Abstract
The purpose of this paper is to clarify the annual variation of temperature in the tunnel at Nokogiriyama observatory. Measurements of temperature in the tunnel and of air temperature at Nokogiriyama observatory were carried out by using thermistor thermometers during the period from March 1971 to March 1973. The data of observation was analysed by method of least squares. The theoretical distribution of temperature in the rock was calculated under the assumption that the whole heat is conducted into rock from the ground surface. As a result, a wide difference between observed and theoretical values was detected. The cause of such a wide difference is believed that the great part of the heat is transported by convection of the air in the tunnel.
