VOL. 7. No. 11
LABORATORY ELECTRIC FURNACE
2721
directly on the line without danger, if 15-ampere or greater capacity fuses are used. A small crucible can be placed in the interior of the cone, and brought to a temperature approaching 1300nC., or incipient white heat. This is sufficient for almost all analytic purposes. All the common fusion mixtures and fluxes can be melted into mobile liquids. The furnace should not he operated for more than an hour a t maximum temperature, as prolonged heating weakens the resistance wire and will ultimately cause it to part and arc; the core of the element will then usually crack, because of the intense localized heat. If a simple break occurs in the wire, without injury to the core, a new length of the wire (Nichrome or Chromel) may he purchased for a slight sum, and the core rewound with it. A coating of alundum cement over the coils will make the device a permanent one, and will increase its maximum temperature. Tube or combustion furnaces may be made similarly, using the now more common cylindrical heating elements.
Department of Agriculture Observing Goldenrod Rubber Experiments. The U. S. Department of Agriculture is watching the Edison-Ford goldenrod rubber experiments with interest, but is not carrying on any similar wotk of its own. The work is still in the non-commercial stage, and farmers are not being encpraged to figure on putting in a crop of goldenrod instead of corn or cotton next spring. That Mr. Edison is really in earnest about finding same native plant that may SeNe as a source of home-mown rubber, a t least in emergencies, is evidenced bv the fact that he had a well-known New Yurk butanist look over a vast number of plants Over 1200 potmtial rubbcr bcarers e,ere examined and identified by this worker bcfuru Mr. Edison settled on the one species of goldenrod that is now engaging his attention. Of the eighty or so distinct species in the goldenrod genus, only one has been selected as being the most promising of results in ~ b b e r . It is known to botanists as Solidago leamenworthii, and its range is restricted t o a comparatively limited area in the southeast. It would probably grow well aver a much larger territory, however, if it should prove profitable as a crop plant. Mr. Edison has informed the Department of Agriculture that even within the limits of this one species there is a wide fluctuation in rubber content. One lot of plants may yield as little as one-half of one per cent an a dry weight basis, another as much as six per cent. The problem then becomes one of selecting the best strain and endeavaring to improve i t by breeding. If goldenrod cultivation bemmes commercially profitable, its propagation will not offer any serious diEculties. Almost all of the species are perennials, sprouting freely from slender underground m n e n , and these rootstocks can be cut up in pieces to plant, like potatoes. Seed need not be used a t all. I n case a specially desirable strain of goldenrod should be developed, this vegetative propagation would he an advantage, for propagation by seed would permit such a hybrid to revert t o its lower-grade ancestral condition, whereas planting by cuttings would keep it up to grade.-Science Service
