REVIEWS 237 



city from the Kern county district. Like the Texas oil, the California 

 product is low in illuminating and high in heating power, three and 

 one-half barrels being equivalent to a ton of coal. The report includes 

 extensive reviews of the oil production of the world. 



Natural gas. — The value of the product was $27,067,500 — an 

 increase of 14 per cent, over the previous year. The pressure, how- 

 ever, has continued to decline, necessitating the expense of compres- 

 sion in order to market an increased production from declining fields. 

 A total of 709,921 domestic fires and 5,742 factories and mills were 

 supplied. The increase per cent, in production was greatest in' 

 Kansas. 



Iron ore. — The production of 28,887,479 long tons was 5 per cent, 

 greater than the production of any previous year and greater than the 

 output of any other country, exceeding that of Germany, our nearest 

 competitor, by more than 50 per cent. Of the twenty-five states 

 mining iron, Minnesota ranked first, Michigan second, and Alabama 

 third. The ores were hematite 93 per cent., magnetite 6 per cent., 

 and carbonate less than i per cent. The Mesabi range in Minnesota, 

 owing to the large deposits and the ease of working them, produced 

 32 per cent, of the total for the United States. About 200 cargo 

 analyses of Lake Superior iron ore are given. The production of pig 

 iron was worth $242,174,000 and exceeded the combined British and 

 German production for the same year. 



Gold. — The production for the year was $78,666,700 — a decrease 

 of 0.6 per cent. California increased her production over a million 

 dollars and Nevada almost as much, her increase coming largely from 

 the new camp of Tonapah in Nye county. Alaska and Colorado 

 showed a decrease of about a million dollars each. The principal 

 producing states and territories, in order of production, were as fol- 

 lows: Colorado, California, Alaska, South Dakota, Montana, and 

 Arizona. About 85 per cent, of the production came from quartz and 

 the remainder from placer mines. 



Silver. — ^The commercial value of the yield was $33,128,400 — 

 about 4 per cent, less than that of the previous year. The greatest 

 gain was in Utah, most of which came from the Park City district. 

 Colorado and Montana showed a material decrease. About 29 per 

 cent, came from quartz mining and the remainder from lead and cop- 

 per ores. 



Copper. — The year's production was valued at $87,300,515 — a 

 decrease of 11 per cent. This decrease was due chiefly to the lower 



