784 



SCIENCE 



[N. S. Vol. XLI. No. 1065 



uniform or locally abrupt. Not only did the 

 cable break, but the repair boat reported that 

 half a mile of it had been buried in debris on 

 the bottom and had to be abandoned and a 

 new piece spliced in. 



It is said that the cable was broken in almost 

 the same place by an earthquake between the 

 years 1882 and 1883. 



To the writer the only adequate explanation' 

 of the breaking of the cable and the burying of 

 half a mile of it is that movement occurred 

 along an old fault escarpment, or fault zone, 

 which marks the boundary between the conti- 

 nental shelf and the deep ocean basin, and 

 that this movement was great enough to cause 

 the earthquake, resulting in a submarine land- 

 slide. It is not known whether the fault dis- 

 placement broke the cable or whether the sub- 

 marine landslide caused by the jar of the fault- 

 ing broke it; of course the jar of the fault 

 movement was the earthquake. 



Nearly all of the later shocks felt were ac- 

 companied by peculiar underground sounds 

 which, at times, seemed to begin to the east- 

 ward of the observer and to die away in 5 or 10 

 seconds to the westward of him. The sound 

 was not unlike the dull boom made by the 

 fracture of ice on large lakes, due to shrink- 

 age, when the weather has suddenly become 

 extremely cold. The noise of these ice frac- 

 tures may begin far to the right of an ob- 

 server and die away in the distance, in a few 

 seconds, to the left of him. After listening, 

 several times, to the underground sounds that 

 accompanied shocks, the writer became con- 

 vinced that they were due to the formation of 

 small shears or strain-relieving cracks in the 

 rocks, formed perhaps considerably below the 

 surface. A search for such cracks was unsuc- 

 cessful, due either to the sparsity of rock 

 exposures or to the fact that cracks might 

 not be distinguishable from ordinary joint- 

 ing, or that they might be parallel, or 

 nearly parallel, to the surface and might not 

 outcrop in the vicinity at all. It is thought 

 that the rock strains would be relieved by many 

 very small fractures along a strained zone 

 rather than by one large break, and the differ- 

 ential movement along each small fracture 



might be extremely small, possibly measurable 

 say in tenths of an inch. 



The breaking of the cable and the burying 

 of a part of it, together with the underground 

 sounds heard several times, as far as the writer 

 can see admit of no other adequate explanation 

 than that herein ascribed to them. 



The other geological principle connected 

 with these earthquakes was that of the elas- 

 ticity of the earth's crust. The writer was on 

 the top of a steep conical mountain peak which 

 stood about 2,000 feet above the surrounding 

 country, when a heavy quake came, causing 

 the mountain to behave like a stiff jelly. One 

 felt as though the mountain were swaying 

 through an arc of several inches. Making 

 ample deductions for the tendency of the senses 

 to exaggerate such an unusual phenomena, it 

 is thought that the swaying motion in a hori- 

 zontal plane was actually about three quarters 

 of an inch. It was one of the most impressive 

 demonstrations of the elasticity of solid rock, 

 of the somewhat jelly-like motion that can be 

 imparted to a " rock-ribbed " mountain, that 

 one could well imagine. With the motion a 

 dull, heavy underground rending sound began 

 on the northeasterly to northerly side of the 

 mountain and died away in the distance on the 

 other side, being audible for say 20 to 25 

 seconds. 



These underground sounds had a most terri- 

 fying eiiect on the inhabitants, who believed 

 they were about to be overwhelmed by some 

 volcanic catastrophe. The investigation was 

 very successful in assuring them that these 

 dreaded sounds were quite harmless and were 

 not due to any subterranean fires, and that the 

 near-by mountains were not going to turn into 

 volcanoes and overwhelm them as they feared. 

 In spite of this soothing information, how- 

 ever, a few of the natives were unjust enough 

 to criticize the writer for not stopping the 

 quakes as quickly as they wished. Such is 

 " man's inhumanity to man." 



Donald F. MacDonald 



U. S. Geological Survey 



THE THOMAS SAY FOUNDATION 



An organization, with the above name, was 

 formed under the auspices of the Entomolog- 



