AMERICAN AND FOREIGN ASPHALTS. 191 



pressed asphalt pavements, or converted into " mastic " by mixing it 

 with one tenth to one seventh its weight of purified bitumen from 

 Trinidad and cooking five or six hours. It is then poured into cast- 

 iron molds without bottoms, which are placed on the sanded floor of 

 the shop. These blocks of mastic are fifteen inches in diameter and 

 four inches thick, weighing fifty or sixty pounds each. Those made 

 at Val de Travers are hexagonal in form, bearing a trade-mark of a 

 cross and ? ; those from Seyssel and Lobsann circular; the others ob- 

 long, with rounded corners. 



The Val de TraVers mastic and asphalt rock are imported by the 

 Neufchatel Asphalt Company (54 Astor House, New York) ; the Seys- 

 sel mastic by the New York Mastic "Works (35 Broadway) ; the Lim- 

 mer and Vorwohle rock asphalt by C. Wichtendahl (111 Broadway, 

 room 97). In regard to their uses in this city we shall speak more 

 fully in another place. 



Trinidad asphalt is imported and refined by the Warren Chemical 

 and Manufacturing Company (45 John Street). This substance, as it 

 occurs in nature, is very impure ; about one third of the mass con- 

 sists of water, another third is made up of clay and sand, so that only 

 one third is actually bitumen. It is melted in large kettles and heated 

 for twelve hours to expel the water, the earthy constituents settling to 

 the bottom. This partially purified asphalt, which still contains about 

 twenty per cent of impurities, is poured through a sieve into barrels, 

 where it solidifies. It now forms a brittle mass, which sells for twenty- 

 five dollars per ton. It is too hard for mixing with the pulverized 

 asphalt-rock, or for street pavements. At Val de Travers and Seyssel 

 the residues from the distillation of bituminous shale, known as " shale- 

 grease," are used to soften it, while in other places similar residues of 

 paraffine manufacture or petroleum refining are added to the natural 

 bitumen to form what is known as " prepared bitumen," or mineral tar. 

 In this country the so-called " still-bottoms " from petroleum-stills are 

 used in the proportion of fifteen parts of the latter to eighty-five of 

 the natural asphalt ; the portions may be varied to suit the climate 

 and other conditions. 



Asphalt pavements may be divided into three classes. The first, 

 which is commonly known as mastic {asphalte coide), is best adapted 

 to sidewalks, court-yards, and other places where there is but little 

 heavy traffic. It is prepared by melting the blocks of mastic, already 

 described, in caldrons, adding a small quantity of prepared bitumen, 

 and afterward stirring in thirty or forty per cent of clear grit. When 

 thoroughly mixed it is carried to the spot in pails, and spread with a 

 wooden float by a skilled workman on his knees. It is then rubbed 

 until perfectly smooth, and fine sand strewed over it. Examples of 

 this pavement can be seen in Union Square, Tompkins Square, and 

 several other places in New York city. 



Compressed asphalt is better adapted to heavy traffic, as in street 



