proceedings: philosophical society 555 



THE PHILOSOPHICAL SOCIETY OF WASHINGTON 



The 754th meetmg was held on March 13, 1915, at the Cosmos Club, 

 President Eichelberger in the chair; 50 persons present. 



Mr. G. K. Burgess gave an illustrated account of Some researches 

 in metals at the Bureau of Standards, descril^ing investigations now 

 being carried out on the preparation, properties, and failure of metals 

 and alloys. The methods developed for determining critical ranges 

 with the thermoelectric and resistance pyrometers and their applica- 

 tion to pure iron in w^hich the characteristics of the A2 and A3 trans- 

 formations were brought out, were described. The application of the 

 micropyrometer to the determination of monochromatic emissivities 

 of metals and oxides in the solid and liquid states were demonstrated 

 in the range 900° to 1700°C. Cooperative work with some of the 

 technical societies in the preparation of alloys and the determination 

 of suitable specifications for typical bronzes and brasses was described. 

 A study of the volatilization of various grades of platinum ware with 

 the object of forming a basis for defining the quality of such ware for 

 exact chemical analysis has been made. Investigations are being made 

 on the causes of failure of railway rails, the deterioration of fusible tin 

 boiler plugs, and failures of wrought bronzes and brasses used in engineer- 

 ing construction. The paper was discussed by Messrs. White and C. A. 

 Briggs with references to improved method for casting steel ingots and 

 the precise character of stresses in bronze bolts and bars. 



Mr. W. Bowie then gave an illustrated account of The errors of 

 precise leveling. Very accurate determinations of elevations above 

 some adopted datum have been made possible by the great improve- 

 ments of the wye level during the past half century. In 1912 the 

 International Geodetic Association defined leveling of high precision 

 as that which must have a probable accidental error not greater than 

 1 mm. per kilometer and a probable systematic error not greater than 

 0.2 mm. per kilometer. The effect of most of the errors of precise 

 leveling can be eliminated by the method employed. There are, how- 

 ever, errors of refraction in leveling on steep slopes which depend upon 

 the time of day and the weather conditions. It is concluded from an 

 investigation carried on at the Coast and Geodetic Survey that, on an 

 average, the afternoon running gives a greater difference in elevation 

 between two points than a morning running. The difference is greater 

 in cloudy than in sunshiny or clear weather. It is also greater during 

 wind than in calm. The speaker is of the opinion that the runnings in 

 the afternoon in wind and in cloudy weather give results nearer the 

 truth than in the forenoon in calm and in sunshiny weather. In the 

 discussion Mr. Winston gave some details of leveling across Florida; 

 Mr. Burgess referred to possible lines across Mexico and the Isthmus 

 of Panama for determining possil^le difference in the ocean levels; 

 Mr. SosMAN raised question as to difference of results with time particu- 

 larly on the Atlantic Coast; Mr. Burgess referred to possible effect of 

 expansion coefficients of materials in ground on values. Mr. Bowie ■ 



