98 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



Bechstein's Photometer, with Proportional Graduation and 

 Decimally-divided Scale.* — This instrument, which is made by 

 Schmidt and Haensch of Berlin, is an improved form of certain others 

 manufactured by the same firm, and is shown in figs. 19 and 20. The 

 following advantages are claimed for it : — (1) Easy portability and small 

 weight ; (2) absence of unit-marks ; (3) convenient legibility in the 



Fig. 19. 



graduations ; (4) simple calculation with extreme accuracy of measure- 

 ment ; (5) long range of measurement both downwards and upwards ; 

 (6) special protection of the parts important for the constant of the 

 given medium ; (7) universal application ; (8) moderate price. 



It will be seen from the figures that the instrument consists essentially 



* Zeit. f. Instrumentenk., xxvii. (1907) pp. 178-83 (6 figs.). 



