286 



abstracts: economic geology 



There is no sure way to guard against the contaminating influence of 

 metal-vapors upon a thermo-element in laboratory or industrial practice, 

 altho glazed porcelain is usually effective. There are very simple 

 and rapid means of detecting contamination in an clement and deter- 

 mining its distribution, and with a second element at hand for an occa- 

 sional comparison there is little of serious danger from this cause. In 

 any case, the slight inconvenience is well worth while wherever consider- 

 able accuracy is sought, for there is no other device yet available, in 

 the region between 1100° and 1600°, which is comparable with the 

 thermo-element in sensitiveness and general practicability. 



In conclusion, the list of standard melting-points is given in tabular 

 form, together with an estimate of the degree of trustworthiness to be 

 accorded to each. Beside it for convenient comparison is the present 

 Reichsanstalt scale. It may be added that no indication of a limit to 

 the temperature attainable with the nitrogen thermometer or to its 

 ultimate accuracy was discovered during the present investigation. 



In addition the following temperatures were incidentally obtained: 



A. L. D and R. B. S. 



ECONOMIC GEOLOGY.— The production of asbestos in 1910. J. S. 

 Diller. Advance chapter from Mineral Resources of the United 

 States for 1910, pp. 1-13. The types, modes of occurrence and impor- 

 tant deposits of asbestos in the United States. J. S. Diller. U. S. 

 Geological Survey Bull., 470-K, pp. 3-22, with 2 maps. 1911. 

 The annual production of asbestos for 1910 in the United States was 

 3,693 tons, about one-twentieth as much as that of Canada whose output 

 for the same time was 75,578 tons, which is 78 per cent of the total pro- 

 duction of all countries. Georgia and Vermont are the chief producers 



