A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Dale Lichtblau
Date: 2019 May 8, 20:08 -0700
I re-watched the Smithsonian Channel's "Titanic's Final Mystery" recently. Tim Maltin's fascinating theory is that the lookout didn't see the iceberg until seconds before the allision due to significant refraction at the horizon. This led me to wonder exactly what the CN procedures were at the time. The Titanic's CQDs gave rather precise positions, e.g., 41.46 N, 50.14 W (to be read as 41 deg. 46 min., I gather). Then I thought that NavList must have something on that question. And, lo, I find the recent "Titanic's last stars" posts! But I'm also looking into the history of the telegraph. Morse suggested that longitude could be determined using the telegraph around 1839, and the experimental telegraph line from Washington, D.C. to Baltimore was officially opened on May 24,1844.
"A couple of weeks later, in June 1844, Charles Wilkes used the telegraph line to establish the longitude of Baltimore. (Wilkes was a Commander in the US Navy and also explorer who in 1838 had led the US Exploring Expedition that discovered inter alia the continent of Antarctica).
Longitude by "Wire"
Wilkes adjusted a clock to local time, using astronomical observations, and installed it at the Washington telegraph office. Lieutenant Henry Eld, a veteran of Wilkes’ expedition, did the same in Baltimore. For three days the officers at each end of the line took turns sending pulses every 10 seconds, in time with the beat (tick) of their clock. The officer on the receiving end tried to note the exact local time when he heard the electromagnet click. When the click came between the beats of his clock, he estimated the fraction of a second. When he finished, the officer sending the signals transmitted the exact local hour and seconds at which he had sent the 10 second sequences. The differences in time between the two stations were averaged to give the longitude. Wilkes reckoned that the Capitol in Washington was 1 minute 34.868 seconds of time west (0.39528 degrees west) of Battle Monument Square in Baltimore ("Longitude by wire and wireless," Paul Wise, June-December 2014, https://www.xnatmap.org/adnm/docs/2013/long_aust.htm).
It appears that Wilkes had attempted "telegraphic longitude" a couple years before Alexander Bache's (he of the U.S. Coast Survey) similar effort in 1846, as recounted in the "Telegraphic longitude article" thread here on NavList beginning on 24 Dec 2003 by Paul Hirose. The original article referenced a Professional Surveyor magazine article that I've not been able to download.
I find it all very interesting.