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PRESIDENT JEFFERSON'S ENCODING/DECODING INSTRUCTIONS

PART I: In this activity, you are playing the role of President Jefferson in Washington D. C. You have just learned about a plan by the British Government to extend its fur trading commerce into the Oregon Territory. You must quickly prepare a brief message for Captain Lewis who is now in St. Louis getting ready to leave on a western expedition. You write "Beware of British Fur Traders" and encode it using a system agreed upon previously. This is how you do it:

1. Print the message in the squares on the top row of the chart below.
2. To encode and decode a message, a secret keyword must be chosen. In this case, the keyword used by Jefferson and Lewis was ARTICHOKES. Write the letters of the keyword underneath the message in the middle row of the chart, repeating as necessary.
   
3. Next, encode the message. Using the coder/decoder matrix, find the first letter of the message (B for Beware) on the vertical (Y) axis (far left column of matrix). Follow the row across the matrix until it intersects with the first letter of the keyword (A for Artichokes) on the horizontal (X) axis (topmost row). The letter in the box at the point where B and A intersect becomes the code letter, in this case C. Place the code letter beneath the keyword letter as shown in the chart below. Continue in this manner until all letters of the message are encoded.
   

PART II: After a couple of weeks (they really had "snail mail" in those days) you receive a reply from Captain Lewis that you must decode in reverse.

1. The encoded message is in the middle row of the charts below.
2. Copy the keyword ARTICHOKES continuously in the top rows.
3. Using the coder/decoder matrix, find the first letter of the keyword (A for Artichokes) on the X axis of the matrix. Follow the column downward until you find the first letter of the encoded message (J). Follow that row to the box on the Y axis. The letter in that box is the first letter of the decoded message, in this case, I. Continue in this manner until all letters of the message are decoded.