This section is from the book "Amateur Work Magazine Vol6". Also available from Amazon: Amateur Work.
Mica is much used in electrical machinery, as an insulator beteween the segments of commutators. For this purpose the mica must be sott. Large sheets of mica are in demand for lamp chimneys and other novelties. Scrap mica is ground fine for fire-proofing material, as a lubricant, and for wall papers.
Comparatively little has been heard about radium this year, due to the fact that the cost of the salt is almost prohibitive, and that the experiments to date, while interesting, have proved little or nothing as to the actual value of the element.
Alloys of bismuth have been employed for fusible plugs for steam boilers and in fire extinguishing apparatus; but lately it has been found that these plugs alter peculiarly when exposed to heat for any length of time, and often will not melt at the proper temperature.
A British naturalist recently recovered two live toads which had been buried in solid rock for unknown periods. One of the toads had been dug out of clay six feet below the surface, and the other was found embedded in a quarry. The only infirmity noticed that both had their mouths tightly closed; otherwise they were active.
The use of soapy water as a lubricant for air-cylinders is recognized as good practice, says the "Mining Press." Even where oil is used as the regular lubricant, soapsuds should be fed in from time to time to clean out the valves and discharge ports. There are many well-authenticated cases in which only soapy water is used as the lubricant. Soapsuds and Dixon's flake graphite mixed make an ideal lubricant for air-cylinders, for by the addition of graphite far less soapy water is necessary than would otherwise be required. Hand oil pumps will pass soaspsuds and graphite perfectly satisfactorily, or the graphite may be fed separately in a dry state through a separate cup, while the soapy water passes through the regular lubricators. There is only one caution necessary in this method, namely, to introduce sufficient oil before shutting down the compressor to prevent rusting of the cylinders and valves when the machine remains idle. Rust, however, forms very much less rapidly in the presence of graphite than upon surfaces not thus coated-in fact, it cannot form at all upon a surface completely covered with a film of graphite.
A piece of metal is not a homogeneous single thing. It is a collection of grains and granules that built it up just as the granules built up a glacier. The grains of metal are irregular in shape and unequal in size. Their existence is revealed by polishing and etching the surface of the metal and examining it under a microscope, when the grains can be readily distinguished by differences of texture and the boundaries between them can be clearly traced. Investigation shows that each grain is, in fact, a separate crystal, and the irregular boundaries are due to casual inequalities in the rates at which the various crystals have grown during their formation. .
Detonators for exploding dynamite consist ordinarily of a mixture of mercury fulminate, and potassium nitrate or chlorate, placed in a copper capsule; when the cap is to be fird with a fuse, the fulminate is covered with shellac, collodion, thin copper foil, or paper, and the end of the capsule is left open ta receive the end of the fuse.