The Cordova daily times., 1922-09-19
CE0PHONE IS
 NEW METHOD
 SAVING MINERS

CHICAGO, Sept 19.-Casts and res as war instrument and used amid the reek and slaughter of the World War for the detection of earth and rock sounds made in the construction of military mines and tunnels, the geo. phone promises to become an active factor in the saving of lives of miners entombed as result of fire and ex- plosion.
 In the course of tests conducted by the Bureau of Mines in the bu- reau's experimental mine near Pitts burg, Pa, blows with a sledge on the coal face were heard, by means of the geophone, at a distance of $50 feet, with various rooms and entries inter- vening.
 On suspended pipe line light ham, mering with the knuckles was detected at distnce of 1,500 feet. Ordinary talking and singing could be detect ed through 150 feet of solid coal. By the use of two geophones, one instru- ment to each ear, it is possible to de- termine the direction from which a sound is coming through the earth, and thus to locate the approximate position of the entombed miner, bu- reau experts claim. The bureau has given recommendation for a signal code of poundings by sledge or other means which will establish communi- cation between the rescuing party and those entombed.
 The novel instrument known as the geophone was invented by the French during the war to detect sap. ping and underground mining opera tions. It was developed by the United States Engineers and the instruments now used by the Bureau of Mines were made according to plans drawn by them, except for the introduction of different diaphragms. The mine geo phone is sensitive, yet extremely sim pie and easily portable. It is essen tially a small seismograph, as it em bodies the same principles as the pon derous apparatus that records earth quake tremcrs.
 If the instrument is placed on the ground and any one is pounding or dig ging in the vicinity, energy is trans mitted as wave motion to the earth and the earth wave into an air wave which is heard by the ear as sound and at the same time magnifies the wave so that the sound is louder thar | if the ears were placed in direct con | tact with the earth.
 The observations of the Bureau O. Mines indicate that the geophont should be quite useful in the location of mine fires. They are said also t( supply a quick and fairly accurate method of mine surveying. If two tunnels were being brought together from any direction the progress o the tunnels could be observed by means of the geophone, and their rela tive positions determined.
 Another application of the possibili ties of the instrument in mine survey ing is in the prevention of accident in blasting through. If two tunnels are approaching each other, or art passing a short distance apart, it i necessary to determine the relative ! location in order that men may b. warned to keep away from that poin of danger. Occasionally" said one 0 the bureaus experts, "churn-drill hole are dropped from the surface to min
 workings for running pipes and fo
 ventilation. When these borings com 1 from considerable distance they some times drift, and instead of breakin! through into the workings they com
 down into the solid. The question
 then is to locate them and to deter mine whether or not the hole is deel
 enough to come into the workings Here the geophone finds useful field
 for not only the direction of the hole but it's elevation can be determines
 accurately. The manifest advantag
 of the geophone for use in mine res
 cue work has led the Bureau of Mine to place the instruments on it's mine rescue cars, which are constantly be ing called to assist in the succor o
 entombed men at mine fires and eS