xiv Proceedings. [November 13th, 1906. 



out some little time ago, as a property peculiar to the white 

 pebbles found on the coast at Whitby. All quartz pebbles show- 

 it remarkably well, and practically all the forms of silica which 

 have been tried — including agate, chalcedony, rock crystal, opal, 

 flint, &c. Smooth surfaces are not so effective as slightly 

 roughened ones. When the substance used is translucent, it is 

 quite lighted up at each stroke. Mr. Joseph Burton finds that 

 quartz which has been fused is very effective. It is somewhat 

 vesicular, and of lower specific gravity than ordinary rock crystal, 

 and rubs away more easily. There is no doubt that the lumi- 

 nosity is connected in some way with the breaking away of small 

 particles, mostly in the form of dust. Mr. Burton also find- 

 that whereas ordinary felspar only shows this property in a very 

 small degree, the same substance previously heated almost to 

 fusion shows it almost as well as quartz. Common glass does 

 not show it, but a specimen of glass "frit," rich in lead, and 

 very hard does to a slight extent. 



This curious luminosity may be partly due to the hardness 

 of the material, but that it is not entirely so is shown, by the 

 fact that whereas a slight luminosity is shown when a piece of 

 corundum or a piece of native emery is rubbed against a piece 

 of silica, there is none whatever when two pieces of corundum 

 or two pieces of native emery are knocked together. 



There is a curious smell produced by the impact of any of 

 these bodies which become luminous, a smell which has been 

 compared to that of ozone. Mr. T. L. Phipson, in a book on 

 Phosphorescence, published in 1870, says that he has shown that, 

 in the case of quartz, ozone is produced. 



But Mr. Taylor has not been able to verify that observation. 

 Mr. F. Jones and Mr. Burton also made careful tests for ozone, 

 and both failed to obtain any evidence of its presence. 



Miss M. McNicol, B.Sc, read a paper entitled "The 

 Proembryo and Bulbils of La?nprothani7ius alopecnroid.es 

 (Braun)." This plant, which occurs in various countries of 

 Europe and also in Africa, is characterised by the possession of 



