The plaintiff manufactures lumber in South Carolina. The defendants are lumber merchants in Boston. The action is in contract to recover damages for the breach of a contract for the purchase of lumber by the defendants. In the Superior Court there was a verdict for the plaintiff. The case is here on the defendants’ exceptions to the court’s rulings, and to the admission of evidence.
On May 10, 1920, the defendants made a written contract with the General Electric Company to supply it with lumber at its plants in Schenectady in the State of New York, Pittsfield in this Commonwealth, Erie in the State of Pennsylvania, and Bloomfield in the State of New Jersey; provision was made therein for a modification in price in the event of a general price revision. To fulfil the contract the defendants made the contract in suit to purchase lumber from the plaintiff, dated July 2, 1920; it was executed by the plaintiff on July 27, 1920, and a short time thereafter was signed by the defendants. It required a minimum of three million feet of lumber, with a maximum of four million feet, at the defendants’ option. Deliveries were to be in such *47quantities and at such times as the defendants ordered, shipments to be in “approximately equal monthly quantities during the contract period,” the seller agreeing to make extra heavy shipments “during the fall months.” There was no provision in the contract between the plaintiff and defendants for a price reduction in the event of a general price revision in the market. The purchaser had the right to route all shipments. No time limit was set for performance but it seems to have been assumed that it was to be completed in one year. One of the clauses was, “This contract subject to delay from strikes, accidents, wreck of cars containing goods, or other causes beyond our control, and subject to cancellation from destruction of our mill.” The defendants gave various orders for lumber; in August, September and October the plaintiff shipped a total of twenty-five cars. The defendants wrote the plaintiff, requesting more deliveries of lumber in August. The plaintiff’s sales manager wrote excusing delay on the ground of continued rain. At the trial the plaintiff relied upon a car shortage as the reason for its delay. The defendants granted a price revision to the General Electric Company in October, 1920, and wrote the plaintiff asking it to revise its price for the lumber. The plaintiff refused, and later, by letter of October 25, repeated its refusal. The defendants telegraphed the plaintiff’s mill to stop all shipments, and on October 26, notified the plaintiff that owing to its failure to perform the contract and make deliveries, the defendants cancelled the contract.
There was evidence that in August the plaintiff was ready to ship additional lumber, but was prevented by railroad embargoes and a shortage of railroad cars; that in September it endeavored to make more deliveries, but found it impossible for the same reasons; and that like conditions existed in October. We consider the defendants’ exceptions in the order they are argued in their brief.
1. The defendants moved for a directed verdict. The refusal to allow this motion raises the main question in the case. The plaintiff relies for its failure to make shipments on the clause in the contract excusing delay because of *48“causes beyond our control.” In answer, the defendants contend that by relying on this clause the plaintiff is suing on a defence, and not on a performance. If the contract contained no clause excusing the plaintiff from performance, and the delay was so important that it amounted to a breach of the contract, the defendants could have refused to go on and could have brought an action for the plaintiff’s nonperformance. Whether the breach was serious enough to justify the1 defendants in refusing further performance, as a general rule, is a question of fact for the jury. Casavant v. Sherman, 213 Mass. 23, 27. National Machine & Tool Co. v. Standard Shoe Machinery Co. 181 Mass. 275. Eastern Forge Co. of Massachusetts v. Corbin, 182 Mass. 590, 593. Dudley v. Wye, 230 Mass. 350. Miller v. Benjamin, 142 N. Y. 613, 617. If the plaintiff’s failure were not so serious as to go to the root of the contract, an action for the defendants’ breach would he. A delay not going to the essence of the contract would not prevent a recovery if the defendants refused to go on with the agreement.
The parties agreed that deliveries of lumber were subject to delay from causes beyond the plaintiff’s control. The shortage of cars and the embargo, the jury could find, were beyond its control and were not occasioned by any act or omission of the plaintiff. On this finding the plaintiff was excused from performance within the time agreed. Durden-Coleman Lumber Co. v. William H. Wood Lumber Co. 221 Mass. 564. See Garfield & Proctor Coal Co. v. Pennsylvania Coal & Coke Co. 199 Mass. 22, 42. An embargo or shortage of cars might be so permanent and extensive “that the foundation of what the parties are deemed to have had in contemplation has disappeared, and the contract itself has vanished with that foundation.” F. A. Tamplin Steamship Co. Ltd. v. Anglo-Mexican Petroleum Products Co. Ltd. [1916] 2 A. C. 397, 406, 407. See North German Lloyd v. Guaranty Trust Co. 244 U. S. 12; Allanwilde Transport Corp. v. Vacuum Oil Co. 248 U. S. 377; Metropolitan Water Board v. Dick, Kerr & Co. Ltd. [1918] A. C. 119. These cases, however, are not applicable. The conditions were not such that the foundations of the contract were taken away and its per*49formance rendered impossible for such a length of time that the defendants could repudiate it.
2. The defendants contend that there was error in the instruction given the jury, to the effect that time was of the essence if the plaintiff entered into the contract with knowledge of the contract of the defendants with the General Electric Company for the deliveries of lumber, “in the same amounts of the same sizes ... at the same times,” and if it was made for the purpose of supplying the material to enable “the defendants to meet their obligations . . . with the General Electric.” We do not find that the defendants excepted to this instruction. It was sufficiently favorable to them. The contract in suit contained no reference to the contract of the defendants with the General Electric Company. The plaintiff’s knowledge of such contract was a question of fact. There was no error of law in this instruction.
3. The judge correctly instructed the jury on the question of waiver. The waiver of a claim for damages was not involved. See Garfield & Proctor Coal Co. v. Fitchburg Railroad,. 166 Mass. 119. In the case at bar one of the issues before the jury was the defendants’ waiver of the plaintiff’s failure to perform. The defendants accepted slow deliveries. The effect of this could be considered by the jury on the question of the defendants’ waiver of the right to rescind the contract because of nonperformance by the other party. Norrington v. Wright, 115 U. S. 188.
4. The defendants excepted to the portion of the charge wherein it was stated in substance that if the plaintiff treated the buyer fairly with reference to its other customers, and supplied the buyer ratably, the plaintiff did its full duty to its customers with reference to shipments. Whether the defendants were treated ratably was a question of fact. There was evidence tending to support the plaintiff’s contention that they were so treated, and supplied ratably with other customers. The plaintiff, because of the difficulty in making shipments, was not obliged at its peril to make equal monthly shipments according to the contract, beginning August 1. It was protected by the clause of the contract excusing it from delay arising from causes beyond its control.
*505. The defendants excepted to the refusal to give the twentieth request, in effect, that if the defendants were entitled to cancel the contract, their motive was immaterial. On this point the jury were told: “The defendants would have no right to cancel this contract merely because the plaintiff refused to revise the price schedule. No inference should be drawn against any party to a contract if he stands on his contract and on his legal rights under it. Assuming that was the reason for cancellation and the only ground for cancellation that existed at the time, the cancellation would not be justified. Assuming that was a reason for cancellation but at the same time there was a good ground for cancellation because of unreasonable delays in delivery, the defendants would have a right to insist upon the unreasonable delays provided in your consideration of the case you find the delays were a breach of the contract.” The request was correctly covered by this instruction and the defendants cannot complain that the exact language of the request was not given.
6. The defendants’ seventh request was as follows: “If the plaintiff shipped only four cars in August, and six cars in September, then in the absence of proving an excuse for larger shipments beyond the plaintiff’s control, the plaintiff did fail in a substantial manner to perform its contract, and cannot maintain this action.” The plaintiff’s failure to perform was a question of fact; and the request was properly covered by the remarks of the court on this subject. There was no error in its refusal.
7. The subject matter of the eighth and ninth requests was sufficiently covered in the charge, as was the tenth request. There was no error in refusing the defendants’ remaining requests in this connection.
As to the amount of lumber ordered, that too was for the jury; the amount appropriated also was a question of fact. These issues were left to the jury under appropriate instructions.
8. The exceptions to certain testimony of the witness Mills must be overruled. His computations were based in part on lumber manufactured before the contract was.made. *51The plaintiff was not prevented from appropriating to the contract lumber already manufactured. The testimony of the witness relating to such appropriated lumber was material and relevant.
9. Answers to certain interrogatories filed by the defendants, to be answered by the plaintiff’s president, were put in evidence by the defendants. The plaintiff then offered answers to interrogatories 6, 7, 8, 9 and 25. To the admission of these answers the defendants excepted. By G. L. c. 231, § 89, the party interrogated may require the whole of the answers, upon any one subject matter inquired of, to be read, if a part of them is read. The subject matter inquired of by the defendants and the answers given in the interrogatories excepted to, related to the lumber manufactured by the plaintiff during the period covered by the contract. There was a sufficient identity of the matters inquired about to allow the admission of the answers.
10. On the issue of damages the jury were fully and accurately instructed. Many questions of fact were involved, including the question of the available market for the goods. See McLean v. Richardson, 127 Mass. 339. The duty of the plaintiff to mitigate the damage did not necessarily require. the jury to consider the price paid by the General Electric Company to the defendants. The defendants cannot complain because of the refusal to give the nineteenth request.
11. Requests twelve and thirteen, relating to the cancellation of certain portions of the General Electric Company’s contract with the defendants, were refused properly. Even if that company cancelled portions of its contract, it would not be conclusive that the defendants were entitled to cancel their contract with the plaintiff, and as we construe the bill of exceptions, the General Electric Company never did cancel any part of its contract. These instructions, therefore, became immaterial.
12. The testimony of the witness Moore was not subject to exception.
We have examined all the questions argued in the defendants’ brief. We find no error in the conduct of the trial.
Exceptions overruled.