Turbulence in thermal convection has been investigated experimentally in a 1.0×1.0㎡ variable-height, closed convection chamber. The experiment was performed with air(Pr = 0.71) over the range $1\times10^6$＜Ra＜$1\times10^8$. Based on the statistical homogeneity in horizontal planes, vertical distributions of time mean temperature and its r.m.s. fluctuations were measured using thermocouple sensors of 25㎛ thickness. Mean temperature and r.m.s fluctuation profiles were compared with previous experiments. Mean temperature profiles are in good agreement with their results but the level of the r.m.s fluctuations are about 30% lower than their data. Mean temperature and its gradient fields were correlated well in terms of Chung's conduction layer scales, which means that thermal boundary layer has the charateristics of a layered structure. The heat transfer correlation obtained through the present experiments are Nu = 0.152 $Ra^{0.286}$, which agrees well with previous measurements.
