to decide whether or not the change from the overhead to the up-feed system was a material one, for the reason that we are of the opinion that, under the facts and attending circumstance, the doctrine of equitable estoppel applies, and the defendant has waived the right to have the overhead system of heating installed.
In 'discussing the doctrine of equitable estoppel, Professor Pomeroy says that acquiescence consisting of mere silence may also operate as a true estoppel in equity to preclude a party from asserting legal title and rights of property, real or personal, or rights of contract. 2 Pom. Eq. Jur. 3d. ed., § 818. The general doctrine is that, if one maintains silence when in conscience he ought to speak, equity will debar him from speaking when in conscience he ought to remain silent. In other words, to constitute silence an estoppel there must be both the opportunity and the duty to speak, and the action of the person asserting the estoppel must be the natural result of the silence, and the party maintaining silence must be in a situation to know that some one is relying thereon to his detriment. Indiana Lumbermen’s Mut. Ins. Co. v. Meyers Stave & Mfg. Co., 164 Ark. 359, and cases cited; and Brownfield v. Bookout, 147 Ark. 555.
*362This principle of equity and of natural justice, under the facts and attending circumstances of this case, decides the case against the defendant. The undisputed proof shows that the contract was prepared by the architects of the defendant, and that they were to have general charge of supervising and directing the installation of the heating plant in the theatre and two stores of the defendant. The judgment of the architect about the kind of heating system was taken.. The overhead system was adopted because it was understood that the boiler was to be located in the basement, and that it could not be set deep enough in the ground to install the up-feed system and .at the same time to get proper drainage. This seems to have 'been understood by the plaintiff as well as the architect. The superintendent of the plaintiff discovered, before the work of installing the heating system had begun, that the basement would be deeper than the profile showed, and that proper drainage could be secured. He at once informed the architect of this fact. The architect then instructed him to change from the overhead to the up-feed system. It was known that it would cost somewhat less to install the up-feed system than it would the overhead system, and the plaintiff agreed to make a corresponding reduction in its price. The architect does not remember, but thinks that he told the defendant of the change a day or two later. In any event, the foreman of the defendant was told of the change.
It was also shown that the defendant lived in the town where the work was being done, and himself directed the superintendent of the plaintiff to make some minor changes in the work as it progressed. After the heating system had been installed, fires were placed in the engine and the water in the boiler heated for the purpose of testing the plant. The defendant was present, and, after the building had been sufficiently heated, ordered the fires drawn. He was not a witness in the case. Under the circumstances just detailed, it is fairly inferable that he knew that the change from the over*363head to the up-feed system had been made, and that the change was due to the instructions given by his own architect. In the face of these facts, the defendant permitted the plaintiff to go ahead with the installation of the heating system under the changed plans. If he proposed to dispute the rights of his own architect to change the plans under the contract, good faith required that he should have done so before the plaintiff went to the trouble and expense of installing the heating system. The evidence shows that the plaintiff acted in perfect good faith in the matter, and in reliance upon the instructions given its agent by the architect of the defendant. The conscience of the defendant was therefore touched in the matter, and, after allowing the plaintiff to install the changed system without objection on his part, he must he presumed to have consented to the change, and the doctrine of equitable estoppel applies in this case.
Counsel for the defendant also seek to uphold the decree on the ground that the up-feed system was not properly installed, and that, on account of the defects in the work, the plaintiff should not be entitled to recover. On this point the testimony is in direct and irreconcilable conflict. On the part of the plaintiff it was shown by the architect and by the superintendent and foreman of the plaintiff that the work was done in an efficient manner, and that there was no defect in the work, except one minor leak, which they offered to repair. On the other hand, it was shown by the defendant that the system was not properly installed. The witnesses on each side gave in detail their reasons.for testifying as they did. Here again it is not necessary to decide where the weight of testimony on this point lies. The contract provides that the architect shall have general supervision and direction of the work. The work was performed according to the architect’s instructions and was approved by him. After the defendant refused to pay for the work, the plaintiff offered to make a test of the system and to show the defendant that it had been properly installed, and that it would heat the buildings *364in an efficient manner. The contract provided that the architect of the defendant should make decisions on all claims of the owner or contractor. He approved of the work done by the plaintiff, and, as we have already seen, it is fairly inferable that the defendant was present during all the time the heating plant was being installed. The architect’s decision is conclusive that the work was done according to' the specifications, and there is nothing-in the record to show that his decision was the result of gross mistake or the failure to exercise an honest judgment in the matter. Boston Store v. Schleuter, 88 Ark. 213; Carlile v. Corrigan, 83 Ark. 136; Hatfield Special School Dist. v. Knight, 112 Ark. 83; and Hot Springs Ry. Co. v. Maher, 48 Ark. 522.
The result of our views is that the chancellor erred in rendering a decree in favor of the defendant, and, for that error, the decree must be reversed, and the cause remanded with directions to the chancery court to render a decree in favor of the plaintiff, and for such further proceedings as he may be entitled to in equity.