456 abstracts: technology 



quired to oxidize 500 feet of ore like that now existing would require the 

 contributions of rainfall during a period longer than physicists and 

 geologists are willing to allow for the entire age of the earth. It is 

 thought, therefore, that a large part of the oxygen must have been de- 

 rived from air that circulated through the oxidized capping. 



A theoretical discussion of the chemical reactions involved in the 

 alterations of the rocks and in the deposition of metallic sulphides in 

 them is presented. The conclusion is reached that if the solutions were 

 originally acidic the metallic minerals were probably deposited only 

 after an alkaline or neutral condition had been attained. 



R. W. Stone. 



TECW^SiOLOGY. —Materials for the household. Bur. Stand. Circ. No. 

 70. Pp. 259. Dec. 5, 1917. 

 This circular describes the more common materials used by the house- 

 hold, comprising paint materials, cement, clay products, lime, plasters 

 and stucco, wood, metals, bituminous roofing, inks and dyes, adhesives, 

 paper, textiles, rubber, leather, cleansers and preservatives, fuels, 

 illuminants, and lubricants, and concludes with a chapter on quantity 

 in the purchasing of materials. Each title is treated under the general 

 heads of composition and definition, sources, properties, uses, tests, 

 preservation, hints as to selection and use, and references. 



TECHNOLOGY. — Gas mantle lighting conditions in ten large cities in 

 the United States. R. S. McBride and C. E. Reinicker. Bur. 

 Stand. Tech. Paper No. 99. Pp. 37. October 29, 1917. 



From a careful inspection of about 4500 gas mantle lamps in service 

 in ten cities, a summary of the condition of mantles, glassware, pilot 

 hght, and other particulars was made in order to determine to what 

 extent the customer benefited through periodic maintenance service. 



By these observations it is found that a lamp not on regular mainte- 

 nance is hkely to be defective five and one-half times as frequently 

 as a lamp which is regularly maintained. Also it is shown that on the 

 average 1 in 3 of the lamps on regular maintenance was not in good 

 condition whereas the defects noticed in the lamps not so maintained 

 average more than one for every lamp. 



The principal defects in maintenance systems were also investigated 

 and one satisfactory system of estimating the expenses for maintenance 

 work together with a set of unit costs is presented, based upon the 

 analysis of the operation of ten gas companies. A suggested table of 

 costs for each type of unit is given. C. E. R. 



