81 



On the Recent Calcareous Deiiosits of the Cotteswolds. Read at 

 Gloucester, March 6th, 1873. By G. F. Platne. 



In the study of the older formations which compose the crust 

 of our globe we find such abundance of interesting detail in the 

 composition and disposition of the igneous rocks, and of the 

 sedimentary strata, with their innumerable enclosed organisms, 

 to engage our attention, and are so impressed with the magnitude 

 of the deposits which have taken place, and with the lapse of time 

 necessary for such vast and varied changes to have resulted, 

 that we are tempted to think lightly of those geologic changes 

 which are occurring in our own time. And yet it is by accurate 

 observation of the mode and effect of existing agencies that Ave 

 arrive at just conclusions as to the means by which the older 

 formations have been produced. In this way is it that of late 

 so much light has been thrown on the subject of former denuda- 

 tion, by noting the effects of rain and rivers on the present surface 

 of the earth. In this way, as so ably brought before us at 

 our last meeting by Dr. Weight, many difficult problems are 

 solved regarding the former glaciation of lands which now enjoy 

 temperate climates, by a reference to the action of existing 

 glaciers. In this way many of those thinnings out of particular 

 strata, and those changes in mineral composition, as well as in 

 the character of their enclosed organisms, which form such 

 striking and often perplexing problems when such strata are 

 studied over extended areas, may be explained by a study of the 

 deposits now taking p^ace in our existing seas and oceans, and by 

 observing the effect of the action of existing cm-rents and tides 

 on these recent deposits. 



In some degree, I trust, the subject of this paper, by pointing 

 out geologic re-formations now taking place, may illustrate some 

 of those combined chemical and mechanical operations which 

 have led to the deposition of many of the older strata. 



