of vieiv of the Kinetic Theory of Matter. 23 



In order to consider the character of electrical discharge phe- 

 nomena a little more fully at the superior limit of pressure (or 

 molecular density), it may be permissible to state again that 

 the pressure at which the stratification phenomenon makes 

 itself apparent, depends only on our ability to distinguish a 

 dark from a bright line ; that these striae widen and grow 

 farther apart as the pressure of the gas decreases, and con- 

 versely, become finer and more closely crowded together as the 

 pressure of the gas increases. So that if a tube, in the stratifi- 

 cation state, transmitting electrical discharge, have the pressure 

 of the gas continuously increased, from a pressure at which 

 the striae are plainly visible to a pressure at which they can no 

 longer be seen, one would admit that electrical discharge takes 

 place by the same mechanism in the last state as when the 

 striae were visible. If the pressure be increased to atmospheric, 

 and the discharge take place disruptively, we would admit 

 that the type of transaction is the same as in the stratified dis- 

 charge. Likewise, if we compress the gas to a liquid (and 

 that liquid be a conductor), from considerations of the con- 

 tinuity of the gaseous and liquid states of matter, we ought 

 to expect the type of transaction to remain unchanged. Finally, 

 if we change the liquid to a solid (and that solid be a conduc- 

 tor), the same considerations as above would lead us to believe 

 that conduction through this solid takes place by a type of 

 transaction represented by stratified discharge in gases. 



From this brief, general view of electrical discbarge phe- 

 nomena, several facts would seem to be indicated. First, that 

 electrical discharge through a gas is primarily a transaction in 

 that gas, and ought, therefore, to be studied from the stand- 

 point of gas theories. Second, that the general type of elec- 

 trical conduction is represented in the stratification phenome- 

 non. Third, that the elementary mechanical actions in 

 electrical discharge can best be studied in discharge streams. 

 Fourth, that the study of the elementary mechanical transac- 

 tions in electrical discharge is not a study merely of some 

 interesting light phenomena, but rather a study of the ele- 

 mentary actions in electrical conduction, not only in gases, but 

 in liquid and solid conductors as well. 



§ 2. For a long time it has been well known that a most 

 remarkable similarity exists between thermal and electrical 

 phenomena. Some of the most important laws and theorems 

 in electrical science have been developed from, or suggested 

 by, the appropriate thermal analogies. Many instances might 

 be cited, but one of the most striking, as well as one that illus- 

 trates how completely, even in very complex cases, these analo- 

 gies hold, is the adaptation by Lord Kelvin of Fourier's solu- 



