Disputes over time: seismograph record
For many years after the Explosion there were arguments over the exact time it happened. Some people said it was 9:06, others 9:05 or 9:07. Some said it was definitely just before…or just after, or exactly at, 9 o'clock.
The last word on the subject came from the seismograph at Dalhousie University. Its record was in storage for years, until researchers Alan Ruffman and David Simpson found it at a geological observatory in New York.
The seismograph recording proves the explosion happened at 9:04:35, plus or minus 10 seconds. this allows for 0.57 seconds for the vibration to travel from the harbour to Dalhousie…and allows for the fact that the seismograph's clock was itself 10 seconds fast.