42 



KNOWLEDGE & SCIENTIFIC NEWS. 



[Feb., 1905. 



Cnj'Juctfd h'l F. Shillington Scales, f.r.m.s. 



Fibrous Constituents 

 of Paper. 



Paper is generally understood to be made from 

 "rags." This is, however, only partially true, as 

 papers maj- be considered to be roughly divided into 

 two classes : white printing and writing papers, of 

 which only certain of the writing papers have much 

 rags in them; and coarse wrapping and bag papers, 

 including brown papers, which are almost entirely 

 innocent of rags. Of late years in particular a revolu- 

 tion has taken place in paper-making by the use of 

 wood-pulp. Twenty years or so ago the use of wood 

 was limited to what is known as " mechanical wood- 

 pulp," short broken fibres torn from logs by means of 

 some grinding apparatus, and it was considered im- 

 possible for satisfactory fibres with good " felting " 

 properties to be obtained from so stiff and intractable 

 a substance as wood. Then came the introduction of 

 chemical wood-pulp, in which the logs of wood have 

 been treated by the soda bisulphite or sulphate pro- 

 cesses, the result being soft white fibres which are now 

 more largely used in paper-making than any other 

 material. 



The testing of a sheet of paper is, in England, almost 

 entirely a question of experience. Colour, feel, hard- 

 ness, absorbent properties, strength, freedom from dirt, 

 specks, and other imperfections — all these are decided 

 by looking at and handling the paper only, and the 

 buyer would probably be much puzzled if it were 

 suggested that he should make a microscopical 

 examination of the papers he had bought. The result 

 is that there is in England no standard of comparison 

 by reference to which disputes as to qualitv may be 

 readily settled. In Gcrinany, on the other hancJ, at 

 Charlottenburg, there is a Government Laboratory for 

 the sole purpose of testing papers, not only those used 

 by Government departments, but any others which may 

 be submitted. This does not necessarily show, how- 

 ever, that such a laboratory is needed here, for 

 whilst a more uniform set of standards might be 

 of service, the requirements of various papers vary 

 -so greatly that rigid, inelastic tests may easily be very 

 misleading. 



The microscopical examination of paper, however, 

 limited, as it generally is, to the ascertaining of the 

 fibres of which the paper is made, has no such dis- 

 advantages other than those due to the necessity for 

 training and experience in such a matter, and it is a 

 matter of surprise that this branch of paper-testing has 

 not received more attention in this country. It may be 

 of interest to many of the readers of these columns if I 

 endeavour briefly to explain the methods of recognition 

 of the various fibres, avoiding as far as I can all 

 technicalities. 



(Tn !•> i-fntinued.) 



Royal Microscopical Society. 



/\t a mcetiiii; lulil on I )rt'i'ml)or Ji at jo, Hanover 

 Square, Mr. G. C. Karop in the chair, Mr. Conrady read 

 a short paper explaining .in experiment he exhibited to 

 prove the phase-revers;il in the second spectrum from a 

 grating of broad slits, the mathematical proof of which 

 was given in his paper on " Theories of Microscopical 

 \'ision," read before the Society at its last meeting. 

 The object consisted of two gratings, one above the 

 other, similar in e\cry respect except that one had 

 broad and the other narrow slits. In accordance with 

 what was theoretically predicted by the author, the 

 difference was brought out when the direct light plus 

 the first and second spectra of one side were admitted, 

 but when the direct light was cut off by the movement 

 of a shutter the image of the broad slits underwent a 

 startling change. The lines jumped across to positions 

 midway between the correct ones, showing there was 

 an antagonism of phase between the light of the first 

 and that of the second spectrum. Sonic photographs 

 were exhibited bv Mr. Rhcinherg which showed the 

 effects produced by cutting out the various spectra of 

 one side, and he suggested to Mr. Conrady that the 

 experiment should be made to test the correctness of 

 the theory. Mr. J. W. Gordon then gave a summary 

 of his paper " On the Theory of Highly Magnified 

 Images," and illustrated his remarks by numerous dia- 

 grams shown on the screen. A discussion ensued in 

 which Messrs. Rheinberg, Beck, and Conrady took 

 part, and Mr. Gordon briefly replied. 



The Quekett Microscopical Club. 



'I'lie .(iSth ordinal-}' ineeling of the Club was held on 

 December 16 at 20, Hanover Square, W., the Presi- 

 dent, Dr. E. J. Spitta, V.P.R..\.S., in the chair. After 

 the ballot had been taken for the new members, the 

 President announced that fifty members had been 

 elected during the p;ist year, and congratulated the 

 Club upon the increase, which he hoped would be full\ 

 maintained in the future. 



Mr. C. G. Curties, F.R.M.S., exhibited and described 

 the new Nernst electric lamp arranged for use with the 

 microscope, and also one of Baker's " Diagnostic " 

 microscopes, a model combining extreme portability 

 with firmness. 



Mr. D. J. .Scourfield, F.R.M..S., gave an interesting 

 lecture on " Fresh Water Biological .Stations," illus- 

 trated by lantern \iews of the exterior and interior of 

 the principal fresh water biological stations in Europe 

 and America. He pointed out that they had their 

 origin in the general deepening of biological research 

 which followed the establishment of the Naples and 

 other marine biological stations, between the years 

 1870-1890, aided by the rise of Limnology, which in 

 itself was largely due to Professor F. A. Forel, who 

 had shown by his work on Lake Geneva what might be 

 done by a systematic study of lakes. The first fresh 

 water biological station in England was started in 

 1902 at Sutton Broad, Norfolk, by Mr. Eusfacc 

 Gurney, anfl although the station was as yet but little 

 known, it had already been the centre of good work, 

 and deserved every encouragement. 



Improved Methods of Working with the 

 Vertical Illuminator. 



I am indebted to a correspondent for the following 

 methods of using the vertical illuminator : — 



