The Mayan and other Mesoamerican cultures used a vigesimal number system based on base 20, (and, to some extent, base 5), probably originally developed from counting on fingers and toes. The numerals consisted of only three symbols: zero, represented as a shell shape; one, a dot; and five, a bar.
Silent Spring is a book that talked about how the pesticides make a detrimental effect on the environment, especially on birds. The chemical industry was accused by Carson of spreading disinformation.
