But in this is the whole difficulty as far as regards the best granite road; for, supposing for a moment that all the other conditions were fulfilled--that it was hard and smooth--one great element is to be taken into consideration, from which no skill and science can exempt the best and firmest Macadam; and that is the effect of atmospheric changes on the surface of the road. The difference of tractive power in summer and winter must be immense, and the great disadvantage of mechanical, as compared with animal draught, is its want of adaptability to the exigencies of an ordinary road. A steam-carriage of ten horse power cannot under any circumstances, when it encounters a newly mended part of the road, or a softer soil, put forth an additional power for a minute or two, as a team of horses can do; so that equality of exertion is nearly indispensable for the full advantage of an engine. We accordingly find that the opponents of steam-travelling on common roads, gained their object by covering the highway with a coating of broken stones fourteen inches deep. Through this it was impossible to force the coach without such a strain as to displace or otherwise injure the machinery. But when a system of locomotion, containing so many advantages, has so nearly been brought to perfection, in spite of the many difficulties presented by the common modes of making a road, it would be inconceivable blindness in the parties interested in the subject to overlook the certain mode of success offered to them, by merely laying down a portion of the road in wood. Who those parties are we have already pointed out. They are the inhabitants and owners of property in towns and neighbourhoods at some distance from railway traffic; and if the proprietors of great lines of railway saw their own interest, they would be foremost in adopting the new method as an auxiliary, and not view it as a rival or an enemy. For it is very evident that nothing can be so beneficial to a railway already in operation as a branch line, by which a hitherto unopened district can be united to their stations. And the difference of expense between the two systems--namely, between an iron railway and a wooden pavement--is so great, that the latter is scarcely beyond the power of the poorest neighbourhood. An iron branch was at one time proposed between Steventon and Oxford. The same sum which would have been required for this purpose, according to the estimates, would have laid down an excellent road in wood from Steventon through Oxford to Rugby; thus connecting the three great arteries of the country--the Great Western, the Birmingham, and the Midland Counties Railways. It will be found that the great lines of railway have been forced, at an unavoidable and foreseen loss, to spread out minor or tributary lines, which, if the system of wood-paving had been in existence, might have been laid down at less than a third of the expense, and producing a proportionate profit.