As may be obvious by now, it is helpful in the understanding of this book to see the earth as having a single soil (as it has a single atmosphere), nearly all of it 10,000 or more years “old,” or in development, since the bulk of its surface “parent material” was laid down. In addition to those cited by Hamaker, some other examples of results obtained with ground gravel (mixed rock) materials may help illustrate the great potential to restore youthfulness and productive fertility to any and all soil
