An audiphone for deaf people.
Sound-bridge for measuring resistance of tubes and other materials for conveying sound.
A method of testing a magnet to ascertain the existence of flaws in the iron or steel composing the same.
Method of distilling liquids by incandescent conductor immersed in the liquid.
Method of obtaining electricity direct from coal.
An engine operated by steam produced by the hydration and dehydration of metallic salts.
Device and method for telegraphing photographically.
Carbon crucible kept brilliantly incandescent by current in vacuo, for obtaining reaction with refractory metals.
Device for examining combinations of odors and their changes by rotation at different speeds.
From one of the preceding items it will be noted that even in the eighties Edison perceived much advantage to be gained in the line of economy by the use of lamp filaments employing refractory metals in their construction. From another caveat, filed in 1889, we extract the following, which shows that he realized the value of tungsten also for this purpose. "Filaments of carbon placed in a combustion tube with a little chloride ammonium. Chloride tungsten or titanium passed through hot tube, depositing a film of metal on the carbon; or filaments of zirconia oxide, or alumina or magnesia, thoria or other infusible oxides mixed or separate, and obtained by moistening and squirting through a die, are thus coated with above metals and used for incandescent lamps. Osmium from a volatile compound of same thus deposited makes a filament as good as carbon when in vacuo."