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other such mode of reckoning ; or if I had not 

 vowed never to mention inches, I would say tons 

 per square inch, which is common (perhaps too 

 common) in engineering. All such measure- 

 ments ignore the difference of gravity in different 

 localities, except some more precise measurements 

 in which an allowance for the force of gravity to 

 reduce it to a standard of lat. 45 is made, or it is 

 left to the person using the measurement to make 

 the reduction. For all purposes, however, in which 

 it would be desirable to apply a correction for 

 the varying force of gravity in different places it 

 is convenient to use Gauss's absolute unit, and not 

 the terrestrial-gravitation unit of force. I may say 

 in passing, that the mere idea, which lurked or 

 was visibly manifested, according to the degree of 

 understanding, in the old formula of elementary 

 dynamics F = m -r- was an immense step ; and 

 the realisation of that idea, the bringing of it into 

 practical use, has contributed more than anything 

 else I know to the intelligent treatment of 

 dynamic problems and their application to both 

 scientific and engineering matters. The system 



