The many rules of thumb that are available to compare cat ages to human ages are usually based upon total life expectancy. An average catâs life expectancy is around 17 years, and a humanâs is around 84 years.This leads to a rough equivalency of five-to-one. But it is not an apples-to-apples comparison.onventional wisdom holds that each year for a cat is equivalent to seven years of development and aging for a person. Or that each cat year is equivalent to five human years. Or that the first two years are equivalent to 21 years, and each subsequent year is equivalent to four or five years.
The Cast Iron Plow. A bill has recently passed the Senate of the United States, and is now pending in the House of Representatives, to extend the patent of Jethro Wood for seven years, which he obtained in 1814, and renewed in 1819, claiming to have invented the cast iron Plowshare.
Suddenly the fields with the heavy, fatty and moist clay soils became those that gave the greatest yields. Thomas Barnebeck Andersen. The world changed when a plough that could plough deep and turn over heavy clay soil was invented in the Middle Ages. Armed with massive amounts of data, researchers are now trying to document how a small technology leap turned the distribution of wealth on its head in medieval Northern Europe.