As the area along the line became more urbanized, objections to the soot and noise produced by the locomotives increased, and transport was switched to cars that were powered by horses and mules. For decades in the late 19th century, desire for a mode of transit more swift and powerful than horses but without the disruptive effects of locomotives resulted in a number of systems being tried out. Experimental systems included overhead cable propulsion (with a cable clamp patented by P.G.T. Beauregard in 1869 later being adapted for the San Francisco cable car system), and several innovative designs by Dr. Emile Lamm, including ammonia engines, a "Chloride of Calcium Engine", and most successfully Lamm Fireless Engine which not only propelled pairs of cars along the line in the 1880s but was adopted by the street railways of Paris.