A. WEEKLY 
ILLUSTRATED JOURNAL OF SCIENCE. 
“© To the solid ground 
Of Nature trusts the mind which builds for aye.’—WORDSWORTH. 
No. 1555, VOL. 60] 
THURSDAY, AUGUST 17, 1899. 
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APPARATUS 
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One great merit in the design of this Apparatus is that itis a purely | 
Mechanical method, and does not depend at all upon Optical methods of 
magnification that so frequently are a difficulty in early Practical Physics 
work, he measurement reduces itself to the readings of two Micrometer 
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A DIRECT MECHANICAL METHOD. 
ABSOLUTE READINGS OBTAINED. 
‘SIMPLEST DESIGN. 
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