March 4, 1920] 



NATURE 



'3 



heavier strokes they are disjointed and irregular. markings in ordinary metallic lead for crr^nhJ, 

 Jhe fibres of the paper may be brilliantly lit up Throu/h the kindness S Mr T P ri ^ ^r 

 LP^^.^'!,'!!:„«,L^^_^-J"^^-P^'^^,-h-H reflect th^ MSS^tpt^met I ht'^bein able ' ^TI'v^.l 



ight, especially in those places showing a metallic 

 Justre to the naked eye. Less pure forms of 

 [raphite show more numerous striations, but 

 *iese are always more or less disjointed and 

 regular, and quite distinct from the fine stria- 

 ions in modern pencil markings. 

 The composite pigments (containing sulphur) in 

 irly specimens of pencils in South Kensington 

 [useum, which Mr. T. H. Court kindly placed 

 my disposal, show a faint greyish pigment, with 

 ;asional striations, whilst Brockedon's graphite 

 '843). (Fig. 2) and other kinds of compressed 

 raphite produce lines which show a rich black 

 igment with silvery dashes and lines distributed 

 Fairly uniformly all over 

 the field. 



Modern pencil com- 

 positions, mainly of 

 graphite, clay, and wax, 

 all have a similar micro- 

 scopic appearance in the 

 vertical lines made by 

 them on paper, which is 

 quite different from the 

 markings of the old 

 pencils of natural 

 graphite, and in most 

 cases from those made 

 from the o 4 d c o m - 

 ■ pressed graphite pow- 

 der. In the modern pig- 

 ments the fine siliceous 

 particles, derived from 

 the clay and impurities 

 in the graphite, are 

 evenly distributed, and 

 appear in the pigment 

 on paper as fine beaded 

 striations, which are 

 uniform and parallel 

 throughout the line 

 (F'g:- 3)- Chemical 

 methods of d i s t i n 

 guishing between 



these pigments have been described by the present 

 writer (/. Soc. Chem. Ind., 1919, xxxviii., 383T). 

 Some particulars of early pencil markings are 

 given in a curious book by C. T. Schonemann 

 [I'ersuch eines Systems der Diplotiiatik, Leipzig, 

 1818. 2 vols.) upon the codices preserved in the 

 libraries in Germany. In vol. ii. (p. 108) it is 

 asserted that lines in blacklead (Reisblei) had 

 been drawn on the "Codex Berengarii 

 Turonensis " of the eleventh or twelfth century, 

 which was in the Wolfenbiittel library. The 

 "Codex Guidonis Aretini de Musica " (eleventh or 

 twelfth century) in the Gottingen library contained 

 vertical and horizontal lines showing traces of 

 blacklead (p. 112), whilst the "Codex Theophili " 

 (twelfth century) in the Wolfenbuttel library 

 showed very fine vertical lines in blacklead. 



Now, as graphite was not known until about 

 1560, it is obvious that Schonemann mistook the 

 NO. 262 VOL. lOS] 



ite. 

 , . , ^. the 



department, I have been able to examine 

 specimens of early pencil marks in the writing 

 and drawings in manuscripts in the British 

 Museum. The earliest example was a drawing 

 in the Stowe MSS., "Arms of Ancient Nobilitie" 

 (705). of the early seventeenth century. The 

 particles composing the lines of this drawing all 

 reflected the light brilliantly, but were much 

 smaller, and lacked the striations which are 

 characteristic of metallic lead. On the other hand, 

 the lines had not the appearance of any form of 

 graphite, the particles being disjointed and not 

 showing any connecting interrupted striations, as 

 are often to be seen in lines of graphite having a 

 metallic lustre. It is therefore probable that this 



I. — Typic il early g aphite 

 marking. 1831. X 20. 



KiG. 2. — Brockedon's compressed FiG. 3. — Typical modern Cumposite 

 graphite, 1843. (M.ark made pencil. X 20. 



by specimen 

 M useum). 



GeoloKiral 



drawing was done with a metallic pencil in which 

 lead did not predominate. 



A later MS. (1691) (Add. 



;5o) includes 



drawings in which the lines show the large 

 isolated particles with the vertical striations char- 

 acteristic of metallic lead. In another Stowe 

 MS., 686 {circ. 1630), the lines in the drawings have 

 the appearance of ordinary graphite. The pencil 

 markings in two note-books of Sir Thomas Cotton 

 (Harley, 6018, about 1630-40) and Cotton .Ap- 

 pendix, xlv. (1640-44), have all the characteristics 

 of graphite. 



The writing in Lord Hardwicke's "Notes on 

 Briefs" (1718) is undoubtedly in graphite, but a 

 drawing by Vertue (Add. MS. 21 11) (1741) 

 has the appearance of metallic pigment. A 

 note-book of Hogarth (Egerton MS. 301 1) (prior 

 to 1753) contains heavy pencil writing, the pig- 

 ment of which is a particularly rich graphite. 



