It is no exaggeration to say that the mining companies, in their own interest, will be forced to subscribe enough to the stock of the company to insure its success. The Arizona Copper Mining Company is now paying $100 per ton for the transportation of its ores from the mines to Colorado city. One year's freight money at this rate would build many miles of the road. The silver mining companies will be only too glad to get their ores to market at so cheap a rate, as their proportion of the subscription to the railroad. Iron and coal are both found in the Territory,--the former especially in great abundance. Texas has guaranteed the road to El Paso, by her generous legislation; Arizona will build it, with her mineral wealth, to Fort Yuma, the eastern boundary of California, and California will do the rest. The first terminus of the Southern Pacific Railroad will doubt less be on the Gulf of California, at the Island of Tiburon, or more probably Guyamas. A steam ferry across the Gulf, a short railroad across the peninsula of Lower California to a secure harbor on the Pacific, (where a steamer will take passengers and freight in four days to San Francisco,) is the most natural course of this route. In view of this probability, all the available points for such a terminus on the Gulf have been, or are in progress of being, secured by capitalists, either by obtaining grants from the Mexican Government, or by purchase from private individuals. Already Guyamas is owned in great part by English and American capitalists. A port on the Gulf of California is necessary to our Pacific possessions, and must be ours sooner or later. The longer it is delayed, the worse for American progress on the Pacific. Arizona needs it at once, as a depot for the export of her ores, and for the import of goods for the supply of her population. The Mormon war has closed for years the great emigrant road to California and Oregon, over the South Pass and Salt Lake valley, leaving open only the route along the 32d parallel of latitude, through Arizona. This route is by far the most practicable at all seasons of the year, and the closing of the South Pass route by the Mormon difficulty is an additional and urgent argument in favor of the early organization of this Territory. Fifty thousand souls will move towards the Pacific early in the spring, if the route is opened to a secure passage. The present condition of Arizona Territory is deplorable in the extreme. Throughout the whole country there is no redress for crimes or civil injuries--no courts, no law, no magistrates. The Territory of New Mexico, to which it is attached by an act of Congress, affords it neither protection nor sustenance. The following extracts from letters received by the writer tell the story of the necessity for early action on the part of Congress, in urgent terms. TUBAC, GADSDEN PURCHASE, August 15, 1857.