Page:The New International Encyclopædia 1st ed. v. 17.djvu/460

* SAFETY-LAMP. 420 SAFFLOWER. fhe flame, while there was a wire gauze cylinder above. Stephenson's, familiarly called the Oeor- du lamp, was actually in use at the Killing- w'orth mines. In its general principle it was the same as Da^•J''s. the main difference being that the Stephenson lamp had a glass cylinder be- sides the gauze one, to re- sist strong currents of air, and that glass without gauze is not safe from frac- ture. In the Gray lamp, which is considered one of the best safety-lamps, the air enters at the top and passes down through four tubes and then a strip of gauze before reaching the flame. The products of combustion pass up a cylin- drical chimney, which is of smaller diameter half way to the top in order to avoid down currents and to keep the air near the burner as vitiated as pos- sible and thus retard com- bustion. In the French and Belgian collieries Mueseler's lamp is in almost universal use, and it is also employed in England and America. It consists of a glass cylin- der immediately around the flame, and of wire gauze above. An internal metal chimney opening a short distance above the flame creates a strong upward draught, which causes the freed air to pass briskly down from the wire gauze, and so keeps the glass cool and insures thorough combustion. In connection with improvements in the safety- lamp various devices increase its safety and effi- ciency as a detector of the presence of fire-damp. By mechanical arrangements the danger of the safety-lamp being converted into an 0{)en-flame lamp by any chance or mishap is obviated. In nearly every instance there is some device for locking the gauze about the flame after the lamp has been lighted. This is done to prevent by any possibility the naked flame from coming in direct contact with the exterior atmosphere, and the locking device is operated either by a key, a pow- erful magnet, or compressed air. The presence of fire-damp is shown by an elongation of the flame of the lamp and the formation of a luminous cap or blue flame, which increases in size with the amount of gas present in the atmosphere. The miner tests for the gas by turning his flame down to a point where it is practically non- luminous and then noting the size of the cap. As detectors of fire-damp the various lamps have been ranked as follows: Gray, Mueseler, Mar- saut, Morgan, Davj', and Stephenson. For this special purpose lamps have been devised which burn alcohol or some other substance and give a sensitive flame. Of these the Pieler lamp, which burns alcohol, is one of the simplest arrange- ment, which has been modified by Chesneau in a lamp burning methyl alcohol containing cuprous chloride, which indicates the gas not only by the cap but hy the changed color of the flame. The DAVY SAFETY-LAMP. Claves lamp contains, besides a luminous flame of oil, a supply of compressed hydrogen, which is burnt at a small jet and is used for testing where the air contains less than tliree per cent, of the gas. The use of electricity has become very gen- eral in mines, both for lighting and power, and it is obvious that the incandescent lamp, as it burns in vacuo, and is perfectly safe in an at- mosphere of any gas, however explosive, fur- nishes the best possible means of illumination. The only objection raised against the incandes- cent lamp for mines is that with proper insula- tion, suitable wiring, and the rough usage it re- ceives, the expense of the light is very large in comparison to the wire-gauze lamp. Portable electric lamps for miners are also used, but their use has never been widespread, owing to the diffi- culty of carrying a battery large enough to sup- ply the light for a reasonable time, the tendency to get out of order with rough usage, and the high cost of the apparatus. Consult Graves and Thorp, Chemical Technology, vol. ii. (Philadel- phia. 1895). SAFETY-VALVE. A circular valve placed on an opening in the top of a steam boiler, and kept in its place either by weights above it, by a lever of the second order, with a weight capa- ble of sliding along the arm, or by a spring. In stationary engines one valve is frequently found sufficient, and the pressure on the valve is produced in the first or second of the meth- ods indicated above. In locomotive engines (see Locomotive), on the contrary, there are always two valves. Whenever the tension of the steam in the boiler rises above a certain amount (the weight in pounds with which the valve is held down divided by the area in inches of the under- surface as exposed to the steam), the valve is forced upward and, the pressure on the boiler thus relieved, the valve sinks to its place. The only precaution necessary is to be sure that the valves are not too heavily loaded or fastened. The grate surface is now the commonly accepted unit by which to determine the size of the safety- valve." The United States regulations for steam vessels require that lever safety-valves shall have an area of not less than one square inch to two square feet of grate surface in the boiler, and this proportion also obtains in good stationary engine practice. SAFFI, sitf'fe. A seaport of Morocco. See S.FI. SAFFLOWER (OF. saflor, safleur, from Olt. saffiore, asfiore, from Ar. vsft'ir, saflfowcr, from safra', yellow, influenced by popular etymology with Eng. foiver), 'Carthamus tincforius. A branching annual plant of the natural order Compositae, two or four feet high, with dark orange or vermilion flowers. It is a native of In- dia, whence it probably spread to Egj'pt and the Levant, where it became naturalized. It is ex- tensively cultivated in Southern Europe, espe- cially France, and in some parts of South Amer- ica, for its corollas, which are picked by hand in dry weather, dried in a kiln, and formed into small, round cakes used as yellow and red dyes. The safflower of Persia is generally esteemed the best. Safflower is sometimes called bastard saf- fron, and is used to adulterate saffron. The yel- low coloring matter is valueless as a dyestuff, and since the red (carthamic acid or carthamine)