68 FEDERAL REPORTER.
and silicious marl contains 50 per cent, of the same chemical substance, a grant of the exclusive right to use infusorial earth, or silicious marl, gave also the right to use quartz, flint, or feldspar; the five articles being, substantially, silica. The sufficient answer to this theory is that, acknowledging the facts which have been stated to be true, and that these articles are, chemically, very similar, yet practically, for use in the arts, the respective classes of articles which are named in, the two patents possess very different properties. Infusorial earth is a vegetable tissue, "porous and delicate in structure," friable and of chalky texture, and not possessing the hardness and sharp angles and needle-like points of powdered quartz, flint, and feldspar, qualities which cause the quartz, flint, or feldspar to find a permanent lodgment in the pores of the wood, and to thoroughly fill them, so that a new, hard, unabsorbent, permanent surface is formed. As charcoal and the diamond are alike chemically composed of carbon, yet are very different substances in the arts, and are used for different purposes, so quartz and infusorial earth, though chemically similar or substantially identical, are dissimilar in the uses to which they are adapted. Infusorial earth, though chemically silica, is unfitted for the purposes of filling wood, for the reasons which render chalk or starch unfitted, while powdered quartz bas been found to possess qualities which make the plaintiff's article the only efficient and useful filler known to the cabinet manufacturers of the country. Silicious marl is as illy adapted as infusorial earth, because, while marl contains more sand than is found in infusorial earth, yet the sand is in rounded and not angular grains. Feldspar breaks, like quartz, into angular fragments, and is also non-absorbent.
The chemical character of the articles named in the two patents, and the difference for practical use between the two classes of articles, are tersely and clearly stated in the following extract from the testimony of Prof. Samuel W. Johnson, one of the experts called by the plaintiff. The scientific experts of the respective parties were not at variance in regard to the scientific facts, or the scientific conclusions from the
