This lecture delves into the historical experiment of Joule's paddle wheel, aiming to understand the experimental practice of the past. By replicating the experiment, the instructor explores the precision and accuracy achieved, shedding light on the challenges faced by Joule in communicating his work. The lecture also discusses the old brewing practices, emphasizing the practical knowledge of heat measurement among brewers and the transition to a more standardized and mechanized brewing process. Through the analysis of Joule's unique equipment and experimental setup, the lecture highlights the importance of precision instruments and skilled human operators in scientific experiments.