Inventions and Technology
Murdoch's Blackboard (also known as Chalkboard) is the precursor of the modern day Crime Board and Link Chart. Detective William Murdoch uses his to display formulae to floor plans; suspects and crime scenes; photos and word puzzles; radio waves to sea currents; and even football tactics and race skating moves all in the service to solve crime mysteries.
One's modern ears might assume that 'chalk board' or 'chalkboard' sounds like the original usage, but, in reality, 'blackboard' was the term used until the middle of the 20th century ( MM Writers make the switch too - see ep.718 ). The slate blackboard began to give way to boards manufactured with steel boards coated with porcelain enamel. The green boards gained popularity as they reduced glare and the residue chalk powder was less obvious. Thus, the term ‘chalkboard’ gained general use once black was no longer the only standard color.
Erasable slates, a cheap but durable substitute for costly paper and ink, have been in use for centuries. By 1800, James Pillans, headmaster of the Old High School of Edinburgh, Scotland, wanting to offer geography lessons to his students that required larger maps, connected a number of slates into a single large field. In 1801, George Baron, a West Point mathematics teacher, also began to use a board of connected slates to illustrate complex formulas to large audiences. Although the term blackboard did not appear until 1815, the use of these cobbled-together slates spread quickly; by 1809, every public school in Philadelphia was using them. By 1840 blackboards were manufactured commercially, smoothly planed wooden boards coated with a thick, porcelain-based paint. In the 20th century, blackboards were mostly made of porcelain-enameled steel that could last 10 to 20 years. While black was long the traditional color for blackboards, a green porcelain surface, first used around 1930, cut down on glare, and as the green surface became more common, the word chalkboard came into use.
Chalk predates the blackboard. The chalk isn’t actual chalk but gypsum, the dehydrate form of calcium sulfate. Gypsum is found naturally and can be used straight out of the ground in big chunks, but it can also be pulverized, colored, and then compressed into cylinders.
- The On Set Dresser (Props) Stephen MacDougall is responsible for the Blackboard and is the one who does most of the writing on it, not Yannick Bisson who plays Murdoch.
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