144 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 92 
the Museum. As Mr. Powell had stated in his letters, there were no 
scars on the surface. The field slopes gently northward from a rounded 
crest encircled by the 280-foot contour line to the south fork of Beaver- 
dam Creek, which is 0.6 mile away and flows at an altitude of 220 feet 
above sea level. The meteorite lay about 250 feet above sea level and 
about midway between the top of the slope and the creek bed. Shallow 
wooded valleys leading to Beaverdam Creek lie just east and west of 
this field, and the two slopes grade evenly together. There is no indi- 
cation that this plowed field has eroded very rapidly, nor is there any 
evidence of craterlike depressions. 
After Mr. Powell pointed out the spot, we shoveled away the weath- 
ered, sandy soil down to the hardened surface on which the meteorite 
had rested. This proved to be compact, sandy clay of the Hawthorne 
formation of middle Miocene age, which at this place is covered by 
about 24 inches of loose sandy residual soil. Nothing was found in 
the Hawthorne sediments that could be taken as evidence of any dis- 
tortion or disturbance. One would suppose that a freely falling body 
of this size would certainly crush or shatter even any consolidated 
rocks on which it fell. Surely this sandy clay, under the blow of so 
many thousand-foot pounds, would spatter away. The craterlike scar 
might not be preserved for an indefinitely long time, but such a de- 
pression would last for at least several hundred years. Plowing and 
harrowing would tend to erase such a scar, but it is doubtful if either 
normal cultivation or natural agencies would level it within a single 
century. The present owner of the land has tilled this field for nearly 
50 years, and, as the farm belonged to his father, he would almost 
certainly have heard about it if such a large meteorite had fallen on 
his farm within the past 75 years. 
General topographic features of this district suggest that erosion 
has not been very rapid. There is no apparent geological evidence to 
indicate that the general surface of this area has been reduced at a 
rate faster than 1 inch each 100 years; in all probability erosion has 
been at an even slower rate. 
Depth of penetration—Many factors, each with an almost unlimited 
number of variabilities, determine the depth to which a meteorite 
penetrates into the ground. Among the important factors are the 
rigidity of the meteorite, its shape, velocity of descent, and the nature 
of the material on which it landed. Meteorites of equal weight and 
velocity would not all bury themselves to the same depth in loose 
sand, because different meteoritic individuals have different rigidities. 
Some stony meteorites are rather friable when found, but just how 
firm these objects were prior to their impact with the earth is not 
known. It seems likely that iron meteorites, all other things being 
equal, would penetrate deeper than stony ones because of their greater 
rigidity or toughness. 
