ANSWERS TO CORRESPONDENTS: Why are dams made curved instead of straight across?

Most dams in this country are straight, not curved. The arch dam, as the curved type is known, is effectively an arched bridge turned on its side, with the centre…

ANSWERS TO CORRESPONDENTS: Were trebuchets built in situ and then abandoned after a siege?

Early trebuchets were built on site. As they grew increasingly large and powerful, wagons carrying sections of prefabricated trebuchets were brought to a siege and assembled in situ. A trebuchet…