It seems that you have missed the necessary options for this, but anyway, as I searched for it, here is the answer. What is so unique about the north american midwest that results in having more tornadoes than anywhere in the world is that the northward movement of warm moist air from the gulf of Mexico; the southward movement of dry cold air from Canada; and the lack of mountains preventing the convergence warm gulf air with cold Canadian air. Hope this answers your question.
The third one is the answe
An astrolabe is a primitive angle-measuring tool. It can be used to - very in-exactly! - measure the altitude above the horizon of a celestial body like the Sun, Moon or Polaris in order to calculate your position.
Medieval gunners used the astrolabe to calculate the height of towers and buildings, in order to more accurately aim their cannons.
Joseph Pierce I believe.<span />
