M. TECHNOLOGY. 533 



a few drops of rain-water, rubbing it up with the finger, 

 then bringing it to the consistency of ordinary drawing-ink 

 with more water, and allowing it to stand for some time 

 best overnight. It will keep in this condition for several 

 days, with the addition of water as may be necessary. Care 

 must be taken not to touch the surface of the paper with 

 the fingers. The tracing is transferred to stone by first plac- 

 ing it between folds of damp paper, to soften the tapioca 

 coating, and then laying it face down upon a lithographic 

 stone, and, with moist paper on top of it, subjecting it to 

 pressure three times in succession ; then passing a fine, moist 

 spouge over it, and again pressing it as before. The paper 

 thus loosened is finally entirely removed, leaving only the 

 paste and tracing on the stone, which is next well washed 

 with pure water, then coated with a solution of gum arabic, 

 dried, washed with pure water, treated with acids, inked, and 

 printed from in the usual way, affording, if proper care has 

 been taken, 4000 to 5000 impressions. 6 C, May 14, 1874, 

 195 



INDESTRUCTIBLE INK. 



An ink closely resembling that forming the characters 

 upon the Egyptian papyrus may be made, it is said, by dis- 

 solving gum lac in an aqueous solution of borax, and adding 

 lamp-black in suitable quantity. This ink is claimed to be 

 almost indestructible, resisting both time and chemical agents, 

 and becoming a beautifully lustrous black. 4 B, August^ 

 1874,782. 



NEW MANNER OF PRODUCING SHADED YARNS. 



Instead of the usual method of letting down the yarn from 

 time to time deeper into the dye-bath, by lowering the rods 

 on which it is hung upon movable pins in holes in vertical 

 supports, in order that successive portions may be more deep- 

 Iv shaded, it is much simpler, as well as much more econom- 

 ical, to' dye first the whole skein in the bath, in the usual 

 manner, to the lightest shade desired; allow it to hang, and 

 draw off the bath by a stop-cock, or dip it out until its level 

 is where the next deeper shade on the yarn is desired; then 

 to lift the yarn, strengthen the bath, and hang it in again ; 

 and thus to continue as needed, to impart the different shades, 



