May 1, 1903.] 



SCIENCE. 



709 



Berkeley the exploration was continued by 

 tlia*scriter. 



The work of excavation has been gener- 

 ously supported by Mrs. Phoebe A. Hearst as 

 a part of the investigation being carried on 

 with a view to determining the antiquity of 

 man in California, and has been conducted 

 under the direction of Professor J. C. Mer- 

 riam. Through the kindness of Dr. W. C. 

 Bruson and Mr. D. P. Doak, the controllers 

 of the property, a lease has been secured, and 

 the deeper portion of the cave will be explored 

 during the coming summer. 



The system of galleries which comprises the 

 Potter Creek cave extends in a northwest- 

 southeast direction, in a general way parallel 

 with the strike of the limestone. The floor 

 of the principal chamber is 42 feet beneath 

 the opening communicating with the winding 

 passage leading to the exterior. It can be 

 reached only by a vertical rope ladder secured 

 above to a convenient stalagmite pillar. This 

 chamber haa a length of 106 feet and is 29 

 feet wide at its widest part. It narrows to a 

 width of four feet at the extreme northwest 

 end. Both walls slope toward the west, the 

 west wall overhanging. The vaulted roof 

 rises at least sixty feet above the floor. Nu- 

 merous massive pendants ornament the hang- 

 ing wall. 



The floor of the large chamber was of pebbly 

 clay and cave breccia. The main deposit was 

 in the form of an alluvial fan with its apex 

 in the narrow northwest end. The surface^of 

 the fan was in general convex, flattening some- 

 what toward the center of the chamber. A 

 thin superficial layer of stalagmite was pres- 

 ent on the margin of this deposit adjoining 

 the west wall. In the southeast end there 

 is also a fan, rising almost as high as the one 

 just described. The surface of this slope 

 down almost to the lower edge is covered with 

 a firmly compacted cave breccia and is strewn 

 with large fallen blocks of limestone and 

 broken stalactites. 



Work was begun in the clay about the 

 middle of the main chamber, near the margin 

 of the northwest fan, and was carried toward 

 the northwest end. The surface of the de- 

 posit was staked out in four-foot squares, and 



each of these sections was worked in ten-inch 

 levels, all the specimens from each level being 

 labeled with the number of the section and 

 the depth at which they were found. 



The structure of this fan was as follows, 

 in descending order: 



A. Pebbly clay with gravel lenses, 4 to 13 J 

 feet. 



B. Persistent gravel stratum, 6 inches to 

 IJ feet. 



C. Volcanic ash, up to 1| feet. 



D. Clay with fallen limestone blocks, up to 

 3 feet. 



E. Stalagmite cementing angular blocks of 

 limestone (false floor), 18 inches or more. 



The pebbly clay (stratum A), is a reddish 

 clay similar to that produced by the subaerial 

 decay of the limestone and intrusive diabase. 

 It contains abundant angular fragments of 

 blue limestone and occasional pieces of stalac- 

 tite from the roof. This deposit varies in 

 thickness from four feet to thirteen and a 

 half feet. A layer of stalagmite partly cap- 

 ping this reddish earth on 'the west margin 

 rarely exceeds a few inches in thickness, usu- 

 ally averaging from half an inch to an inch. 

 It is closely associated with the pendants 

 fringing the west wall, and has been largely 

 deposited by water dripping from them. 



Beneath the capping stratum ^f clay, two 

 main gravel lenses are distinguishable. These 

 roughly parallel the surface of the fan and 

 feather out toward the northwest margin. The 

 gravel strata, so called, are composed of angu- 

 lar, drip-washed limestone fragments, and 

 could readily be formed by water falling from 

 the roof and washing the small limestone 

 fragments out of the clay. These strata vary 

 from three or four inches to a foot and a half 

 in thickness. On approaching the west wall, 

 the gravel lenses were in some cases found to 

 coincide with sheets of stalagmite. The 

 gravel strata are separated by beds of clay, 

 similar in every respect to the first clay 

 stratum described. On the disappearance of 

 the gravel all these clay strata blend. 



Beneath the persistent gravel layer (stratum 

 B) is a deposit of fine particles of volcanic 

 glass (stratum C), which appear to have 

 drifted into the cave by wind action in Qua- 



