I have just seen in the Comptes Rendus (June 27) an account of some experiments, on this subject, made by M. Galopin in the laboratory of Professor Pictet. As the effects obtained by him seem to be somewhat greater than my own experiments had led me to expect, I was induced to repeat my calculations with the view of trying to account for the difference. Unfortunately, M. Galopin's work is confined to 500 atmospheres, a pressure which lies a little beyond the range of my experiments ; so that no very trustworthy comparison can be made. M. Galopin's results have one advantage over those of the direct experiments of the same kind which I made, inasmuch as he was able to use ordinary thermometers, while I employed thermo-electric junctions, in measuring the rise of temperature by compression. But they have a corresponding disadvantage, in the fact that mine were obtained instantaneously (by means of a dead-beat galvanometer) and required no correction; while his had to be corrected for the heat-equivalent of his apparatus to an amount not easy to estimate with accuracy.