LECTURES ON OEOLOGT. 249 



mass is the residence of innumerable animalculse, which, like bees 

 are actuated by a common instinct in the construction of their ha- 

 bitations, and the preservation of their species. But a more 

 attentive observation of their habits has proved that these zoophytes 

 more closely resemble plants than they were imagined to do, and 

 that each lamina, tree, or mass of coral, is the stony skeleton of a 

 single animal, adhering to the submarine rocks by means of roots, 

 as lichens, fungi, and trees do to the soil ; throwing out branches 

 which bear and shed their fruit — the young coral j and, like vege- 

 tables, dying when deprived of their bark. This bark is the fleshy 

 part of the zoophyte, and connected with it are the polypi, or coral 

 insects, as they were called, but which are now considered as so 

 many distinct mouths, constantlj employed in catching their prey, 

 and supplying nourishment to the whole bark or fleshy portion, to 

 enable it to add by fresh deposits of calcareous matter to the 

 growth of the trunk or skeleton. 



Coral requires for its growth water holding lime in solution, 

 which will explain its abundance in the Italian seas, where that 

 mineral is supplied, as we have seen, by the rivers and springs 

 flowing from volcanic regions. The rapid formation of coral 

 islands in the South Pacific, and their peculiar configuration, has 

 been accounted for upon similar grounds. These islands are most 

 abundant in the vicinity of volcanoes, and are of a circular or 

 crescent-like form, with a deep lake in the centre, in which pumice 

 and scoriae have been found. From these circumstances, and from 

 the fact that coral will not grow at a greater depth in the sea than 

 about 100 yards, many geologists believe that the coral islands are 

 the summits of submarine volcanoes, capped and raised above the 

 surface by the labours of the zoophytes. 



A comparison of a recent coral rock, with the Dudley limestone, 

 will enable us to affirm with some confidence that when the latter 

 was formed volcanic action had hardly commenced in its vicinity ; 

 no scoriae or basalt are found in it, and although the important 

 condition of a tropical sea was present, as is indicated by the 

 associated fossils, yet we never meet with coral in rock-like 

 masses ; it is entirely in lumps or fragments imbedded in strata of 

 almost unvarying thickness. We cannot, therefore, consider that 

 Dudley and the Wren's Nest were ever coral reefs, but we must 

 suppose that they owe their peculiar form to the upheaving power 

 of volcanic action. 



LECTURE III. 



The Lecturer first pointed out the distinction between true coal, 

 one of the lowest secondary formations, and lignite or fossil wood, 

 which is found in many of the secondary and tertiary strata 3 and 

 then described the most important of the English coal fields. 



The south Staffordshire coal field extends about twenty-five 

 miles in length, from near Stourbridge, across Cannock Chase, to 

 Rugeley, having an average breadth of four miles. It is divided 

 into three portions by the intersection of basalt and limestone from 



