Sullivan Machine Co.,' was a case involving a patent for a rock-boring implement, consisting of a hollow metal boring head armed with diamonds, and which when moved with a combined rotary and forward motion, bored an annular hole into rock, leaving a central core to be subsequently broken by a wedge and then readily removed. The defendant used

a rock-boring tool, consisting of a hollow metal boring head, but having its bottom partly plugged so as to leave two holes elsewhere than in the centre of the head, and having a convex surface armed with diamonds. This tool bored a simple hole into rock without leaving any core to be afterward removed. The change of form involved a modification of the action, and perhaps a modification of the utility of the invention, but it was held not to avoid infringement of a claim which did not mention the annular form of the implement.

$368. Elizabeth v. Pavement Co.' was a case based on the Nicholson pavement patent. That pavement consisted primarily of rows of parallel-sided wood blocks, set endwise, on a continuous foundation, the rows being separated by parallel-sided strips of board, set edgewise between them, and resting on the same foundation, and about half as wide as the blocks were long. The defendant made a pavement differing from the Nicholson in nothing, except that the sides of the strips were not parallel with each other, the strips being thicker at the top than at the bottom edge, and except that the upper angles of the strips were let into corresponding notches cut in the sides of the blocks. The Supreme Court held that though this change in the form of the blocks and of the strips might constitute an improvement in point of utility, it did not operate to avoid infringe

ment.

$369. Patents for compositions of matter give rise to questions of infringement somewhat peculiar to themselves.

'American Diamond Rock Boring Co. v. Sullivan Machine Co. 14 Blatch, 119, 1877.

Elizabeth v. Pavement Co. 97 U.

S. 137, 1877.

Infringement depends, in such cases, upon sameness or equivalence of ingredients, and upon substantial sameness of the proportions of those ingredients. Omission of one or more of the ingredients of a patented composition of matter, avoids infringement, as truly as omission of one of its parts avoids infringement of a patent for a combination of mechanical devices.' Addition to a patented composition of matter, of an ingredient which the patent purposely avoided, and which when added substantially changes the character of the composition, also avoids infringement." But an addition which results in no substantial change of character, and which was made merely for the purpose of an attempt to evade the patent, will not have that effect."

§ 370. Substitution of one equivalent for another, in a patented composition of matter, is generally as ineffectual to avoid infringement as is like substitution in a machine. An equivalent for one ingredient of a patented composition of matter is anything which in that composition performs the same function as that ingredient. In the case cited, it was held that chloride of zinc in solution was an equivalent of common dry salt, in the composition of matter covered by the patent at bar, "because in the process of manufacture they practically produce the same results." No attention was given to the question whether they produced that result in substantially the same way. So also the Supreme Court has held that the term "equivalent" means "equally good " when it refers to the ingredients of compositions of matter.' Where the composition of matter involved, is a compound of metals, an equivalent of either of those, is another metal having similar properties, and producing substantially the same effect in that composition."

§ 371. A substituted ingredient may perform the required

function better than the patented ingredient, and may perform that function in a somewhat different manner, and still be an equivalent for the latter.' In the case cited the patent covered a compound of nitro-glycerine and absorbent matter, of which infusorial earth was stated to be the preferred variety. The absorbent matter, when mixed with three times its weight of nitro-glycerine, absorbed the whole, and still retained the form of a powder. This compound made dynamite. The defendant's compound consisted of nitro-glycerine and mica scales mixed in nearly equal proportions, the mica scales not absorbing the nitro-glycerine, but merely holding it in suspension upon their surfaces. This compound was called mica powder. Its use at the Hoosac Tunnel demonstrated its superiority over dynamite, in point of efficiency, economy, and safety; and there is evidently a difference between a powder which absorbs a liquid as in minute capillary tubes, and one which does not absorb, but which carries a liquid upon the surfaces of its particles. But notwithstanding these differences Judge SHEPLEY in an accomplished opinion, held the mica powder to infringe the dynamite patent. So also, in a later case on the same patent,' the same judge held a certain gunpowder to be an equivalent of the infusorial earth, because it performed every function of the latter substance, though it also performed the additional function, at the time of the explosion of the compound, of co-operating with the nitroglycerine in rending the rock, instead of remaining, like infusorial earth, an inert substance. The doctrine which results from this case is that one ingredient is an equivalent of another in a composition of matter, if it performs the same function, even though it also performs another function, which that other is wholly incompetent to accomplish.

§ 372. When a patent expressly states that the composition of matter which it covers, does not include a specified ingredient of similar compositions, the substitution of that

Atlantic Giant Powder Co. v. Mowbray, 2 Bann. & Ard. 447, 1876.

Atlantic Giant Powder Co. v. Goodyear, 3 Bann. & Ard. 161, 1877.

ingredient for one of those covered by the patent, is enough to avoid infringement, even though the two ingredients perform the same function in that composition of matter. But this does not amount to saying that the two things are not equivalents. It merely amounts to the doctrine that a patentee may disclaim a particular equivalent if he chooses.' And where a particular construction is disclaimed that disclaimer is binding even if it was unnecessary.

§ 373. Changes of the proportions of the ingredients of a composition of matter will not avoid infringement of a patent for such a composition, where those changes do not affect its essential character in any way more important than to increase its bulk more than they increase its cost.'

§ 374. The doctrines of the last five sections appear to be applicable to compositions of matter in general, whether they consist of chemical unions, or of mechanical mixtures, or of metal amalgams. Jurisprudence will doubtless follow science, if science hereafter shows any reason for distinguishing between the different classes of compositions of matter in respect of questions of infringement; but no such distinctions are yet traceable in the adjudicated cases.

§ 375. A design patent is infringed by any design which, to general observers interested in the subject, or to purchasers of things of similar design, has the same appearance as that of the design covered by the patent. The fact that an analysis of two forms of design discloses differences between them, is therefore insufficient to show lack of that substantial identity of appearance, which constitutes infringement. Such a question of identity is to be decided on the basis of the opinions of average observers, and not upon the basis of the opinions of experts.

§ 376. The comparative utility of the plaintiff's and the

1 Byam v. Farr, 1 Curtis, 260, 1852. Cartridge Co. v. Cartridge Co. 112 U. S. 624, 1884.

3 Eastman v. Hinckel, 5 Bann. & Ard. 1, 1879.

4 Gorham v. White, 14 Wallace,

528, 1871; Perry v. Starrett, 3 Bann. & Ard. 485, 1878; Dryfoos v. Friedman, 18 Fed. Rep. 824, 1884; Tomkinson v. Mfg. Co. 23 Fed. Rep. 895, 1884.

defendant's process, machine, manufacture, or composition of matter, is not alone a criterion of infringement; because the observed superiority of one over the other may have arisen from superiority of the materials or of the workmanship used in constructing the specimens under inspection. Indeed it has been held that the superiority or inferiority of utility in a defendant's machine, does not necessarily import non-infringement, even where it can be traced to slight differences in mode of operation.' No man is permitted to evade a patent by simply constructing the patented thing so imperfectly that its utility is diminished.' On the other hand, a defendant's machine may be better than that covered by the patent in suit; but if that superiority resulted from some addition to the latter, it will have no tendency to avoid infringement. Nor is infringement avoided by the fact that the defendant constructed and used his machine to produce one of the simpler of the forms of things produced by the machine of the plaintiff, and was thus enabled to produce a larger number in an equal space of time. The superiority or inferiority of a defendant's process, machine, manufacture or composition of matter, as compared with that covered by a patent upon which he is sued, can generally be traced to its cause. When that can be done, attention should be taken from the difference in utility, to the cause of that difference. Non-infringement will result if that cause is such a difference in function, mode of operation, or character of construction, as is of itself sufficient to justify that conclusion. In some cases, however, it may not be possible to ascertain the cause of the observed difference of utility between two inventions, or to detect the existence of any such cause otherwise than by its effects. In such a case, a decided difference of utility is evidence tending to show substantial

1 Waterbury Brass Co. v. Miller, 9 Blatch. 77, 1871; Shaver v. Mfg. Co. 30 Fed. Rep. 72, 1887.

2 Chicago Fruit House Co. v. Busch, 2 Bissell, 472, 1871; Roberts . Harnden, 2 Clif. 506, 1865.

3 Pitts v. Wemple, 1 Bissell, 87, 1855; Carter v. Baker, 1 Sawyer, 512, 1871.

Blanchard v. Beers, 2 Blatch. 420, 1852.