do not so interpret this expression. In the first place the patent nowhere uses the words "by beating the air into the mass." Therefore these words, as quoted by the Supreme Court, were not quoted from the patent, but were taken from the testimony of a witness who used them in describing the process as discovered and developed by the patentees. This being so, we do not think these words, as used by the Supreme Court in describing the process, can be construed as a limitation upon the process.

It further appears that the Supreme Court, in distinguishing the process of the patent from processes of other patents relied on as inticipations, found that the lifting force which separates metallic particles of the pulp from other substances resides chiefly "in the buoyancy of the air bubbles introduced into the mixture by an agitation greater than and different from that which had been resorted to before." By this expression the defendant insists that the court explicitly limited the patent to agitation caused by mechanical means, thereby excluding from its scope such agitation by pneumatic means as was used in part in the defendant's practice. As this expression is susceptible of an entirely different meaning, presently to be considered, we find nothing said by the Supreme Court which indicates that it limited the agitation of the patent to agitation by mechanical means.

The defendant further maintains that the Supreme Court gave to the patent a narrow construction when it used these words:

"While we thus find in favor of the validity of the patent, we cannot agree with the District Court in regarding it valid as to all of the claims in suit. As we have pointed out in this opinion, there were many investigators at work in this field to which the process" of the patent "in suit relates when the patentees came into it, and it was while engaged in study of prior kindred processes that their discovery was made. While the evidence in the case makes it clear that they discovered the final step which converted experiment into solution, 'turned failure into success' (The Barbed Wire Patent, 143 U. S. 275 [12 Sup. Ct. 443, 36 L. Ed. 154]), yet the investigations preceding were so informing that this final step was not a long one, and the patent must be confined to the results obtained by the use of oil within the proportions often described in the testimony and in the claims of the patent as 'critical proportions' amounting to a fraction of 1 per cent. on the ore. *

We are inclined to the opinion that by this expression the court intended a limitation only upon that one feature of the patent to which the expression was addressed. The District Court had held valid certain claims in which the proportion of oil was described simply as "a small quantity," and the Supreme Court in reversing that finding and holding those claims invalid, used the quoted words of limitation in confining the patent to the results obtained by the use of oil in the critical proportions of less than 1 per cent.

From this recital of the litigation of the invention of the first patent it appears that in construing the claims of the patent we are greatly aided by the opinion of the Supreme Court in being told with authoritative finality that the process involves invention and in being shown in which of its elements invention resides; but it is equally clear that in determining the breadth and scope of the claims, we are without the aid of any adjudication in which their scope has been decided or even considered.

The elements of the patent in which invention is found are oil, air and agitation. These were old in the art, possessing as we have shown, known characteristics and functions, and had they performed in the process of the patent no new or different function or had they produced no new or different result, it is clear they would have anticipated the patent and defeated its claim to invention. But a finding by the Supreme Court that the invention was not anticipated by the old uses and results of these elements is in effect a finding that these elements as used in the process of the patent perform or develop new uses and functions or produce different results. And such we find to be the fact.

The invention, as we have said, is founded upon a discovery. Its patentability depends upon the medium disclosed in the patent by which the force or principle of the discovery is brought into action. Three new uses of old elements are disclosed by the patent, producing a new result. The first relates to oil.

The affinity of oil for metal was known, and though old, was employed in the invention; but that this affinity in a given condition is greatest when its quantity is relatively least or that the affinity increases with the decrease of oil below a given quantity (less than 1 per cent.) is the soul of the discovery and was wholly new. But the discovery did not consist of this alone. The newly discovered phenomenon of the minute quantity of oil is not a chemical phenomenon. Oil in pulp in minute quantity if inert and left alone will do nothing and produce nothing. Something must be done to develop it. The phenomenon not being susceptible of development by chemical change, is developed by physical change of the pulp. As a medium or means of producing that change and creating the condition under which the phenomenon arises, the patentees pointed out-agitation.

The agitation of the patent does several things, old and new. It mixes the oil with the metal of the ore. This is old. Then by its greater intensity and longer duration it stirs the pulp into a froth, developing at once its own new use as a frothing means and still another new function of oil-that of a frothing agent. Both are new.

But froth is made of air as well as oil. Air in bubbles is used for its old function of assisting or escorting metal particles to the surface. But it is also used for the entirely novel purpose of supplying one of the essential elements of froth, froth being the new result intended.

Thus oil is used for its newly discovered characteristics of greater metal affinity when in minute quantity and for its new function as a frothing agent; air for the new purpose of supplying an element of froth; and agitation for its new purpose of bringing the two together and causing them to co-act and produce the new result of a metalcarrying froth. In other words, in so employing these old elements for new purposes, the new things which the patentees told the art are that a radical decrease of oil in conjunction with a radical increase of agitation, develops to its highest potentiality the known affinity of oil for metal and produces a physical change in the pulp in the form of a froth by which metal recoveries are made possible and commercially profitable. The importance of these disclosures, scientifically and commercially, is manifest.

In approaching a consideration of the scope of the patent, we lay aside those features of the discussion in which the plaintiff demands by broad construction the highest reward for a great contribution to a feeble art, and in which the defendant, contending for a narrow construction, emphasizes the servitude of a great art to a patent monopoly. The rights of an inventor and of an art in an invention are established by law and are not affected by other considerations. Speaking generally, the statutes give an inventor a patent monopoly of his invention to the extent of his patent disclosures, and to that extent the art is servient to his monopoly. Everything touching the invention not disclosed by the patent is free to the art without regard to the value of the inventor's contribution. So the question of law in this case, involving as it does large interests and perhaps far-reaching commercial results, is no different from similar questions constantly appearing in controversies of smaller compass. The question simply is whether certain practices come within the scope of the patent claims. But the question of infringement has grown far beyond the borders of the case and we are really asked both by the plaintiff and defendant to determine the scope of the patent in such terms as will inform the art as well as the owners of the patent the precise field covered by the patent and the extent of the field left free to the art. Such a decision to be useful must of course be predicated upon facts that make it legally possible, for otherwise we encounter the futility and the mischief of construing a patent in general terms and without reference to the occasion or thing which calls for its interpretation. To avoid this error we shall confine ourselves to the precise issues of this case as developed by the evidence, and without regard to other considerations we shall construe the patent with reference to the particular practices which are represented by one party to be within its scope and by the other to be beyond it.

The defendant practiced four processes of ore concentration, using in all the fomenting agent of oil in the critical proportion of the patent. Two processes were practiced before suit was instituted, the third during the progress of the trial, and the fourth after the record had been completed and the trial closed. As the infringement found by the decree relates to the processes appearing in the record, only those processes are before us on appeal.

First Process.

The defendant company owns and operates a large porphyry copper mine at Miami, Arizona. The ore is low grade and of a kind peculiarly responsive in concentration to the process of the patent.

The defendant employed a metallurgical mining engineer to develop and install in its reduction works an oil-flotation concentration plant. The engineer made repeated visits to the mill of a neighboring copper company, a licensee of the plaintiff, studied the process of the patent there in practice, and reproduced it in the mill of the defendant. This was a small plant, of a capacity of but two tons per hour or forty-eight tons per day, operated during the period from December, 1913, to August 5, 1914. It was used evidently more as a testing or experimental

plant for another process then being developed than for commercial

purposes.

This constituted the defendant's first process, and as infringement was not disputed, we affirm without discussion that part of the decree holding infringement by this process.

Second Process.

On August 7, 1914, two days after the discontinuance of the first process, the defendant started its second process in a plant which it had constructed during the practice of the first. This plant may best be understood by a diagram furnished by the defendant and by its own detailed description of its operation appearing in its brief:

"The material treated in the flotation plant at Miami is received through the launder or trough A, the same bearing the legend 'Original Pulp Feed.' This material is a freely flowing pulp, and flows into the box or tank B, upon which the following inscription appears, 'Sump from Which Pulp is Pumped.' The oil or other modifying agent is supplied to the pulp through the pipe L, marked 'oil feed.' A centrifugal pump C raises the pulp from the sump B, and forces it upwards through a pipe D, from which the pulp passes into an inlet funnel E. The pulp flows from the funnel E downward through a pipe F and enters the Pachuca tank G through the side thereof, as shown in the drawing. A small air pipe H extends downwardly from the top of the Pachuca to a point near the bottom thereof, where it delivers an air jet at the point designated I. The small air pipe II is surrounded by a larger pipe J, open at both ends. There is an annular space between the pipes H and J, and the air entering the lower end of the large pipe J, through the pipe H, permeates the pulp contained in the pipe J with small bubbles, which have the effect of forming a mixture of air and pulp of lower specific gravity than the

pulp alone. The lightened column of air and pulp in pipe J rises and is projected against a conical deflector K, and then falls into the main body of the Pachuca. The circulatory movement of the pulp in the Pachuca tank has the effect of thoroughly mixing the oil with the pulp. The pulp flows from the top of the Pachuca tank into a box M, whence it is conducted by the launder or trough N to the air cells, marked 1, 2, 3 and 4.

"The air cells 1, 2, 3 and 4 are similar in construction. The bottom of each cell consists of four plies of canvas, beneath which are eight air compartments, separate and distinct from each other, extending in a series from end to end. The canvas bottom of the machine is inclined, thus making the cell deeper at one end than at the other, and it is for the purpose of getting an even distribution of air that the eight compartments are used, it being obvious that if there were a single air compartment most of the air would escape at the shallow end, where the water pressure is least. Air under slight pressure is supplied to the compartments beneath the cells 1, 2, 3, 4 and 5, by means of a blower designated by the letter M upon the drawing. The air is conducted through a pipe marked 'Air Main' from the blower, and branch air pipes, shown most plainly at the right of cell No. 1, conduct the air to the several compartments beneath the cells. The degree of air pressure necessary is quite slight, and, as stated by Mr. Yerxa, it is necessary to use merely enough pressure to overcome the hydrostatic head of the pulp and to force the air through the permeable medium, that is, the canvas bottom.

"The air so pumped beneath the canvas bottoms of the cells 1, 2, 3, 4 and 5 passes upward through the pores of the canvas into the pulp, and the bubbles rise through the pulp in a manner similar to the rising of the bubbles through a glass of carbonated water."

For the purpose of this discussion, the details of the apparatus and of its operation, may be simplified by referring to its four essential parts: C, centrifugal pump; E, a break or open space between the pipe of the pump and the Pachuca tank which does not appear on the diagram or in the defendant's account of the operation; G, Pachuca tank and its appliances; and 1, 2, 3, 4 and 5, Callow cells.

Before following the steps or rather the flow of the defendant's process, we should have in mind the theory of its practice. The defendant maintains that the process of the patent is "an agitation froth process," that is, a process by which the desired metal-bearing froth is. obtained by agitating pulp containing the critical quantity of the frothing agent (oil) "to cause" the froth to arise or "until" a froth is formed. It says that its process, in contradistinction to the process of the patent, is a "bubbles process" (containing the same critical quantity of the same frothing agent), by which air, introduced into the pulp from below, passes through the pulp "without any agitation whatever,' and arises to the surface in short-lived evanescent metal-bearing bubbles forming a "foam." It maintains that by introducing air into the pulp by sub-aeration it produces a foam or froth otherwise than by agitation, that nowhere in the process is there agitation, or that, at most, there is only such agitation as appears in the prior art.

Agitation "to cause" a froth or agitation "until" a froth is formed, being the disclosed means of the patent to produce the phenomenon of the critical quantity of oil, and aeration without agitation being the defendant's claimed means of causing or obtaining the same phenomenon from the same critical proportion of oil in the form of an evanescent foam, the controversy revolves around the elements of aeration and agitation.