126 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



SPONTANEOUS ELECTRIC CUEHENTS. 



The studies of Count clu Moncel upon the electric currents 

 found on telegraph lines will go far toward explaining the 

 oris^in of the so-called " G^round currents." He states that he 

 finds stronar currents on a line of wire havins; one end hans;- 

 ing free in the air, and that these vary with the moisture and 

 the temperature. He has shown that they are not due to 

 atmospheric electricity, because they never exist when the 

 line is perfectly well insulated ; and on such a line only a 

 thunder-storm has any effect. Du Moncel considers the ob- 

 served electricity to originate in couples formed by the sus- 

 pended wire on the one hand, and the earth plate on the other, 

 the earth itself and the telegraph poles forming the moist in- 

 termediate medium. He explains why the observed currents 

 are, in fine, clear weather, positive during the day and nega- 

 tive during the night, but the reverse in rainy weather; and 

 he elucidates the phenomena observed by Matteucci in a se- 

 ries of very careful experiments made on the plains of Lom- 

 bardy. Telegrcqoher^ 1873, 49. 



A NEW RELATION BETWEEN ELECTRICITY AND HEAT. 



Dr. Guthrie, in a paper read before the Royal Society of 

 London, gives the result of his study of a new and possibly 

 important relation between electricity and heat. He finds 

 that when an electrified insulated body is presented to a 

 heated body (especially when the latter is in communication 

 with the earth), the latter has the power of completely dis- 

 charging the former of its electricity. The discharging power 

 of a heated body diminishes with distance and increases with 

 its temperature, and specially depends upon the heat rays of 

 high intensity. The discharging power of a small white-hot 

 platinum Avire exceeds that of a large cannon-ball heated to 

 the temperature of boiling w^ater. This power does not de- 

 pend upon the temperature of the electrified body. Negative 

 electricity is always discharged more easily than positive, 

 but the difference in this respect diminishes (with certain va- 

 riations) as the temperature increases. Similar effects are 

 obtained whether w^e use galvanic or static electricity. As 

 hot iron discharges electricity most easily, so, on the other 

 hand, a ball of white-hot iron refuses to be charged. As the 



