From: Yevgeniy Traube <y.traube1@verizon.net>
To: Teacher2Teacher Service
Date: Nov 12, 2007 at 20:28:18
Subject: Re: slide rule

Thank you for your answer. I used in the past engineering logarithmic devices
(slide-rules). They had 3 things: 1) the holder; 2)the slider; 3) the
transparent cursor with a vertical line in the middle. To count you need to
do 2 movements (for example for 8 + (-3): 1)move the 0 of the slider till 8
on the holder (as you described); 2) move the vertical line of the cursor 3
units to the left from 0 on the slider and read 5 under the line on the
holder. In this case you change the mental shift along the slider which you
described above with mechanical shift. It is more comfortable for users.
With the best wishes Yevgeniy Traube

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