delivered the opinion of the Court:
1. The question at the threshold of the case is that of the validity of the Hoffman patent, the infringement of two of the claims of which is the subject-matter of the suit.
Beginning a number of years ago, the increased and increasing use of very heavy record books in public and private offices made it important to obtain a shelf so constructed as to permit the constant, safe and convenient handling of such books — weighing sometimes thirty pounds and more — and at the same time to preserve their covers from the constant and severe abrasion incident to the use of the ordinary book shelf.
It appears from the evidence that this demand was first attempted to be met many years ago in the Patent Office itself by the use of rollers of wood and metal. These extended across the shelf from side to side, with journals at each end revolving in bearings provided in cleats attached to the wooden cases.
The evidence tended to show that these were not very effective, because the rollers often warped or sagged in the middle, and abrasion was not prevented; and also because handling was often attended with injuries to hands or fingers.
Quite a number of roller shelves have been invented from time to time, and many have been patented. One of the best of these was a shelf that was made for use in the *212office of the clerk of the court of Wayne County, at Richmond, Indiana. This was made in 1872 or 1873, and was not patented. It consisted of the ordinary wooden shelf with two wooden rollers inserted in spaces cut therein, some four to six inches from the front edge. There was a notch in the outer‘edge of the shelf making a hand hole for grasping the book in the process of withdrawing the same from the shelf.
Some of the inventions most relied on as anticipations of the invention claimed by the plaintiff will now be noticed.
(1) The Jewell and Yawman experiment of 1886 need not be described. In all the decisions made in the interference proceedings between defendant, as their assignee, and the plaintiff herein, that was found to be nothing more than an incomplete and abandoned experiment. There is no testimony to warrant us in coming to a different conclusion.
(2) Adams Patent Roller and Extension Axle, March 23, 1886. This consists of a series of rollers inside the shelf, with two rollers attached to and extending some inches beyond the front edge of the same. These last have a space between them and rest upon a spring. Their extension in front of the shelf prevents a door closing in upon the shelves in their case.
(3) Harris Patent Improvement in Safe Cases for Books, September 6, 1870. This is called an improved case and has rollers for use in the shelf located some distance back from the front edge thereof.
(4) Boone’s patent, September 12, 1876, is for improved book shelves. The improvement consists in a single roller attached to the front edge of an ordinary shelf for books— apparently small books inserted in an upright manner, though capable of use in either way — and a little above the same. The purpose as expressed is to prevent the abrasion of the books by the sharp front edge of the shelf.
(5) Wolfe’s patent, October 7, 1879, is for an improve*213ment in book cases. In his case, a series of small, narrow rollers, like wheels, are mounted in boxes resting on the shelf , and extending from front to rear. The books may rest directly upon these or upon a movable shelf mounted on them.
(6) Conant Patent Roller Shelf Book Case, April 21, 1885. This calls for a case with shelves wherein the rollers revolve on journals in bearings on strips or cleats attached on both sides of the case from front to rear. It seems to be an improvement of the method used in the Patent Office as above described. The rollers run across the shelf, and one of them is very near the front edge of the shelf so that the recess in the binding at the back of the book may rest upon it.
Other patents were referred to in the defendant’s answer, but none save the foregoing are found in the evidence introduced.
In the light of the art as shown in the shelves and cases above described, it remains to examine the plaintiff’s claim of invention.
Claims one and two of his patent, which are in controversy here, read as follows :
“1. In a storage case for books, &c., the combination of a supporting rack or shelf composed of metallic strips and having a re-entrant bend or recess in its front edge, and rollers journalled in said rack and projecting above and in front of the same on each side of said bend or recess, substantially as described.
“ 2. In a book shelf the combination of a supporting frame, a series of horizontal rollers, the front roller in two separated sections, the intermediate part of the frame being carried back to permit the admission of the hand between said roller sections, substantially as described.”
Plaintiff claims to have invented a shelf through a combination exhibiting more than ordinary mechanical skill. As stated by his expert witness:
*214“ The second claim of the Hoffman patent is, as I understand it, for a book shelf embracing the combination of a number of features or elements recited therein, arranged and operated substantially as described in the specification, and the novelty of the claim, as far as my knowledge goes, resides in the structure termed the book shelf and embracing the features or the combination of elements set forth, and adapted for the purposes described. It does not, as I understand it, necessarily depend upon the novelty of any one or more of the features or elements recited.”
The peculiar features claimed for the combination of plaintiff are the frame and the arrangement of the rollers.
The shelf is made of this frame of metal bars and strips, which are rigid, and strong enough, and so arranged as to contain bearings for the rollers as distributed. These rollers are so arranged as to support the book equally throughout and prevent warping. The front rollers extend slightly beyond the front of the frame, preventing abrasion of the book and supporting its back in co-operation with the interior rollers. The front of this frame is carried back, or recessed, so as to leave a space between the two front rollers admitting the hand behind them in grasping the book. Besides forming' the bottom of the shelf and supporting the book, the frame braces and supports the light metallic sides of the case in which it is bolted at the required distances. It is claimed that no such frame had ever before been constructed until the shelves of defendant were made in infringement, as alleged, of plaintiff’s patent. This claim seems to be borne out by the testimony.
In the evidence taken and the cross-examination of plaintiff’s experts the defendant seems to have relied chiefly, if not entirely, upon the Adams patent and the wooden shelf of the clerk’s office at Richmond, Indiana.
Both have been described above. In the Adams arrangement only do we find the two forward rollers with a space or recess between them. These, however, perform no such *215function as the front rollers of plaintiff’s shelf. They are attached to the shelf by a spring; their purpose is claimed to make eas}7 the entrance of the book only. They do not support the book when in, and in fact do not facilitate its entrance, or prevent its contact with the front of the shelf because of the spring upon which they work. Their position prevents the closing or sliding of a door in front of the case. They have no real connection with the system of rollers inside, and the recess between answers no useful purpose. This invention was of so little value that the witness Jewell — one of the inventors of defendant’s shelf — was compelled , on cross-examination, to say that it had no practical use-
The Richmond shelf has the hand hole devised for that use onty, and without connection with the rollers, or extending back to or between them. Plaintiff does not claim the hand hole as his invention ; but such a novel construction of frame and arrangement of rollers as that he obtains the obvious advantage of the rollers at the front edge of the shelf, set in the frame without springs, and the recess between them by means of which, without weakening the shelf, the hand can be passed behind the rollers to grasp the back of the book.
So far as the remaining patents above set forth are concerned,'we have been left to consider them upon their specifications and drawings in comparison with the plaintiff’s claims.
Whilst this duty devolves upon the court, it might have been rendered less difficult had the mechanical experts been called upon to point out their several resemblances and differences. Bischoff v. Wethered, 9 Wall. 812, 815; see, also, Heald v. Rice, 104 U. S. 737, 749.
In this regard it maybe said that defendant’s chief object in this case has been not so much to show that plaintiff’s patent did not cover an invention, but that it must be so restricted in its scope that his own frame and shelf, can not be declared an infringement.
*216Those other patents have been described above, and after what has .been said in respect of the Adams patent and the Biclimond shelf, we think it sufficient to say that they do not constitute anticipations of the plaintiff’s claims.
Invention consists in the combination of old elements as well as in the discoveiy of an element entirely new, provided it produces a new and useful result. “ New elements in such a patent are not required, and if such a defence were allowed, not one patent of the kind in .a thousand of modern date could be held valid.” Parks v. Booth, 102 U. S. 96, 104.
Looking at plaintiff’s combination of frame and adjustment of rollers in his patented shelf, in the light of the art as disclosed by the constructions aforesaid, has he produced something new and useful as the result of inventive talent rather than of mere mechanical skill?
As has been well said by the Supreme Court of the United States: “It is not easy to draw the line that separates the ordinary skill of the mechanic, versed in his art, from the exercise of patentable invention, and the difficulty is specially great in the mechanic arts where the successive steps in improvements are numerous, and where the changes and modifications are introduced by practical mechanics.” Krementz v. S. Cottle Co., 148 U. S. 559.
We have found the answer to the foregoing question one of great difficulty, and it is not without some doubt of its soundness that we have reached the conclusion that plaintiff is entitled to the award of invention.
The very fact of the existence of a reasonable doubt arising on the case made by the defendants, is sufficient to sustain the claim of the plaintiff, for it. is well settled that the patent, in actions for infringement, is prima facie evidence of invention as well as that the patentee is the original inventor. Lehnbeuter v. Holthaus, 105 U. S. 94, 96; Cantrell v. Wallick, 117 U. S. 689, 695; Gandy v. Main Belting Co., 143 U. S. 587, 596.
*217The general superiority and utility of the plaintiff’s shelf are reasonably apparent, upon examination of the drawings and models. The desired objects that have been attained by his shelf were in the minds of skilled mechanics working to the same end, and yet no one of these hit upon plaintiff’s successful combination of frame and roller adjustment. Grant that, by certain modifications, the Adams, or the Conant, and possibly other inventions might have been made to perform the functions of the plaintiff’s, still it is apparent from their drawings and specifications that these were not in the minds of their patentees. They cannot, therefore, upon that ground merely, be regarded as anticipations. Topliff v. Topliff, 145 U. S. 156, 161.
The evidence tends also to show that plaintiff’s shelf, by reason of its superiority, has practically superseded all other roller shelves in the market; and the schedules of sales made by defendant of similar constructions show a wide-extended and increasing market. Now, whilst wide-extended sales and speedy general use are not themselves to be regarded as proving invention, still they have always been recognized as having considerable weight where the existence of patentable novelty is otherwise a matter of doubt. Krementz v. S. Cottle Co., 148 U. S. 556, 560; Potts v. Creager, 155 U. S. 597, 660.
The difficulty before alluded to, that often attends the demarcation of the boundary line between the exercise of ordinary mechanical skill and that of patentable invention, is shown in two series of decisions by the Supreme Court of the United States, some of which counsel in this case, as well as in others, find difficulty in distinguishing from each other.
Among those declaring in favor of the exercise of inventive talent maybe mentioned the following: Smith v. Goodyear Dental Vulcanite Co., 93 U. S. 486; Loom Co. v. Higgins, 105 U.S. 580; The Barbed Wire Patent, 143 U. S., 275; Gandy v. Main Belting Co., 143 U. S. 587; Topliff v. Topliff, 145 U. S. *218156; Krementz v. S. Cottle Co., 148 U. S. 556; Potts v. Creager, 155 U. S. 597. In this last case 'the decisions either way are extensively reviewed. See also Dubois v. Kirby, 158 U. S. 58, 63.
Among the numerous decisions against the exercise of patentable invention, the following may be enumerated: Reckendorfer v. Faber, 92 U. S. 347; Pickering v. McCullough, 104 U. S. 310; Market St. Ry. Co. v. Rowley, 155 U. S. 621; Knapp v. Morss, 150 U. S. 221.
From the decision in the last of those cases, Mr. Justice Brown and Mr. Justice Shiras dissented, on the ground that the claim of invention was within the rule of Loom Co. v. Higgins, Topliff v. Topliff, and others, supra.
For the reasons before given, we have concluded that the plaintiff's claims call for the application of the doctrine of the first series of cases cited above, and must therefore be awarded the merit .of invention.
This case is clearly distinguishable from that of Durham v. Seymour, 6 App. D. C. 78. In the first place, the claimant had been denied a patent by the Commissioner of Patents, as well as by the trial court, and the burden of showing patentable invention was heavily upon him. In the second and most important place, whilst his combination was one of merit, it was plain that there was no new arrangement by which any one of the old devices had been made to operate differently, or more effectively, than when used separate^. Besides, the most important of these devices had been patented to him separately, and the very important part of his combination, namely, the mode of supporting the entire system of drainage, had been unquestionably anticipated.
We have not been unmindful of the opinion expressed by Judge Lacombe in Fenton Manufacturing Co. v. Chase, 73 Fed. R. 831. On the contrary, that has been the chief occasion of the doubt heretofore expressed in respect of the soundness of our conclusion. The question of patentability *219came before the learned judge upon motion for preliminary injunction, unaccompanied by the evidence which this record contains, and the order was, of course, not final. Upon the presentation there made, Judge Lacombe seems to have entertained the idea that the claim was for the “hand hole” made by the re-entrant bend or recess of the front part of the frame.
This is quite different from what we have conceived to be the claim of the patentee and the merit of his combination.
Our conclusion is, we think, supported also by the following recent decisions in the circuit courts of appeals for the third and eighth circuits: Taylor v. Sawyer Spindle Co., 75 Fed. R. 301; Mast, Foos & Co. v. Dempster Mill Manufacturing Co., 82 O. G. 338.
2. There can be no doubt that, under the well-established rule in such cases, the claims of the Hoffman patent should be restricted to the specific combination described. Knapp v. Morss, 150 U. S. 221, 228, and cases cited therein. Consequently, if the shelves as manufactured and sold by the defendant show a substantially different combination, or one omitting one of the elements of the plaintiff’s, there can be no infringement.
Applying this test to the facts, we find that the rigid frames of each construction are sustantially the same. Whilst the strips of one run at different angles from those of the others, the object and effect are identical. These have the same bearings for the rollers and a like adjustment of the latter for the support of the book.
The difference contended for by the defendant is pointed out in the front bar of the frame.
In the Hoffman shelf the space between the front rollers is made by bending back the front strip or bar. In that of defendant the same thing is accomplished by fastening the two front rollers to the strip by means of a bracket.
There is no difference of purpose, effect or operation be*220tween the two shelves as thus constructed. We can not agree to the contention that |the Hoffman claims must be limited to a shelf showing a recess between the front rollers made by bending back the front strip and in no other way. The defendant’s recess made by fastening the two front rollers in a bracket riveted to the front strip is but another simple, mechanical means by which the intermediate part of the frame is “carried back to permit the admission of the hand between the roller sections,” as set forth in the plaintiff’s second claim. There is no new element introduced, no new or different result accomplished, no improvement made by this slight change in construction; and we must regard it as a colorable evasion merely.
“It ais well-known doctrine of patent law, that the claim of a combination is not infringed if any of the material parts of the combination are omitted. It is equally well known that if any one of the parts is only formally omitted, and is supplied by a mechanical equivalent, performing the same office and producing the same result, the patent is infringed.” Water Meter Co. v. Desper, 101 U. S. 332, 335; Fay v. Cordesman, 109 U. S. 408, 421; Seymour v. Osborne, 11 Wall. 516, 556; McClain v. Ortmayer, 141 U. S. 419, 425.
3. The next point in defendant’s appeal arises on the exceptions taken to the auditor’s report of the damages assessed on account of' the profits realized on sales of the two infringing constructions specifically named in the decree. Little, if anything, could be added to the statement of the auditor explaining the grounds of his findings. The burden of proof was upon the plaintiff, and he undertook to satisfy it by examining certain officers and agents of the defendant corporation and requiring statements from the books, showing cost, sales, prices, and so forth. Whatever uncertainty there was in arriving at the real profits was due to the business methods of the defendant and the character of the statements made by its officers in explanation thereof. The auditor’s statement of the process by which he ascer*221tained the sum reported is plain and careful, and we see no reason to disturb his conclusion. Like him, we perceive no conflict between that conclusion and the decision in Keystone Mfg. Co. v. Adams, 151 U. S. 139.
4. The last question for determination is that arising on the plaintiff’s appeal from so much of the decree as refused him recovery of the damages found by the auditor on account of the sales made by the defendant of what is called his “New No. 4 Shelf.”
The defendant’s exceptions were founded and sustained upon the ground that the inquiry into the sales of this construction were not within the terms of the decree declaring the infringement and referring the matter of damages thereby sustained to the auditor.
In this we think the court erred. Whilst that decree expressly mentioned the two constructions designated as No. 17 of defendant’s catalogues and “Exhibit Hausman’s sketch,” it was not necessarily limited so as to cover them alone.
This new No. 4 shelf is substantially the same as the other two. It has the same roller bearing frame, with the two front rollers in brackets riveted to the remainder of the frame. There is only a slight difference in form embodying no difference whatever in purpose, effect, or operation. The journals of the front rollers, instead of working in a bracket formed by an extension of the end bar of the frame and a riveted piece near the center, as in the two described constructions, revolve in a single piece bent forward at each end for the purpose; that is, riveted to the bar coming behind it. The ends being bent forward at right angles make a square recess between the two front rollers instead of the elliptical shaped recess of the other two and of plaintiff’s shelf. We agree with the auditor that this is but a color-able change of form, and that it therefore comes within the scope of the decree and the reference.
The authorities which he cites fully sustain his views of *222his duty and authority in the premises. Turrill v. I. C. R. Co., 5 Bissell, 344; Knox v. G. W. Q. M. Co., 6 Sawyer, 430, 436; Ball Glove Fastening Co. v. Ball & Socket Co., 53 Fed. R. 245; Wooster v. Thornton, 26 Fed. R. 274.
The evidence supporting his finding of the amount of the damages under this head is like that in support of the first item, which we have declared to be satisfactory.
It follows from what has been said, that so much of the decree as has been appealed from by the defendant below must be affirmed, and so much of it as has been appealed from by the complainant must be reversed, with costs to the latter. The cause will therefore be remanded with directions to reform the decree below by vacating so much thereof as sustains the exceptions to the master’s report, and by decreeing recovery by the complainant of the amount reported by the auditor as damages on account of the infringement of his patent by defendant’s “New No. 4 Shelf.” It is so ordered.