From around 1870, ticker tape was used to transmit stock price information over telegraph lines. A paper strip ran through a special machine (the stock ticker) which printed abbreviated stock company names (just like today, each listed company had its unique combination of a few letters from the alphabet) followed by a numeric stock transaction price and volume. While printing, the machine made a ticking sound, and that is why it was called a stock ticker. The ticker tape had a huge impact on financial market trading, as information from trading floors in different parts of the world could now be transmitted huge distances in a quick and efficient way.…
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Invisible ink
Invisible ink is invisible either on application or soon thereafter, but can later be made visible by some method. The need to send private messages has existed since time immemorial, and invisible ink is for instance mentioned by Aeneas Tacticus, a Greek author who lived in the 4th century BCE and wrote about the art of war. Among other things, he published a guide for secure military communications. Regrettably, his surviving treaty does not include any detailed information about how invisible ink is made or from which ingredients. In the 3rd century BCE, the Greek writer Philo of Byzantium – who lived most of this life in Alexandria – described…
