ABSTRACTS: OPTICS 341 



METALLURGY. — Conservation of tin in bearing metals, bronzes, and 

 solders. G. K. Burgess and R. W. Woodward. Bur. Stand. 

 Tech. Paper No. 109. Pp. 9. 19 18. 



This paper gives practical suggestions for the conservation of tin in 

 bearing metals, bronzes, and solders; much of the data having been 

 obtained from questionnaires sent to representative manufacturers and 

 users of the above named alloys. Tables are given showing the chemical 

 composition and physical properties of many of the suggested alloys 

 and also for service tests of genuine babbitt and a high lead bearing 

 metal. Tentative recommendations for standard grades of bearing 

 metal are also included. 



Proper solders for various industrial uses are recommended and a new 

 solder consisting of a preponderance of lead with small amounts of 

 tin and cadmium is described. R. W. W. 



PHYSICS. — Preliminary determination of the thermal expansion of 

 molybdenum. Lloyd W. Schad and Peter Hidnert. Bur. 

 Stand. Sci. Paper No. 332. Pp. 9. 19 19. 



The thermal expansion of an exceptionally pure specimen of molyb- 

 denum (99.85 per cent) was determined from — 142° to +305° C. A 

 short description of the apparatus and of the method used in obtaining 

 high and low temperatures is given. 



The results are shown in the form of tables, from which were com- 

 puted, by the method of least squares, the following two empirical 

 equations which satisfy the observations: 



Li = Lo(i + 5.15 i X io~® + 0.00570 f^ X 10"^) and 



Li = Lo(i + 5.01 t X io-« + 0.00138 t- X io-«) 

 where L< is the length of the specimen at any temperature t within 

 the proper range; in the first case +39° to — 142° C, and in the second 

 case +19° to +305° C. The probable error of the length computed 

 from these equations is less than 3 X io~^ per unit length. P. H. 



OPTICS. — Optical conditions accompanying the striae which appear as 

 imperfections in optical glass. A. A. Michelson. Bur. Stand. 

 Sci. Paper No. 333. Pp. 5. 1919. 

 Striae are conveniently divided into two classes; first those which 

 appear as isolated bright streaks ; second, those in which such streaks are 

 numerous, forming bright irregularly continuous bands. Optical in- 

 vestigation with two forms of interferometers show that the former 



