Mowry v. Whitney,
81 U.S. 620 (1871)

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U.S. Supreme Court

Mowry v. Whitney, 81 U.S. 14 Wall. 620 620 (1871)

Mowry v. Whitney

81 U.S. (14 Wall.) 620


1. Asa Whitney's patent of April 25, 1848, for an "improvement in the process of manufacturing cast iron railroad wheels," was for a process, not for a combination.

2. Where only vague and uncertain directions could be given as to the degree of foreign heat to be applied in any particular case, there, when a patentee in his specification, establishes a maximum and a minimum, the ascertainment of the proper intermediate degree may be left to the skill and judgment of the operator practicing the process.

3. It is as true of a process, invented as an improvement in a manufacture, as it is of an improvement in a machine that an infringer is not liable to the extent of his entire profits in the manufacture.

4. In such a case, the question to be determined is what advantage did the infringer derive from using the invention over what he had in using other processes then open to the public and adequate to enable him to obtain an equally beneficial result? The fruits of that advantage are his profits, and that advantage is the measure of profits to be accounted for.

5. When a patent is for an entire process made up of several constituent steps or stages, the patentee not pretending to be the inventor of those constituents, his claim to the process as an entirety does not secure to him the exclusive use of the constituents singly. What is secured is their use when arranged in the process.

6. The profits recoverable from an infringer are the measure of the patentee's

Page 81 U. S. 621

damages, and though called profits, are really damages, and unliquidated until a final decree is made.

7. Interest upon unliquidated damages is not generally allowable, and should not be alloyed before a final decree for profits.

Appeal from the Circuit Court for the Southern District of Ohio; the suit being a bill by Whitney for an alleged infringement by Mowry, of a patent which Whitney had for an improvement in the process of making wheels for railcars. The case was thus:

Wheels for rail cars require to be made in a special way. The "tread" of the wheel, as it is commonly called -- that is to say, the periphery -- the surface which runs over the rail -- must be very hard, or else it will wear out. On the other hand, the interior portions of the wheel, especially the hub, against which there is no friction, but on which there is great strain, need not be so hard, but must be very tough. Now here are requisites which by a law of the metal do not coexist in the same casting. Iron can be very hard only when it exists in a state of laminated crystallization, and then it is brittle. It can be very tough only when it exists in a state of granulated crystallization, and then it is soft. Now how is the "tread" to be made very hard and the interior very tough? This was the first problem in regard to iron car wheels. And it was thus solved. It had been long observed that where molten iron was cooled suddenly, it came out solid in the laminated or hard and brittle form, but when cooled slowly it came out solid in the tough and softer form.

The problem, of course, then was to cool rapidly the part of the melted mass of iron which was to make the "tread" of the wheel, and to cool more slowly the rest which was to make the interior of the wheel -- that is to say, the spokes and hub. To do this, the moulds into which the molten iron was to be cast were made of sand, surrounded by a circle of iron; this circle, called in the manufacturer's language a "chill." Iron being a rapid conductor of heat and sand a slow one, the part of the molten mass which came against

Page 81 U. S. 622

the iron or chill -- the part, in other words, of the molten mass which was to form the tread -- was cooled rapidly and came out in the laminated and hard (though brittle) form, while the parts of the wheel nearer to the hub, and especially the hub itself (which is a very thick part of the wheel, and where a very great strain is put when the rail car is in motion), cooling slowly, the requisite toughness was obtained, through this part (and particularly the hub, owing to the greater mass of it) coming out in the granulated and tough (though soft) form. The cut below, which represents a piece fractured from off that part of the wheel including the flange, which runs over the rail, indicates the two forms. The lower part or chilled "tread" (which in the ordinary car wheel itself is about half an inch deep) being distinguished by its laminated crystallizations and light gray color, and the upper part which runs in the direction of the hub by its granular crystallization, and a deeper gray line.


This problem, therefore -- the problem of obtaining a hard tread, and a tough interior and hub -- was solved. The thing desired was attained through the process of a sand mould with an iron "chill."

But of this good result in one way, a very bad one in another was the consequence. The wheels had no strength. And here was the cause. A mass of iron in its molten state

Page 81 U. S. 623

is larger than the same mass of iron when cold. Now here the molten iron was poured into the mould at the hub. Thence it flowed out through the sand mould of the spokes to the tread. There it came in contact with the chill, and as soon as it touched the chill, it was cooled, crystallized, and reduced in volume almost instantly. The metal immediately behind it, on the contrary, being in contact with the sand, parted with its heat more slowly and remained in a fluid or semi-fluid state much longer. Thus it happened that the periphery of the tread cooling and shrinking first, reduced its diameter, while the hub and spokes remaining in a fluid or soft state, presented little or no resistance to the contraction of the tread or rim. But as these spokes and


hub subsequently parted with their heat and passed into the solid state, an inherent strain began to be exerted between the rim and hub. The spokes were too short. Restoration of so much of their length as had been diminished by the

Page 81 U. S. 624

prior cooling and shrinking of the rim was demanded. All parts of the wheel having passed into the solid state and become comparatively unelastic, the spokes were severed by mere tensile strain before the temperature of the whole mass was reduced to that of the atmosphere. And the same result followed when, instead of spokes, disks or plates were used on the sides of the wheel, as shown in Figure 3.

To obviate this effect, a rude practice was, on the one hand, to uncover and expose to the air the thick parts of the wheel, sometimes, in addition, pouring cold water on them, while on the other the thin portions would be covered with burning fuel or hot sand. Still, however, the wheel would always strain and usually break.

The great matter now was to remove this difficulty. One plan was to divide the hub into sections, as shown in Figures 2 and 3, instead of casting it solid. This, of course, relieved the spokes from the tensile strain they were subjected to when connected with the solid hub, the spokes connected with each of the sections being left comparatively free to contract in length (only, however, it may be added) by carrying the section of hub to which they were attached with them.

To restore the requisite strength to the hub, the spaces between these sections would be subsequently filled with pieces of metal of the exact size of the spaces, and wrought iron bands would be shrunk on to each end of the hub so as to hold firmly together all the sections and the metal fillings or plates between them. Figure 4 illustrates the metal fillings or plates and bands that would be put into and on the hubs.


Wheels of this description were used till 1840. At that date, our roads began to be made more substantial, and higher velocities upon them being demanded, the cast spoke-wheel, thus filled out at the hub, began to show great defects. The expense of filling the spaces between the sections was considerable. There was difficulty in putting the

Page 81 U. S. 625

wrought iron bands on the ends of the hub and of boring out the divided hub so as to make it fit well on the axle and to secure it from becoming loose. Yet if these things were not effectually done, the wheel broke or changed its position on the axle, and the cars were thrown from the track.


To avoid these difficulties other means were employed to compensate for the unequal cooling and shrinking of the parts. These were nearly all confined to making the hub solid and connecting the hub and rim by a disk or plate, which was generally made double, two plates extending from hub to rim, in form convex, as in Fig. 5, or otherwise curved, so as to be susceptible, as was supposed, of contracting or expanding in diameter as much as would be required by the unequal cooling and contraction before noticed. In one of these forms, the hub was also divided, as shown in Fig. 5, it being expected that with the shrinking of the outer disks it would about close up. These wheels, when skillfully made, were an improvement on the spoke-wheel, with the hub divided into sections, so far as safety was concerned, but they were still faulty.

What, in this obviously not yet perfect art of making cast iron car wheels, was wanted was some way to make such wheels, having a solid hub, and either spokes, or any desired form of plates, single or double, straight or curved, as represented in Figs. 6 and 7 below, and possessing all the requisites of durability and strength in the respective parts, and yet free from the defects which had attended, up to this time, all wheels yet made, and not requiring the expenditure of special labor upon the mould or pattern before casting, nor upon the finishing of the wheel for use, after it had been cast and cooled -- some new and effective device which should eradicate and annihilate the difficulties which have been already imperfectly described, and which were still baffling manufacturers and inventors in this art. A new process of

Page 81 U. S. 626

prolonging the time of cooling, in connection with annealing wheels would, if rightly conceived, secure the desired end.


It was in this state of the art and of its necessity that Whitney made a claim for what he called "a new and useful improvement in the process of manufacturing cast iron railroad wheels," and on the 25th of April, 1848, obtained a patent for it for fourteen years.

The specification in his patent was thus:

"My improvement consists in taking railroad wheels from the moulds in which they are ordinarily cast as soon after being cast as they are sufficiently cool to be strong enough to move with safety, or before they have become so much cooled as to produce any considerable inherent strain between the thin and thick parts, and putting them in this state into a furnace or chamber that has been previously heated to a temperature as high as that of the wheels when taken from the moulds. As soon as they are deposited in this furnace or chamber, the opening through which they have been passed is closed and the temperature of the furnace or chamber, and its contents, gradually raised to a point a little below that at which fusion commences,

Page 81 U. S. 627

when all the avenues to and from the interior are closed and the whole mass left to cool no faster than the heat it contains permeates through, and radiates from the exterior surface of the materials of which it is composed. By this process, all parts of each wheel are raised to the same temperature, and the heat they contain can only pass off through the medium of the confined atmosphere that intervenes between them and the walls of the furnace or chamber; consequently the thinnest and thickest parts cool and shrink simultaneously together, which relieves them from all inherent strain whatever when cold."

"The figure below represents a vertical cross-section of the FURNACE OF CHAMBER, wherein is shown a pile of wheels as they"


"are placed to be annealed. The cover of the furnace, being movable, is raised when the wheels are put in, and then closed and covered with earth to prevent the too rapid escape of the heat. The damper in the flue leading to the chimney is also closed after the wheels are put into the furnace and the opening in the lower wall stopped by an iron plate banked with earth, which prevents the escape of the heat in that direction. [Footnote 1] "

Page 81 U. S. 628

"To heat this furnace, I have used anthracite coal, it requiring less than one-fourth of a ton to anneal two tons of wheels. The heat required to perform the process may, however, be obtained by the use of any other fuel that may be less expensive at the place where the process is to be performed, or the requisite heat may be taken in a suitable conduit from the furnace in which the metal is melted from which the wheels are made, after it has performed that office, to the chamber in which the annealing process is to be performed. In either case, however, the furnace or chamber must be made of such form, and have such appendages connected with it, as to enable the operator to control the quantity and intensity of the heat used by admitting more or less of it into the chamber, and of excluding it entirely."

"The advantages resulting from the process of prolonging the cooling and annealing as above described are that the wheels may be made much stronger, when made of the same weight, than they can be when cast and cooled in the ordinary manner, and railroad wheels having any form of spokes or disks connecting the rim and hub, if subjected to this process, will not require their hubs to be cast in sections and the spaces between the sections subsequently filled with some suitable metal and wrought bands put on to the hub."

"Wheels subjected to this process of cooling and annealing will be stronger without bands on their hubs than those of the same weight cast and cooled in the ordinary way having the wrought iron bands on. In this way, the original cost is diminished and the wheels rendered more durable than they would be when made in any of the ways heretofore employed."

"I do not claim to be the inventor of annealing castings made of iron or other metal, when done in the ordinary way; nor do I claim to be the inventor of any particular form or kind of furnace, in which to perform the process. But what I do claim as my invention and desire to secure by letters patent is the process of prolonging the time of cooling, in connection with annealing railroad wheels in the manner above described -- that is to say the taking them from the moulds in which they are cast, before they have become so much cooled as to produce such inherent strain on any part as to impair its ultimate strength, and immediately after being thus taken from the moulds, depositing them in a previously heated furnace or

Page 81 U. S. 629

chamber, so constructed, of such materials, and subject to such control that the temperature of all parts of the wheels deposited therein, may be raised to the same point (say a little below that at which fusion commences), when they are allowed to cool so fast, and no faster, than is necessary for every part of each wheel to cool and shrink simultaneously together, and no one part before another. [Footnote 2]"

Whitney being in possession of his patent as already described, one Mowry, of Ohio, conceived that he too had made a valuable improvement in the same branch as Whitney professed to have made one, and on the 7th of May, 1864, also obtained a patent. His specification, illustrated by a vertical cross-section of his furnace, says:

"My invention consists in the use of charcoal or other equivalent substance, interlaid with the wheels in the annealing pits, in connection with the regulated admission of air, for the purpose of heating the wheels up to a proper temperature, prolonging the heat, and permitting them to cool in the course of a given time, gradually, as will be more particularly explained below."

"The operation of my invention is as follows:"

"A layer of charcoal having been laid on the perforated bottom of the annealing pit, the wheels, as they are turned out of the moulds red hot, are placed in the pits, with a layer of charcoal between each wheel, a layer of charcoal being laid on the uppermost wheel, and on this a perforated metal plate is laid."

"The charcoal becoming now ignited by the hot wheels, the cover of pit is then laid on and the damper opened so as to admit just sufficient air to effect the combustion of the contained charcoal in the space of seventy-two hours, less or more, as may

Page 81 U. S. 630

be found necessary for the annealing operation. The draft of air in the apparatus shown on drawings is from above downward, but it may, without affecting my invention, be from below upwards by conveying the air from the horizontal flue up through the pits and through the aperture in cover, and from thence through flues into the main shaft or chimney C; the result will be the same in both cases, and the adoption of one or the other plan will be dictated by convenience."


Under his patent, Mowry employed a process of annealing such as it described, and Whitney thereupon filed a bill to enjoin him as an infringer. Mowry answered, denying infringement, alleging the invalidity of Whitney's patent for want of novelty and for want of utility,

"Inasmuch as the said process would ruin and destroy the hardness on the rim of the car wheels, known as the 'chill,' and thus greatly detract from the usefulness and durability of the wheels. "

Page 81 U. S. 631

A large amount of testimony being taken on both sides, the cause was brought to a final hearing on the pleadings and proofs, and all the issues being found for Whitney, the cause was referred to a master to taken and state an account of the gains and profits which the defendant had derived from the infringement of Whitney's patent.

The master reported, on the 1st of August, 1868, that Mowry had made use of Whitney's patent in the manufacture of 19,819 wheels, and for the use of the process in making these wheels charged him:

Profits on these wheels . . . . . . . . . . . $91,501.86

Interest on the said profits to

1st August, 1868. . . . . . . . . . . . . . 19,984.21

He further reported that Mowry, prior to the 1st of April, 1861, and without the use of the process complained of in this cause, had built up his business to its then condition. That the use of the process did not diminish, but did increase the cost of making the wheels manufactured by Mowry. That while Mowry used the said process, he did not make any difference in the quality of iron used for the manufacture of car wheels, nor in the weight or form of car wheels, nor by reason of the use of such process, in their price. That Mowry's business was apparently not increased by the use of the process, and that he had sold the wheels he had since manufactured without the process complained of as readily as those manufactured by use of the process, and at the same prices.

[The patentee himself, it should be here added, in 1862, when applying for an extension of his patent, had stated under oath that he believed there was no essential difference in the cost per pound of making cast iron chilled car wheels of the various patterns, and by the different modes in use, provided the same skill and system controlled the manufacture; that by his process he was enabled to make them lighter than those made in any other way for a similar service, and therefore could afford to sell them at the same price per wheel as other makers, and save the cost of the

Page 81 U. S. 632

difference in weight; that this saving of metal he deemed to measure the essential advantage he had over his competitors, and also the profits arising from his patent, and he estimated that ten pounds per wheel would be a fair average of the metal saved by his process. [Footnote 3]]

Mowry excepted to the charge made, as above stated by the master, of profit derived by the entire manufacture of the wheel, and the case was recommitted to the master with instructions to inquire:

1st. Whether the wheels made and sold by Mowry had or could have any market value without being subjected to the process patented by Whitney.

2d. If they had or could have been made to have such value by any annealing or slow cooling process outside of the Whitney patent, how much additional value, if any, they derived from being subjected to that patented process?

To this the master returned that he was unable to report any division of profits, and, being uninformed as to what was covered by the patent, he reported that if the entire process of reheating and prolonged cooling used by Mowry in the manufacture of the wheels was an infringement of the complainant's patent, the total profit realized by the defendant from the manufacture and sale of the wheels was due to the use by him of the complainant's invention.

He reported secondly that if there was no infringement of the complainant's patent, unless the wheels were subjected to the process of reheating -- that is to say if the process of slow cooling used in connection with reheating was old, and not a part of the complainant's invention, nor included in his patent -- no part of the profits realized by the defendant from the manufacture and sale of the wheels was due to the use by him of the complainant's invention.

[This second finding of the master the court set aside, sustaining an exception to it that not only the entire process described in the patent, but each part of such entire process, was the invention of Whitney, and the use of any material,

Page 81 U. S. 633

substantial and essential part of such entire process -- the slow cooling being a substantial and material part, whereby only an improved chilled cast iron railroad wheel could be made, and beneficial effects the same in kind, if not in degree attained, that were attained by Whitney's entire process -- was an infringement of Whitney's patent, and that the profits derived from the use of such material, substantial and essential part should be accounted for in this case.]

But the master, in addition to the second finding thus, as just mentioned, set aside, further found that had the wheels manufactured by the defendant been left to cool in the open air, they would have had no value as car wheels, and have been worth only the value of the iron of which they were made; that reheating in connection with slow cooling, or slow cooling without reheating, was indispensable to make marketable cast iron wheels of the configuration of those made by the defendant; that there was no reheating process for the manufacture of cast iron car wheels outside of the complainant's patent.

The master also found that the wheels could have been removed from the moulds and finished without being subjected to the reheating process or without any extraneous heat, and he specified two modes in which it might be done. Wheels so manufactured, he reported, have and did have, during all the time in which the defendant used the complainant's process, a market value equal to that of wheels manufactured by that process.

There were some other findings which may be briefly noticed:

1. That the 19,819 wheels were annealed wheels, and sold as such.

2. That if the complainant's patent included prolonging the time of cooling the wheels, as used by the defendant, the process conferred upon them their entire market value, above their weight in iron, but not so if the complainant's patent covered only the application of extraneous heat to the wheels after they are taken from the moulds.

3. That taking annealing to mean reheating in connection

Page 81 U. S. 634

with slow cooling, no other process of annealing in connection with slow cooling than that patented to the complainant and that described in the patent of the defendant appeared to have been known.

4. That the wheels made by the defendant required no treatment other than that described in the complainant's patent to complete them as annealed wheels.

5. That still taking annealing to mean reheating in connection with slow cooling, the annealed wheels could not have been made by any process outside the complainant's patent.

Upon these findings, the court below decreed against Mowry the entire profits made by him in the manufacture and sale of the wheels from beginning to end; the profits resulting from the reheating, and regulated slow cooling in connection, and those also which might have resulted from mixing and melting the iron, casting in moulds, making the chill, and from the possible advance on the iron above its cost, with $10,980.22 additional interest on the whole, from the 1st of August, 1868, when the original reports were made, to August 1, 1870; at which time the subject was finally heard.

The final decree thus stood:

Profits on 19,819 wheels . . . . . . . . . . $ 91,501.86

Interest to date of original report

(August 1, 1868) . . . . . . . . . . . . . 19,984.21

Interest on $91,501.86 (from August 1,

1868, to August 1, 1870) . . . . . . . . . 10,980.22



From this decree Mowry, the defendant, appealed.

Page 81 U. S. 639

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