What signs of business and commerce does Mendelssohn notice on the houses?

In Mendelssohn's "Venice: A Sketch," he notices signs of business and commerce on the houses in Venice, such as the presence of shop signs, awnings, and goods displayed outside. These signs indicate the economic activity and trade happening within the city, showcasing the bustling commercial life of Venice during Mendelssohn's visit. The visual cues of these signs on the houses provide insight into the vibrant mercantile culture of Venice in the 19th century.