Final answer:
The line 'In this mood of mind' in the given text indicates that the narrator is in a particular state of mind or mood.
Step-by-step explanation:
The line 'In this mood of mind' in the given text indicates that the narrator is in a particular state of mind or mood. The use of the phrase suggests that the narrator is feeling a certain way or experiencing a certain emotional state. It implies that the narrator's previous experiences and encounters with other researchers have influenced their current mindset and attitude towards their studies. This line signifies a shift in the narrator's perspective and interests, leading them to focus on mathematics instead of their previous scientific pursuits.