How is the madness of the narrator portrayed in the passage above?

Amid the thought of the fiery destruction that impended, the idea of the coolness of the well came over my soul like balm. I rushed to its deadly brink. I threw my straining vision below. The glare from the enkindled roof illumined its inmost recesses. Yet, for a wild moment, did my spirit refuse to comprehend the meaning of what I saw. At length it forced—it wrestled its way into my soul—it burned itself in upon my shuddering reason. O for a voice to speak!—oh, horror!—oh, any horror but this! With a shriek I rushed from the margin and buried my face in my hands—weeping bitterly.