and the chain lines still ran up and down. No matter how the book has been trimmed, it is always possible by this means to see that it was originally a folio. In a quarto the paper is again folded, so the chain lines run across the sheet, and a section of the watermark appears in the upper left corner of the sheet. With an octavo the chain lines run up and down, as in a folio.

As the earliest paper was made on crudely formed molds covered with a loosely woven cloth, we must accept the wove sheet as the original type of paper. The laid mold came into use a few centuries later, and as it was the first kind of mold from which a sheet of paper could be taken while wet, this invention must be considered the first real step in paper making, and it was from this original Persian laid mold that the art of paper making has developed. After the laid bamboo mold came the laid wire mold-first fabricated with iron wire and in later years with brass, the material used at present for

FIG. 1. By examining the laid and chain lines in old books it is possible to detect whether a volume has been reduced in size by trimming the margins.

both laid and wove molds. Then in the eighteenth century the woven. type of mold was reinvented, but instead of using the woven cloth of the Chinese, from which a sheet could not be taken while wet, woven wire was used, which furnished a firm and rigid surface. At the close of the eighteenth and the beginning of the nineteenth centuries came inventions for making paper by machine. These inventors used the original idea of the transfer, or Persian bamboo mold, only in the case of the machine the mold was continuous and formed the paper not in single sheets, as the hand mold, but in any desired length.

In modern machine-made paper the laid and chain lines are produced by means of a roller (dandy roll), which impresses these lines in the paper after the wet sheet has been formed. Therefore, machine-made paper of the laid type is nothing more than an imitation, for the laid wires are not necessary in the forming of the paper, as they are with a handmade sheet.

Smithsonian Report, 1921. Mitman.

PLATE I.

LEAD.

By CARL W. MITMAN,

Curator, Divisions of Mineral and Mechanical Technology, United States National Museum.

[With 6 plates.]
FOREWORD.

The Division of Mineral Technology, a part of the Department of Arts and Industries of the United States National Museum, is engaged in preparing exhibits designed to enhance the popular conception of the many mineral resource industries, their technology, economics and general social bearing. With the cooperation of active producers there have been obtained series of models, photographs, drawings, and raw and finished products which by their arrangement, set forth for many of the important minerals, the condition of their occurrence; the operations followed for their extraction; the processes of manufacture; the nature of the products and their adaptability

to use.

Unfortunately, the opportunity of visiting the National Museum is not had by everyone and the present article is prepared, therefore, to disseminate in story form the salient features observed in the exhibit devoted to the lead industry.

GENERAL CONSIDERATIONS.

The uses of lead in the things of everyday life are almost without end. It is present in the home, in paint, in glassware, china, and pottery, and in the piano; in the church, in the pipe organ, and stained-glass windows; in the office, in the typewriter, in the windowpanes, and window-sash weights; in the factory, in the bearings of all revolving machinery; in the automobile, in its engine bearings, tires, and even its license tag; in ships, airplanes, and locomotives. Without it the printing of newspapers, books, and magazines would be seriously hindered; madame would have difficulty in obtaining the right "hang" to her costume and duck hunting would be out of the question altogether.

Considering these random uses, together with the fact that there is an automobile available for every 10 inhabitants in the United