328 NATURE AND MAN. 



number having been washed down by rain and rivers. After 

 floating for a longer or shorter time, so as to be carried about by 

 winds and currents, perhaps to very considerable distances, they 

 would become water-logged and sink to the bottom, and there 

 undergo gradual disintegration. They were always found in 

 greatest abundance in the neighbourhood of volcanic centres, 

 such as the Azores and the Philippines; and within their areas, 

 again, were found tufaceous deposits — dust and ashes which had 

 been carried by the winds blowing over the craters. But there were 

 also occasionally found, at several hundred miles' distance from 

 any land, small pieces of obsidian and basaltic lavas, whose presence 

 there could only be accounted for by subtnarine volcanic action. 



In association with the clays there were found remarkable 

 deposits of manganese, sometimes incrusting corals, etc., with a 

 coating of greater or less thickness, but more generally forming 

 nodular concretions, varying in size from little pellets to several 

 pounds in weight, which were usually found to include organic 

 bodies, such as sharks' teeth or whales' ear-bones. The following 

 summary of this curious class of facts is given in Lord George 

 Campbell's " Log-letters " : — 



"In some regions everything at the bottom, even the bottom 



" itself, would appear to be overlaid by and impregnated with this 



"substance. Sharks' teeth of all sizes (many gigantic, one was 



"four inches across the base) are frequent, and are sometimes sur- 



" rounded by concentric layers of manganese of nearly an inch in 



" thickness. A siliceous sponge, bits of pumice, radiolaria and 



" globigerinae, and lumps of clay, have all been found forming the 



" nuclei of these nodules. We have caught in one haul, where 



" there has been no reason to suppose that the trawl has sunk 



"more than two inches in the clay, over 600 sharks' teeth, 100 



"ear-bones of whales, and fifty fragments of other bones, some 



" embedded in manganese an inch thick, some with only just a 



" trace of manganese on them, and some with no trace at all. 



" These sharks' teeth are all fossil teeth, the same as are found 



"in great quantities in Tertiary formations, particularly in Swiss 



"Miocene deposits.* 



* The writer does not seem aware of the extraordinary abundance of 

 similar sharks' teeth and whales' ear-bones in the so-called " coprolite pits " 

 of our Suffolk crag. 



