On Salt Solutions and Attached Water. 105 



as voltaic-induction currents are to be observed in one of the 

 wires when a galvanic series is alternately closed and opened 

 by the other. If the roller be now placed in a vessel, and this 

 be little by little filled with water, the charge-currents in the 

 former wire diminish, and cease altogether when the water 

 quite fills up the intervals between the wires, whereas the elec- 

 trodynamically induced currents become even more intense. 



For telegraph-conductions these electrodynamically induced 

 currents are, as we have already remarked, of no consequence, 

 since they do not increase with the length of the conduction ; 

 but the telephone, being so extremely sensitive, is still excited 

 by them if the inducing currents are not extraordinarily feeble. 

 It will therefore be necessary to lay down special cables for 

 telephones, just as special posts are needed for them when the 

 wires are carried above ground. 



As follows from the above, the telephone is still capable of 

 essential improvement; in a short time telephones will as- 

 suredly be constructed which will convey both speech and 

 musical tones beyond comparison more loudly, more distinctly, 

 and with greater purity to moderate distances than they have 

 been hitherto by the Bell telephone. The telephone will then 

 render service to intercourse in cities and between neighbour- 

 ing towns which will far surpass what the telegraph can per- 

 form for short distances. The telephone is an electrical 

 speaking-tube which, just like an ordinary speaking-tube, can 

 be managed by every one, and can be a perfect substitute for 

 personal conversation ; but as at very short distances it will 

 never supplant the speaking-tube, just as little will it be able 

 to take the place of the telegraph for greater distances. Yet 

 in the limited circle of its practicability it will soon be num- 

 bered among the most important pillars of modern civilization, 

 if external hindrances do not prevent its development and 

 application. 



XIY. On Salt Solutions and Attached Water. 

 By Frederick Guthrie. 



[Continued from p. 44.] 

 On the Separation of Water from Crystalline Solids, inCurrents 

 of Dry Air. 



§ 184. rTIHE high water-worth of many of the cryohydrates 

 J- (§ 88), and the want of evidence of simple arithme- 

 tical relationship between the atomic numbers of the water and 

 salt of almost all these bodies, invited me to reexamine a few of 

 the most definite and stable crystalline salts containing water. 

 And this invitation was the more pressing because, in the 



