The Bank of Time - Four Revolutions in the Earth Sciences - page 16

have for the whole duration of geological time, down to the miocene tertiary [ sic ]
epoch . . . 152,675,000 years.”
Estimating the time from the Miocene to the present at one-third that amount,
Haughton concluded that the whole duration of geological time requires “a minim-
um of two hundred millions of years” (268). Thus in order to bring his calculus in-
to the range that Kelvin allowed, after saying he was by no means willing to divide
by ten to do so, Haughton then divided by ten. As Kelvin's biographer Burchfield
put it, this juggling was “little short of a swindle.” 19 Haughton got away with it, as
geologists cited his calculation as further evidence that the Earth is no more than a
few hundred million years old.
American geologists soon began to make their own calculations. One of the
most thorough came from Charles D. Walcott (1850-1927), the discoverer of the
“wonderful life” of the Cambrian Burgess shale, as Stephen Jay Gould titled his
topic on the subject. In 1894 Walcott became director of the U.S. Geological Sur-
vey and in 1906 succeeded Samuel Langley as secretary of the Smithsonian Insti-
tution. Walcott decided to calculate the time required for the deposition of a par-
ticular sequence of Paleozoic rocks he knew well and extrapolate from there to the
age of the Earth. 20 He distinguished between rocks like sandstone that are depos-
ited mechanically and limestones that are formed chemically or biologically. After
a number of assumptions and corrections, Walcott estimated the duration of Paleo-
zoic time at 17.5 million years. He used estimates made by others of the length of
the other eras—really little more than educated guesses—to come up with a total
for geologic time of 55 million years. 21 Geologic time, Walcott concluded, “is of
great but not of indefinite duration. I believe that it can be measured by tens of
millions, but not by single millions or hundreds of millions of years.” 22
Dropping with Harmonic Regularity
Geologists were not the only ones to fall sway to Kelvin. George Darwin
(1845-1912), second son of Charles, like Kelvin had been “second wrangler” at
Cambridge: runner-up in the annual university mathematics contest. George Dar-
win would go on to become a professor of Astronomy at Cambridge, president of
the Royal Astronomical Society, and president of the British Association. His in-
terests were quite different than those of his father and much closer to Kelvin's.
Kelvin and others had been interested in the “figure” of the Earth—its departure
from a perfect sphere—and of the effect of tides in the solid Earth in slowing the
planet's rotation. In 1877, George Darwin wrote a paper titled “On the Influence
of Geological Changes in the Earth's Axis of Rotation,” just the sort of work that