the Igneous Platform. 195 



altered, very compact lava. While they are outwardly brown, 

 they are within of a lead-gray ; sometimes of a deep Indian-red, 

 the color of ferric oxide. Some of them show occasional angu- 

 lar inclusions of a soft whitish clay, apparently from their shape 

 altered phenocrysts. Some of these fragments are rounded, 

 ovoid to sub-angular, and appear distinctly like water-worn 

 pebbles. They are about the size of a hazel nut. That the 

 rounded form is a natural one is shown by the fact that the 

 pebbles have a thin outer coating, or crust, of brown colored 

 substance ; when this is broken into, as remarked above, they 

 are lead-gray within. This would indicate that the pebble had 

 altered after it had received its shape. 



The material from 518-573 feet, both the fragments and 

 fine debris, is a rich earth-brown, and resembles indeed clots of 

 dried earth ; some of it is full of harder, more compact pieces, 

 whose shape and nature indicate small pebbles of decomposed 

 lava, while others, which are filled with rather regularly-spaced 

 calcite spheroids the size of shot, are evidently pieces of altered 

 amygdaloid. The brown earth acts as a cement in holding the 

 crumbly fragments together. 



The thin layer, 573-574 feet, is the blackish one mentioned 

 above; it is quite clearly an altered amygdaloid. The dark, 

 compact mass is filled with whitish to pale brown calcite balls, 

 varying in size from fine shot to peas. Its significance is dis- 

 cussed beyond. 



From 574 to 583 the brown earthy material recurs filled 

 with calcite ovoids, and hence a broken down and altered 

 amygdaloid. It is more amygdaloiclal than any of the preced- 

 ing samples. 



Zone of Unoxidized Material. 



At 583 feet a change occurs, the samples are no longer 

 brown and weathered, bat blackish to dark or medium gray in 

 color, and it is clear that, whatever opinion may be held as to 

 the cause of this difference, they have been subjected to a 

 different set of conditions from those which affected the fore- 

 going material. There is one slight exception to this rule, as 

 noted below. 



The sample taken between 583 and 615 feet is evidently a 

 broken-up amygdaloid ; it consists of a mixture in nearly equal 

 parts of whitish calcite spheroids the size of fine to coarse 

 shot, and small particles of a compact gray lava of the same 

 size. There are also a number of brown and reddish altered 

 fragments in it. Although it might be assumed that the 

 crushing of the amygdaloid was done by the drill, it is believed 

 that the latter merely penetrated a layer of amygdaloidal 



