1894] NEW-YORK MICROSCOPICAL SOCIETY. 35 



writing or document and the date thereof, making a curious and 

 interesting history. 



The usual processes of paper-making are well known, but I will 

 mention enough of them to indicate why it becomes so difficult to 

 detect adulterations and admixtures therein, either chemically or 

 microscopically. The chief reason why we cannot separate the 

 component substances of paper microscopically, is because the 

 linen or cotton rags, or both of these mixed, are placed in the 

 *' beating machines," equipped with long knives and flail-like 

 arms, which tear up and beat out all traces of their original textile 

 nature. With protracted maceration in strong alkalies the mass 

 is reduced to a jelly-like pulp. This mass is retained in hot water 

 for many hours, bleached with chloride of lime, sized with gela- 

 tin, or resin soap, and alum dissolved in soda. China clay is 

 sometimes added to improve its weight and surface rather than 

 its quality. One would think that these tearing, macerating, and 

 chemical pulping processes would be quite sufficient to obliterate 

 all traces of the original fibres ; but when to this is added old 

 paper to be reworked, then the difificulty of optically separating 

 the original fibres becomes extremely aggravated, so that while 

 one knows upon microscopical examination that he has not pure 

 linen paper before him, he nevertheless finds himself embarrassed 

 in determining what he sees in the broken-up and tangled mix- 

 ture, however carefully he may arrange it upon the slide. You 

 may demonstrate this for yourselves by looking at slide No. 6, 

 this being our " suspected paper " which was offered for linen 

 (Plate 39, Fig. 6). 



When, however, a percentage of wood pulp ready for paper- 

 making is mixed with linen, or linen and cotton pulp, and espe- 

 cially if the wood is of the coniferous order, such as spruce or 

 white pine, etc., then the woody admixture is quite easily dis- 

 cerned, although it may have been cut to pieces and pulped. 



In slide No. 8 you will see a fair example of a spruce-pulp 

 paper by one of the chemical reductions, known as the " soda 

 process " (Plate 40, Fig. 8). 



Now as to the modes of manufacturing wood pulps for paper- 

 making. 



There are two general methods, one known as the " mechani- 

 cal " or "ground wood," and the other as the " chemical " pulp 



