Weekly Link Dump for 2010-06-04

• Washburn Park Water Tower
  The Washburn Park Water Tower poses as a landmark of early 20th-Century architectural achievement within the Tangletown neighborhood in south Minneapolis, Minnesota, and has been doing so for nearly 75 years. Perched on top of one of the highest points in south Minneapolis, the tower is given the privilege to boast its unique location and role as an unofficial “beacon” for incoming planes landing at Minneapolis-Saint Paul International Airport, yet remains hidden from much of the residents and visitors that pass by the base of the hill each day.
• Louisville Sewer Explosions
  The Louisville sewer explosions were a series of explosions that destroyed more than two miles (3 km) of streets in Louisville, Kentucky, United States on February 13, 1981. The blasts were caused by the ignition of hexane vapors which had been illegally discharged from a Ralston-Purina soybean processing plant located near the University of Louisville.
• Battle of the Beams
  The Battle of the Beams was a period early in the Second World War when bombers of the German Air Force (Luftwaffe) used a number of increasingly accurate systems of radio navigation for night bombing. British “scientific intelligence” at the Air Ministry fought back with a variety of increasingly effective means, involving jamming and distortion of the radio waves. The period ended when the Germans moved their bomber forces to the East in May 1941, in preparation for the attack on the Soviet Union.
• Halt and Catch Fire
  Halt and Catch Fire, known by the mnemonic HCF, was originally a fictitious computer machine code instruction claimed to be under development at IBM for use in their System/360 computers, along with many other amusing instructions such as “Execute Operator”. One apocryphal story goes back to the late 1960s, when computers used magnetic core memory. The story goes that in order to speed up the core memory on their next model the engineers increased the read/write currents in the very fine wires that were threaded through the cores. This worked fine when the computer was executing normal programs, since memory accesses were spread throughout memory. However, the HALT instruction was implemented as a “Jump to self”. This meant that the same core memory location was repeatedly accessed, and the very fine wires became so hot that they started to smoke – hence “Halt and Catch Fire”.
• Glacial Lake Outburst Flood
  A glacial lake outburst flood can occur when a lake contained by a glacier or a terminal moraine dam fails. This can happen due to erosion, a buildup of water pressure, an avalanche of rock or heavy snow, an earthquake, volcanic eruptions under the ice, or if a large enough portion of a glacier breaks off and massively displaces the waters in a glacial lake at its base.

Images:
Washburn Water Tower, a Public Domain image from Wikimedia Commons
Hubbard Glacier May 20.2000, a Public Domain image from Wikimedia Commons