1862.] mJLL — CARBONIFEROITS STRATA. ^ 133 



stony skeletons and habitations. Carbonate of lime, however, when 

 dissolved by the agency of free carbonic-acid gas, does not interfere 

 with the transparency of the water ; and this transparency is the all- 

 important condition to the organic growth of limestones. And not- 

 withstanding that the amount of carbonate of lime in solution in the 

 mid-ocean is often extremely minute, yet its solubility enables it to 

 be carried to all parts of the ocean where no particle of sand or clay 

 can reach ; and thus it may be possible that all sedimentary forma- 

 tions have had their contemporary calcareous representatives at some 

 one or more parts of the globe. 



(g.) There is one objection which may be urged against this view 

 of the relations of true sedimentary and the calcareous strata. In the 

 cases just cited of the Carboniferous Eocks of Belgium and West- 

 phalia, and of the Great Oolite of our own country, the development 

 of the sandstones and shales from the one direction, and of the lime- 

 stones from the opposite, are not strictly contemporaneous. Thas the 

 lower and upper sandstone and shale of the Great Oolite, which are 

 thickest in the North, are earlier and later than the ^' white lime- 

 stone," which is most highly developed in the South. This, however, 

 arises from the very slow progress of those changes in the character 

 of the land and sea which have conduced to the differences of the 

 strata formed in each district. While the lower series of sandstones 

 and shales were being formed over the Yorkshire area, the sea-bed 

 was gradually preparing for the future development of calcareous 

 strata over the Oxfordshire area ; and while limestones were forming 

 under Oxfordshire, the sea of Yorkshire was stiU sufficiently charged 

 with sand and mud to prevent their full development in that quarter. 

 Another change occurred : the Yorkshire sea again became charged 

 with sand and mud, which so far extended its influence to Oxford- 

 shire as to check the formation of pure limestone. 



In this instance, as in others, there was a series of oscillations as 

 the two agencies alternately predominated ; but, while each in turn 

 obtained the ascendency, the influence of the other never entirely 

 ceased within certain limits. Thus, while sandstones and shales 

 were accumulating in Yorkshire, sandy limestones and calcareous 

 shales were forming in Oxfordshire, as the influence of the calcareous 

 element was always more or less in force in the southern direction, 

 when it was entirely overpowered by the ascendency of the sedi- 

 mentary element in the north. And if we adopt the conclusion of 

 Bischof, that it is impossible for any carbonate of lime to be preci- 

 pitated at the bottom of the open sea by chemical action, but only by 

 the intervention of organized beings, we must allow that these 

 agencies, by whatever terms they may be designated, are not mere 

 figures of speech, but real and ever-acting forces of nature. 



It is difficult to represent by means of a diagram what is here 

 discussed; but perhaps fig. 3, representing the Great Oolite of 

 Yorkshire and Oxfordshire, may assist in rendering my meaning 

 more clear*. (See also fig. 1, p. 131.) 



* I am aware that Dr. Wright, than whom there is no better authority, calls 

 in question, on palaeontological evidence, the parallelism here stated, which is, I 



