" Having now given the outline of my first project, I proceed to my second, which will explain the meaning of the sailing vessels in the foreground of the drawing, that are apparently issuing out of a canal lock. My intention in this was to exhibit an easy and obviously practicable mode, of transferring heavily laden vessels directly out of the water on to the railway, where they might be propelled by the wind with much greater velocity than through the water ; and at the same time show how admirably Mr. Palmer's railway is adapted as a branch and from canals and rivers, or to form an important connecting line between them. In cutting a canal, which has to proceed down a declivity, and to ascend another, numerous locks must be constructed at an enormous expense; these would cause great loss of time and inconvenience in the traffic, which may be obviated by the adoption of this suspension railway as a connecting communication. The railway I propose is to be constructed as usual, elevated upon pillars, and not to terminate on arrival at the lock gates B, but to pass over it, and terminate at the other end, just within the second gates A, and be supported upon pillars from the floor of the lock, the same as on dry ground. In the annexed cut, (which is a plan,) the double train of vessels are supposed to have all entered the lock, half on one side of the rail, and half on the other, and they are hooked on to the axle-trees of the wheels which, are already upon the rail for that purpose. The gates next to the river or canal are then closed, and all being fast, the water is let out of the lock by a sluice at D. till it falls below the bottom of the outer gates; at which time the vessels are all suspended on their axles in the air. The gates being next opened, and the wind fair, they sail across the valley, or are propelled by the other means provided by the patentee." Having now noticed the principal arrangements in several different kinds of railways, and the motive power employed, we shall proceed to inquire into the nature and extent of the effects produced. The resistance to the motion of carriages arises from three causes, whether travelling on the common road, or on railways; but they vary in their relative proportions according to the nature of the surface passed over. Thus the resistance to the motion of a car riage on the common road, arising from the obstructions or inequalities of the surface,, to the rolling of the periphery of the wheels, is greater than that of the rubbing at the axles ; while on a railway, owing to the smoothness of the sur face, the contrary is the case. According to the experiments made by Mr. Stephenson and Mr. Wood, the resistance at the periphery of the wheels on a good level railway does not exceed about a thousandth part of the insistent weight, while the same kind of resistance upon an ordinary turnpike road, according to our own observations, does not average less than a twenty-fifth part; or forty times that of the railway. It is from the reduced amount of this, the first mentioned kind of resistance, that railways possess such great advantages for locomotion ; for in the second kind, that of the axles, the difference of fric tion cannot be material, nor can the resistance from air, (the third kind,) be at all different, presuming, of course, that the opposed surfaces and the velocities are the same in each.
Mr. Palmer, in his description of his railway, justly remarks, that if some accurate means of ascertaining the resistance of roads and railways were on all occasions used, their improvement would be much advanced. The real value of either being then unequivocally compared, the amount of defect could no longer be a matter of mere opinion. The proprietors would then know whether an apparent inferiority arose from the difference of horses, or difference of cir cumstances ; and it would be of great advantage to introduce a clause in con tracts, which would determine the effect to be produced. The methods by which resistance of roads and railways has been ascertained, have not been sufficiently accurate, or have been too inconvenient for general use. The dynamometers, which denote the resistance by the degree of extension given to springs attached to the carriage, are convenient as portable instruments, but do not denote the measure with the necessary precision. The resistances are not
equable, from the irregularities of the surface ; neither does the force which draws the carriage continue equable. When horses are employed, those instru ments are of no service whatever. The effect of the unequal force or resistance occasions a vibratory motion to the indicating point, and we can never have confidence in any result they exhibit. Similar defects are observable in all the instruments I have seen.
" Having had frequent occasion to ascertain these resistances, I constructed an instrument which, by removing the imperfection referred to, has been com pletely successful. The problem was to make such an instrument as would indi cate very small differences, but which would not yield suddenly to a change of resistance. I therefore connected to a spring dynamometer a semicircular close copper vessel, containing water ; at the centre is a spindle, on which an arm or fan is fixed, and which very nearly corresponds with the inside of the vessel. The springs are so connected with the spindle, that they cannot be acted upon without the arm or fan turning upon its centre, and passing through water. In order to pass through the water, the latter must escape by its sides ; and the space being extremely small, it cannot pass rapidly, but will yield to the smallest force. (See a drawing and description of this instrument, under the head DYNAMOMETER.) " By way of exhibiting the difference of resistance upon different railways, I have attached a table containing experiments on several.
"The first column contains the articles second, the resistance in proportion to the weight ; the third, the whole effect produced, i. e. including the weight of the carriage by one horse, or one hundred and fifty pounds, at two miles and a half per hour ; the fourth, the usual effect, or the load conveyed, in pounds; the fifth, the same, in ordinary measures ; the sixth, the inclination, expressed by decimal fractions, on which a railway, whose resistance is equal to that specified, should be constructed, that the resistance of the loaded carriages downwards may be equal to that of the empty carriages upwards ; the seventh, the effect produced under such circumstances ; the eighth, the useful effect under the same, the weight of the carriages being deducted. In each experi ment, the power is assumed at one hundred and fifty pounds, moving at the rate of two miles and a half per hour. In the inclinations, the weight of the horse itself, as part of the effect produced, is not taken into account, that the table may equally serve where mechanical force is applied. Some allowance must therefore be made where horses are used, but the difference in the incli nations given will be very trifling.
The following table was published antecedently to the formation of the Man chester and Liverpool railway, the resistance upon which, on a level plane, may be considered as a medium between the two last-mentioned results, dud is, about a two-hundred and thirty-fifth part of the weight. It is also necessary that the reader should take into hie consideration that the experiments given by Mr. Palmer, as respects his own railway, were conducted upon a well-made, full sized model, while the others were probably upon portions of rail considerably deteriorated by wear or neglect ; for it is not otherwise possible to conceive so great a difference in the results, as are shown in the table; bearing in mind that they are all considered to be on a level, and that the surface material of all is iron. Without being able to give any precise data for our opinion, our obser vation has from to time time led us to regard the ordinary resistance upon tram roads to be not half that stated by Mr. Palmer ; we therefore conclude, that the Surry and Llanelly tramroads must have been in a very dilapidated state, or covered with dirt. One very important fact is, however, communicated with the following table, that of the great difference of resistance found upon the Cheltenham tramroad, by being merely slightly covered with dust, as it exhibits in a very stroll light the superior advantages afforded by the edge-rail, in being so much less liable to the lodgment of dust.