  We report on a measurement of the cosmic ray energy spectrum by the Telescope
Array Low-Energy Extension (TALE) air fluorescence detector. The TALE air
fluorescence detector is also sensitive to the Cherenkov light produced by
shower particles. Low energy cosmic rays, in the PeV energy range, are
detectable by TALE as "Cherenkov Events". Using these events, we measure the
energy spectrum from a low energy of $\sim 2$ PeV to an energy greater than 100
PeV. Above 100 PeV TALE can detect cosmic rays using air fluorescence. This
allows for the extension of the measurement to energies greater than a few EeV.
In this paper, we will describe the detector, explain the technique, and
present results from a measurement of the spectrum using $\sim 1000$ hours of
observation. The observed spectrum shows a clear steepening near $10^{17.1}$
eV, along with an ankle-like structure at $10^{16.2}$ eV. These features
present important constraints on galactic cosmic rays origin and propagation
models. The feature at $10^{17.1}$ eV may also mark the end of the galactic
cosmic rays flux and the start of the transition to extra-galactic sources.
