The International Practical Temperature Scale of 1968″ is briefly introduced with emphasis on its utility for low temperature thermometry. The chief difference between IPTS-68 and IPTS-48 which had been in use until replaced by the former is described with remarks which may help experimentalists to use the new Scale. Technical informations in the textbook of IPTS-68 are summarized in tables.
Recently, resistive-cryogenic dc cable system or superconducting dc cable system is actively investigated as the underground cable transmission at each country. It is a very interesting problem to compare the each cable system from viewpoints of techniques and economics. We have done the economical comparison of conventional dc cable system, the resistive-cryogenic dc cable system and superconducting dc cable system. We get the results from this comparison as below, 1) The Break-even power of superconducting cable system was great effected by the value of transmitting voltage, for example, in case of 220kV of transmitting voltage, breakeven power is about 5GW, in case of 880kV, it is about 2GW. 2) In case of the transmitting power is more than 2GW, the superconducting cable system is the most economical system than any other cable system. 3) The economical domain of resistive-cryogenic cable system is small.