438 KANSAS CITY REVIEW OF SCIENCE. 
smooth surface and in being much less elastic than those of either animal or veg- 
etable origin, in consequence of which all efforts to spin and weave them by 
modern machinery have until very recently entirely failed. In addition to ami- 
anthus and mountain-leather, there are several other varieties of asbestos, for 
instance, mountain-cork, which is a brownish or dirty-white deposit, less flexible 
and less regular than amianthus and mountain-leather, and so light as to float on 
water; mountain-wood, a soft, opaque, brownish colored variety, which melts tO' 
a black slag before the blow-pipe ; and lastly, the common asbestos, which has 
recently been descovered in large quantities in Canada, in veins from one inch to 
two inches thick, and which is the kind most generally used for manufacturing 
the various articles to which we shall have occasion to refer. 
The introduction of asbestos for such purposes as engine-packing and joint- 
ing for pipes has been attended with very considerable difficulty. Of all mater- 
ials, it is perhaps that which requires the most careful manufacture and intelli- 
gence in adapting it to its special purposes; and wheii these have not been suffi- 
ciently exercised, users have been disappointed, and have not unfrequently given 
up the trial'in disgust. As already stated, the peculiarity incidental to asbestos- 
fiber for a long time baffled all attempts to spin it into yarn without the intermix- 
ture of a certain proportion of flax or other vegetable fiber. Within the last few 
years, however, the difficulty has been overcome, and yarns capable of with- 
standing great tensile stresses can now be readily produced by machinery specially 
constructed for the purpose. One of the most important applications of this yarn 
is for the manufacture of steam-packings. In making packing, it was at first not 
sufficiently recognized that the fibers of asbestos were apt to be largely charged 
with minute particles of pyrites; and until this fact was appreciated, it was often 
found that the piston-rods were scored, the damage being attributed to the action 
of the asbestos itself, instead of to the impurities it contained. To obviate this 
defect, it therefore became necessary to thoroughly cleanse the asbestos from all 
stone and grit before spinning, for which duty machinery had to be adapted.. 
The yarn now produced is quite pure, and is capable of being woven into almost 
any kind of fabric. But it was soon ascertained that special cases required 
special treatment, and though the plaited packing was generally satisfactory, it 
became evident that something else was wanted in the case of steam-engines 
with extremely high piston speeds. To meet this demand, the yarn was first 
woven into a cloth, which, being slightly water-proofed with vulcanized India- 
rubber, was rolled up into a rope in much the same way as the canvas is treated 
in what is known as Tuck's packing, only without the rubber core. This pack- 
ing answered admirably, and is much used in cases where the rapid destruction of 
ordinary packings gave rise to most serious inconvenience. The enduring powers 
of this asbestos block-packing are quite remarkable. In ~ one place, on being 
taken out after twelve months' working with steam of seventy pounds pressure, 
it was found to be perfectly good, and was accordingly replaced. It has often 
been erroneously stated that asbestos packing could be used without lubrication.. 
No greater mistake could exist. It not only requires a good supply of oil, but 
