
    McCASLIN MACH. CO. v. McCASLIN.
    (Supreme Court, General Term, First Department.
    November 15, 1895.)
    Evidence—Expert Testimony.
    In an action to compel the assignment of letters patent pursuant to a prior agreement between the parties that any invention made by defendant while in plaintiffs employ should become the property of plaintiff, a drawing made by defendant while in its employ was intro-, duced in evidence by plaintiff, who offered to show by an expert that the subject-matter of the drawing and of the letters patent was identical. Held, that the refusal to admit expert testimony to show what the drawing indicated was error.
    Appeal from special term, Yew York county.
    Action by the McCaslin Machine Company against George W. McCaslin to compel him to assign certain letters patent claimed by reason of a prior contract with the inventor while in plaintiff’s employ. The complaint was dismissed, and plaintiff appeals. Reversed.
    This action was begun February 16, 1893, to compel the defendant to assign to the plaintiff two letters patent, No. 486,789 and No. 486,809, issued by the United States to the defendant February 22, 1892, for “certain improvements in conveyers,” to compel the defendant to account for the rents and profits received under said letters, perpetually to enjoin defendant from incumbering or assigning said letters, and for the recovery of damages. October 20, 1888, the plaintiff was incorporated with a capital stock of $20,000, under the statutes of this state, by Charles W. Hunt, John Allen, Charles C. King, George Martin Luther, and George W. McCaslin, for the purpose of manufacturing chain conveyers for conveying coal, grain, and such articles. December 8, 1885, letters patent No. 331,961 were granted by the United ■States to William Griesser for a new and useful conveyer; August 7, 1888, letters patent No. 387,241 were granted to George W. McCaslin for an improved conveyer; August 20, 1889, letters patent No. 409,330 and No. 409,612 were granted to George W. McCaslin for improved conveyers,—which four patents were assigned to the plaintiff. October 27, 1888, the persons who organized the corporation entered into a contract, of which the following is a copy:
    “For and in consideration of one dollar, each to the other of us in hand paid, and in consideration also of the sum of one dollar to each of us paid by the McCaslin Machine Company, we do hereby severally agree that if we, or either of us, shall (during the time we shall be interested as stockholders, trustees, officers, or employes of the McCaslin Machine Company) invent or discover any improvement upon or new method of making any machine or machinery relating to or to be used in’making the chain conveyer now owned ■and used by said company, or any other machinery manufactured or to be manufactured by said company, that we will at once assign the invention or discovery, and any application for patents, and any patents issued thereon, to said company. Dated October 27,1888.”
    Upon the organization of the corporation the defendant became and remained a shareholder therein until January, 1891, and was employed as its general manager from the date of its organization until May 19,1891, when he resigned. November 22, 1892, letters patent No. 486,789 were issued by the United States to the defendant upon his application for “certain improvements in conveyers,’.’ and on the same day (November 22,1892) letters patent No. 486,809 were issued by the United States to the defendant upon his application for “certain improvements in conveyers.” It is alleged in the complaint that the inventions secured by these letters were devised and made by the defendant while he was a stockholder and employé of the plaintiff, and that they, and all the rights secured by the letters, belonged to the plaintiff. The defendant denies this allegation in his answer, and alleges that the inventions secured by the letters were made after he ceased to be a shareholder in and an employé of the plaintiff. February 11, 1893, the defendant assigned said two letters patent to Robert McCaslin in consideration of $2,000, which was recorded in the United States patent office May 19, 1893, who in May, 1893, assigned said letters patent to the McCaslin Conveyer & Trust Company, of Cleveland, Ohio.
    Argued before VAN BRUNT, P. J., and FOLLETT and PARKER, JJ.
    Antonio Knauth, for appellant.
    Thomas Ewing, Jr., for respondent.
   FOLLETT, J.

The important issues of fact contested before the special term were (1) whether the inventions described in the letters were made by defendant while in plaintiff’s service; (2) whether the inventions were an “improvement upon, or new method of making, any machine or machinery relating to or to be used in malting the chain conveyer now owned and used by said company, or any other machinery manufactured or to be manufactured by said company,” and so within the terms of the contract. Both of these issues were found in favor of the defendant, and, if they were well found, that is an end of the case, unless errors wTere committed in the reception or rejection of evidence. To make a case against the defendant it was necessary to establish that, while in the plaintiff’s service, he so far developed the inventions subsequently patented that they were substantially perfected. While it was not necessary to show that all of the minute details had been worked out, it was necessary to show that the subsequent claims made by the defendant, and recognized as new and patentable by the patent office, could have been readily understood and applied. An imperfect invention, resting ini theory,—a mere conception, and not so far perfected as to be patentable,—which the defendant subsequently perfected, is not embraced within the contract. Reed v. Cutter, 1 Story, 590, Fed. Cas. No. 11,645; Christie v. Seybold, 6 U. S. App. 520, 5 C. C. A. 33, 55 Fed. 69. While the defendant was in the employment of the plaintiff he made a drawing representing certain proposed improvements in conveyers, which, on the trial of this action, was introduced in evidence by the plaintiff for the purpose of showing the identity of the improvements shown by the drawing and those patented under the letters. • For the purpose of making it plain that the improvements described in the drawing and those subsequently patented were substantially the same in principle,, the plaintiff called an expert, and proposed to show by him wherein the improvements described in the drawing and in the claim upon which the patents were issued were alike. To this the defendant objected, and the objection was sustained, and an exception taken. The court ruled that it would not permit an expert to testify as to what the sketch indicated. In this* we think, the court erred. It is competent to permit mechanical experts to describe the differences- and similarities of inventions'shown by different drawings, claims, and models. This rule is so well settled that it does not require the citation of many authorities. Bischoff v. Wethered, 9 Wall. 812; Spring Co. v. Edgar, 99 U. S. 645; Allen v. Blunt, 3 Story, 742, Fed. Cas. No. 216. Of course, cases may arise so simple in their character that the testimony of experts may not be required to make the similarities and differences between various patents, claims, and drawings plain to the mind of a judge or jury; but this, we think,, was not such a case, and that the court erred in rejecting this class-of evidence.

The judgment and order should be .reversed, with costs to the plaintiff to abide the event. By the reversal of the judgment it becomes unnecessary to consider the appeal from the order denying a motion for a new trial on the ground of newly-discovered evidence, which falls with the reversal, and neither party has any further interest in it, or the appeal therefrom, except the costs which might be awarded, and would not exceed $20 and disbursements; and the order is set aside, without costs to either party. All concur.  