▶ Your Answer :
The reading passage contends that the origin of forts built with stones that are vitrified can be explained three theories. On the contrary, the lecturer represent counterargument for each of those by several points.
First, the writer acclaims that signal fires was the reason for the vitrification of the forts. The incessant heat would have made vitrified surfaces. However, lecturer maintains that if forts had been used to signal fires, it would have affected only a few areas, but all upper parts of forts were vitrified. This counters author's acclaims that because vitrified stones are most common on the upper parts of the wall, they were used to signal fires.
Second, according to the reading, lightning caused the stones of the forts to be vitrified. The uneven appearance of the walls can be explain by the lightening. This is because a single lightning strike is sufficient to make rock to be vitrified. On the other hand, the professor emphasis that the walls of the forts are huge. This means that the dozen of the lightening were required to affected them. Furthermore, the forts were very old, it is obvious that there are cracks
The last points suggested in the reading is that forts were built by using volcanic rock. This implies that the vitrification process already occurred before the construction. The ancient population of Scotland might had used volcanic rocks to build fortresses. However, the speaker refutes the arguments, saying there is no evident that volcanic eruptions occurred near the forts. The professor says that the ancient residents utilized local materials to construction. Moreover, it was impossible for them to move heavy rocks |