The source article linked from the submission mentions electrically synced clocks with the master in the Observatoire. I don't know why pneumatically synced cl

The source article linked from the submission mentions electrically synced clocks with the master in the Observatoire. I don't know why pneumatically synced clocks were preferred. Maybe it was cheaper to integrate the clocks themselves into the system? Patents? <http://www.douglas-self.com/MUSEUM/COMMS/airclock/airclock.htm http://www.douglas-self.com/MUSEUM/COMMS/airclock/airclock.h...> > At the Paris Observatoire a high-standard astronomical regulator clock was kept running on correct mean time by astronomical transit observations, being corrected daily. Pulses of electricity were sent every second to secondary clocks around the city, the wires being run through ducts in the sewers. Two loops starting and ending at the Observatoire carried thirteen clocks between them, the farthest being at a distance of seven and a half kilometres, or nearly four and a half miles from the observatory. The clocks were of a high standard, so they could keep good time even if the synchronising pulses failed. (The pulses synchronised the clocks but did not drive them, they were weight-driven in the conventional way) The secondary clocks were furnished with second-hands, and were placed so that they could be easily seen from the street, usually in prominent positions. They further distributed time by sending electric signals once an hour to synchronise various public clocks. The system came into operation in 1878.