Defendant in error instituted suit in the circuit court of the United States for the northern district of *258 California for an infringement upon his letters patent for improvement in a drying apparatus for drying fruit.

The allegations in the declaration are:

The charge is that defendant—

Turning to the letters patent, we find what are the inventions claimed by Cassidy. He says:

In describing this second invention the applicant says:

Plaintiff in error says in his brief:

Defendant in error says in his brief:

It contains two claims. Infringement is charged of the second only.

Again,—

Again,—

Prom the foregoing it would appear that there was no contention but that defendant in error’s patent was for improvements in fruit dryers, and not for a fruit dryer. In the subsequent consideration of this case this may become important.

Plaintiff in error urges that the circuit- court committed an error in allowing Cassidy to give an opinion as to the relative costs between *259 his patented fruit dryer and the Alden fruit dryer. The witness stated that he had for a number of years been engaged in mechanical pursuits; that he had seen a, great many fruit dryers of different kinds; that he thought his knowledge of mechanics sufficient to permit him to give an intelligent opinion as to the cost of a piece of machinery when he saw it. This question was then asked him: “With that as a basis, I will repeat the question, and will ask you which in your judgment would be the cheapest to construct, yours or the Alden?” The objection of plaintiff in error to this question was “because the witness says he does not know what the Alden dryer would cost.” It will be t een that the objection was not that the witness was not competen! to give an opinion as to the relative costs of these two macMin s, or that this was not a competent way of proving their relative costs. It is urged by plaintiff in error that the cost of building the Ah ¡en dryer was capable of exact proof. There is no evidence to show (his, and this was not the objection made. A party objecting to the introduction of evidence must specify the point of objection definitely, and none other will be considered. The fact that the witness did not know the exact cost of the Alden machine would be no objection to Ms giving his opinion, as a competent expert, as to its cost. A party is never injured by a question propounded to a witness unless he can show injury from the answer thereto. In this case the answer was much narrower than the question would have warranted. In response thereto the witness said: “I think, so far as the shifting apparatus is concerned, this would be 50 per cent, cheaper than the Alden, — fifty or seventy-five.” This was competent evidence upon the question as to the utility of the machine of the defendant in error.

The next error claimed by plai ntiff in error to have been committed by the circuit court is in its refuting to instruct the jury to find a verdict for defendant, when the plaintiff in the court below had rested Ms case upon the evidence then presented. The ground upon which it is urged that the court should have given this instruction seems to be that it appeared from the evidence that there was no novelty in plaintiff’s patent; that it was superseded by the Alden machine; that Cassidy had substituted in Ms patent only mechanical equivalents for those devices used in the Alden. Plaintiff introduced Ms patent in evidence. This was prima facie proof of the validity of his patent. In the case of Mitchell v. Tilghman, 19 Wall. 390 , the supreme court said:

In Walker on Patents the rule is expressed that the patent, when introduced in evidence, is prima facie proof of its own validity, unless it appears on its face not to be such a document as the statute prescribes. Walk. Pat. § 491. When letters patent are introduced in evidence the burden is cast upon the defendant to show that they are not good, or that the patentee is not the first inventor. Blanchard v. Putnam, 8 Wall. 420 ; Seymour v. Osborne, 11 Wall. 516 -538. The question of anticipation or wani of invention is a matter of defense. The question of anticipation cannot he raised without notice specifying the anticipating invention. Section 4920, Rev. St. The ques *260 tion as to whether, considering the previous state of the art,' no invention was made by the patentee may be raised without notice. But the want of invention in a patent is a matter of defense unless the thing for which a patent is claimed shows on its face that it is without invention. Walk. Pat. § 599. In the following cases want of invention is spoken of as a defense: Mahn v. Harwood, 112 U. S. 354 , 5 Sup. Ct. Rep. 174, and 6 Sup. Ct. Rep. 451; Hendy v. Iron Works, 127 U. S. 370 , 8 Sup. Ct. Rep. 1275. The evidence given by Cassidy concerning the Alden dryer was brought out by defendant on cross-examination. It would appear to have been an attempt on its part to make out its defense in this way. If the evidence of Cassidy had any tendency to make out defendant’s defense, it was a matter for the jury to determine its weight. And they should have been able to find from it, beyond reasonable doubt, that there was no invention in his patented devices, or that they had been anticipated. Coffin v. Ogden, 18 Wall. 120 ; Walk. Pat. § 76. It was not pretended that the Cassidy machine showed want of invention on its face. This result was to be reached only .by evidence. Under such a condition there could have been no error in the court refusing to take the case from the jury, and decide the issue of fact presented itself. Defendant in error urges that plaintiff in error waived the exception to the refusal of the court to instruct the jury to find for defendant by proceeding in the cause and introducing evidence on its part. In the case of Railway Co. v. Cummings, 106 U. S. 700 , 1 Sup. Ct. Rep. 493, the supreme court said:

In tbe case of Insurance Co. v. Crandal, 120 U. S. 527 , 7 Sup. Ct. Rep. 685, the supreme court held that, under such circumstances, the ruling of the court “cannot be assigned as error because the defendant at the time of requesting such an instruction had not rested its case.” This doctrine was affirmed in Robertson v. Perkins, 129 U. S. 233 , 9 Sup. Ct. Rep. 279. Under these controlling authorities, the contention of defendant in error on this point must be sustained.

Plaintiff in error urges that under the evidence it was wrong to have left it to the jury to determine whether or not gravity catches were mechanical equivalents for spring catches, for the reason that defendant in error narrowed his claim by an amendment of his application for a patent so as to, leave out of his claim for spring or other catches the words “other catches.” It does appear from the record that defendant in error, in his application for a patent, first claimed “spring or other catches,” and then amended to “spring catches.” This was done by direction of the patent office, on the ground that the application was not proper in form. There is a decision of the supreme court that urges that such applications should *261 not Tbe received, because of indefi idleness and liability to misconstruction. But we do not think that this can be classed as a disclaimer of any other catches which would be a mechanical equivalent therefor. Such was not the object of the amendment, or the reason for requiring the same. Generally, a patentee, no matter what the character of his patent may be, can claim mechanical equivalents known to exist at the time of the application, whether he claims them or not in his application. Walk. Bat. § 350; Vulcanite Co. v. Davis, 102 U. S. 230 ; Tatum v. Gregory, 41 Fed. Rep. 142. There may be a rule of strict construction applied to patents that do not embrace pioneer inventions when considering this question. But there is no dispute but that the gravity catches were known mechanical equivalents for spring catches at the rime of defendant in error’s application. There would seem to he no room, then, for construction upon this point. If defendant in error is entitled to mechanical equivalents at all, he should be in this case. We hold that this point is not well taken.

The court in Ms instructions submitted to the jury the question as to whether there was invention in the paient, and as to whether defendant in error was the first ini entor of tbe devices mentioned in Ms patent; and also tbe question is to whether gravity catches were the mechanical equivalent for spring catches known at the time oí the patentee’s application. These are all questions of fact, and in a law case should he submitted to (he jury under proper instructions as to the law' applicable to the same. This, we think, was properly done by the court. Blaintiff has assigned and claimed many errors as committed by the court in regard to the refusal to instruct as requested by it, and in giving cei tain instructions to tbe jury. Considering the charge as a whole, we think, upon the matters above stated, it ivas correct and sufficient. B uder these circumstances, we think it a prod i;less expenditure of time to consider and review in this opinion all of the alleged errors.

The plaintiff in error, upon another issue not above stated, namely, upon the question of damages, asked the court to instruct the jury that, under (.he evidence presented, the plaintiff could not recover more than nominal damages, if any. As stated before, defendant in error claimed two improvements in fruit dryers. He sued for an infringement of but one of these claims. His claim for damages cannot be broader than for the infringement he claims. In other words, he cannot claim damages for anything more than this one device. He is injured ouly to the extent of the use of that part of his patent which has been infringed. The evidence as to damages consisted of evidence of a license fee which he had fixed for both of Ms devices, and evidence of the profit to be made in manufacturing fruit dryers containing both of these improvements, and also certain unpatented features. The authorities a,re full upon tbe point that a party cannot recover as damages the prolii s to be derived from the manufacture of the whole of a machine, when only a portion of the same contains a patented feature. Garretson v. Clark, 111 U. S. 120 , 4 Sup. Ct. Rep. 291; Dobson v. Carpet Co., 114 U. S. 440 , 5 Sup. Ct. Rep. 945; Philp v. Nock, 17 Wall. 460 . The burden of proving damages for the in *262 fringement of a patent is upon the plaintiff, and he must establish his damages by competent evidence, and they must not be left to be surmised or arrived at from conjecture by the jury. Garretson v. Clark, supra; Blake v. Robertson, 94 U. S. 728 . It is true that when there is no evidence which can be produced of a license fee, or the profits to be derived from the manufacture of the patented device, the jury may be called upon to determine what would be a reasonable license fee when proper evidence is introduced tending to establish that fact. Walk. Pat. §§ 563, 564. But the evidence in this case did not have a tendency to establish that fact. Ho evidence was introduced for that purpose. Ho evidence of the relative utility or value of the two devices naméd in the patent was presented. The proof of a license fee for two improvements in fruit dryers is not competent, in order to show the damage sustained by an infringement of one of these improvements. Philp v. Nock, 17 Wall. 460 ; Seymour v. McCormick, 16 How. 480 . The market price of two pieces of land could not be proven in order to show the market value of one of these pieces. A license fee, when established and agreed to by the public, is only a means, of estimating the market value of a patented machine or device of which the patentee had been deprived by infringement. Seymour v. McCormick, supra, 490 , opinion; Packet Co. v. Sickles, 19 Wall. 617 ; Rude v. Westcott, 130 U. S. 152 -165, 9 Sup. Ct. Rep. 463. Plaintiff’s evidence was of such a character, then, in our opinion, as not to give the jury the means of arriving at any more than nominal damages for plaintiff. The damages found cannot be deduced from any evidence in the case, but must have been reached' by surmise or conjecture, and the evidence was not of the character to have warranted the same. It was therefore error in the court below to have refused plaintiff in error’s request to instruct the jury that they could find only nominal damages for plaintiff. For this error the judgment of the court below is reversed and set aside, and the cause remanded for further proceedings.