after making the foregoing statement, delivered the opinion of the court.
The general rule is clear that in an accounting of profits derived from the infringement of a patent the plaintiff has the burden of proof, and the infringer is chargeable only with the actual gains and advantages derived from the use of the invention. The scope of the rule is well defined in Garretson v. Clark, where it is said:
“When a patent is for an improvement, and not for an entirely new machine or contrivance, the patentee must show in what particulars his improvement lias added to the usefulness of the machine or contrivance. He must separale its results distinctly from those of the other parts, so that the benefits derived from it may be distinctly seen and appreciated. The rale on this head is aptly stated by Hr. Justice Blatchford in the court below. ‘The pat-' puteo.’ he says, ‘must in every case give evidence tending to separate or apportion the defendant’s profits and the patentee’s damages between the patented feature and the unpntented features, and such evidence must be reliable and tangible, and not conjectural or speculative; or he must show, by equally reliable and satisfactory evidence, that the profits and damages are to be calculated on the whole machine, for the reason that tlio entire value of the whole machine, as a marketable article, is properly and legally attributable to tlie patented feature.’ ”
In Dobson v. Carpet Co., where the infringement was of a design for carpets, it was said:
“Tli is court lias, in a series of decisions, laid down rules as to wliat are to be regarded as ‘profits to be accounted for by the defendant,’ and what as ‘actual damages,’ in suits for the infringement of patents; and no rule has boon sanctioned which will allow, in the case of a patent for a design for ornamental figures created in the weaving of a carpet, or imprinted on it, tlie entire profit ‘from the manufacture and sale of the carpet, as profits or damages, including all the profits from the carding, spinning, dyeing, and weaving, thus regarding the entire profits as due to the figure or pattern, unless it is shown by reliable evidence that tlie entire profit is due to the figure or pattern. * * * The same principle is applicable "as in patents for inventions. The burden is upon tlie plaintiff, and if be fails to give the necessary evidence, but resorts, instead, to inference and conjecture and speculation, he must fail for want of proof. * * * There is hut one safe rule, — to require the actual damages or profits to be established by trustworthy legal proof.”
In Make v. Robertson the patent was for combinations relating to a stone-breaking machine, apparently not less an entirety than a windmill, and it was there said:
“No license fee charged by the complainant is shown. The burden of proof rests upon him. Damages must be proved. They are not to be presumed. The complainant made a profit of $40 an inch on the width of the jaws of the numerous machines lie had sold. But inventions covered by other patents were embraced in those machines. It was not shown bow much of the profit was due to those other patents, nor how much of it was manufacturer’s profit. The complainant was therefore entitled only to nominal damages.”
To .show an exception from the rule or a distinction by which to justify the decree in the present case, the decision in City of Elizabeth v. American Nicholson Pavement Co., 97 U. S. 126, 24 L. Ed. 1060, is relied upon. The infringement in that case was of the Nicholson reissued patent for “a new and improved wooden pavement,” of which, in discussing the question of profits, the court, at page 141, 97 U. S., and page 1007, 24 L. Ed., said:
*784-“The Nicholson pavement was a complete thing, consisting of a certain combination of elements. The' defendants used it as such, — the whole of it, * * * Equally, without foundation is the position taken by the appellants that other pavements, approaching in resemblance to that of Nicholson, were op$n to the public; and that the specific difference between those pavements -and Nicholson’s was small, and that therefore the Nicholson patent was entitled to only a small portion of .the profit realized. Nicholson’s pavement, as before said, was a complete combination in itself, differing from every other pavement. The- parts were so correlated to each other, from bottom to top, that it required them all, put together as he put them, to make the complete whole, and to produce the desired result. The foundation impervious to moisture, the blocks arranged in rows, the narrow strips between them for the purposes designated,- the filling over those strips, cemented together, as shown by the patent* were all required. Thus combined and arranged, they made a new thing, like a new chemical compound. It was this thing, and not another, that the people wanted and required. It was this that the appellants used, and, by using, made their profit, and prevented the appellee from making it. It was not the case of a profit derived from the construction of an old pavement together with a superadded profit derived from adding thereto an improvement made by Nicholson, but of an entire profit derived from the construction of his pavement as an entirety.”
It is possible to see tbe truth of the holding in that case, but in the present case we are not able to perceive or to believe that by using'the' Nichols inventions the appellant made the entire profit derived from the manufacture and sale of windmills. The second patent is only for an' attachment, which doubtless may be usefully employed, especially in power mills, but if left off or removed no equivalent in its place is imperative. It is not an improvement upon the first invention, though it may, of course, be used in connection therewith. like the Albee device, it is an independent improvement, which may.be used upon any windmill in which there is on the tower an annular rack which is “permitted a slight rotation upon its support.”. There can, therefore, be no good reason for supposing that the profits derived from the manufacture and sale of the mills in which that device was employed were all due to its use. The first patent is -more important* in that it shows improvements upon indispensable parts of a windmill, but it does not in itself, like the Nicholson invention, constitute “a complete thing,” certainly not “a new thing, like a new chemical compound.” On the contrary, windmills resembling in general structure and in many essential parts mechanically identical with the. Nichols mills had been long in use before this patent was applied for. It does not profess to be for an entire device, but for improvements only, and they not general and comprehensive of an entire mill, but limited to “the method of mounting,” of which the specified purpose is to lessen friction and secure a smooth and easy movement of the parts designated. The claims differ in minor particulars, but no one or all of the five can be regarded as embodying a complete windmill, the entire profit of the manufacture and sale of which should, or could fairly, be attributed to . the presence of the patented combinations.
The decree below will be reversed, and the cause remanded, with direction-to give a decree for nominal damages only, unless in file discretion -of- the court there shall be another reference for the purpose of admitting competent evidence of profits.