DESCKIPTION OF THE OOLITES 593 



deposited at the same time as the oolites and other materials of the shale. 

 A megascopic study of a piece of the material different from those de- 

 scribed above shows many small, irregular pieces of impure calcite or 

 rather calcareous shale. This material contains also small nodules of 

 limonite, some nodules being one-half inch in diameter. The oolites are 

 disseminated through the sandy shale which surrounds this calcareous, 

 limonitic material. All the different materials occurring in these shales 

 show by their relationship that they were deposited simultaneously. 

 Some of the shales contain numerous grains of what appears to be glau- 

 conite. It is possible that the green shale may owe its color, in part at 

 least, to this mineral. The color of the red and yellow phases is due to 

 iron oxides. 



SUMMARY 



The oolites are found scattered throughout the shale, which may or may 

 not be sandy. They are of two sizes, the larger averaging about .6 milli- 

 meter and the smaller about .15 millimeter in diameter. They are com- 

 posed of silica and are nuide up of concentric spheres. These concentric 

 spheres have approximately the same diameter in each sort of sliale, but 

 not the same in the various sorts. Xone of the oolites have a nucleus, 

 altl rough some of them contain considerable clay in the inner sphere. As 

 a rule, they are without a radial or tangential arrangement. There is a 

 faint radial arrangement in the oolites of the yellow shale, but they do 

 not show a cross between crossed nicols. Sand grains are scattered 

 throughout the shale and the oolites, but are in no way related to the 

 growth of the oolites. Irregular grains of calcite occur in the green sliale 

 and in the oolites in it, but are not related to the oolites. The relation- 

 ship of the oolites to each other and to the surrounding material indicates 

 that their growth was attained before the beds were consolidated. 



Origin" 



INTRODUCTION 



The writer believes that the oolites were always siliceous as they are 

 now. While this conception of the origin may appear unusual, yet the 

 evidence is such as to strongly support the view. As will be shown later, 

 much silica is being added to the waters of the sea by all streams. This 

 silica must be deposited because it is not now a constituent of the sea- 

 water in ap])reciable amounts, so it should not be regarded as so verv 

 unlikely that some of it may have assumed the spherical form of oolites 

 in the rocks. Such forms are typical of all amorphous substances, and 



