You may have noticed – or you may not have. Take a look at a clock face with Roman-style numerals. Most of them show four as “IIII” rather than “IV”. What’s up with that? We were taught in grade school (at least I was) the subtractive notation for Roman Numerals: when you count higher than three or eight you can subtract one from the next highest five or ten and save yourself a numeral. So why don’t clocks do this? Rather, why do they do this for nine but not four?

The simple answer is that this is tradition: that’s the way clock faces have always been made. But that’s not really an answer as to why. Turns out we are mighty long on theories and short on facts as to the origin of this tradition.
Theory One has it that the heavy strokes of “IIII” aesthetically balance out the “VIII” on the other side of the clock, but that theory ignores that “V” does not balance out “VII”, and also ignores the fact that “IIII” was used on the very earliest clocks, which use a 24-hour face.
Theory Two is that clock-makers spelled four as “IIII” because it was more economical: you could cast all the characters needed for a clock face with four “X”s, four “V”s and twenty “I”s. Nice and symmetrical. But this theory ignores the fact that most clocks with cast numerals had the whole number cast as one piece, not as individual characters. Another problem with this theory is that there does not seem to be a decline in the use of “IIII” for clocks with painted faces. And finally, the “IV” saves you three “I”s for a “V”, so that should be more economical.
Theory Three has it that the tradition originated with Roman sundials, and “IIII” was easier for peasants to understand than the use of the subtractive “IV” (this theory relies on the supposition that poor people must also be stupid). Another problem with this theory is that old sundials use “IX” for nine. What? Peasants could figure out nine but not four?
The “Right” Theory – I’m inclined to believe the practice originated something like this: clocks spell the Roman four as “IIII” because that was the common practice in all writings using Roman numbers at the time clocks were invented, around the 13th century. To be sure, the use of subtractive notation was in use at the time, e.g. nine was always “IX”, not “VIIII”, but four was an exception. Why is this? The theory is that “IV” was simply inappropriate for Romans to use for a number, because it was the first two letters, and consequently abbreviation, for “IVPITER”, the Latin script spelling for the god Jupiter. Jupiter was not just any god, he was the king of the gods. So out of respect for Jupiter or perhaps just to avoid misunderstanding, four had to be “IIII”. I first read about this theory in an article by Isaac Asimov some 30 years ago, in Isaac Asimov’s Science Fiction Magazine, if I remember correctly. If the theory was good enough for Isaac Asimov, by golly, it’s good enough for me. The real answer may be lost to history, but it’s certainly a fun little anomaly to guess about.
Sources:
[1] FAQ: Roman IIII vs. IV on Clock Dials, UBR, Inc.
[2] Why does a clock face have ‘4’ as ‘IIII’ instead of ‘IV’ ?Askville by Amazon, Askville by Amazon
[3] CLOCKING THE FOURS: A NEW THEORY ABOUT IIII, Paul Lewis Post
[4] Time is racing, www.24hourtime.info

The Boston Molasses Disaster or Boston Molasses Flood is one of the more bizarre disasters in American history. On January 15, 1919 a huge molasses tank failed explosively, sending a flood of hot, sticky, sweet molasses through the streets of Boston’s North End.

The steel tank, operated by the Purity Distilling Company, was 58 feet high and 90 feet in diameter, and held something close to its capacity of 2.5 million gallons. When the tank burst, the concussion of the explosion or “rush of air” was strong enough to knock a truck into Boston Harbor. The splitting seams sent rivets shooting out like bullets, and pieces of steel flew out like shrapnel. The real destruction, however, came from a 7 to 15-foot high, 35-MPH wave of molasses with a pressure of 2 tons per square foot. The molasses swept buildings off their foundations, crushed the girders of an elevated railway and swallowed up dogs, horses and people in its path. 21 people were horribly killed – crushed or burned or drowned in molasses. Another 150 victims were injured. It took six months and 87,000 man-hours to clean up the molasses.
As you might expect, over a hundred lawsuits were brought in the months and years following the disaster. Over 3,000 witnesses testified in court, and 45,000 pages of testimony and arguments were generated. The Purity company tried to blame the tank’s failure on an outside explosion, a bomb planted by an anarchist (the disaster occurred right after World War I, when the “anarchy scare” was at its height). The supposed motive was because the molasses was destined to be made into industrial ethyl-alcohol, which was used in the munitions industry. The prosecution argued that the tank was not reinforced properly and was not properly inspected. Other factors could have come into play, such as the fact that the temperature went from 2°F the prior day to an unseasonably warm 41°F the day of the explosion, and internal pressure could have built up in fermentation or other processes. In addition, the tank had only been filled to capacity eight times, putting a cyclical load on the structure. After 6 years, the trials eventually found no evidence for a bomb and laid the blame on the Purity company. Around a million dollars was paid out to claimants (about 12 million today).
A number of urban legends have persisted in the years following the disaster, such as the one which states that on a hot summer day, one can still smell molasses in the North End. Another legend purports the tank was overfilled in expectation of Prohibition (since molasses is also used to distill into rum). Time has distanced us from the tragic nature of the incident and allows us to appreciate the local’s name for it: “The Boston Molassacre”.
Sources:
[1] What caused the great Boston Molasses Flood?, The Massachusetts Historical Society
[2] The Molasses Disaster of January 15, 1919, Yankee Magazine
[3] Jan. 15, 1919: Morass of Molasses Mucks Up Boston, Wired Magazine
[4] Boston Molasses Disaster, Wikipedia