440 JOURNAL OF THE WAvSHINGTON ACADEMY OF SCIENCES VOL. 11, NO. ]S 



Sphere has been used up to recent years are briefly described. The recent 

 appHcations of the sphere in a manner that affords the absolute determination 

 of the reflection factor are also described, and several new ways of using the 

 sphere are pointed out. One of the new ways consists in a combination of 

 the sphere with the Martens polarization photometer, which enables a direct 

 comparison to be made between the brightness of the sphere wall and the 

 brightness of the test surface which closes an aperture in the sphere. The 

 sphere wall is illuminated by directing a narrow beam of light through an 

 aperture on to a spot of the sphere walls adjacent to the aperture that is 

 closed by the sample. The sample is illuminated by the sphere wall, but is 

 screened from the direct light from the illuminated spot. The ratio of bright- 

 ness which is obtained by means of the Martens photometer is exactly the 

 reflection factor of the test surface. 



Thus the reflection factor is determined by one observation without further 

 calculation, and without the use of a standard reflecting surface. This method 

 may be modified so that the transmission factor may likewise be determined 

 absolutely. The theor}^ of the hollow sphere (commonly referred to in tech- 

 nical literature as the Ulbricht sphere) is given to show how this reflectom- 

 ■eter in theory and practice conforms with it. The use of the sphere in 

 some such manner as this is a step toward standardization. E. K. 



METALLOGRAPHY. — The structure and related properties of metals. Bur. 

 Standards Circular 113. 1921. 



This circular is a comprehensive discussion of the phase of metallography 

 indicated by the title. With but very few exceptions, the numerous illus- 

 trative examples which have been used throughout the text as types have 

 been taken from the results of examinations of metallographic specimens 

 submitted to the Bureau for examination and test. 



In the discussion of the methods for revealing the structure of metals, the 

 various reagents used in the macroscopic study of metals are described par- 

 ticularly as related to the purpose for which they are used, that is, for reveal- 

 ing chemical unhomogeneity, crystalline heterogeneity, physical unsoundness 

 and mechanical nonuniformity. The principles underlying the action of 

 etching reagents are discussed, and a list of suitable reagents for revealing 

 the microstructure of the common industrial metals and alloys given. 



Chief among the conditions which affect the structure of an alloy is chemical 

 composition, and for any particular system of alloys this is graphically sum- 

 marized in the constitutional or structural diagram. The structure is also 

 profoundly affected by temperature; for example, upon heating, an alloy 

 tends to assume a condition of physico-chemical equilibrium by diffusion, 

 etc., so that after heating, the structure may be profoundly different from 

 the initial state. Grain growth and phase changes upon heating are also 

 of importance, particularly the latter, as it is to this property that the value 

 of heat treatment as a means of obtaining wide variations in the physical 

 properties of steel and other alloys is due. The mechanical deformation 

 which constitutes the "working" of a metal also has a decided effect upon 

 its structure. 



GEODESY. — Relation between plane rectangular coordinates and geographic 



positions. Walter F. Reynolds. U. S. Coast and Geodetic Survey, 



Spec. Publ. 71 (Serial 159). Pp. 89, figs. 2. 1921. 



Control surv^eys covering large areas are made and computed by the use 



of geographic coordinates (latitudes and longitudes) because of the curvature 



of the earth. For this reason results of triangulation in publications of the 



