Boyle's law of the gas, and "k" is a constant. The equation states that the product of pressure and volume is a constant for a given mass of confined gas and this holds as long as the temperature is constant. For comparing the same substance under two different sets of conditions, the law can be usefully expressed as The equation shows that, as volume increases, the pressure of the gas decreases in proportion. Similarly, as volume decreases, the pressure of the gas increases. The law was named after chemist and physicist Robert Boyle, who published the original law in 1662. This relationship
Theory of intervening opportunities Theory of intervening opportunities Theory of intervening opportunities attempts to describe the likelihood of migration. Its hypothesis is that this likelihood is influenced most by the opportunities to settle at the destination, less by distance or population pressure at the starting point. Stouffer's law of intervening opportunities states, ""The number of persons going a given distance is directly proportional to the number of opportunities at that distance and inversely proportional to the number of intervening opportunities."" Stouffer theorises that the amount of migration over a given distance is directly proportional to the number of opportunities at the place of destination,