But the railroad should not stop here; it should branch away along the shore to the point where now the town of _Martinez_ is being laid out,--a very pretty site facing the straits of Carquinez; thence it should strike the valley of San Jose--one of the richest spots in California and which would support, a million of industrious inhabitants--and following along the coast terminate at San Diego. The advantages of uniting the two opposite points of the country by means of a railroad, will not only help its speedy settlement--an important consideration in many respects--but will be equal to gaining a free port on the coast of Mexico for the exclusive benefit of American citizens. By the means of _Santa Fe_ and _San Diego_, should the railroad be constructed as indicated above, the Union will have the command of the largest share of the Mexican trade. So far as we know, and we have taken considerable pains to ascertain the fact, we may assert that there is no better route for a railroad from the States to California. No other passage through the _Sierra Nevada_ can be found but the one we have indicated. There is none to be found between the heads of the Sacramento and San Joaquin rivers. We have rambled over that region, and the conformation of the country gives us confidence in saying that it is not at all favorable to such a passage; and besides, supposing that such a passage could be found, a single fact in relation to the subject will destroy all hopes of effecting the object; we mean that from the line where the auriferous region terminates, to the very ridge of the _Sierra Nevada_--the region of granite, occasional limestone, and Masses of sand-stone--snow lies for six months, accompanied with intense cold; the depressions of the mountains are filled up with it to such a degree that the tops of the highest trees only peep through it as if they were but so many insignificant bushes. In fine, the snow levels the tops of the mountains into a continuous plain, as it were, through which the melting sun alone, by degrees, can effect a passage towards the end of June or the beginning of July. This is the time when the Snowy Mountains can be traversed. The government a few weeks ago sent an expedition in search of such a passage through the Northern portion of the gold region about the head of the Sacramento river. We feel sure that the attempt will be fruitless.