HISTORY AND PROGRESS. 185 



is stated to be got over at the almost incredible rate of 1,200 

 words in the same time. 



The following facsimile of Bonelli printing is cut from a 

 strip printed at the 1864 Conversazione at the Institution of 

 Civil Engineers : 



BY THE BQNELL! INSTRUMENT: 



s '.'. 



VII. OVERLAND LINKS. 



102. The overland line wire, stretched between two stations, 

 is suspended by insulated hooks from posts in the ground. 



The first line of this nature, which was put to any useful 

 purpose, was the double line- wire of Gauss and Weber, erected 

 principally for researches into the laws of the galvanic cur- 

 rent, between the physical cabinet and the Observatory at 

 Grottingen, a length of 3,000 yards, suspended between the 

 towers of the city and on cross-pieces on poles sunk in the 

 ground. The insulation of the wire from the poles was 

 effected by means of felt wrapped round the cross-pieces on 

 which the wires were twisted. The insulation of this line 

 was of course very imperfect. 



The posts generally pressed into the service of the tele- 

 graph abroad are young firs (pwws sy/^m). They are 

 selected from 25 to 30 feet long, and at ike top seldom less 

 than 5 inches diameter. The bark is stripped off and the 

 posts smoothed, champhered off, and either impregnated or 

 the lower ends charred up to about 8 feet from the bottom. 

 Every tenth post is, or should be, a stretching post, stronger 

 than the others. 



The wooden posts mostly in use here are of English larch ; 

 but foreign timber, although dearer, is preferable on account 

 of its greater durability. 



Impregnation with a solution of sulphate of copper is the 

 invention of a Frenchman, Dr. Boucherie. His process 

 seems to possess important advantages over others, accom- 

 plishing as it does, at the same time, two essential objects 



