IN THE MUD OF THE LEVANT. 9 



of this problem under advantageous circumstances. 

 The sedimentary accumulation is now going on. 

 The organisms which constitute it, are unaltered 

 in their structure ; and indeed, many of them still 

 contain green animal matter, shewing them to 

 have been living when they were collected. They 

 have been subjected to none of the changes 

 produced by long-continued chemical action, or 

 mechanical pressure ; and, consequently, in this 

 example we may form some estimate of how much 

 is owing respectively to organic and inorganic 

 causes. 



It has long been known to geologists that in both 

 the Adriatic and the Mediterranean a modern 

 calcareous stratum is in process of formation. On 

 examining several specimens of this sediment, 

 brought me from the Adriatic side of the Levant, 

 under a magnifier having a power of 250 diameters, 

 I found that what, to the unassisted eye, appeared 

 to be a fine powder, mixed with fragments of 

 broken shells, is mainly, if not entirely, an accu- 

 mulation of organic atoms, of which the greater 

 number are minute and perfect organisms, varying 

 from l-20th to l-2000th of an inch in diameter. 

 These consist chiefly of Foraminifera, micro- 

 c 



