Big grey re-crossed near the Arnold.

39. The Grey is proposed to be recrossed near the junction of the River Arnold, and the line carried to Cobden on the north-east bank, passing through those magnificent coal-mines known as the "Brunner Mines," and thus opening communication with a vast coal-field of enormous importance and value.

Reason for bridging twice.

40. You will observe that the River Grey is bridged twice, apparently without necessity. This I have done because the south-west bank, the proposed bridge, presents more difficulties than the opposite bank. The land is high and of small agricultural value, while on the south-west bank the land is flat and rich, and, at no distant day, will be of great value; besides which, gold-digging is carried on extensively on this bank, at Noble's Gully, Nelson's Creek, Red Jack's Creek, as well as up the River Arnold, and other places; and, as I think the extra bridges will be as cheaply constructed as the difference of the cost of a line on each bank lying between the points of crossing, while a more valuable country is put in more easy communication with the railway than otherwise would be the case, I prefer bridging the Grey twice, so as to secure what I conceive to be the most desirable line.

Line passes through Sandstone, and Limestone.

41. From the River Arnold to the town of Cobden the line would be chiefly in side formation, passing through coal, sandstone, and limestone.

Gradient 1 in 60.

42. I do not anticipate that the ruling gradient along the entire route need to be more severe than 1 in 60, which is a good working gradient for such a country as is under consideration, and one on which full control may be had by brakes over a descending train. I should, therefore, recommend that the maximum gradient should not be greater than this.

Beyond 1 in 60 severely taxed.

43. When you get to gradients steeper than 1 in 60, the effect of gravity becomes largely increased, and the power of a locomotive engine is severely tested to overcome this force, while that of the brakes is greatly reduced in descending the incline.

Friction of 1 ton on Level.

44. On a well constructed railway, in fair working order, the friction to overcome one ton drawn on the level, ranges from seven to ten lbs. Calling it ten lbs., the friction to overcome the friction of the 200 tons drawn on the level, would be 2,000 lbs.

Power lost when level departed from.

45. Leaving out of consideration (for the sake of simplicity), the effects of resistance of the atmosphere, weight of the engine, as well as fractions, the following table will show what an extent of power is lost when a railway departs from a perfect level and a right line. I need hardly say that the resistance from curved rails is not taken into account in this table:—

Effects of gravity.

46. TABLE TO ILLUSTRATE THE EFFECTS OF GRAVITY.
    (LOAD DRAWN ON THE LEVEL, 200 TONS.)

47. From this table can be observed the rapid increase of the consumption of the engine's power to overcome gravity as the gradients are increased; and it follows that (leaving the speed the same throughout, and not noticing the weight of the engine itself) if a locomotive exerts its full power on the level, the gross tons that it can haul from terminus to terminus, will be confined to that which it can draw up the steepest gradient on the line.

Consumption of power to overcome gravity.

48. Hence the importance of adopting a reasonable gradient as the one, so that engines of light weight may be able to draw the gross load required; for, if this is not observed, and heavy engines become necessary; then it must be noticed that a more substantial and more costly permanent way is unavoidable.

Reasonable Gradient important.

49. Besides these considerations, there are others which should influence the fixing of the ruling gradient. It must be remembered that when a locomotive is drawing a load upon a level, it has only the friction of the moving parts of itself, which is constant, and that of the load drawn, which varies, to overcome; but upon an incline it has not only the gravity of the profitable load it draws to overcome, but that of its own weight as well, which is an unprofitable load; and, therefore, the more steep the gradient is, the more weight the engine must have to haul a given load, and, consequently, the greater the loss of power to overcome the gravity of the engine. Now loss of power is loss of money.

Other reasons for a ruling gradient.

50. All this has reference to ascending gradients, but to safely descend long gradients is of equal importance, and though there is scarcely a limit to the power of brakes, their application is costly; so that safely descending long and severe gradients is simply a question of cost.

Descend of long gradients.

51. Experience has shown me that in practice, gradients of 1 in 60 is the steepest gradient that can be descended in safety by heavy mineral trains with a reasonable application of brakes, and from the foregoing table (No. 1), it may be observed that the power braking required on gradients below 1 in 60 becomes rapidly increased; for to bring a descending train to a state of rest upon a level, 1 in 70, or 1 in 70, the power of the brakes necessary, is represented by 8,400 lbs.; on 1 in 60, by 9,466 lbs.; on 1 in 50, by 10,960 lbs.; while 1 in 40, is 13,200 lbs.

Gradient matters.

52. I have now given you a general description of one of the routes, and its alternate line, which I have examined, with some observations suggesting caution regarding fixing the ruling gradient, and I have to state that upon this route no real engineering difficulties exist; such works as may, in comparison with the rest of the line, be considered costly, are on the River Buller, both in this route and in the others where the valley of the Buller is made use of.

No engineering difficulties in second route.

53. For so long a line the works will be remarkably easy to construct at a very moderate cost, in order to illustrate the character of the chief works necessary, I have attempted to give a short description of them in the book of "Sketch Maps," marked B; to which I beg to refer.

Works easy to construct. Chief works described.

54. The third route which I have examined, is common to the one last described, until the junction of the River Matakitaki with the Buller,

Third Route.

55. Here the route ascends the valley of the Matakitaki until the Glenroy River is reached, when the course changes from south to west, and the saddle of the range dividing the watershed of the Matakitaki and Maruia, is passed by a tunnel about one mile long.

Valley of the Matakitaki.