What do you know today that you didn't know yesterday?

[Anomalocaris]

London still has more than 1,000 gas street lamps, which were installed at the beginning of the 19th century.

Boston streets remain gas illumined by no less than 3,500 lamps.

Interesting tidbit about gas street lighting.    Municipal gas street lights in the 19th century were usually fed from giant central gas tanks that were made from concentric iron rings which telescopes vertically in and out as the gas in used up or replenished.    The amount of gas in the tank is kept track of by paper plot charts which registered the position of the rings.   But the charts tracked not only the amount of gas in tank, but also rapid air pressure changes outside the tank because the gas stored in the tank will compress or expand in response to outside air pressure change and cause the tank to telescope in and out. 

When Krakatoa volcano in what is now Indonesia exploded in 1883,  the atmospheric shockwave propagated out from the volcano and circled the earth 7 times.    We know this because as the shockwave passed over the giant municipal street lighting gas tanks all around the world, the pressure difference caused the tanks to telescope in and out, and the paper track charts left an exact record of when the shockwave passed over each city that had a central gas street lighting system.