From the peculiar shape of the city and the converging of the thoroughfares on Tremont Street, fronting the Common and the old burying grounds, the space between Boylston Street and Cornhill was, at certain hours of the day, in a painful state of congestion. Then the stoppage of the cars, the loss of time, and the waste of temper was something which no nineteenth century man could stand with equanimity. How to relieve the congestion was the difficulty. Should there be an elevated railway, or a new avenue opened through the midst of the city? This was the question. To this subject, Carleton gave his earnest attention. He remembered the day when the now elegant region of the Back Bay was marsh and water, when schooners discharged coal and lumber in that Public Garden, which in June looks like a day of heaven on earth, and when Tremont Street stopped at the crossing of the Boston and Albany railway. Even as late as 1850 the population included within the ten-mile radius of the city hall was but 267,861; in 1890, the increase was to 841,617; and the same ratio of increase will give, in 1930, 2,700,000 souls. In 1871, seventeen million people were moved into Boston by steam; in 1891, fifty-one millions. At the same ratio of increase, on the opening of the twentieth century, there will be 100,000,000 persons riding in from the suburbs, and of travellers in the street-cars, in A. D. 1910, nearly half a billion. Carleton, the engineer and statesman, believed that neither a subway nor an elevated railway would solve the problem. He spoke, lectured, and wrote, in favor of a central city viaduct. For both surface and elevated railways, he proposed an avenue eighty feet wide, making a clear road from Tremont to Causeway Streets. Moreover, he believed that the city should own the roads that should transport passengers within the city limits. He was not afraid of that kind of socialism which provides for the absolute necessities of modern associated life. He expected great amelioration to come to society from the breaking up and passing away of the old relics of feudalism, as well as of the power of the privileged man as against man, of wealth against commonwealth. He believed that transportation within city limits should be under public ownership and control. He therefore opposed the subway and the incorporation of the Boston Elevated Railroad Company. One of his most vigorous letters, occupying a column and a half, in the Boston _Herald_ of July 17, 1895, is a powerful plea for the rejection by the people of an act which should give the traffic of the streets of Boston and surrounding municipalities into the hands of a corporation for all time. He considered that the act, which had been rushed through the legislature in one day at the close of the session, was a hasty piece of patchwork made by dovetailing two bills together, and was highly objectionable. He wrote: