AMERICAN AND FOREIGN ASPHALTS. 189 



curs in West Virginia and other parts of the country. In the mount- 

 ains west of Denver, in Colorado, is a vertical bed of hard and brittle 

 asphalt, not unlike Grahamite, while Albertite is found in small quan- 

 tities in Lorain County, Ohio, and Casey County, Kentucky. 



Bitumen is likewise found in Cuba, and is brought into commerce 

 under the name of chapopote, or Mexican asphalt. 



In Europe asphalt occurs chiefly in limestone, which forms, when 

 crushed and packed, an excellent pavement. The principal points at 

 which it is found are the following : Val de Travers, in the Swiss 

 Canton of Neufchatel, fourteen miles from Neufchatel, and sixteen or 

 seventeen miles by rail from the French borders ; Seyssel, on the 

 Rhone, in the French department of the Ain, about thirty-three miles 

 from Geneva ; Lobsann, a small town in northern Alsace ; Vorwohle, 

 in Braunschweig ; and Limmer, near the city of Hanover. The Ital- 

 ian province of Caserta, in the neighborhood of Naples, supplies Rome 

 with an asphalt much used for terraces and flat roofs. 



The quantity of bitumen in these limestones and the manner of 

 its dissemination are quite varied, but it is generally found that the 

 softer limestones contain more bitumen than those which are harder. 

 The average amount is about ten per cent, but it sometimes reaches 

 twenty or thirty per cent, and occasionally there are cavities in the 

 rock which are filled with bitumen. At other times the quantity sinks 

 to five per cent, or less, while nodules of limestone entirely free from 

 it are also found. The value of the rock depends on the percentage 

 of bitumen, and on other circumstances. If the stone is to be used 

 for making mastic, the higher the percentage the more valuable it is ; 

 but, if used directly for paving, a uniform distribution, not exceeding 

 eight or ten per cent, is desirable. 



Asphalt-stone, to which Malo limits the name of asphaltum, varies 

 in color from gray to brownish-black, according to the richness in bitu- 

 men ; that of medium quality closely resembles chocolate in color. 

 That which is poor in bitumen is hard, and rings like ordinary lime- 

 stone ; but the fatter rock, when struck with a hammer, gives forth a 

 dull thud, like a block of wet plaster, and takes an impression from 

 the blow. If it contains more than ten per cent, it crumbles in the 

 hand, and can be cut with a knife, like chocolate. Good stone, with 

 about ten per cent of bitumen, has a specific gravity of 2*1. Some 

 asphalt-stone is of a spongy, hygroscopic nature, and consequently 

 lighter. 



One peculiarity of the natural rock-asphalt is that, when heated 

 over a fire, it breaks up into a brown powder, and then, at a higher 

 temperature, all the bitumen is expelled, leaving a pure white powder. 

 An unsuccessful attempt was made in the Paris Conservatoire des 

 Arts et Metiers to imitate this asphalt-stone by forcing thick, pasty 

 bitumen into pure limestone by great pressure. When, however, the 

 lime-stone was boiled for a long time in a liquid mass of asphalt, it 



