496 Proceedings. 
REPORT on the Construction and probable Cost of a proposed Exxornic 
Trrrcrapu between Hobart Town and Launceston, Van Diemen’s 
Land; with Remarks on a SusMarinE Tripararn between Van 
Diemen's Land and Australia—connected with Sydney, Melbourne, 
and Geelong. . 
TFirst—Construction of the propozed Hobart Town and Launceston Electric 
Telegraph. 
When the length of the proposed line of Telegraph is, as in the present 
instance, considerable—compared with the number of stations which 
will probably be required—it is always desirable, if possible, to use a single 
wire only; for though the instruments required for commercial purposes 
on this system are more expensive than those which involve the laying of 
the two wires, this increased expense is very greatly exceeded by the 
saving in the cost of wires, both for construction and for repairs. 
Single-wire telegraphs are used almost universally in the United States, 
and are now being introduced to a considerable extent into Britain. 
I therefore recommend that, for the proposed Telegraph, a single wire 
should be used, and also that it should be of galvanized iron, of the size 
No. 8, and suspended from posts and trees, at a height of from 18 to 20 
feet from the ground. : 
In very moist and foggy climates, in districts where it is difficult to find 
materials for posts, in localities where a suspended wire would be exposed 
to damage from storms or violence, and where repairs would be difficult 
of execution, and for lines of communication where the revenue is expected 
to be sufficient to warrant an additional investment of capital for the sake 
of durability, it may be preferable to use a copper wire, coated with gutta 
percha, and encased in an iron wire cord, the whole being buried in the — 
earth; but in the present instance it does not appear to be necessary to have 
recourse to this more expensive mode of construction. 
The posts ought to be of the hardest and most durable wood, which can 
be readily found in the locality: they should be not less than five inches in 
diameter at the butt end, and from three and a-half to four inches at the 
smaller end, and not less than twenty-two feet long. 
They ought to be properly seasoned, roughly pointed at the lower end, 
and charred for about four fect up, and should be planted about three feet 
deep in the ground: where necessary, their stability may be increased by 
haying stays of the same wire which is used for the Telegraph fixed to 
them, but care should be taken not to fix the stays too near the conducting 
wire. 
The wire is fixed to the posts by supports, called insulators, which are 
of various kinds: as the whole efficiency of the telegraph depends on the 
completeness with which these insulators prevent the escape of the 
electric current from the wire to the posts, they ought to be of the best 
kind that can be procured. I recommend a contrivance, called in Britain 
Liddell’s Insulator, originally used in America, 
