Zetetic Astronomy, by 'Parallax' (pseud. Samuel Birley
Rowbotham), , at sacred-texts.com On the shore near Waterloo, a
few miles to the north of Liverpool, a good telescope was fixed,
at an elevation of 6 feet above the water. It was directed to a
large steamer, just leaving the River Mersey, and sailing out to
Dublin. Gradually the mast-head of the receding vessel came
nearer to the horizon, until, at length, after more than four
hours had elapsed, it disappeared. The ordinary rate of sailing
of the Dublin steamers was fully eight miles an hour; so that
the vessel would be, at least, thirty-two miles distant when the
mast-head came to the horizon. The 6 feet of elevation of the
telescope would require three miles to be deducted for
convexity, which would leave twenty-nine miles, the square of
which, multiplied by 8 inches, gives 560 feet; deducting 80 feet
for the height of the main-mast, and we find that, according to
the doctrine of rotundity, the mast-head of the outward bound
steamer should have been 480