76 proceedings: philosophical society 



Mr. H. L. Curtis reported on a method to measure the thickness 

 of a moisture film which forms on a metallic plate by determining the 

 increase of capacity caused by the deposit between two metallic plates. 



Mr. W. J. Humphreys spoke on the cause and results of a terrific 

 explosion outside of a 250-gallon tank of "casing-head" gasoline, an 

 especially volatile gasoline, in south Oklahoma, due to volatilization 

 of the gasoline because of exposure to the heat of the sun and careless- 

 ness in opening the screwcap over the dome of the tank instead of 

 applying some cooling agent, as water, to reduce the vapor tension 

 inside the tank. Some curious effects on nearby structures, due to 

 the explosion, were detailed. 



The 762nd meeting was- held November 13, 1915, at the Cosmos 

 Club; President Eichelberger in the chair; 52 persons present. 



Regular Program 



Mr. D. L. Hazard presented a communication on The magnetic work 

 of the U. S. Coast and Geodetic Survey. The growth of the work to meet 

 the needs of the navigator and surveyor was traced from the reorgani- 

 zation of the Coast Survey in 1843 to the present day, and showed 

 the progress made in the systematic magnetic survey of the United 

 States, begun in 1899. Since that date an average of about 250 new sta- 

 tions and 75 repeat stations have been occupied annually. The first 

 stage of the survey, the establishment of a network of stations 25 or 

 30 miles apart, is nearly completed as far as the accessible portion of 

 the country is concerned, and the investigation of areas of local dis- 

 turbance is in progress. The work on land has been supplemented 

 by observations at sea on the vessels of the survey. The observations 

 at repeat stations have supplied the data needed to determine the 

 change of the earth's magnetism with time. Magnetic observatories 

 have been in continuous operation at Cheltenham, Md., since 1901; 

 Honolulu and Sitka since 1902; Vieques, P. R., since 1903; Baldwin, 

 Kansas, from 1900 to 1909, and Tucson, Arizona, since 1909. The 

 results are published as promptly as possible in suitable form to meet 

 the varying demands. The success of the work is due largely to Charles 

 A. Schott, for 50 years chief of the Computing Division, and to Dr. 

 L. A. Bauer, inspector of magnetic work from 1899 to 1906. 



Discussion: Mr. W. Bowie stated that this work was an excellent 

 example of applied science or engineering and praised the comprehen- 

 sive and systematic scheme followed which supplies both theoretical 

 and practical needs; the prompt publication of results is an admirable 

 feature. 



Mr. R. L. Sanford then gave an illustrated paper on Uniformity 

 of magnetic test bars. This paper dealt with the examination of test 

 bars for magnetic uniformity, the nature of non-uniformities that 

 commonly exist in such bars and their effect on the accuracy of magnetic 

 measurements. All precision methods for magnetic measurement on 

 straight bars assume uniformity along the length of the specimen. If 

 this assumption is not met, errors are introduced which are impossible 



