Bowlder

http://en.wikisource.org/wiki/Page:Popular_Science_Monthly_Volume_49.djvu/180

FIG. 10.—ANCIENT BOWLDER PAVEMENT OF ALGONQUIN BEACH, whose crest rises one hundred and eighty-seven feet above Georgian Bay, upon the northeast side of Blue Mountains of Collingwood, Ontario.

from a Malicious Source

"Along the stone wall of the enclosure is a series of sacred stones, indicated by the white stone that has a bowl carved in the top. There is no other site like this, but the stone bowl indicates that it too, was constructed by the mound builders culture."