Until I read "Measuring America", I was only vaguely aware of the importance of surveying to the economic and political history of the United States. Like most students, I had read that George Washington was a surveyor, but I did not know that he earned more income in that occupation than he did as President, or that his estate on the Potomac was a direct result of his work as a surveyor. The ownership of a continent could not become legal until it was clear what was owned, and that task depended on agreement upon a system by which the measurements were to be made. Contemporary with the French meridian survey (see last month's Pick), Thomas Jefferson devised his own version of a "metric system", based on the length of an iron rod that swings with a one-second period. The system had thoroughly decimal relationships for length, area, volume (one decimal ounce to be the mass of one cubic inch of rainwater, and the inch to be one-tenth of a decimal foot, which was based on the length of the iron rod. Science and technology are not the real focus of "Measuring America" but, as the book makes clear, commerce has always depended on a reliable system of measurement.