188 



EWELL— STUDY OF MODERN MICROMETERS. 



[April 



A + sign indicates that the measured space is too short and 

 a — sign that the space is too long. The unit of measurement is 

 the micron = y oVo" ^"^^^^i- 



No. I. Glass Micrometer by Bausch and Lome — Metric scale. 



Space Measured Relative Correction. 



First To mm — i.o micron. 



Second tV mm — 1.8 micron. 



Third ^v mm + i-O micron. 



Fourth TIT mm + i-O micron. 



Fifth TTj mm +0.8 micron. 



No. II. Photograph by Moller. 



Space. Relative CTrection. 



First TTT mm 0.0 micron. 



Second tV mm — o.i micron. 



Third t^tj mm 0.0 micron. 



Fourth TTJ mm +0.2 micron. 



Fifth tV mm — o.i micron. 



No. III. Glass Scale ruled on the Engine owned by Cornell 

 University. 



Space. Relative Correction. 



First im7 mm -f 0.2 micron. 



Second tu mm +0.3 micron. 



Third tV mm 0.0 micron. 



• Fourth To mm 0.0 micron. 



Fifth To mm — 0.4 micron. 



No. IV. Glass Scale by Zentmayer. 



Space. Rel .live Correction 



First tV mm — 0.4 micron. 



Second ttj mm — 0.5 micron. 



Third tV mm 0.0 micron. 



Fourth t\) mm +0-5 micron. 



Fifth Tu mm +0.4 micron. 



No. V. Glass Scale by E. Leitz. 



Space Relative Correction. 



First TTJ mm +0-1 micron. 



Second tu mm +0.1 micron. 



Third tV mm +0.1 micron. 



Fourth TU mm — o.i micron. 



Fifth TTJ mm — 0.2 micron. 



