1905.] NATURAL SCIENCES OF PPIILADELPHIA. 905 



the rim at its highest point. At the 500-foot level there is but little 

 powdered silica; the material is mostly of broken and unbroken sand 

 grains. Below this point the powdered rock is again met with which is 

 very fine. It is almost, but not quite, as fine as at the surface. This 

 change occurs quite suddenly and is accompanied with a progressive 

 scarcity of meteoric material which is completely absent at 550 feet. 

 From this point down there is again a gradual increase in whole and 

 broken sand grains contained in the material, and at 860 feet it changes 

 color quite suddenly to a reddish-brown sand, which at 890 feet, from 

 the sudden change in hardness and the difficulty of drilling, is almost 

 certainly rock in place. This continues to the fartherest point reached, 

 namely, 1,003 feet below the level of the interior plain. 



It is submitted that, regardless of the fact of whether or not the last 

 100 feet is solid rock or not, that the material penetrated for the last 

 150 feet must be rock in place ; for this reason : The change from white 

 sand to reddish-brown sand is quite marked and sudden, and if this 

 material had been stirred up by the passage of any projectile through 

 it, it would have been so mixed as to be indistinguishable, or at any 

 rate would certainly not have had a definite boundary line between the 

 two materials. For 180 feet below the surface of the plain the filling 

 material is absolutely dry. At this point dampness is perceptible, 

 which increases with the depth until at 200 feet the material is nearly 

 saturated with water ; which fact determined the stoppage of the shafts 

 at this point and the use of well-drilling apparatus for the deeper 

 explorations. 



Meteoric Material Found in the Lower Portions of the Hole. 



The meteoric material found, mixed with filling material, in the hole 

 from the 300- to 500-foot levels is of the following kinds : First, mag- 

 netite in the form of scales, closely resembling hammer slag produced 

 by a blacksmith in welding and forging iron. These films occur in 

 varying proportions among the sand. Second, of more sparing occur- 

 rence are small particles of brownish magnetite, resembling that picked 

 up on the surface. Third, sand grains wholly or partially coated with 

 magnetite and small bunches of sand grains cemented together with 

 magnetite. The first and third forms have undoubtedly solidified from 

 a state of fusion ; the first alone, and the latter when the fused magnetite 

 came in contact with one or more grains of the sand. The appearance 

 of this last form under the microscope is precisely that of broken stone 

 smeared with, and cemented together by, such a fused material as 

 asphalt when prepared for the foundation of an asphalt street. Second, 



