Mr. Justice Story

delivered the opinion of the Court.

This is a writ of error to the judgment of the Circuit Court for the Eastern District of Pennsylvania, rendered in an action brought by Stimpson, the defendant in error, against the plaintiffs in error, for a violation of a patent right granted to him for a new and useful improvement in the mode of turning short curves on railroads.

A patent was originally granted to Stimpson, for the same invention, on the 23d day of August, 1831; and the renewed patent, upon which the present suit is brought, was granted on the 26th of *458 September, 1835, upon the former letters patent “ being cancelled on account of a defective specification;” and the renewed patent was for the term of fourteen years from the date of the original. patent. With the exception of'the recital of the fact that the former letters patent were cancelled “on account of a defective specification,” and the statement of the-prior date from which the renewed patent was to begin to run, the renewed patent is in the precise form in which original patents are granted.

At the trial upon the general issue, a bill of exceptions was taken to certain rulings of the Court upon points of evidence, to the consideration of which we shall at once proceed without any further preface.

The first exception taken is to the admission of the renewed patent as evidence in the cause to the jury. The patent act of 1832, ch. 162, sec. 3," under which this patent was obtained, provides, that whenever any patent shall be inoperative or invalid, by reason that any of the terms or conditions prescribed by the prior acts of Congress, have not, by inadvertence, accident, or mistake, and without any fraudulent or deceptive intention, been complied with on the part of the inventor, it shall be lawful for the Secretary of State, upon the surrender to him of such-patent., to cause a new patent to be granted to the inventor, for the- same invention, for the residue of the period then unexpired for which the original patent was granted, upon his compliance with the -terms and conditions prescribed by the third section of the act of the 21st of February, 1793, ch. 55.

Now, the objection is, that the present patent does not contain any recitals that the prerequisites thus stated in the act have been complied with, viz. that the error in the former patent has arisen by inadvertency, accident, or mistake, and without any fraudulent or deceptive intention; and that without süch recitals, as it is the case of a special authority, the patent is a mere nullity, and inoperative. .We are of opinion that the objection cannot, in point of law, be maintained. The patent was issued under the great seal of the United States, and is signed by the President, and countersigned by the Secretary of State. It is a presumption of law, that all public officers, and especially such high functionaries, perform their proper official duties until the contrary is proved. And where, as in the present case, an act is to be done, or patent granted upon evidence and proofs'to be laid before a public officer, upon which he is to decide, the fact that he has done the act or granted the patent, is prima facie evidence that the proofs have been regularly made, and were satisfactory. No other tribunal is at liberty to re-examine or controvert the sufficiency of such proofs, if laid before him, when the law has made such officer the proper judge of their sufficiency and competency. It is not, then, necessary for the patent to contain any recitals that the prerequisites to the grant of it have been duly complied with, for the law makes the presumption; and- if, indeed, it were otherwise, the recitals would not help the case without th *459 auxiliary proof that these prerequisites had been, de facto, complied with. This has been the uniform construction, as far as we know in ali our Courts of justice upon matters of this sort. Patents for lánds, equally with patents for inventions, have been deemed prima facie' evidence that they were regularly granted, whenever they have'been produced under the great seal of the government; without any recitals or proofs that the- prerequisites of the acts under which they have been issued have been duly observed. In cases of patents, the Courts of the United States have gone one step further, and as the patentee is required to make oath that he is the true inventor, before he can obtain a patent, the patent has been deemed prima facie evidence that he has made the invention. This objection, then, is overruled; and there was no error in the Circuit Court in the admission of the patent.

The next exception is to. the refusal of the Court to allow a witness, Josiah White, to give a description of an invention which he had seen on the Mauch Chunk railroad, in 1S27, which had a groove on one side, and run on the other on a flange for crossing, for the purpose of showing that the supposed invention of the plaintiff was known and in use by others, before the date of his patent. By the patent act of 1836, (which was applicable to the present point,) it is provided in the fifteenth section,- that whenever the defendant relies in his defence on the fact of a previous invention, knowledge, or- use of the thing patented, he shall state in his notice of special matter to be used in his defence, the names and places of residence of those, whom he intends to prove to have possessed -a prior knowledge of the thing, and where the same had been used. The object of this most salutary provision is to prevent patentees being surprised at the trial of the cause, by evidence of a nature which they could not be presumed to know, or be prepared to meet, and thereby to subject them either to most expensive delays, or to a loss of their cause. It is incumbent on those who seek to show that the examination of a witness has been improperly rejected, to establish their right to have the evidence admitted; for the Court will be presumed to have acted correctly, until the contrarv is established.

In the present case, there is no proof on the record that notice had been given according to the requirements of the statute, that White was to be a witness for the purpose above stated. Unless such notice was given, it is plain that the examination could not be rightfully had. The onus probandi is on the defendants to show it, and unless they produce the notice, the objection must fail. In point of fact, it was admitted by counsel, at the argument, that no such notice was, given. In either view, then, from the admission, or from the defect of the preliminary proof of notice in the record,' the exception is not maintainable.

The next exception is to the refusal of the Court to allow certain questions to be put by the defendants to John H. B. Latrobe, a witness introduced by the defendants to maintain the issue on their part. Latrobe, on his examination, stated, “ I know Mr. Stimpson *460 by sight and character. He granted to the. Baltimore. and Ohio Railroad Company the privilege of using the curved ways oh their railroad, and all lateral roads connected therewith. I fix the date of the contract in the early part of October, 1834, because I have then a receipt of Mr. Stimpson’s counsel, for two thousand five hundred dollars. Mr. Stimpson laid his claim against the Baltimore Company for an infringement of his patent, in 1832. It was referred to me by the Company, and I advised them.” The counsel for the defendants then offered to prove by the same witness, the declarations of the plaintiff and his agent, to the witness, that the settlement made with the Baltimore and Ohio Railroad Company with the plaintiff,’was not an admission by the said company of the plaintiff’s right in the alleged invention, but a mere compromise of a pending suit, disconnected with a grant, in writing, made by the plaintiff'to the said company; and to that end proposed to put the following questions, respectively, and in order, to the witness: “ 1. Do you know who was the agent or attorney of James Stimpson, in negotiating the arrangement and settlement between him and the company referred to? Who was he? '2. State if any conversations occurred between James Stimpson, or his agent or counsel, at any time, during the negotiations, regarding the rights claimed by him in the patent for curved ways; without reference to the existence of a written contract, or its contents? 3. What were they-?” The Court refused to allow these questions to be put, for the purpose aforesaid.

Now, (as has been already intimated,) it is incumbent upon those who insist upon the right to put particular questions to a witness, to establish that right beyond any reasonable doubt,,for the very purpose stated by them; and they are not afterwards at liberty to desert that purpose, and to show the pertinency or relevancy of the evidence for any other purpose, not then suggestéd to the Court. It was not pretended at the argument, that the evidence so offered was good evidence in chief, in behalf of the defendants upon the issue in the cause. It was res inter alios acta,’ and had no tendency to disprove the defendant’s title to the invention, or to support any title set up by the defendants; for no privity was shown between the defendants and the Baltimore Company. As evidence in chief, therefore, it was irrelevaht and inadmissible. The sole purpose for which it was offered, so far as it was then declared- to the Court, was to show, that the compromise with the Baltimore Company was not founded on any admission of the plaintiff’s right in the invention. Be it so; it was then inconsequential; for it certainly had no just tendency to disprove his right. If the compromise had been offered on the part of the plaintiff, for the purpose of establishing; his right to the invention, there is no pretence to say that it would have been admissible against.the defendants. In the converse case, it is equally inadmissible for the defendants.

But it is now said that the evidence was in fact offered for the purpose of rebutting or explaining certain statemer ?s made by one *461 Ross Winans, a witness called by the defendants, in his answers upon his cross-examination by the plaintiff’s counsel. Now, this purpose is not necessarily, or even naturally, suggested by the purpose avowed in the record. Upon his cross-examination, Winans stated: “I understood.there -were arrangements made with thé Baltimore Company.- I heard the Company paid five thousand dollars.” Now, certainly these statements, if objected to by the defendants, would have been inadmissible upon two distinct grounds. 1. First, as mere hearsay; 2. And, secondly, upon the broader principle, now well established, although sometimes lost sight of in' our loose practice at trials, that a party has no right to cross-examine any witness except as to facts and circumstances connected with the matters stated in his direct examination. If he wishes to examine him to other matters, he must do so by making the' witness his own, and calling him, as such, in the subsequent progress of the cause. The question then is presented, whether a party can, by his own omission to tatte an objection to the admission of improper evidence brought out on a cross-examination, found a- right to introduce testimony in chief to rebut it or explain it. If upon the cross-examination, Winans’. answer had been such as was unfavourable to'the plaintiff, upon the collateral matters thus asked, which were not founded in the issue, he would have been bound by it, and not permitted to-introduce evidence to contradict it.. There is great difficulty in saying that the defendants ought to be in a more favoured predicament, and to acquire rights founded upon the like evidence to which they did not choose to make-.; ¿y objection, although otherwise it could not have been in the causm- But waiving this consideration, the grounds on which we''think the refusal of the Court was right, are; first, that it was not distinctly propounded to the Court, that* the evidence was offered to rebut or explain.Winans’ testimony; and, secondly, that in the form in which it was put, it proposed to separate the written contract of compromise from the conyersations and negotiations which led to it, and to introduce the latter without - tSé former, although it might turn out that the written paper miglifraost materially affect or control the presumptions deducible from those conversations, and negotiations. We think, that upon the settled principles of- law, parol evidence bearing upon written contracts and papers, ought not to be admitted without the production of such written contracts or papers, so as to enable both the Court and the jury to see whether or not the admission of the parol evidence in any manner will trench upon the rule, that parol evidence is not admissible to vary or contradict written contracts or papers.

The next exception is to the admission of the evidence of William A. Stimpson, Richard Catón, and George Neilson, as -to certain declarations, and statements, and conversations of the plaintiff, as to his invention prior to the date of his original patent; in order to rebut the evidence of the defendants, as to the invention or use by other persons of the same contrivance, before that date. The ob *462 jection is, that, upon general principles, the declarations and conversations of a plaintiff, are not admissible evidence in favour of his own rights. As a general rule, this is undoubtedly true. It is, however, but a general rule, and admits, and requires various exceptions. There are many cases in which a party may show his declarations conflict with acts in his own favour, as a part of the res gestae. There are other cases, again, in which his material declarations have been admitted. Thus, for example, in the case of an action for an assault and battery, and wounding, it has been held, that the declarations of the plaintiff, as. to his internal pains, aches, injuries, and' symptoms, to the physician called to prescribe for him, are admissible for the purpose of showing the nature and extent of the injuries done to him. See 1 Phillips on Evidence, ch. 12, sec. 1, p. 200—202, eighth ed., 1838. In many cases of inventions, it is hardly possible in any other manner to ascertain the precise time and exact origin of the particular invention. The invention itself is an intellectual process or operation; and,.like all other expressions of thought, can in many cases scarcely be made known, except by speech. The invention may be consummated and perfect, and may be susceptible of complete description in words, a month, or even a year before it can be embodied in any visible form, machine, or composition of matter. It might take a year to construct a steamboat, after the inventor had completely mastered all the details of his invention, and had fully explained them to all the various artisans whom he might employ to construct the different parts of the machinery. And yet from those very details and explanations, another ingenious mechanic might be able to construct the whole apparatus, and assume to himself the priority of the invention. The conversations and declarations of a patentee, merely affirming that at some former period he invented that particular machine, might well be objected to. But his conversations and declarations, stating that he had made an invention, and describing its details and explaining itáSoperations, are properly to be deemed an assertion of his right, at that time, as an inventor to the extent of the' facts and details which he then makes known; although not of their existence at an antecedent time. In short, such conversations and declarations, coupled with a description of the nature and objects of the invention, are to be deemed a part of the res gestas; and legitimate evidence that the invention was then known to and claimed by him, and thus its origin may be fixed at least as early as that period. This view of the subject covers all the parts of the testimony of the witnesses objected tp in the Circuit Court; and we are of opinion, that the Court were right in admitting the evidence.

The next and last exception is, to the rejection of the evidence of Dr. Jones, who was offered to prove that there were material differences between the patent of 1831, and the renewed patent of 1835, and to explain these differences. No doubt can be entertained that the testimony thus offered was, or might be, most material to *463 the merits of the defence. And the question is not as fo the competency or relevancy of the evidence, but as to the propriety of its being admitted at the time when it was offered. It appears that the testimony was not offered by the defendants, or stated by them as a matter of defence, in the stage of the cause when it is usually introduced according to the practice of the' Court. It was offered after’ the defendants’ counsel had stated in open Court, that they had closed their evidence, and after the plaintiff, in consequence of that declaration, had discharged his own witnesses. The question, then, is, whether it was at that time admissible on the part of the defendants as a matter of right; or whether its admission was a matter resting in the sound discretion‘of the Court. If the latter, then it is manifest that the rejection of it canno.t be assigned as error.

The mode of conducting trials, the order of introducing evidence, and the times when it is to be introduced, are, properly, matters belonging to the practice of the Circuit Courts, with which this Court ought not to interfere; unless it shall choose to prescribe some fixed, general rules on the subject, undér the authority of the act of Congress. Probably the practice in no two states of the Union is exactly the same; and then - ore, in each state, the Circuit Courts must necessarily be vested with a large discretion, in the regulation of their practice. If every party had a right to introduce evidence at any time, at his own. election, without reference to the stage of the trial’ in which it is, offered, it is obvious that the proceedings of the Court would often be greatly embarrassed, the purposes of justice be‘obstructed, and the parties themselves be surprised by evidence destructive of their rights, which they could not have foreseen, or in any manner have guarded against. It seems to us, therefore, that all Courts ought to be, as indeed they generally are, invested with a large discretion on this subject, to prevent the most mischievous consequences in the administration of justice to suitors; and we think that the Circuit Courts possess this discretion in as ample a manner as other judicial tribunals. We do not feel at liberty, therefore, to interfere with the exercise of this discretion; and, indeed, if we were called upon to say upon the present record, whether this discretion was, in fact, misapplied or not, we should be prepared to say, that we see no reason to doubt that it was, under all the, circumstances, wisely and properly exercised. It is sufficient for-us, however, that it was a matter of discretion and practice, in respect to which we possess no authority to revise the decision of the Circuit Court.

Upon the whole, we are of opinion, that the judgment of the Circuit Court ought to be affirmed with costs.