C 584 ] 
along the Rhine, in my way to Bonne, I faw in the 
river, the waters being pretty low, a rock, which 
Rood a foot or two out of the water. Examining 
it nearer, I found it to be a mafs of thofe prifms of 
bafaltes, the heads of which appeared ; and I had all 
imaginable reafon to think, that it was the top of a 
natural mafs of the Rone. I was convinced by this, 
that there were quarries of it along the Rhine. 
If, in coming near to Bonne, a perfon examines 
the parapet walls, which are built on both fides of 
the high road, he will find them to be of thefe ba- 
faltes Rones. There are many of them in the old 
walls of the ramparts of Bonne and Colen, and in 
the pavements of thofe cities. 
After I had made thele obfervations, I was in- 
formed by Mr. Emanuel Mendez da Cofta, that 
fome authors mention quarries of this bafaltes in Up- 
per and Lower Saxony, and in Silefia. 1 do not 
know, that thofe in the country of NafTau, and the 
territories of Treves and Colen, have been deferibed. 
I thought proper, Sir, to communicate to you 
what little I have learned in a journey, in which I 
had not time enough to make, upon fo curious a 
fubjedt, all the refearches, which I could have 
Wifhed. 
One cannot know too many particulars of this 
remarkable Rone, or compare too many of the fadls, 
which they offer to attentive obfervers. This is the 
true method of attaining, if poffible, fome know- 
ledge of this natural curiofity. 
Thofe, who have made obfervations upon falts, and 
inquiries into Rones, minerals', and metals, know 
how common cry Rail Rations are in nature. A very 
great 
