Answer:
While watching the air pressure change, the change that occur within the barometer is that the barometer (if aneroid barometer) contains within it a partially evacuated (vaccumed) steel corrugated box. The top surface is held by a strong spring to stop it from collapsing.
If the air pressure changes, the surface moves up or down with a decrease or increase in air pressure respectively. This movement is transmitted and amplified by a connected system of jointed lever and chain that passes around a grooved wheel. This transmission is to a pointer that is deflected with these change and movements to give the reading on the scale. The scale is is often calibrated in millibars; higher pressure indicates a bad weather.
Two ways in which the proximity to water has affected Western Europe's economy:
1) Proximity of water can lead to lack of food, which affects economy of the country in various ways.
2) It has wet cool summers and wet, mild winters, so for shelters and cloths, it affects economy by transportation, extra manufacture etc.
Hope this helps!