48 REPORT— 1902. 



theory is that the square of the refractive index of a body should be the 

 same number as its dielectric constant. So fai*, however, from this being 

 the case generally, the exceptions are far more numerous than the coinci- 

 dences. It has been shown in the case of many substances, such as ice 

 and glass, that an increase in the frequency of the alternating electro- 

 motive force results in a reduction of the dielectric constant to a value 

 more consistent with Maxwell's law. By experiments upon many 

 substances it is shown that even a moderate increase of frequency brings 

 the large dielectric constant to values quite near to that required by 

 Maxwell's law. It was thus shown that low temperature has the same 

 effect as high frequency in annulling the abnormal dielectric values. 

 The exact measurement of the dielectric constant of liquid oxygen as 

 well as its magnetic permeability, combined with the optical determina- 

 tion of the refractive index, showed that liquid oxygen strictly obeys 

 Maxwell's electro-optic law even at very low electric frequencies. In 

 magnetic work the result of greatest value is the proof that magnetic 

 susceptibility varies inversely as the absolute temperature. This shows 

 that the magnetisation of 'paramagnetic bodies is an affair of orientation 

 of molecules, and it suggests that at the absolute zero all the feebly para- 

 magnetic bodies will be strongly magnetic. The diamagnetism of bismuth 

 was found to be increased at low temperatures. The magnetic moment 

 of a steel magnet is temporarily increased by cooling in liquid air, but the 

 increase seems to have reached a limit, because on further cooling to the 

 temperature of liquid hydrogen hardly any further change was observed. 

 The study of the thermo-electric relations of the metals at low tempera- 

 tures resulted in a great extension of the well known Tait Thermo- Electric 

 Diagram. Tait found that the thermo-electric power of the metals could 

 be expressed by a linear function of the absolute temperature, but at the 

 extreme range of temperature now under consideration this law was 

 found not to hold generally ; and further, it appeared that many abrupt 

 electric changes take place, which originate i)robably from specific mole- 

 cular changes occurring in the metal. The thermo-electric neutral points 

 of certain metals, such as lead and gold, which are located at or below 

 the boiling-point of hydrogen, have been found to be a convenient means 

 of defining specific temperatures in this exceptional part of the thermo- 

 metric scale. 



The effect of cold upon the life of living organisms is a matter of great 

 intrinsic interest, as well as of wide theoretical importance. Experiment 

 indicates that moderately high temperatures are much more fatal, at least 

 to the lower forms of life, than are exceedingly low ones. Professor 

 McKendrick froze for an hour at a temperature of minus 182° C. samples 

 of meat, milk, &c., in sealed tubes ; when these were opened after 

 being kept at blood heat for a few days, their contents were found to be 

 quite putrid. More recently some more elaborate tests were carried out 

 at the Jenner Institute of Preventive Medicine on a series of typical 

 bacteria. These were exposed to the temperature of liquid air for twenty 



