190>^] on Recent Earthquakes. 189 



lamp moved about outside the box produced no effect upon the paper 

 inside. A self-recording thermometer and a hygrometer showed that 

 the temperature and the moisture in the chamber were practically 

 constant. A similar piece of apparatus was installed at a depth of 

 160 feet, in the King Edward Mine, Camborne, Cornwall. These 

 experiments were commenced at Pan Chalk Pit in February 19 Go, 

 and were continued for four months. They were taken up again in 

 the middle of August 1906, and lasted eight months. A sheet of 

 paper on development was frequently quite clear, but at times it was 

 partly or entirely marked with dark bands, black lines, round black 

 spots, or semi-circular spots along the lower edges. At Shide, the 

 dark bands have not been numerous, but they occurred on nearly all 

 the sheets from Camborne. In certain cases we appear to have three 

 bands, the positions of which apparently coincide with the three holes 

 in the zinc plate. In some of these bands there are hard black lines 

 broken along their length and made up of black spots. 



The black spots vary in diameter from a fraction of a millimetre 

 to 8 millimetres. In the centres of some of these there is a small 

 white or brownish spot. As pointed out by Mr. W. H. Bullock, of 

 Newport, these closely resemble spots which can be produced on bro- 

 mide paper by a tiny electric spark. During a week we may have 

 either no spots, one spot, or a hundred spots. The semicircular spots 

 which I have called singeings, are found on the lower edge of the 

 paper where the brass cylinder joins the aluminium rim. There may 

 be two or three of these per week, whilst at other times they occur at 

 intervals of about half-an-hour. As only ten black spots occurred at 

 the time of large earthquakes we can only regard these as coincidences. 

 Neither dark bands, spots nor singeings appear to be connected beyond 

 what I have mentioned with any particular meteorological conditions. 

 Neither is there any reason for supposing that these effects are due to 

 radio-activity. If a piece of bromide paper is sealed up in a black 

 envelope and another piece is placed in a black envelope, which has a 

 thin glass window, and these are laid on a surface of chalk, the glass 

 window touching the same, say for a period of several days, it was 

 found after development that one piece of paper showed the image of 

 the window, whilst the other had only stains which might be attributed 

 to dampness. With the object of determining whether micro- 

 organisms played any part in the phenomena observed, my friend. 

 Dr. R. C. Brown, M.D., of Parkhurst, has made cultures from 

 scrapings from the surface of the chalk before which my cylinder 

 was exposed. Cultures were also made from scrapings taken from the 

 open chalk. Micro-organisms were found in both. These have been 

 exposed to a moving photographic surface similar to that used in 

 the pit, but they gave no evidence of luminosity. The conclusion 

 for the present is that the luminosity occasionally seen at Pan Pit 

 may result from a very feeble brush or glow-like electrical discharge. 

 If this be the case it would also account for the bands on the photo- 

 graphic paper, the other markings being due to minute sparks. 



