Opinion by
Mr. Justice Dean,On the 14th of November, 1890, the parties to this suit entered into a written' agreement, by which the plaintiff agreed, for the consideration of $31,000, to erect, according to plans prepared by it, on Twentieth and Mary streets, South Side, Pitts-burg, for defendant, “ One Continuous Melting Regenerative *179Tank Melting Furnace, with twelve working holes, designed to work thirty-six window glass blowers, in three shifts of twelve blowers each per day of twenty-four hours; the furnace to be operated with fuel gas manufactured from coal by what is known as ‘Wellman’ producers. First party to erect three of said producers, and connect same with gas valve of said furnace by flues or conduits of suitable size to convey the gas from producers to valve in sufficient quantity to operate said furnace. First party further agrees to erect twm additional producers, and connect same by flues or conduits of suitable size with two blowing furnaces, and three flattening ovens erected or to be erected by second party, also with floater kiln hereinafter named to be erected by first party.” The contract was to be completed not later than 15th of September in the next year; with the proviso, however, that should the work be delayed by failure of defendant to comply with the agreement, or by remodeling its buildings, or by any cause beyond plaintiff’s control, the time was to be extended. In addition to the work stipulated for in the written contract, by a verbal agreement between them the plaintiff agreed to erect, on the same premises, a “flattening oven ” for $2,125. The written agreement embodied general specifications of the character of the work to be done, and the results to be accomplished.
The plaintiff, claiming it had fully performed its contract, on or about the 1st of December, 1891, filed a mechanic’s lien against the premises, on the 18th of March, 1892, claiming a balance due and unpaid on the contract of $11,941.65, with interest from date of completion of work, and issued sci. fa. thereon for judgment; to this, defendant filed affidavit of defense, denying any indebtedness on the contract, and averring that, on the contrary, plaintiff was indebted to it in the sum of $10,366.74, because of damages sustained by reason of plaintiff’s nonfulfillment of its contract, both as to design and quality of work done, and failure to finish it within the stipulated time. At the trial, the court below treated the questions in dispute as ones of fact mainly, and submitted the evidence bearing on them to the jury. The verdict was for plaintiff in the sum of $3,055.88, instead of the $11,941.65 claimed, and it now appeals, assigning twelve errors to rulings on admission or rejection of evidence, and charge of the court.
*180The dispute between the parties arises, principally, because of opposite construction of this paragraph in the contract:
“ First party (plaintiff) guarantees that the work will be done in a thoroughly workmanlike manner, and that all material used will be of the best quality for the purpose required, and further, that the gas flues or conduits, will have capacity sufficient to supply the various furnaces and ovens named, and while not guaranteeing absolutely the successful operation of the furnaces, first party to use every endeavor in their power to make them operate successfully.”
It will be noticed, the contract was to erect a tank melting furnace designed to work thirty-six blowers in three equal shifts per day; the furnace to be operated with fuel gas manufactured from coal, by what is known as the “ Wellman” producer. As necessary to a proper understanding of the contract, a fact clearly established by the decided weight of the evidence should be stated: viz, that this method of melting’ glass in a tank for blowing, instead of in pots, and operating the furnace with fuel gas, instead of with natural gas, or coal, had hardly passed beyond the stage of experiment; therefore, as both parties had full knowledge and experience in glass manufacture, it may be assumed that the plaintiff did not intend to guarantee, absolutely, a successful result, nor did defendant intend to exact such guaranty. The surroundings of parties at the time of making a contract, and the subject-matter thereof, are always admissible to ascertain their intention, if their expressions be ambiguous or disputable. Having in view this situation of the parties, as an aid to the interpretation of the guaranty clause of the contract, already quoted, we are of opinion, the plaintiff was bound to show: — 1. That the work was done in a thoroughly workmanlike manner, and that the material used was of the best quality for the purpose. 2. That the gas flues had a capacity sufficient to supply the furnaces and ovens. 3. That they had used every endeavor in their power to make them operate successfully.
But this was, as to this particular, the full extent of their undertaking; they, by the use of the words, “ while not guaranteeing absolutely the successful operation of the furnaces,” clearly relieve themselves of any undertaking as to a successful result, even after the three stipulations noticed be fully per*181formed; all the hazard of what was an experiment was to be assumed by the party for whom the work was done, and not by the party who contracted to do it. On this interpretation of the contract, plaintiff offered evidence tending to establish that the work was well done, the material of the best quality, the producers and gas flues were of sufficient capacity, and that they did their best to make the furnaces operate successfully. And if this had been all that appeared in the case, they would have been entitled to a verdict for the balance unpaid on the contract, for they did not undertake that either tank melting or fuel gas should prove a success in glass manufacturing.
But it will be noticed, that plaintiff undertook to furnish three “Wellman” producers for the manufacture of natural gas, and to connect them by flues of suitable size to convey the gas from the producer's in sufficient quantity to operate the furnaces. Defendant averred, the producers were not of a size to furnish gas in sufficient quantitjq even if the flues were sufficient; and it adduced evidence tending to show that Wellman producers were of different sizes; that the term itself imported no particular size, and they could be, and often were, made larger than those supplied by plaintiff. In reply to this, plaintiff offered evidence, tending to show that the term “Wellman producer ” meant just such a one as they had constructed, and certainly did not mean a larger one; probably, as it appears to us, the weight of the evidence was with plaintiff as to this fact; nevertheless, it was a disputed fact for the jury. Plaintiff did not undertake that fuel gas should successfully operate the furnace, but it did undertake, if there were producers and flues of sufficient and insufficient size, then it would use “ every endeavor to make the furnaces operate successfully; ” and further, that it would make “ any re-arrangement or changes to the flues and producers, or anything of that kind, found necessary for the successful operation of the furnaces.” If plaintiff did not put in producers of sufficient size according.to plans prepared, which were to be prepared by itself, when it could have done so, it is answerable in damages.
The plaintiff, in undertaking that the work should be done according to plans and specifications prepared by itself, was more than a builder; it was also the architect, and, to a certain extent, the designer of its own work; this fact made it some*182what difficult to define the exact measure of its responsibility; but we think the learned judge of the court below, under this contract, correctly stated the law applicable to the evidence when he said to the jury: “If it is true that a Wellman producer means a producer of a certain size, then defendants could not complain, if three producers were erected, even if they did not produce sufficient gas; or if the producers erected are the largest size of Wellman producers, then they have all they contracted for. But if the Wellman producer is, as the defendant claims, a producer which can be erected of any size, then an agreement to erect producers, as part of a plant to work thirty-six blowers, is an agreement to build those producers of sufficient size and capacity to do their part of the work of said plant, and plaintiff should have so built them.”
This interpretation of the contract, was also- applicable to the damages claimed, because of improper application of heat to the tank, and a defective construction of the flue; plaintiff was answerable for defective and unworkmanlike construction, but was not answerable for incapacity of a new method or process, or for the unauthorized acts of third persons; the conflicting evidence on these questions was fairly submitted to the jury. This disposes of the tenth and eleventh, appellant’s most important assignments of error.
As to the first assignment, appellant offered evidence to prove that defendant, at the time of making the contract, promised plaintiff to provide for it, on the premises, room for storage of certain materials to facilitate performance of the work, and without such promise plaintiff would not have contracted to complete the work by the dajr mentioned in the agreement. This was objected to by defendant, and excluded by the court.
The agreement expressly provided, that defendant would make ready the buildings, and give plaintiff possession on June 1,1891, “ for the purpose of performing the work covered by this contract.” As plaintiff had offered in evidence the written agreement, and relied on it as a ground of recovery, we do not think it was competent to set up a contemporaneous parol agreement in rebuttal of defendant’s claim for damages. It was not a failure on part of defendant to perform any part of the written contract, or any act of defendant subsequent to it, not intended by it, but the offer was to prove a failure to *183perform another and a parol agreement, made at the same time as the written one; no fraud or mistake was alleged which would authorize a modification of the writing. The introduction in rebuttal of such new matter was not warranted by any rule of evidence.
Second assignment. Defendant offered evidence to show,, the tank as built and designed by plaintiff had not sufficient capacity for thirty-six men working three shifts per day. It was objected to, for the reason that plaintiff did not guarantee it would have such capacity. In the construction put upon the contract, in discussing the tenth and eleventh assignments of error, this was admissible. It was not competent for defendant to prove that melting glass in a tank was not a success, but it was competent to prove that this tank was not large enough for three shifts every twenty-four hours, even if the new method would otherwise have been successful.
As to the third assignment, on reading the evidence it plainly appears the offer by plaintiff was admitted ; noting “ objection sustained,” was an error of the reporter, which is shown by the fact that the witness did testify to all the facts proposed to be proved; besides, the course of cross-examination by defendant’s counsel indicates that he had testified in support of the offer. The court below ought to have had this error corrected before certifying the record ; if the records of a court import verity, then it is incumbent on him who certifies to them to see to it, under the full authority given by the constitution to all courts, that manifest errors are corrected.
The twelfth assignment complains of the admission of testi-' mony as to the cost of rearranging and changing flues, which defendant alleged were badlj’- located and defectively constructed.
As we have already noticed, by the contract, plaintiff stipulated that: “ It would make any re-arrangement or changes to the flues and producers, or anything of that kind found necessary for the successful operation of the furnaces, without further cost” to defendant.
Notice to plaintiff, and opportunity to make the change, are implied, before it could be charged with the cost of such change. There was ample evidence of precedent notice to plaintiff to remedy the alleged defects in the construction of this, and other *184parts of the work; it did not believe the contract imposed upon it such obligation, and refused to do so. Whether the change was such as warranted defendant in charging the plaintiff with the cost of it, depended on the finding of the jury as to the fact of defective construction. It was material, theiefore, to defendant to prove when the contract to remedy the defect had been made, if for no other reason than to show the expenditure was subsequent to the notice. There was no error in the admission of the evidence.
All the other assignments relate to the instruction of the court as to the measure of damages, and the admission of evidence relating thereto. The peculiarity of the contract made it difficult to distinguish whether success in operation failed because of defective performance by plaintiff of its contract, as designer and builder, or because of the adoption of new methods; the same peculiarity, also, made the rules determining the measure of damages somewhat difficult of application to the conflicting evidence. The learned court instructed the jury, if they found plaintiff had not performed its contract, then defendant was entitled to damages in: 1. The amount reasonably and necessarily expended in completing the contract. 2. The expense incurred and material lost, in attempting to operate the plant, so long as it was reasonable to operate it, in order to ascertain whether it would operate successfully. 3. The expense incurred, necessary to preserve the tank and material in it, while making necessary changes in flues and- producers. 4. Fair compensation, on the testimony, for the use of the plant while deprived of its use by failure of plaintiff to fulfil its contract.
This was followed, again, by the caution, that if plaintiff had used due skill in its work, but experience demonstrated that the method was at fault, then defendant must bear the loss; that distinction must be made between care and skill and experiment. As is said in McKnight v. Ratcliff, 44 Pa. 156 : “ It is often much easier to discover when an assumed rule for damages will lead to erroneous results, than to point out in all cases, in advance, what the true rule should be.” Logically, the rule laid down by the learned judge would possibly lead to an estimate of what profits might have been made while defendant was deprived of the use of its plant. But it did not lead to that result, for he properly controlled the admission and effect *185of the evidence so as to exclude any estimate based on what speculative profits defendant might have made, and confined the estimate to the actual loss. The court very plainly said to the jury, they were to ascertain “How much it was worth as a plant to a man desiring to use it; how much rent would he pay for it ? .... As I have explained to you, these other items that were admitted in evidence, will not be taken into account as a measure of damages. They are only for the purpose of aiding you to get at the value of the plant; that is, the rental value during the time of the delay.”
While fair compensation for the use of the plant when idle would, theoretically, be reimbursement for loss of profits, yet the impossibility of determining the amount of profits in this case, as in nearly every case of like character, was recognized by the court; such estimate would have been purely speculative as to what, under the most favorable circumstances, might have been made; therefore, the consideration of the jury was limited strictly to what would have been a fair rental value: Sedgwick on Damages, sec. 170. And on this question, all the evidence complained of had a bearing, and there was no error in not excluding it.
A careful examination of the more than 400 pages of testimony, with the many rulings on objections thereto, as well as a consideration of the very full and clear charge of the court, leads us to the conclusion no error warranting a reversal of the judgment was committed.
The judgment is therefore affirmed.