94 REVIEWS 



the Oligocene. The rocks next in order are dacite flows of Oligocene 

 age. The remaining Tertiary history is written in several periods of 

 igneous activity — andesite flows, intrusive latite porphyries, and a 

 basaltic eruption during the Pleistocene.. 



The total bullion production of the camp since the first discovery 

 of ore in 1896 has been about $2,000,000, of which approximately 90 

 per cent has been gold and the remainder silver. The veins are thought 

 to be genetically related to the latite porphyry intrusion and are made 

 up of quartz, chalcedony, opal, calcite, and adularia, carrying incon- 

 spicuous amounts of pyrite and possibly gold, in association with anti- 

 mony, sulphur, and selenium. 



Though the deposits at Republic are not altogether like any others 

 known in the United States, they most closely resemble the lodes of the 

 Great Basin province. Their striking feature is the great amount of 

 •selenium in the ores, and they are thus best correlated with Tonopah 

 and Goldfield, the only other camps in the United States known to pro- 

 duce selenium ores. 



The report closes with a detailed description of the principal mines 

 of the district, of which the New Republic mine is easily the leader. 



R. T. C. 



Notes on Explosive Mine Gases and Dusts with Special Reference 

 to Explosions in the Monongah, Darr, and Naomi Coal Mines. 

 By Rollin Thomas Chamberlin. U.S. Geol. Surv. Bulletin 



383- 

 The results of a series of experiments carried out by the author throw 

 new light on the nature of the explosive material and on the conditions 

 governing explosions in coal mines, and should be of great practical, as 

 well as scientific, value. As soon as possible after the explosions in the 

 mines mentioned, samples of the mine atmosphere were collected and 

 analyzed. Another series of experiments was carried out to determine the 

 probable condition of the gas in the coal, whether (1) imprisoned in"minute 

 cavities, (2) occluded or dissolved in the substance of the coal, or (3) the 

 result of slowly operating chemical processes. This was done by studying 

 the rate of liberation of gas (1) from coal bottled in vacuum, (2) from 

 crushing the coal, and (3) from heating the coal. A careful study was 

 also made of the position and nature of the dust in passage-ways and on 

 timbers in the mines after the explosions. 



