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BELL SYSTEM TECHNICAL JOURNAL 



system to magnify small measurements without the use of a vernier 

 or other mechanical means, and due to its construction is dependable 

 and probably less liable to variation than the liquid gage. Most of 

 the errors due to play between mechanical parts such as gears, 



Fig. 24 — Fluid gage or "prestometer" showing tool part in position for measuring 



micrometer screws, knife edges, diaphragms, capillary tubes, etc., 

 have been considerably reduced. The only moving part except the 

 measuring feeler is a small mirror which is tilted by the upper end of 

 the feeler and reflects the image of a stationary glass scale. The 



