The main theme of Chapter 7 - A Visit to Cambridge is the narrator's experience and observations during their visit to the city of Cambridge.

Introduction:
The chapter begins with the narrator expressing their excitement about visiting Cambridge, a renowned city known for its prestigious university and rich history. The chapter highlights the narrator's anticipation and curiosity to explore the city.

Cambridge University:
The chapter focuses on the narrator's visit to the famous Cambridge University. It describes the beautiful and grand architecture of the university buildings, such as King's College Chapel, Senate House, and Trinity College. The narrator is in awe of the academic environment and the intellectual atmosphere of the university.

Interaction with students:
During the visit, the narrator has the opportunity to interact with some students of Cambridge University. The students are described as intelligent, well-dressed, and confident. The narrator engages in conversations with them, discussing various topics such as literature, science, and politics. The students impress the narrator with their knowledge and intellectual prowess.

The library and its significance:
The chapter also highlights the importance of the library in Cambridge University. The narrator visits the library and is amazed by the vast collection of books and manuscripts. The library is portrayed as a treasure trove of knowledge and a symbol of academic excellence.

Historical significance:
The chapter briefly delves into the historical significance of Cambridge. The narrator mentions the contributions of Cambridge scholars to various fields, including science, literature, and philosophy. The city's rich history and its association with renowned figures add to the charm and allure of Cambridge.

Conclusion:
The chapter concludes with the narrator expressing their gratitude for the opportunity to visit Cambridge. The experience leaves a deep impression on the narrator, who is inspired by the intellectual and academic environment of the city. The chapter highlights the significance of education, knowledge, and the pursuit of excellence.