Mr. Henry G. Hanks, formerly mineralogist to the State of California, gives in his Fourth Annual Report (1884), the following composition of two samples, and states that the results indicate the general character of Californian asphalt rock :--

From Santa Cruz-Asphalt,

Sand,

From Santa Barbara County-Bitumen, volatile portion,

""

fixed, Quartz sand,

19.8

80.2

100.0

35.0

7.2

57.8

100.0

The sand is angular, and consists almost entirely of transparent quartz. The bitumen is soluble in turpentine.

Asphalt rock (such as is used for paving) generally consists of limestone saturated with the bituminous material, which is usually almost free from solid paraffin. The grains forming the asphalt rocks are almost invariably found to be totally unconnected, save by the bituminous matter, and the rocks fall to powder when the bitumen is removed by a solvent. This is the case with such widely different rocks as those of Seyssel, Forens, Lobsan, Limmer, Val de Travers, Kentucky, California, and Athabasca.

M. Durand-Claye has given the following particulars of several descriptions of natural asphalt rock :

In his Report to the Geological Survey of Kentucky on the Occurrence of Petroleum, &c., in Western Kentucky, 1891, Dr. Orton furnishes a full account of the asphalt of California and Kentucky. The following table gives the results of four analyses, quoted by Orton, as showing the composition of the well-known French and German deposits :

TABLE XXXII.-COMPOSITION OF FRENCH AND GERMAN ASPHALT ROCK.

A single analysis of the Limmer rock, made at Columbia College, New York, showed the following composition of the "dried material:

In three samples of asphalt rock from Western Kentucky, Dr. Peter found 9.4, 8.0, and 8.75 per cent. respectively, of matters driven off by ignition.

According to Hilgard,' the asphalt rock of Ventura County, California, contains :

The ash consisted of a fine clay containing a little sand and about 3 per cent. of calcium carbonate.

The asphalt of the North Western Territories of Canada, lying to the north of the land drained by the Peace and Athabasca rivers, has been examined by C. C. Hofmann of the Canadian Geological Survey.2 He reports that this asphalt is dark brownish-black, and becomes soft at 100° F., although quite hard at common temperatures. The material contains 12.42 per cent. of bitumen, 5.85 per cent. of mechanically included water, and 81-73 per cent. of sand. When treated with benzene or carbon bisulphide, the bituminous matter is dissolved out,

1 Tenth Annual Report of the State Mineralogist, California, 1890, 766.

* Ingall and Brumell's Report for 1889 to the Division of Mineral Statistics and Mines of the Geological Survey of Canada, Montreal, 1890, 83.

and the residue consists only of colourless and transparent sand particles which were merely held together by the bitumen.

Mr. W. H. Delano1 considers that the term asphalt should be applied only to bituminous limestone, the composition of which he gives as varying from 7 per cent. of bitumen with 93 per cent. of carbonate of lime to 20 per cent. of bitumen with 80 per cent. of carbonate of lime. He states that the bitumen found in the Trinidad "Pitch Lake" is mixed with 33 per cent. of fine clay, sand and vegetable matter, and 33 per cent. of water; and that refined Trinidad bitumen always contains from 20 to 25 per cent. of fine clay, but is nevertheless so tough, malleable and stringy, that for asphalt "mastic," it is preferable to some other "short-fibred" bitumens chemically purer. Mr. Delano adds that, for use in asphalt paving, bitumen should be free from "dross," perfectly black, not brilliant, of the consistency of bees-wax at 70° F., and free from oils that will evaporate at 480° F. "Mastic" is the name given to the material prepared for use in paving by mixing hot asphalt rock, ground to a fine powder, with such proportion of hot bitumen, similar to that contained in the natural rock, that the product contains about 15 per cent. of bitumen and 85 per cent. of limestone. "Gritted asphalt mastic" is composed of the mastic already described, re-melted with 5 per cent. of bitumen, and from 30 to 40 per cent. of clean, dry fragments of limestone, or sand. For use in preparing mastic, the bitumen extracted from Seyssel asphalt is stated to possess the desired qualities in the highest degree. It is asserted that this bitumen may be heated to a temperature of 500° F., or cooled to many degrees below the freezing point of water, without losing its tenacity and malleability. Its chemical composition iscarbon, 85 per cent.; hydrogen, 12 per cent.; oxygen, 3 per cent.

Natural gas consists mainly of members of the paraffin series, principally marsh gas, which constitutes from about 50 per cent. to about 90 per cent. of the Pennsylvanian gas. Ethane, propane, and certain members of the olefine series are also present, the latter being more especially found in the gas of Baku. Varying amounts of carbon dioxide, sometimes amounting to 10 per cent. or more, and small quantities of carbon monoxide, nitrogen, hydrogen, and oxygen are also found. The Pechelbronn gas contains 3 to 3.7 per cent. of carbon dioxide (Engler). Natural gas dissolves in petroleum, and slowly escapes when the oil is stored. This is said to be particularly the case with the oil of Los Angeles in California. Similarly, natural gas invariably carries with it a certain amount of water and oil which are deposited on compression of the gas. This is the case even with the so-called "dry" gas of the Carpenter well in Westmoreland County, Pennsylvania, and elsewhere. The first analyses of American natural gas appear to have been made by Fouqué, whose results, which were little more than qualitative, are in part incorporated in Table

2

Twenty Years' Practical Experience of Natural Asphalt and Mineral Bitumen, London and New York, 1893.

2 Week's Eleventh Census Report of the United States, 1892, 567.

3 Ashburner, Am. Inst. of Min. Eng., Sept., 1885. + Comptes Rendus, 67, 1045.

XXXIII., taken from the Report of the Committee on Natural Gas, of the Engineer's Society of Western Pennsylvania.

Professor C. C. Howard of Columbus has published the following results of analyses of the natural gas from the Trenton limestone in Ohio :

TABLE XXXIV.-COMPOSITION OF NATURAL GAS (OHIO).

Professor F. C. Phillips1 has determined the composition of natural gas from various sources, but has chiefly worked upon the gas delivered by the Allegheny Heating Company. This organisation takes its supply from a large number of wells drilled over a considerable area, and the results obtained by Mr. Phillips may, therefore, be regarded as representing the average composition of an enormous volume of gas. It is stated that, from 1886 to 1892, no important differences in composition have been observed, although occasionally the odour of the higher paraffins has been more marked than usual. Gas from other localities in Pennsylvania, New York, Indiana, Ohio, and British Columbia has also been examined by Mr. Phillips, and in Table XXXV. the results are tabulated, with a number of determinations made by others. Except in the cases of Kokomo and Vancouver, Mr. Phillips' analyses were made at the wells. Table XXXVI. gives, for comparison, the composition of several samples of Russian natural gas, and the results of two analyses of gas from deep borings at Middlesbro'. Mr. Phillips made a careful search for hydrogen, carbon monoxide (usually, as he points out, included in the constituents of natural gas), olefines, and sulphur compounds, and he maintains that these were entirely absent from the samples examined. From this he draws certain deductions in respect to the origin of petroleum, to which reference will be made in the succeeding section. Except in the case of the gas from a well near Canonsburg, with which, after it had been passed through water for several hours, a feeble Nessler reaction was obtained, ammonia was never found; but in this connection a case is reported, upon the authority of Mr. S. A. Ford, of the Edgar Thomson Steel Works, where masses of solid ammonium carbonate were blown out of a well by the pressure of the gas.

1 Am. Chem. Journ., xvi., 406-429.