These four classes of libraries, memory libraries, pictorial object libraries, “mnemonic” libraries, and picture book libraries, form thus the field. All of them existed before what may be called historical libraries; all are found among uncivilized peoples of all times; all have their faint remainders in popular custom among modern civilized nations, and suggestions of all may be found in child-study. Three of these classes, memory libraries, mnemonic libraries and picture book libraries, correspond to well recognized book forms. The term “mnemonic”, which is commonly used to include quipus, message sticks, wampum, and similar records, is itself not a very exact term, since all outward symbols, whether representative or conventional, are mnemonic. Moreover, what is generally meant by the term is the use as symbols of objects which do not represent or directly suggest their meaning—in short, of object signs with conventional rather than pictured meaning but as a matter of fact image signs with conventional meaning i.e. all ideograms or phonograms are equally “mnemonic” with conventional objects. A better distinction is therefore into the memory libraries, object libraries (including both representative, or pictorial, object sign collections and conventional object sign collections) and image libraries (including also both representative or pictorial images and arbitrary or conventional signs). For practical purposes, however, we may perhaps use the terms, memory, object, mnemonic, and picture, understanding by object, pictorial object, by mnemonic, mnemonic object and by picture, pictorial image, as distinguished from the mnemonic or conventionalized images known as ideograms and phonograms. To avoid confusion in this matter it must be kept clearly in mind that writing is not picture writing because its symbols are pictures, but because they picture something. If an ox’s head or its image (aleph or alpha) stands for an ox it is pictorial writing but if it stands for “divinity” it is ideographic and if, as it usually does, it stands for the sound “a” it is phonetic-alphabetic writing: It is pictorial writing only when it suggests its own meaning. Again it must be said that pictorial writing is not confined to image writing as is usually implied by the phrase “picture writing” but applies just as well to objects. A real ox’s head and horns may mean “ox” or “divinity” or “a” just as well as a painting, drawing or sculpture of it.