THE NATURAL HISTORY SURVEY. 



53 



the wall are coal tar or some similar artificial product. One of 

 the best means of distinguishing coal tar and asphalt is to dis- 

 solve pieces in carbon disulphide, evaporate, put I gramme in 

 5 c. c. fuming sulphuric acid for 24 hours, dilute to twice the 

 volume. Coal tar gives a very dark brown solution, and the 

 Stony Island asphalt gives a faintly colored solution. The 

 percentage of asphalt is too small to increase the value of this 

 rock as a road metal. In some localities the asphalt is col- 

 lected in cavities formed by the dissolution of fossil coelenter- 

 ates, echinoderms, molluscs, etc., as at Stony Island. A large 

 number of pieces of seemingly pure asphalt were taken, and 

 from them four analyses made. Ihey showed 15% of mineral 

 matter, 82% of bituminous matter soluble in carbon disulphide 

 and 2% of nonbituminous matter. Carbon disulphide is taken 

 to dissolve the bitumen. Organic matter left is regarded as 

 nonbituminous, and may be separated from mineral water by 

 ignition. If this nonbituminous matter is present in large 

 quantities, it spoils asphalt for commercial use, since it is liable" 

 to decomposition. Stony Island asphalt has a very small per- 

 cent (2.16). Two-thirds of the mineral matter remaining is 

 soluble in hydrochloric acid (CaCO 3 and Fe 2 O 3 ) and of. the 

 remainder the major part is sand. The bituminous matter is 

 again separated. That portion which is soluble in petroleum 

 spirit is called petrolene. This is regarded as a solvent of 

 asphaltene. Asphaltene is that portion which is soluble in 

 boiling turpentine. The amount of petrolene in Stony Island 

 asphalt is small. Maltha is the name given to the semi-fluid 

 asphalt. The following table presents for comparison some 

 analyses of asphalts from four different regions: 



Peat. 



Under the gravel and above the clay throughout a large 

 part of the region is found a layer of peat and impure lignite. 

 It occurs in beds and pockets, rather than a continuous sheet. 

 It can be seen in many places where excavations are being 



