Another point of resemblance between this kind of library material and that utilized by museums is the fact that its value is so often a group-value--possessed by the combination of objects of a certain kind, rather than by any one in itself. For instance, a common earthenware jar designed by John Jones in the Trenton potteries may have little value, but if you add to it a thousand other earthenware jars, or a thousand pieces of any kind designed by John Jones, or a thousand other specimens made in Trenton, the collection acquires a value which far exceeds the average value of its elements multiplied by thousands. The former may be five cents--the latter five thousand dollars. In the same way an illustration by Mary Smith, clipped from a trashy story in a ten-cent magazine, has little value--zero value, perhaps. But a thousand such illustrations showing the published work of Mary Smith from the time she began until she acquired standing as an illustrator, is worth while. It should not be necessary to tell librarians that the best way to make such a collection as this is not to search for each element by itself but to gather miscellaneous related material in quantity and then sort it. If you have a pile of slips to alphabetize, you do not go through the whole mass to pick out the A’s, and then again for the B’s and so on. You sort the whole mass at once, so that while you are segregating the A’s you are at the same time collecting the B’s and all the rest of the alphabet. Likewise, if you want the illustration work of Jessie Wilcox Smith, for instance, you need not hunt separately for bits from her pen; you need only clip all the illustrations from magazines and papers that would be otherwise discarded. Then you sort these by the names of the illustrators, and you have at once collections not only of Miss Smith’s current work but of that of dozens of other illustrators. This is applicable in a hundred other fields. It should be noted that this group value is potentially present in many large collections of material, whether classified or not into the particular groups in question. For instance, we have a large collection of locality post-cards, filed by cities and towns. Here are groups ready for use. If anyone wants views of Cedar Rapids, Iowa, or Stockton, Cal., to show to a class, or for use with a reflectograph, or to copy for newspaper work, they are already assembled. But also if someone is going to lecture on court houses, it is the work of only a few moments to assemble from the file a temporary collection of fifty or sixty examples. The same is true of buildings of any other type, say college dormitories, railway stations, libraries or warehouses, of parks, mountain scenery and industrial processes and of a hundred other things. The value here is a true group value; it is created by assemblage and becomes dormant again when the items are distributed to their proper places in the file.