MURRAY'S THEORY 95 



Nevertheless it has never been without a rival : even 

 before Darwin published his celebrated work, Ainsworth * 

 had suggested a different explanation. He rightly 

 pointed out that Quoy and Gaimard had not established 

 a limit for all reef-building organisms, and that, although 

 certain corals, such as they had observed, might be 

 restricted to shallow waters, there might yet be others 

 capable of flourishing at greater depths. If so, these 

 deep-water organisms might be engaged in laying the 

 foundations of an atoll on which the shallower water 

 forms might erect the superstructure (Fig. 23). This 

 suggestion seems to have fallen still-born, but the notion 



AlMSWORTH 



FIG. 23. 



of "laying the foundation" of an atoll was not destined 

 to perish : it has been revived of late years by Sir John 

 Murray, who, guided by his observations made when on 

 board the Challenger, was led to suppose that the sub- 

 merged summits of deeply-sunken islands might be raised 

 to within the limit of 25 fathoms, not by the upward 

 growth of corals, but by the incessant downward rain of 

 minute organisms from the surface of the sea. The same 

 agencies which were supposed to be spreading out a layer 

 of chalky mud or ooze over the abyssal floor of the ocean 



-' Gr. W. Ainsworth, " Analysis of a Voyage to the Pacific and 

 Behring's Straits, to co-operate with the Polar Expedition, performed 

 in H.M. Ship Blossom, under command of Capt. F. W. Beechey, E.N., 

 in the years 1825-28," Geog. Jour., vol. i ., 1831. 



