The United States has been preëminent in the development of street railways of all kinds, from the earliest type of horse-car to the modern city and interurban electric cars. Nevertheless, very few of the great general underlying principles upon which these numerous inventions are based have been discovered upon this side of the Atlantic. American inventors have simply excelled in applying the known general principles to practical mechanisms. But although the American inventors have largely monopolized this field of progress, the names of many Europeans also are connected with it. In several instances these foreign inventors, as naturalized American citizens, have done their work in America, being attracted to this country by the exceptional opportunities offered. In recent years the city of New York has not shown conspicuous activity in adopting innovations and improvements on its street-railway lines. Nevertheless, New York was the first city in the world to have a passenger street railway. This, built in the early 20's, and running along Fourth Avenue, had rails made of straps of iron laid on stone ties. On this primitive line an omnibus horse-car, called the _John Mason_, was operated. This car was built on the lines of the early railway carriages, having three compartments, with doors opening at the sides. It was, in short, an early type of the side-door cars now used so universally on all European railways. The driver's seat was high in the air as in the case of the ordinary omnibus, and there were seats on the top for passengers. For several years this primitive road remained the only street railway in existence. But it did not prove a particularly good business venture, and for some time capitalists were wary of investing their money for the construction of other lines. Twenty years later, however, a somewhat similar road, considerably improved, was built on Sixth Avenue. This proved to be a financial success; other lines were soon constructed, and the era of street railways opened. The great advantage of these horse-car lines over the system of omnibuses then in use lay in the fact that greater loads could be hauled with the same expenditure of horse-power, regardless of weather conditions. The contrast in this respect was particularly marked in American cities where the streets, almost without exception, were badly paved. By 1850, several cities in the United States had installed street railways; and by 1870 over a hundred lines had been built. Between 1870 and 1890 this number had been increased to over seven hundred, not taking into account the numerous extensions that had been made to many of the older lines. CABLE SYSTEMS