any group will resemble each other for the purpose in view more closely than any individual in any group will resemble any individual in any other group.

"There is no property of objects which may not be taken, if we please, as the foundation for a classification or mental grouping of those objects, and in our first attempts we are likely to select for that purpose properties which are simple, easily conceived, and perceptible in a first view without any previous process of thought—but these classifications are seldom much adapted to the ends of that classification which is the subject of our present remarks." (J. S. Mill, System of Logic.)

It is clear that a number of objects may be classified on several different bases. For example, a number of books could be divided into groups (1) according to the subject of their contents; (2) according to the language in which the books are written; (3) according to the size of page; (4) according to the binding material; or (5) according to the color of the binding. Each of these may be useful classifications for some purpose. For the student of literature none is of value except the first; for the connoisseur in bindings, only the last three. A classification of animals including classes of land animals and water animals would hardly suit a student of zoology, as it would associate with the shad and perch such differently organized creatures as the porpoise, whale, and seal. Yet such a classification might prove very suitable for a student of fisheries.

Art as a basis.[1]—So in seeking a basis for a patent office classification the purposes of the classification should be the guide. Allegations of ulterior uses[2] (such as may be made merely because the inventor thought of applying his invention to those uses only, or in an effort to get the application examined in a certain division) and other superficial bases should be avoided. That basis will best suit the purpose which effects such an arrangement as will exhibit in suitable groups the "state of the prior art," by which is here meant not necessarily all the instruments of a trade or industry, or all the articles sold by a shopkeeper, as a stationer, but those means that achievep. 6 similar results by the application of similar natural laws[3] to similar substances.

As all inventions are made with the ultimate object of satisfying some human desire, the utility of an invention appears to be a natural basis of classification. It is apparent, however, that most inventions may contribute to numerous utilities besides the ultimate one. Many processes and instruments intervene between the seed planter and the wheaten rolls upon the breakfast table. The plow may be viewed as an agricultural instrument or as an instrument of civil engineering, according as it is used for preparing the field for planting or rounding a road. A radiating coil of pipe may be thought of as a condenser of steam or of alcoholic vapors, according as it is applied to one material or another; as a cooler or a heater, according to the temperature of a fluid circulated through it. A hammer may drive nails, forge iron, crack stone or nuts. Underlying all of these ulterior utilities, there is a fundamental one to which the normal mind will reach in its natural processes and there rest. The plow loosens or turns over the surface of earth; the coil effects an exchange of heat between its interior and exterior; the hammer strikes a blow. A classification of plows in agriculture, road building, or excavating, according to stated ultimate use; of a radiator coil as a steam condenser, still, jacket-water cooler, refrigerator, or house heater; of the hammer as a forging tool, a nail driver, or a nut cracker, appears to separate things that are essentially alike. But classifying a plow on its necessary function of plowing, a radiator on its necessary function of exchanging heat, a hammer on its necessary function of striking a blow, evidently results in getting very similar things together. Assuming for the moment that utility is a reasonable basis of division of the useful arts, it is deemed more logical to adopt as a basis some utility that must be effected by the means under consideration when put to its normal use rather than some utility that may be effected under some conditions. Two of the five predictables of ancient logic are property[4] and accident.[5] The capacity of the hammer to strike a blow, the capacity of the radiator coil to exchange heat, are in the nature of properties. The capacity of the hammer to crack nuts, of the coil to condense steam, are in the nature of accidents—something that followsp. 7 from the impact and the heat exchange because of the particular accidental conditions of operation. To select an accident as a basis of classification is contrary to the laws of thought.

It may be said then that the Patent Office classification is based upon "art" in the strict sense in which the word may be said to be used in section 4886, Revised Statutes, but not necessarily in the looser sense of industries and trades. A proper maintenance of the distinction between the word "arts" of the statute and the phrase "industrial arts" used in the sense of industries and trades is essential to an effective classification for the purposes of a patent office search. Similar instruments have been patented in three different classes, because of the statements that one was designed for cooling water, another for heating water, another for sterilizing milk; in four different classes, because of the statements that one apparatus was to separate solids from the gases discharged from a metallurgical furnace, another to separate carbon from the combustion gases of a steam-boiler furnace, another to remove dust and tar from combustible gas, and another to saturate water with carbon dioxid. Owing to the continuance of a classification based largely on remote use, many applications come into the office setting forth inventions of very general application which nevertheless have to be classified more or less arbitrarily in one of several arts in which they may be used but to which they are not limited.

Function or effect as a basis.[6]—Means of the useful arts are related in different degrees. Resemblances selected as bonds for a number of inventions may be more or less close. It is axiomatic that close resemblances should be preferred over looser ones for classification purposes. Processes and instruments for performing general operations, such as moving, cutting, molding, heating, treating liquids with gases, assembling, etc., are more closely bonded than those for effecting the diverse separate successive operations directed toward complex special results, such as making shoes, buttons, nails, etc. Means of the former sort perform an essentially unitary act—the application of a single force, the taking advantage of a