Messrs J. Murray and J. C. Young have been carrying out experimentally the idea mentioned in my former note on this subject. (Proc. Dec. 1870.) Their first sets of observations, of the results of which I subjoin a specimen, were made with an iron-silver and an iron-platinum, circuit working opposite ways on a differential galvanometer. The resistances (including the galvanometer coils) were in this particular experiment 53·1 and 25·9 B.A. units respectively, so that but very slight percentage changes could be produced in them by the elevation of temperature of the junctions.