Marsh was preaching to his Stockbridge companions on the voyage and, if they cared to attend, to the workers at the Shot Tower and the fledgling hamlet of Helena.
The Shot Tower, on the south bank of the Wisconsin, was a prominent landmark for early travelers. Here's a picture of how it looked in the 1830s. Increase Lapham wrote of it in his 1844 Geographical and Topographical Description of Wisconsin:
"HELENA, is situated on the Wisconsin river, near the mouth of Pipe creek, seven miles below Arena, fifteen miles from Dodgeville, and about the same from the Blue Mounds. The most important business done at this place is the manufacture of shot, by the "Wisconsin Shot Company" -- the only place in Wisconsin where shot is manufactured."
Whitney bought lead from the region's miners, and hauled it to the top of the bluff where it was melted. Carefully measured scoops of molten metal would then be dropped down the tower, forming into spheres as they fell and hardening when they hit a pool of cold water at the bottom. The tower's early history is told in this 1923 article from the Spring Green newspaper.
Lapham continued: "The view of the valley of the Wisconsin from the top of the shot tower at this place is described as very fine, extending a great distance. The river is seen winding through the rich, flat valley, which is bordered on both sides by high hills, with here and there rocky cliffs, separated by well wooded coves or vales. Besides the operations at the shot tower, there is much other business done at Helena, in the shipment of pig lead, and the receipt of lumber from the Upper Wisconsin, to supply the surrounding country."
Felt somewhat fatigued by my journey, still my health was good and was enabled to perform the duties of the day very comfortably. About eleven o'clock a few collected and I preached upon the subject of hope, showing the true and false kind. In the p.m. [I preached again,] upon the suffering of a wounded spirit...