in favor of the defendants, practically rendering the patents invalid,
on the ground that the inventions claimed under them had been
disclosed by the Hall patents of 1858 and the Hayward patent of 1863.

The two patents upon which the suits for infringement rested
principally were No. 249,970, granted to N.C. Mitchell, in 1881, and
No. 300,720, granted to the same, in 1884. About the same time the
Rubber Reclaiming Company, formed in 1890 by the combination of five
leading rubber reclaiming plants, and working under license from the
company above named, was resolved into the original elements. There
were about that time five other rubber reclaiming plants in the United
States, operating either the "acid" or the "mechanical" process,
besides nine general rubber factories producing their own reclaimed
rubber by the "acid" process. While several of the latter--rubber shoe
concerns controlled by the United States Rubber Company--have been
consolidated, there has been an increase in the number of rubber
manufacturers reclaiming their own rubber, since the end of the patent
litigation, so that the total number of reclaiming plants now probably
is twenty.

The first step in any process for reclaiming rubber is the grinding of
the waste, for which purpose several machines have been designed
specially, an early patent for disintegrating rubber scrap by
"subjecting it to the abrading action of grindstones" having failed to
meet with favor. The most usual chemical treatment is a bath in a
solution of sulphuric acid in lead-lined tanks. Generally heat is
employed to hasten the process, through the medium of steam, in which
case the tanks are tightly closed. The next step is the washing of the
scrap, to free it of acid and dirt, after which it is sheeted by being
run between iron rollers and hung in drying rooms. As soon as it has