DISCOVERY 



in a further communication to Xatiire (1922, 109, 516), 

 confirm the a priori conclusions upon the observations 

 of Schonemann. In several MSS. of the thirteenth 



MARKING MADE WITH METALLIC LEAD. 



Fig. 3 

 Magnification 



Fig. 2.— marking made with LEAD PENCIL CONTAINING BORROWDALE 

 GR.WHITE. Period 1831. Magnification 20. 



Fig. 3.— marking made with pencil of COMPRESSED GRAPHITE. 

 Period 1843. Magnification 20. 



and fourteenth centuries ruled lines similar to those 

 described by Schonemann are present, and in each case 

 they are in a pigment of metallic lead or other metal. 

 All the early pencil writing in annotations in books 

 in the Bodleian is in a pigment of metal. Notable 

 instances of such writing are to be found in the horn 

 notebook of Casaubon (1613) and in the diaries of 

 Anthony Wood (1676-85). 



Pencils of natural graphite, made by cutting the 

 mineral into strips which were fi.xed in a wooden 

 holder, produce lines which show masses of brown or 

 black pigment, whilst in heavier strokes the fibres 

 of the paper are lit up by the adhering particles. 

 Occasionally particles of siliceous impurities will occur, 

 and will produce irregular disjointed striations appear- 

 ing white on the dark background of the pigment, 

 as shown in Fig. 2. 



The first occurrence noted of writing in a graphite 

 pencil in the Bodleian Library is in a note made by 

 Anthony Wood in A Collection of Poems on Affairs 

 of State (168S). The masses of pigment are quite 

 uniformly distributed and none of them shows the 

 lustre or striations of the particles left by lead or 

 other metals. The earliest instances of graphite 

 writing discovered in the British Museum were in two 

 notebooks of Sir Thomas Cotton, one of about 1630 

 to 1640, and the other 1640 to 1644. Other interesting 

 examples in the British Museum are to be found in 

 Hogarth's notebook, the pencil marks in which are 

 particularlv free from any siliceous striations, and in 



Flaxman's drawings of the early nineteenth century, 

 \\hich are in an exceedingly fine type of graphite. 

 The gradual failure of the Borrowdale graphite 

 mines led to the adoption of various sub- 

 stitutes. In the first place, graphite dust 

 was compressed into solid blocks, which w^ere 

 then cut up like the original mineral. Pencils 

 made from such compressed graphite pro- 

 duced markings which can be readily dis- 

 tinguished from the natural graphite. The 

 lines show a regularly distributed series of 

 high lights quite different from the lighter 

 striations due to siliceous impurities in 

 graphite, and apparently due to distribution 

 of pigment on the fibres of the paper. 



Subsequently the process of making pencils 

 invented in 1795 by Conte, of Paris, came 

 into general use, and by about 1870 had 

 practically displaced the older method. 



In the modern method of pencil-making, 

 finely powdered purified graphite is mixed 

 with China clay in proportions varying with 

 the hardness of the pigment required, and 

 the mass kneaded into a paste, which is 

 forced through small openings in a cylinder 

 so as to produce circular threads of pigment. These 

 are dried, heated in a covered crucible, and glued into 



Fig. .|.— lines made with a modern CHEAP COMPOSITE 



pencil. 



The striations indicate the sequence of strokes. Magnification 20. 



grooves in a wooden holder. In some processes wax 



is forced into the finished pigment by means of pressure. 



The microscopical appearance of the lines made by 



