In connexion with the railways noticed above, we may mention several extensive surveys, which have been made for works of this description. One of these by Mr. Telford, extends across the country from Glasgow to Berwick upon-Tweed, a distance of 125 miles, with a rise of 636 feet to the water-shade, in the parish of Dolphingstoun. The survey from Bei-• wick to Kelso, by the late eminent Mr. Rennie, has been farther continued up Gala Water to Dalkeith, Edinburgh, and Leith, by Mr. Stevenson, who has al so made a survey upon the opposite side of the Frith of Froth, on an uninterrupted level from the river Tay, through the great valley of Strathmore to Aber deen, with branch-lines to the ports of Stonehaven, Montrose, Arbroath, Dundee, and Perth, comprising upwards of one hundred miles of level road. A colla teral line has likewise been traced by the same engi neer from the confluence of the rivers Earn and Tay, through the county of Fife to the westward of Dunferm line, with various branch lines communicating with the Frith of Froth. An extensive survey has lately been made by Mr. James, for connecting Liverpool with Manches ter by a railway, notwithstanding the water communi cations already established between these places by the river Mersey and the Irwell canal. It may further be mentioned, that after looking forward for many years for a canal across the country between the Tyne and the Solway, (a track of all others the most desirable for such a work,) a railway is now contemplated, even by those who were most anxious that this improvement should be a navigable canal. These operations, or•cer tain compartments of them, may be expected ere long to be carried into effect, as the benefits of the railway system are every day more apparent. A public rail way is indeed now executing, under the direction of Mr. Granger, between the Forth and Clyde canal, and the extensive coal field in the vicinity of the Monk land canal near Airdrie.
In noticing the construction of railways in this place, we conceive it only to be necessary to describe what may be considered the chief points of the system, leav ing minor details, which may now be examined in al most every district of the country, by those who are professional or curious. In pursuance of this view we observe, that every practicable effoi t should be made, to form the line of draught upon our level, or upon a ,succession of level reaches, connected either by inclined planes or perpendicular lifts, according to the circum stances of the ground. The line of direction of a rail way is another feature of this measure, which in many instances is too apt to be overlooked. It has been ob jected to a canal with long reaches in direct lines, that the water is apt to be collected at the further end during high winds, so as to overflow its banks ; but as this does not apply to a railway, it ought to be carried as directly as the situation of the country will admit; and wherever a turn becomes unavoidably necessary, it should be formed upon a curve of as large a radius as can be conveniently procured, attention being at the same time paid to lay the inner rail somewhat lower than the outer one, by which part of the friction in bringing round the wagons will be avoided. To show the advantage of the direct line more fully, we observe, that in an up-hill draught a carriage may be conceived as in the state of being continually lifted by increments proportional to its rise and progress upon the road. In winding about, a similar effect is also produced, as the carriage may be said to be continually brought from a state of rest to that of motion, in a man ner perhaps not less detrimental to the effective power of the horse, than the up-hill draught. Though the horizontal or level line is the most desirable, where the traffic is reciprocally carried both ways, yet where the load is all in one direction, a declination towards the point of discharge will naturally be given at such a rate as the situation of the ground will afford, the downward draught being always regulated according to the number and weight of the empty or return-wa gons which the horse can draw. Perhaps this will be
best accomplished by a fall of four inches to the chain of 22 yards, being at the rate of one perpendicular to 198 horizontal.
To ascertain the effective power of an active horse, the proper criterion seems to be that of his weight. In the year 1817, the writer of this article made some ex periments upon this subject, which he verified by the French instrument called the dynamometer,* applied to trackage upon the Forth and Clyde canal, and also on the Carron Company's railways, when it appeared, that a horse weighing about 10 cwt., in his ordinary working state, exerted a force equal to 160 lb.; and that a force of about 12 lb. was sufficient for the trackage of one ton upon a well-laid level railway. This, by cal culation, gives 13 tons and 7 cwt. as the work of a horse, which in practice is equal to about 10 tons of goods, exclusive of the wagons. We arc, however, aware that 8 or 9 tons in many cases proves full work, when the rails are not laid upon proper principles, or not kept in good order.
Some interesting experiments on this subject have been made and obligingly communicated to us by Mr. Joasias Jessop, son of the late etninent engineer of that name, at his iron works of Butlerly, near Derby. That gentleman, whose science and experience give great weight to his opinion, had, upon one occasion, a horse weighing about 10 cwt. yoked to 41 cwt., or 504 lb., suspended over a pulley in a pit, which the horse drew up with extreme labour, the same weight requiring the united exertion of eleven men. Mr. Jes sop is led from observation, to estimate the friction of a well laid edge railway, to be equal to a rise in the road of about four inches in a chain. He further finds, that upon one of his edge railways, with a rise of inches to the chain, a horse takes eight tons up-hill, and is never allowed to work with less than six tons : from all which we conclude, that a horse such as we have al luded to, will track 10 tons of goods upon a level rail way, exclusively of the weight of the wagons, as dai ly exemplified in the work done upon the railways at the collieries of the Earl of Elgin, and Sir John Hope of Pinkie. Since, therefore, so ni ich more can be clone upon a level than upon an inclined road, it is to be re gretted that so little attention is paid to the formation of the former, which gives so decided an advantage, especially to the railway system. It is even not un common to hear of a preference being given to an un dulating line of road, on the supposition that the horse is more latigucd by a constant draught upon a level road, than by the irregular exertions of an up and clown hill journey. This opinion is attempted to he supported by such statements, as that the horse's chest is thereby enlarged, and his wind improved, and that differ-at muscles are brought into action on every change of po sition. It never seems to he taken into account, that relief is occasionally given by the slow motion up hill, which after all, is not half so beneficial for the animal, as the same slow pace would be upon a level road. Here the postboy generally performs his stage of 12 miles at least hall an hour sooner than he would navel the same distance upon a hilly road. Under the article ROADS and Hicilways, we shall show the fallacy of the doc trine above alluded to, by quoting Dr. Barclay, so emi nent in comparative anatomy, and for his scientific knowledge in all that regards muscular motion. These arguments about hilly roads can hardly, however, be said to apply to the railway system, where the power of the horse is understood to be adapted to a uniform strain ; and it is upon this principle that we perceive more fully the advantages of a level line of road.