241? Mr. W. Crum on the Manner 



unacquainted with the microscopic appearance of cotton, 

 d'Apligny argued that as no vegetable substance in its growth 

 can receive a juice without vessels proper for its circulation, 

 so the fibres of cotton must be hollow within. And of wool, 

 he says, the sides of the tubes must be sieves throughout their 

 length, with an infinity of lateral pores. We may gather also 

 that he conceived dyeing to consist, first, in removing a me- 

 dullary substance contained in the pores of the wool, and af- 

 terwards depositing in them particles of a foreign colouring 

 matter. 



But Bergman, in his Treatise on Indigo, in 1776 upset all 

 this, and attributed to cotton a power of elective attraction, 

 by which all the phaenomena of dyeing were referred to 

 purely chemical principles. Macquer soon adopted the che- 

 mical theory, and it was keenly advanced by Berthollet, who 

 succeeded Dufay, Hellot and Macquer in the administration 

 of the arts connected with chemistry. Berthollet has been 

 followed by all, so far as I know, who have since that time 

 written on the subject, but nothing like evidence has ever been 

 produced ; and if we only consider that chemical attraction 

 necessarily involves combination, atom to atom, and conse- 

 quently disorganization of all vegetable structure; that cotton 

 wool may be dyed without injury to its fibre, and that that fibre 

 remains entire when, by chemical means, its colour has again 

 been removed, we shall find that the union of cotton with its 

 colouring must be accounted for otherwise than by chemical 

 affinity. In particular processes, as we shall afterwards see, 

 attraction is no doubt exerted ; but it is an attraction con- 

 nected with structure, and therefore more mechanical than 

 chemical. 



When we examine with a powerful microscope a fibre of 

 cotton, dyed either with indigo, with oxide of iron, chromate 

 of lead, or the common madder-red, the colour appears to be 

 spread so uniformly over the whole fibre that we cannot decide 

 whether the walls of the tube are dyed throughout, or that 

 the colouring matter only lines their internal surface. But 

 the microscope shows that the collapse which occurs in raw 

 and bleached cotton is very considerably diminished in the 

 dyed. 



The greater number of specimens of Turkey-red which I 

 have examined show the same uniformity of colour, but in 

 others of them little oblong balls appear all along the inside of 

 the tube, of the fine pink shade of that dye, while the tube itself 

 is colourless. It is in stout cloth dyed in the piece that these 

 rounded masses occur, and the observation has been confirmed 

 by several of my friends who are practised in microscopic re- 



