MODERN STREET-PAVEMENTS. 87 



the persistent efforts of some of the best engineers of the age, by 

 which all obstacles have been gradually overcome. The first trials 

 were made with mastic, consisting of the powdered rock melted 

 with mineral tar as a flux, and mixed with sea-grit which was laid 

 upon an ordinary concrete foundation ; they were followed by experi- 

 ments with mastic, cast into blocks at the workshops, and laid with 

 wide joints, which were filled in again with heated mastic. Next we 

 hear of tests with broken asphaltic rock, rammed in a cold state upon 

 a macadam foundation. And finally these intelligent labors were 

 crowned by the splendid improvement of the compressed rock pave- 

 ment, for which the rock, reduced by heat to powder and rammed 

 and rolled while yet hot, into a homogeneous, tight covering, is laid 

 upon a perfectly dry ordinary concrete foundation composed of 

 crushed stone and cement. This simple improvement virtually adapts 

 the old principle of a barn-floor of rammed clay, for thrashing, to the 

 requirements of the open air, by making it water-proof. In place of 

 the mastic, which attains consistency, by the congelation of the melted 

 mass, without application of pressure, this " merely compressed body, 

 in which the molecules of bitumen and limestone are soldered together 

 by heat and ramming," obviates all tendency toward brittleness, with- 

 out in the least interfering with the advantages of perfect homogeneity 

 or water-proof qualities. It stands to reason that the mastic, which, 

 notwithstanding its mixture with grit, is more or less pitchy, would 

 be surpassed in elasticity and pliability by a merely kneaded mass. 

 These pavements are reported to have withstood the extreme heat of 

 Bombay, Hindostan, as well as the greatest known cold. Not afford- 

 ing any escape to the terrestrial heat through joints, they are kept 

 warm and open from below in most cases when block-pavements pre- 

 sent an icy surface. Their smooth, seamless face, being almost entirely 

 free from abrasion by attrition or atmospheric action, meets the me- 

 chanical and hygienic objections to block-pavements, both of stone 

 and wood, as well as of macadamized roads. 



The asphaltum pavement is clean and fit for traffic a few hours 

 after being laid, while new or repaved stone roadways must be cov- 

 ered for months with heavy layers of sand, to be drifted by the breeze 

 in dry weather and added to the mud in rainy spells. Repairs can be 

 made to the asphaltum pavement in dry days of a cold winter, while 

 with stone pavements any defects must be endured until spHng. Be- 

 sides the sanitary advantages, the saving in temper, clothes, shoes, 

 and furniture, is not to be overlooked. The popularity of this pave- 

 ment in the two largest cities of Europe, where, with immense traffic 

 and most extensive experience on the relative value of pavements, the 

 demands on the municipal authorities are inexorable, serves as a proof 

 that smoothness of surface does not cause any danger with this mate- 

 rial. Being elastic but not soft in summer, and hard but not brittle in 

 winter, it possesses with a slight yield the power of readjustment in 



