Rub two pieces of fine lump sugar together in the dark; the effect is produced, but in a much greater degree, by two pieces of silex, or quartz: but that which affords the strongest light of any thing, is a white quartz* from the Land's End.

The white pebbles found on the banks of the Mersey, although not a pare quartz, answer the purpose perfectly well. It is singular, that the friction is invariably accompanied by a strong sulphureous smell.

considerable quantities of which are brought to Bristol., and enter into the composition of china ware. By means of two pieces of such quartz, pretty forcibly rubbed together, you may distinguish the time of the night by a watch: but, what is more surprising, the same effect is produced equally strong by rubbing the pieces of quartz together under water.