The following is a passage in Mary Shelley's Frankenstein. I am wondering what the boldfaced "This" refers to.
Before, dark and opaque bodies had surrounded me, impervious to my touch or sight; but I now found that I could wander on at liberty, with no obstacles which I could not either surmount or avoid. The light became more and more oppressive to me, and the heat wearying me as I walked, I sought a place where I could receive shade. This was the forest near Ingolstadt; and here I lay by the side of a brook resting from my fatigue, until I felt tormented by hunger and thirst. This roused me from my nearly dormant state, and I ate some berries which I found hanging on the trees or lying on the ground. I slaked my thirst at the brook, and then lying down, was overcome by sleep.