138 Mr. John Milne [March 20, 



caused mechanically, may be due to the disturbance of some adjacent 

 magnetic magma. If this is the case, then at particular stations where 

 the movements due to teleseims correspond with unusual disturbance 

 of magnetic needles inasmuch as a magnetic magma is denser than 

 common rock, at these stations the value for (/ should be higher than 

 that which would be anticipated. For certain stations this appears to 

 be the case. 



Another series of investigations which may widen our knowledge 

 respecting conditions and operations beneath our feet, are based 

 upon the light effects which have been so frequently observed at 

 the time of large earthquakes. Accounts of luminosity in the heavens 

 and on hills as accompaniments to large earthquakes are common. At 

 the time of the Valparaiso earthquake, August 17, 1906, the attention 

 of very many people was attracted to lights which appeared upou the 

 hills. Captain Taylor, of the R.M.S. " Orissa ", compared these to 

 chain lightning which extended as far as the eye could reach. An 

 acquaintance of mine, Mr. Gr. E. Naylor, of Valparaiso, told me that 

 he saw the lights repeatedly, and they took place immediately before 

 a shock, there being only a fraction of a second of time between the 

 two. He described them as having a bluish tinge, to others, however, 

 they appeared yellowish. An ordinary explanation for these appear- 

 ances is that they are due to the rubbing together of rock surfaces or 

 the discharge of frictionally produced electricity. These observations 

 suggest that with a megaseismic collapse not only do we get mechani- 

 cal disturbances which pass through and over the surface of the world, 

 but that part of the initial energy at the origin is converted into some 

 other form of energy which possibly may find a response at very 

 distant places. This latter transmission would, however, take place 

 with a velocity comparable with that of light. If anything of this 

 sort has a real existence seismologists may hope to record earthquakes 

 at the moment they take place. This consideration and the observa- 

 tion that from time to time a quarry in the Isle of Wight, known as 

 Pan Chalk Pit, appeared to me to be luminous suggested the possi- 

 bility of hypogenic activities giving evidence of their existence in the 

 form of light. Pan Pit faces north and in winter it is not reached by 

 the sun. Its glowings apparently rise and fall in intensity, and are 

 most noticeable after a dull damp day. The experiments I made were 

 as follows : at the end of a chamber 20 yards from the mouth of a 

 tunnel driven into the chalk, a hole about 2 feet square was excavated. 

 Into this a box with a light-proof door was cemented. The back of 

 the box which touched the chalk was made of zinc. In the zinc three 

 holes of different sizes were made along a vertical line. A cylindrical 

 drum, covered with bromide paper and driven by clockwork, was 

 brought up to within one-eighth of an inch to these holes. A rim 

 on the bottom part of the drum had a clearance given to it by cutting 

 a horizontal slit in the zinc plate beneath the holes. Neither the 

 drum, the paper, or the rim touched the zinc plate or the chalk. The 

 rate of movement of the paper was 90 mm. per day. A small electric 



