Temperaure dependence of the energy gap in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Bi</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Sr</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><…

High-resolution electron-energy-loss spectroscopy has been used to determine the magnitude and temperture dependence of the energy gap for oxygen annealed ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{8}$ single crystals. Below the ${\mathit{T}}_{\mathit{c}}$, low-energy excitations are detected in the energy-loss spectra. These spectra are proportional to the frequency-dependent resistivity, \ensuremath{\rho}(\ensuremath{\omega}), and thus the energy gap can be determined directly from the onset of \ensuremath{\rho}(\ensuremath{\omega}). We find that at low temperature 2\ensuremath{\Delta}=6${\mathit{kT}}_{\mathit{c}}$ and that \ensuremath{\Delta} develops sharply for T${\mathit{T}}_{\mathit{c}}$. The similarity of these results to the predictions of models that consider spin interactions suggests that higher ${\mathit{T}}_{\mathit{c}}$'s may be obtainable in this material.