234 



ANNUAL OF SCIENTIFIC DISCOVERY, 



The use of this substitute has a great advantage. The material is 

 added to the bath, and you may pass several thousand pieces through 

 the same bath, by adding a little additional arseniate of soda. The 

 same bath may thus be used for several thousand pieces without being 

 changed ; but in the old plan, where cow -dung was used, it was neces- 

 sary to change the bath after a few pieces had been passed through 

 it ; so that the application of these phosphates and arseniates to the 

 purposes of the calico-printer has enormously aided him in diminishing 

 the necessity for labor. Sir Lyon Playfair's Lecture. 



The Action of Mordants in Dyeing. In a paper on the above 

 subject, recently read before the London Chemical Society, by Mr. 

 W. Crum, the author opposed the idea that in dyeing, any chem- 

 ical union took place between the fabric and the dyeing material. He 

 regarded the action in some cases as one of adhesion to an extended 

 surface ; in others, where the coloring matter (or mordant and coloring 

 matter) is in solution, absorption took place. The structure of the 

 fibre bears out this view, for on examining cotton under the micro- 

 scope it is seen to be composed of flattened tubes with translucent 

 walls, permeable, no doubt, to fluids. When mordants are used they 

 are often deposited within the fibre, and retained there mechanically, 

 and afterwards, combining with the dye, serve to fix it in the mate- 

 rial. What is technically termed dead cotton does not take the dye, 

 for, being immature or imperfectly formed fibre, it possesses no central 

 tube ; it occurs in small quantities along with ordinary cotton, and 

 remains white and unaffected after mordanting and dyeing. Mr. 

 Crum exhibited numerous specimens of dyed and printed cotton fab- 

 rics in which threads and bundles of undyed dead fibres were very 

 well seen. 



MINERAL OILS. 



The Journal of the Franklin Institute publishes the following table 

 of the economy of using petroleum oils as compared with Philadelphia 

 gas, spermaceti, paraflme, and adamantine candles : 



Naphthometer, or Benzine Detector. This new instrument, the 

 invention of Messrs. H. J. Smith and W. Jones, of Philadelphia, con- 

 "sists of a reservoir with a tightly-fitting cover, from the top of which 

 projects a tube, surrounding a wick tube. A thermometer also passes 



