Final answer:
Dr. Oliver Wendell Holmes noticed certain superstitious impressions related to his family mansion, which had a significant impact on his spirit and morale of his existence.
Step-by-step explanation:
Dr. Oliver Wendell Holmes noticed certain superstitious impressions related to the dwelling he lived in. He mentioned that the physical features of his family mansion, such as the gray walls, turrets, and the dim tarn, had a significant impact on his spirit and the morale of his existence. These impressions were conveyed in terms too shadowy to be restated. His observations indicate that he was deeply affected by the atmosphere and influence of his home.