Question: Huey J. Rivet patented an "amphibious marsh craft" for hauling loads and laying pipeline in swamps. Rivet's model could "walk" over stumps for extended periods while carrying heavy loads. Later, Robert Wilson, who had once worked for Rivet as a welder, began marketing a similar craft. The craft sold by Wilson differed from the craft described in the specification accompanying Rivet's patent application in several respects. Overall, though, the Wilson boat performed much the same functions about as effectively as the Rivet craft, and used much the same engineering techniques and concepts to do so. Has Wilson infringed Rivet's patent?