30 THE GEOLOGY OF BERMUDA. 



great measure washed out by rains from the "red earth." The follow- 

 ing interesting passage is quoted from the letter above mentioned : "I 

 think it most probablethat in the far past there would be a great quan- 

 tity of this sand on the shores of the then Bermuda. This, however, 

 as the island sank, and the coral grew, would become less and less 

 in proportion to the coral sand. Some of it would, one may be sure, 

 always be carried uj) by the wind along with the coral sand, and these 

 grains would accumulate in the 'red earth,' which one must regard as 

 the residue after the removal of the calcareous matter. In this way, 

 much of this volcanic sand may have belonged to the original Bermuda. 

 Much of it, I cannot but think, has been carried to the island by i:)um- 

 ice stone. Volcanic and other dust carried by the winds will doubtless 

 have contributed to the mineral particles we now find in the rock of 

 Bermuda." The considerable abundance of menaccanite, magnetite, 

 augite, olivine, and other volcanic minerals in the sands at various lo- 

 calities may be due to the fact that the material has been repeatedly 

 worked over — now blown up in sand-dunes, now washed down to the 

 shores by the rains. Thus the comparatively insoluble grains would 

 be concentrated and reconcentrated by the removal of the more soluble 

 calcium carbonate. Whether these volcanic grains are in part indigen- 

 ous, as Mr. Murray supposes, or have all been transported to the island 

 in the form of pumice or otherwise, we might reasonably expect that 

 they would now occur here and there in considerable abundance as the 

 result of this process of concentration. 



Nelson reports the occurrence of "small pieces of oxide of iron, of 

 very questionable origin; menaccanite, found near the ferry between 

 St. George's Island and Bermuda or Main Island; arragonite; and a 

 minute quantity of manganese in the red earth." * Among the nodules 

 of oxide of iron I have recognized both hematite and limonite. J. Mat- 

 thew Jones has noticed the occasional occurrence of iDieces of trap, 

 doubtless brought among the roots of drifted trees.t George W. Hawes, 

 Ph. I)., late of the United States National Museum, has noticed the 

 occurrence of pebbles of a variety of kinds of rocks. In a letter to me, a 

 few weeks before his death, he wrote concerning them as follows : " One 

 is a beautiful augite porphyry with large crystals finely formed of augite, 

 and most of them are eruptive rocks; but I have two that are plainly 

 silicious, apparently metamorphic rocks. I have found two quartz (Hint) 

 pebbles, small in size, and one I took out of the inside of a sponge." 



*" Op. (At,, p. 105. t Geological Features of tlie Bermudas, p. 22. 



