Prof» Hagem.Jim has’ likewise attempted to measure the diff¬ erences in temperature of the water current "by resistance ther¬ mometers. The water at Bonn is extremely unsatisfactory, con¬ taining a great deal of sediment and with the thermometers he has tried, i* soon clogs up and becomes short-circuited. A Suggestion. The new platinum resistance thermometers of Heraeus. enclosed in fused quartz tubes, should be especially advantageous for measuring the temperatures of the ingoing and outcoming water current. According to Wrede in Berlin, these resistance thermometers are extremely sensitive. Their use is to be thoroughly investigated in the construction of our new chambers. Temperature of air current.—-In order to measure the differ¬ ence in temperature between the ingoing and outcoming air current, Prof. Hagemann uses both thermal junctions nd resistance ther¬ mometers but the latter were, at the time of my visit, out of order. He feels very dissatisfied with the thermal junctions. Very long junctions are used and Prof. Hagemann feels convinced that there v/as heat conducted along the junction wires through the vestibule and hence there was an error. His present system is very complicated and I fail to see that it is any more effec¬ tive than that we were using at Middletown. I suggested a scheme we have in miad for the new apparatus of having the ingoing c~ir go», in. in a tube encircling the out¬ coming air and thus use the outcoming air as a regulator of the te werature of the ingoing air. For regulating the temperature of the air, Prof. Hagemann has a large water cooling tank such as was used in the Middletown apparatus, very much enlarged. He also has an electrical heating