street and alley should drain as promptly and thoroughly as the houses erected on it. A proper observance of these maxims has materially contributed to the reduction of the annual death-rate of London within the last two centuries from forty-two to twenty-two per thousand, notwithstanding the unprecedented increase in the numbers and density of the population. An average decrease of thirteen per cent, in the death-rate has been traced directly to the influence of modern sanitary works, introduced into cities mostly during the last twenty years; and a thorough reform in pavements must give still more striking results.
The material for pavements is mostly decided upon by non-professional municipal authorities, and upon these an enlightened public opinion must exert a beneficial influence. A condensed review of the subject, in the light of history, technical science, hygiene, and finance, will help excite reflection, and to mature rational views, and will furnish a timely contribution to the literature of the day. Manufacturing industry, commerce, and railroads, those important motors of modern civilization, have combined to increase the number and size, and to concentrate the internal traffic of large cities, so that horses and vehicles have steadily increased, absolutely as well as in proportion to the population. Under the same influences an enormous wealth, formerly unknown, has been amassed in the cities, and whole streets have risen, lined by majestic buildings, in uninterrupted succession; while, even in the older or less pretentious streets, houses of a mere utilitarian character disappear, to make way for structures with an elevated standard of architecture. What at an earlier epoch was the proud privilege of the famous capitals of Italy, the exceptional luxury of their dwellings and mansions, is now to be found in most modern cities, though the effect be not as overpowering, on account of a want of harmony in the style.
Simultaneously with the higher wants resulting from greater wealth and closer contact, whole cities have been transformed from loose aggregates of irregularly-scattered houses into well-organized systems, all the elements of which, though serving individual purposes, are intimately connected by the complicated net-works of pipes supplying fresh water, discharging waste water and soil, and furnishing light during the night to the streets as well as to the houses, from cellar to roof; to which, perhaps, the inventive genius of the age may add, before long, the supply of heat for domestic necessities and personal comfort. In such a complex organism, the roadways and sidewalks are not merely spaces set apart for light, air, and traffic, but they are component parts of the wonderful machinery devoted to these purposes, and bear close relations to the dwellings which they separate and connect, and the restorative veins of which they cover as a protecting crust.
Of all these coöperating agencies, the least attention, until recent-
