234 MAYOR— THE REEFS OF TUTUILA, SAMOA. 



shores along which corals are growing. I find, for example, that 

 the coarse brown bottom mud of the mid-channel line of Pago Pago 

 Harbor near the inner end of the harbor between Blacklock's Wharf 

 and Pago Pago Stream consists, by weight, of 67 per cent, of vol- 

 canic material insoluble in hydrochloric acid and 33 per cent, of 

 calcareous elements composed of shells, Halimeda, etc. At moor- 

 ing buoy " B " about one third the distance from the inner end to 

 the mouth of the harbor the bottom mud is finely divided, brown in 

 color, and 51 per cent, volcanic. At mooring buoy " C," however, 

 which is only 300 meters outward beyond buoy " B," the bottom 

 mud is brown-gray in color and contains only 18.5 per cent, of vol- 

 canic elements. While at the mouth of the harbor the mud is a 

 finely divided light gray deposit and contains only 6 per cent, of vol- 

 canic material. Thus the bulk of the volcanic silt is deposited on 

 the harbor bottom before it goes more than one-third the distance 

 from the inner end of the harbor to the mouth. 



Thus, as Davis shows, coral reefs could form more readily 

 around an emerged or a still-stand shore-line. Davis is the most 

 active defender of Darwin's coral reef theory, yet the sequence of 

 fringing reefs being converted into barrier reefs through subsi- 

 dence of the land or by rise of sea level, and finally the conversion 

 of these barrier reefs into atoll rims has not been proven even in a 

 single instance, although it is the crux of Darwin's theory. As 

 Davis admits we have not been able to read the history of the atolls, 

 for there is no central island whose shore line can be interpreted. 



There is on the contrary evidence that barrier reefs have in many 

 places arisen as barriers along the seaward edges of submerged pla- 

 teaus and remained such throughout their history, or have fused in 

 places with fringing reefs which grew contemporaneously outward 

 from the shores. Thus we have Vaughan's evidence that the old 

 elevated reef of Florida which now constitutes the islands from 

 Soldier's Key to the southern end of Big Pine Key is not a mere 

 elevated part of the limestone platform upon which it grew for the 

 platform is of oolitic formation and contains very few corals. 



As has been pointed out by Daly, Darwin's theory does not ex- 

 plain the nearly uniform depth of about 20 fathoms, and the re- 



