  We present a consistent optimal estimation retrieval analysis of ten hot
Jupiter exoplanets, each with transmission spectral data spanning the visible
to near-infrared wavelength range. Using the NEMESIS radiative transfer and
retrieval tool, we calculate a range of possible atmospheric states for
WASP-6b, WASP-12b, WASP-17b, WASP-19b, WASP-31b, WASP-39b, HD 189733b, HD
209458b, HAT-P-1b and HAT-P-12b. We find that the spectra of all ten planets
are consistent with the presence of some atmospheric aerosol; WASP-6b,
WASP-12b, WASP-17b, WASP-19b, HD 189733b and HAT-P-12b are all fit best by
Rayleigh scattering aerosols, whereas WASP-31b, WASP-39b and HD 209458b are
better represented by a grey cloud model. HAT-P-1b has solutions that fall into
both categories. WASP-6b, HAT-P-12b, HD 189733b and WASP-12b must have aerosol
extending to low atmospheric pressures (below 0.1 mbar). In general, planets
with equilibrium temperatures between 1300 and 1700 K are best represented by
deeper, grey cloud layers, whereas cooler or hotter planets are better fit
using high Rayleigh scattering aerosol. We find little evidence for the
presence of molecular absorbers other than H$_2$O. Retrieval methods can
provide a consistent picture across a range of hot Jupiter atmospheres with
existing data, and will be a powerful tool for the interpretation of James Webb
Space Telescope observations.
