M. TECHNOLOGY. 541 



any, greater, while there are the advantages of cheapness of 

 material in the sulphate of soda and of quality in the glass, 

 since it may contain much less alkali. The number of fur- 

 naces need not necessarily be increased, as the same furnace 

 may be used for the different operations. 14 (7, CCXV., 

 1875,358. 



THE MICROSCOPIC STUDY OF FIBRES USED IN THE FABRICA- 

 TION OF PAPER. 



The study of vegetable fibres has already occupied many 

 observers; and the classical memoirs of Aleau and Vetillart 

 are well known. These researches have generally had for 

 their object the application of vegetable fibres to the textile 

 arts; their application to the manufacture of paper has been 

 less fully considered, but forms the- subject of an extensive 

 work recently published by Gerard, who has especially stud- 

 ied those vegetable fibres that enter into the composition 

 of the pulp of the paper manufactures. He has determined 

 with the microscope the form, dimensions, and special char- 

 acters of these fibres, and, in order to illustrate his results, 

 has reproduced the microscopic appearances by means of 

 photography. He states the conditions which must be ful- 

 filled by the fibre that is to produce good paper as follows : 

 First, with reference to the length of the fibre, he finds that 

 the pulp styled " short refined" is composed 'of fibres of from 

 0.3 to 0.5 of a millimeter in length, while if it is from one to 

 one and a half millimeters long, it is " long refined." Rarely 

 does it surpass this latter length; and as there is no vegetable 

 fibre that he has examined which is not at least equal to this 

 latter length, he concludes that they are all, so far as that is 

 concerned, proper for the manufacture of paper. Second, it 

 is an important consideration that the fibre should be fine as 

 well as lon<r in other words, the ratio of its length to its di- 

 ameter should be at least fifty to one. Third, the fibre should 

 be elastic, and submit to twisting with ease. It is this that 

 gives solidity to the sheet. On the other hand, the tenacity 

 of the fibre is a matter of only secondary importance; as is 

 seen if we notice that when a sheet of paper is torn the fibres 

 themselves are never torn, but simply slide over and separate 

 from their neighbors. According to their relative value in 

 the manufacture of paper, he classifies the fibres as follows: 



