AND THE PHOSPHATIC BEDS NEAR MONS. 33& 



the phosphatic deposit, taken at its mean depth of 70 feet, there 

 exists a quantity of tribasic phosphate of lime equal to that con- 

 tained in the bodies of 80 living human beings *. 



To what cause can the deposit of so prodigious a quantity of phos- 

 phate of lime be attributed? 



Three points are indisputable : — 



1. The phosphate contained in the brown chalk of Ciply is of 

 animal origin, as is proved by the large proportion of nitrogenized 

 organic matter contained in it. 



2. It was deposited in a sea that nourished a numerous fauna of 

 shells, and in which existed fish and great marine Saurians. 



3. Its deposition was effected tranquilly, as is proved by the 

 great regularity of the beds, and by the condition of the fossil 

 shells, which have often their two valves united. 



So far as I know, there has been no discovery, up to the present 

 time, in other parts of the globe, of phosphatic beds analogous to 

 those of the environs of Mons ; but there exists in nature a fact 

 which may perhaps explain the formation of the beds of the brown 

 chalk of Ciply. In the ' New Universal Geography,' by Elisee Eeclus, 

 the following statement occurs t : — 



" At the period of change of the monsoon, chiefly in October and 

 November, millions of all kinds of dead fish are thrown up by the sea 

 on the coasts of Pcrim and of Aden. In order that the air should not 

 be tainted, the inhabitants set to work to bury this mass of putrefied 

 flesh. What is the cause of this mortality among the fish ? The 

 natives attribute it to some poisonous substance, whilst King ascribes 

 it to electrical phenomena caused by the change of the season X' 

 The myriads of organisms which perish under the incessantly re- 

 newed layers of successive organisms, suffice in many localities to feed 

 springs of the oily materials, which ooze out upon the seashore "§. 



The cause that leads to the mortality of the animals inhabiting the 

 waters of the Gulf of Aden does not, however, concern the question 

 before us. The important fact is, that at certain seasons of the 

 year, i. e. periodically, there is an accumulation, on certain parts of 

 the southern coast of the Peninsula of Arabia, of animal substances 

 very rich in tribasic phosphate of lime. There is no reason why we 

 should not admit that the same phenomenon may have been in 

 action at different periods of geological time. One may therefore 

 ask, whether it was not to a similar action, coincident perhaps with 

 a slow depression of the coast, that the formation of the Brown Phos- 

 phatic Chalk of Ciply may be attributed. 



Discission. 



The President said that two important considerations arose from 

 this paper : — (1) that these beds were amongst the very highest in 



* See on this subject the calculations of M. Melsens, 'Bulletin de TAcad^mie 

 Royale de Belgique,' 2^ ser. vol. xxxviii. p. 40. 



t Vol. ix. pp. 8(')9, 870. I 'Geographical Magazine,' 1877. 



§ Oscar Fraas, ' Aus dem Orient.* 



