Show TESTS INDICATE THAT RADIO WAVES PENETRATE EARTH AND ROCK tests conducted by the united states bureau of mines in a colorado metal mine indicate strongly Z that radio waves will penetrate feet or more of rock strata these preliminary iii experiments were observed by dr A S eve director of the department of physics mcgill university montreal who is conducting a study for the bureau of mines of the possibilities of various methods of geophysical prospecting for the location of underground mineral deposits the experiments participated in by dr eve were conducted with a set with nine electron tubes in the caribou mine of the american mining and prospecting company at caribou colorado the first test was held at a depth of feet where by means of a loop a strong and clear reception was obtained of a musical concert given at denver fifty miles distant the evidence pointed strongly to the conclusion that this clear reception was due to the penetration by the radio waves of the solid rock strata although there was a remote possibility that the reception was obtained through shafts and cross cuts toward which however the loop did not point the nearest metal conductors iron rails were 66 feet away the next series of experiments was conducted at a depth of feet when mushy reception was obtained from denver this type of reception was however as goodas good g as could be obtained above ground round at the time of making the test the night being unfavorable for general radio reception this series of tests was conducted at the end of a crosscut cross cut reached with many turns and feet from the main shaft A pipe came down the shaft and followed the tunnel up to 80 feet from the point of observation in previous experiments conducted by the bureau of nunes mines at its experimental mine near pittsburgh pa it was at first concluded that radiation and induction would penetrate rock for considerable depths subsequent investigations have shown that in every case the transference of radiation was by some conductors in the mine electric wires wires pipes or rails all of which abound in modern mines it is possible that at caribou the radio waves excited the conductors in the shaft and these in turn excited rails and pipes which abrought the radiation to within 70 feet of the experimenters and and that the strong amplification of the radio apparatus ratus enabled the radiation to bridge the gap ap this dr eve ve considers is improbable but not impossible on the other hand he was impressed with the fact that the loop did not point towards neighboring conductors or along ong the tunnels but it did point at both levels within a deiv ew degrees of the source at denver the evidence is strong b but out not absolutely conclusive that wireless waves will pene ate feet of rock to an extent which enables them to be received received with powerful amplification it is desirable that these ese investigations should be followed by further research bork ork on the subject the experiments conducted at the caribou mine tend to infirm confirm the view that radiation passes through rock with of course 1 nuch much attenuation it is known that radio signals 1 ill I just penetrate through a good conductor like seawater sea water w oa a maximum depth of about fifty or sixty feet and there Is that no reason why radiation should not penetrate to ten times at distance through a poor conductor like dry rock it 11 is is felt that further investigations should include a i parison of the penetration of radio waves from a dis tance nce exceeding ce eding many wave lengths and of radio waves gen aerated rated at a distance less than a wave length |