456 RECENT PROGRESS IN PHYSICS. 



traversing the wire with uniform rapidity, while the mechanical 

 effects are the result, in part at least, of an interrupted transmission. 

 If the quantity of electricity is too great to be conducted off continu- 

 ously, it will accumulate in separate places at which its progress is 

 impeded by some cause, until it is in the condition to break through 

 the obstacles. Hence the increase of the coefBcient of retardation. 

 The places interrupting the discharge are indicated by the bending. 

 The retardation becomes less again by fusion, because here, at least 

 in part, a disruptive charge occurs. 



Different kinds of transmission of electricity take place in non- 

 metallic substances. In discharges through the air, by means of 

 sparks, brushes, &c., an interrupted transmission takes place, while 

 the gradual passage of electricity through the air, recognized in the 

 laws of Coulomb, is regarded as the continuous discharge of an elec- 

 trified body. A battery can be perfectly, continuously, and quietly 

 discharged by a tube of water, but by increasing the charge a spark 

 •will appear in the tube, which is broken with violence — discontiuous 

 or explosive discharge. 



That the discharge passes through water in different ways is shown 

 most distinctly by introducing the thermometer, together with the 

 tube of water, into the circuit. With four jars the result was : 



As long as a continuous discharge takes place in the water, the 

 discharge is so much retarded as to indicate no heating ; but with a 

 slight increase of the charge the rupture of the tube is made, and 

 with it a sudden elevation of temperature in the thermometer. 



[to be continued in the next espokt.] 



