Dr. Bolley on the Theory of Dyeing* 487 



form combinations, and organic dye stuffs, that is to say, a review 

 of the relations that result from the appUcation to the fibre of 

 both mordant and dye. In the last two divisions, also, cer- 

 tain well-known phsenomena of the art of dyeing are noticed, 

 which contribute nothing to the proof that we have to do with 

 chemical combinations. 



To Chevreul's views and labours we shall have to return pre- 

 sently. We must now notice the chief results of three several 

 works which possess the common merit of pursuing the method 

 of actual observation, the more so because they have nowhere 

 been influenced by the desire to uphold a common theory of 

 dyeing. 



A. Oschatz*, in the year 1848, published a treatise well worthy 

 of attention, " On the Structure of the most important Fibrous 

 Substances used in the Arts," at the conclusion of which there is 

 a short chapter entitled " Microscopic Contribution to the Theory 

 of Dyeing." The conclusion which he draws from his observa- 

 tions are expressed in his own words as follows : — 



" If thin sections of coloured fibres be taken and submitted to 

 microscopic examination, it will be seen that the entire sub- 

 stance of the fibre is equally coloured. The thickness of the 

 cell-walls, even in cotton fibre, leaves no doubt on this point ; 

 and the fact that in some cases, especially in cotton dyed Tiu'key 

 red, the external layer of the cell-wall is more deeply coloured 

 than the rest, is not to be set against the universal observation 

 that in wool and silk the whole section displays the most entire 

 uniformity of tint. 



" By the establishment of this universal fact, of the reality of 

 which any one may convince himself in the way above indi- 

 cated, a starting-point at least is secured for future theories. 

 The separation of the particles of colouring matter which have 

 been disseminated throughout the organic substance is as little 

 to be detected, even with the highest magnifying powers, as that 

 of the particles of lime-salts in the organism of bones, or of silicic 

 acid in the cell-walls of shave-grass or ordinary grasses. If, 

 therefore, the chemical union of the dye stufi" with the substance 

 of the fibre be not admitted, we are forced to suppose the par- 

 ticles of colouring matter so small and so equally disseminated 

 as to defy the most powerful microscopes.''' 



Vcrdeilf, in December 1.858, transmitted to the French Aca- 

 demy a communication " On the Dyeing of Fibres of Animal 

 and Vegetable origin," the substance of which may be summed 

 up as follows : — 



* Berlin Geioerbe-, Industrie- undHandelsblatt, Nos. l.to 14. Also Po' 

 lytechn. Centralblutt, vol. ii. p. 1415. 

 t Comptes Rendus, December 1858, No. 24. 



