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On the electrical conductivity of copper fused with mica
CURRENT TOPICS.
726
[J. F. I.
were, as was the custom at that time, good classical scholars and, therefore, familiar at first hand with the early Greek philosophers, who, as is pointed out in our histories of chemistry, suggested a theory of the composition of matter which is singularly like that dominant to-day. Meldrum’s essay “The Development of the Atomic Theory ” is interesting throughout. H. L. On the Electrical Conductivity of Copper Fused with Mica. SUB-LIEUT. A. L. WILLIAMS. (Phil. Mug., September, 1920.)-TO prepare the material an electric arc was struck between an iron or copper plate serving as an anode and a carbon rod as cathode. The arc was shifted over to the mixture of copper and mica lying on the plate and fusion followed. “ In making up the samples studied, about equal proportions of copper and mica were used.” The resulting material seems to be uniform throughout, about as hard as glass and more brittle than copper. It is malleable at 2000~ C. The outstanding characteristic is the great reduction in its electrical resistance caused by an increase of temperature. A specimen whose resistance was 91,010 ohms at gg” C. was foun,d to have only 11,370 ohms at 2~8~ C. For another specimen the data are 16,oco ohms at 27” C. and .5 ohm at 850” C. For mixtures of iron and mica similar results were obtained. The author makes the suggestion that the copper-mica mixtures may prove of use in signalling and in sound-ranging “ as the changes of resistance, due to changes of temperature, are quite considerable, being some thousands of ohms per degree centigrade with some samples.” Prof. J. C. McLennan of the Univers8ity of Toronto has caused the experiments to be repeated and extended in his laboratory by Miss Mackey and Miss Giles. Some of the results above quoted are from their data. G. F. S. High Altitudes
in the United States. (U. S. Geological Sumtey Igzo.)-Many people believe that Mount Washington, in New Hampshire, is the highest mountain Mount Washington in the eastern part of the United States. stands 6293 feet above sea level, according to the Survey, but many peaks in the Southern Appalachians are several hundred feet higher than New Hampshire’s famous mountain. The highest mountain in the Appalachian system-the highest point in the United States east of the Rockies-is Mount Mitchell, in North Carolina, which stands at an elevation of 6711 feet. The highest mountain in Tennessee, Mount Guyot, stands 6636 feet above sea level.
Press Bulletin
No. 457, October,
726
[J. F. I.
were, as was the custom at that time, good classical scholars and, therefore, familiar at first hand with the early Greek philosophers, who, as is pointed out in our histories of chemistry, suggested a theory of the composition of matter which is singularly like that dominant to-day. Meldrum’s essay “The Development of the Atomic Theory ” is interesting throughout. H. L. On the Electrical Conductivity of Copper Fused with Mica. SUB-LIEUT. A. L. WILLIAMS. (Phil. Mug., September, 1920.)-TO prepare the material an electric arc was struck between an iron or copper plate serving as an anode and a carbon rod as cathode. The arc was shifted over to the mixture of copper and mica lying on the plate and fusion followed. “ In making up the samples studied, about equal proportions of copper and mica were used.” The resulting material seems to be uniform throughout, about as hard as glass and more brittle than copper. It is malleable at 2000~ C. The outstanding characteristic is the great reduction in its electrical resistance caused by an increase of temperature. A specimen whose resistance was 91,010 ohms at gg” C. was foun,d to have only 11,370 ohms at 2~8~ C. For another specimen the data are 16,oco ohms at 27” C. and .5 ohm at 850” C. For mixtures of iron and mica similar results were obtained. The author makes the suggestion that the copper-mica mixtures may prove of use in signalling and in sound-ranging “ as the changes of resistance, due to changes of temperature, are quite considerable, being some thousands of ohms per degree centigrade with some samples.” Prof. J. C. McLennan of the Univers8ity of Toronto has caused the experiments to be repeated and extended in his laboratory by Miss Mackey and Miss Giles. Some of the results above quoted are from their data. G. F. S. High Altitudes
in the United States. (U. S. Geological Sumtey Igzo.)-Many people believe that Mount Washington, in New Hampshire, is the highest mountain Mount Washington in the eastern part of the United States. stands 6293 feet above sea level, according to the Survey, but many peaks in the Southern Appalachians are several hundred feet higher than New Hampshire’s famous mountain. The highest mountain in the Appalachian system-the highest point in the United States east of the Rockies-is Mount Mitchell, in North Carolina, which stands at an elevation of 6711 feet. The highest mountain in Tennessee, Mount Guyot, stands 6636 feet above sea level.
Press Bulletin
No. 457, October,