144 Vulcanos. 



peopled with organic beings, animals, and vegetables of sin> 

 pie structure ; the latter giving rise by their carbonization 

 to the coal strata* At length, as the temperature of the ocean 

 and atmosphere diminished further, the quantity of water 

 taken into circulation decreased; the continents were no longer 

 deluged by perpetual floods of rain, and organized nature took 

 possession of them also ; the marine deposits contained less of 

 precipitated matter, and became more earthy, and less crystal- 

 line } strata of shales, dull limestones, chalk, marl, sands, and 

 clay, succeeded those of clay-slate, marbles, and sandstones, until 

 the gradual change wrought by the slow refrigeration of the 

 outer zones of the globe brought about the condition in which it 

 exists at present. 



" The author remarks that, from the circumstances of their 

 origin, the rock formations of every kind or age must have been 

 more or less strictly local ; and that, though the formations of 

 any particular epoch will unquestionably have some points of 

 general resemblance all over the globe, it would be absurd to 

 suppose the same series of leds to have been deposited contem- 

 poraneously over the whole of its surface. 



" The author sums up, by attributing the production of the 

 mineral masses, as at present observable on the surface of our 

 planet, to three sources, distinct in their nature, but of which the 

 products have been often confused and mingled together from 

 circumstances, of isochronism or collocation. These are, 



" 1. The precipitation of some minerals, particularly silex and 

 carbonate of lime, from a state of solution in water, as its tempe- 

 rature was diminished, &c. 



" 2. The subsidence of suspended or fragmentary matter from 

 water; together with the accumulation and decomposition of the 

 shells of molluscae, corals, &c. 



" 3. The elevation of crystalline matter through fissures in the 

 crust of the globe. 



"The author conceives, that all the characteristic differences 

 observable in the successive formations of every kind, may be 

 satisfactorily traced to the gradual diminution in frequency and 

 energy of those productive causes, the varying nature of the 

 original materials acted on and the chemical and mechanical 

 changes they have undergone during the process ; and with due 

 allowance for these circumstances, these three modes of produc- 

 tion are perhaps fully equal to account for the origin of all the 

 mineral masses of the earths surface. They have also one im- 

 mense advantage over other hypotheses, and which speaks vol- 

 umes in their favor, and " this is, that they are still in operation" 

 and producing results completely analogous to those which are 

 here attributed to them. In fact, (the author says,) the theory 



