INTRODUCTION 747 



"This may be well seen where waters highly charged with bicarbonate of 

 lime flow slowly into some nook or bay, on tropical coasts, and even in locali- 

 ties where the rise and fall of tide is small, as, for instance, around Jamaica. 

 It is in such situations, under favorable conditions, that the little grains 

 termed oolites, formed of concentric coatings of calcareous matter, may be 

 sometimes observed to form. A slight to and fro motion, produced by gentle 

 ripples of water, may occasionally be seen to keep the carbonate of lime de- 

 positing in movement and dividing into minute portions, so that instead of a 

 continuous coating of calcareous matter upon any solid substance beneath, a 

 multitude of these little grains is produced. As might readily be anticipated, 

 a small fragment of shell and even a minute crystal of carbonate of lime is 

 suflacient to form a nucleus for the concentric coatings of these oolitic grains." 



In 1862 Ferdinand Cohn described the formation of the "sprudel- 

 stein," or pisolite, of the Carlsbad springs as due to the activity of algae. 

 Thus early in the study of oolites two very different theories were ad- 

 vanced to account for the origin of the oolite grains. The first consid- 

 ered them as simple chemical precipitates, accumulated layer by layer 

 on nuclei kept in motion by agitated waters. This is perhaps the most 

 widely accepted view even ai) the present time, although, as will be pres- 

 ently shown, it is not as simple in its application as it would at first seem 

 to be. The second theory holds that the oolites are the products of or'- 

 ganic activity, and that the carbonate of lime was separated from the 

 water by the organism and deposited around some nucleus to which the 

 organism adhered. The majority of authors have considered algae as the 

 active agents, although some have considered protozoa responsible for 

 certain oolites. 



Historical Eeview 



It is not the purpose of the present paper to review in detail all of the 

 literature which has appeared on the subject of oolites, but rather to call 

 attention to a few of the more important contributions and to point out, 

 in as far as it is possible to do so, how these views have affected or failed 

 to be recognized in the later discussions of the subject. A bibliography 

 is appended which contains all of the important references to the litera- 

 ture on this subject which have come to the writer's attention during the 

 preparation of this paper. 



In 1872 Dana, while describing the formation of beach sands around 

 coral reefs, noted the fact that these sands were very frequently oolitic. 

 He says:^ 



"In most localities the rock is an oolite or oolitic limestone. The grains be- 

 come coated by the agglutinated carbonate of lime, and each enlarges thus to 



J. D. Dana: Corals and Coral Islands, 1872, p. 153 (edition of 1879). 



