(concurring). I will briefly state the ground upon which my concurrence rests:

The Supreme Court, in sustaining the claims, carefully noted those which were limited to a fraction of 1 per cent., and the decision explicitly confined the patent to the results obtained by the use of oil within the proportions often described in the testimony and in the claims. Claims 1, 2, and 3 use the language, “amounting to- a fraction of 1 per cent, on the ore.” Claims 5, 6, and 7 express amounts, percentages on the ore. Claim 12 uses the words of limitation, “amounting to a fraction of 1 per cent, .of oil on the ore.” Claims 9, 10, and 11 make no reference to a fraction of 1 per cent., but do contain the words, “a small quantity of oil.”

The essence of the invention was in the use of this extremely small fraction of 1 per cent., and the Supreme Court, while sustaining the fraction of 1 per cent, claims, held invalid the small quantity claims, 9, 10, 11, because they were too broad. No monopoly could be given on the use of a small quantity of oil for that was old. It was new, however, to avoid the use of larger quantities. The patent must be confined to the use of critical proportions. Now,'keeping in mind that by the decision the court has limited the invention to the critical proportions often described by the testimony and in the claims, we naturally ask: What are the critical proportions described in the specifications ? Page 1, line 79, of the specification says:

And on line 96 we have :

*247 We thus have given to us one-half of 1 per cent, or less as the critical proportion described — preferably one-tenth of 1 per cent, is to be used.

We also ask: What is the evidence wherein there is often described the “critical proportion”? A summary'of it is that it is very nearly one-tenth of 1 per cent, or two-tenths of 1 per cent, as may be required for particular ore. All through the evidence it appears that minute and critical amounts of oil are to be used as necessary to make the process successful. From one pound of oil to the ton of ore ’(five-hundredths of 1 per cent.) to four pounds per ton (two-tenths of 1 per cent.) were the limits in practical work as stated by witnesses.

Again, when counsel had the colloquy (quoted in the opinion of Judge ROSS) with the Supreme Court, the guiding thought evident in the mind of the inquiring justices was to stamp precision upon the point when invention in the process began to appear. With apparent definite purpose of meeting the interrogatories, plaintiff told the court that “invention” began to come when in the descending uses of percentages of oil as small a quantity as five-tenths of 1 per cent, was used, and was first present when three and two-tenths of 1 per cent, was used. Of course, a court should cautiously consider a response often quickly made by counsel in answer to questions put from the bench lest an injustice may follow by attaching undue weight to an isolated argumentative answer. But in this matter- we are earnestly trying to gather the scope and accurate meaning of the expressed thought of the court. We may therefore refer to the fact that the exact position of the plaintiff as to the invention was called for, not once, but twice, not generally, nor indirectly, but positively, simply and unequivocally. Hence, in the controversy as to the true interpretation of the opinion the questions put and answers given may be fairly resorted to, not as conclusive at all, but as aids toward a better understanding of the statement of the limitations of the claims of the patent and of the definition of the invention included in its language.

Nor do I think there is ground for saying that discrimination was had between known oils — whether vegetable, mineral, or animal. To oily liquids which have a “preferential affinity to metalliferous mat- „ ter” must the plaintiffs be held, and in using kerosene or fuel oil defendants are but employing oils which the patents authorize the use of', and when defendants use proportions beyond the critical ones of oil — ■ not oleic acid, but other oils — they are not infringing. Oils doubtless vary in being adaptable for use. Some will probably secure more froth than others, and oil formulae may in their ingredients depend upon the particular ore to be treated and upon the economic relationship to the problem under solution. But the froth developed in using the minute quantities of oil is, I think, essentially of a character like the froth shown when different quantities of oil are used — the difference being largely by reason of a special quantity or kind of oil or the special extent of the agitation applied. The experiments made before us prove this.

In the Cattermole process the froth was held to be distinguishable from the froth produced in the patented process of the critical pro *248 portion of oil by the fact that certain remarkable and great results come from the use of the critical proportion which were not obtained when the quantity used in the Cattermole process was employed. By using the critical proportion of oil as defined, patentees get the maximum froth. They have discovered a process — not a froth — and the process is limited to the use of oil in the specified critical proportion.

The sequel of these views is that, inasmuch as defendants keep out of the limits made for the plaintiff by the decision of the Supreme Court by using more than the critical proportion, they do not use plaintiff’s process.