QUICKSANDS AND FIRE-STONES 69 



still a matter open to investigation as to whether the 

 flashing of pieces of quartz and rock-crystal when rubbed 

 together with heavy pressure is of the nature of the 

 flashing of the heated crystals of other minerals, or 

 whether there is any chemical action set up by the 

 friction — an action which is certainly suggested by the 

 very peculiar smell produced. Since the flashing can 

 be produced under water and other liquids, it should be 

 easy to obtain some evidence as to the chemical nature 

 of the flame — whether acid or alkaline, whether capable 

 of acting on this or that reagent dissolved in the water, 

 and whether setting free any gas of one kind or another. 



Any one of my readers who chooses can produce 

 the wonderful orange-coloured flame by rubbing two 

 quartz or flint pebbles together in the dark, and can 

 have the further gratification of producing with the 

 utmost ease the mysterious and weird phenomenon of a 

 flame under water, and may, perhaps, by further experi- 

 ment, explain satisfactorily this unsolved marvel which 

 has haunted some of us since childhood. 



