Geology and Magnetism, 501 



and rise in the atmosphere, are again returned into the earth by 

 means of the currents. Nothing can be destroyed ; on the contrary 

 whatever substances we may consume, reduce, or decompose, become 

 again, by means of the enveloping magnetic fluid, what they were 

 before they existed in form of vegetable, stone or water, active 

 agents in the business of the world, and main supports of vegetable 

 aud animal life, and are still susceptible of running again and again 

 the same round, as circumstances may determine." 



Mr. Hopkins next explains the identity of magnetic and 

 galvanic currents, rejecting the commonly received opinion 

 that they move at right angles, which is at variance with the 

 analogy of all other physical forces, which act in a line 

 extended between two points, the point from which the 

 force emanates and that against which it is exerted. When 

 a magnet is exposed to electrical action by means of two con- 

 ducting wires bent into helices, a spiral current is produced. 

 This Mr. Hopkins refers to a general law of all fluids, which 

 when forced through tubes, have a tendency to a spiral direc- 

 tion, as commonly observed in a funnel. The funnel how- 

 ever, we think an unfortunate instance, for we are disposed 

 to refer the spirial direction of the fluid passing through 

 it a good deal to its shape, and we doubt much if fluids 

 forced through square tubes, would indicate any tendency 

 to a spiral direction. We do not know how far Mr. Hopkins' 

 views may depend upon such a law. With regard to electro- 

 magnetic action, Mr. Hopkins remarks, the mean direction 

 of the spiral corresponds with the direction of the wire : 

 11 therefore we may safely consider the magnetic needle, 

 enveloped as it is in the great terrestrial magnetic fluid, indi- 

 cates the direction of the currents." 



" We have now to prove that the currents move through the 

 magnetic needle from south to north. In the battery we find that 

 the currents of hydrogen move from the zinc to the silver plate, 

 along or through the connecting wire. We find by experiments 



3 T 



