Boston in Transit - The Book Figure 3.29 - The “Bell Mouths” at Section 4, 1898 Brightly whitewashed tunnels reflect bright electric light where the subway’s tracks head south, towards the Pleasant Street Incline. The tube on the right was for southbound streetcars. The tube on the left was for cars heading northbound (towards the photographer) into Boylston Street Station. In the distance (right), two streetcars pause where the southbound tube splits again.