D.—No. 60.

AVELLINGTON TO NAPIER RAILAVAY.—WELLINGTON TO MASTERTON. No. 1. Mr. Rochfort to the Hon. W. Gisborne. Sir,— Wellington, 12th August, 1871. I have the honor to send herewith plans, sections, report, and estimate of that portion of the Wellington and Napier Line of Railway between Wellington and Masterton. As might be expected, the cost of this line, with a mountain 1,330 feet high above the sea level to surmount, and four large rivers to bridge, somewhat exceeds the ordinary average of New Zealand railways. I estimate a line of 3 ft. 6 in. gauge, with stations and sidings, can be made and equipped for about £4,857 per mile. From AVellington to Petoni the line will skirt the road on the seaside; and, on inspecting the plans, you will see that the curves are so fitted to the road that a minimum amount of embankment is attained. This can be made cheaply, by throwing down the rock cliffs in mass, which then will have to be carried only a short distance; at the same time the road will be widened. From Petoni to the crossing-place of the Hutt River near Silver Stream, the line is forced near the river, and causes rather heavy cutting. The place known as the Gorge is passed on this side without any difficulty. The crossing of the Hutt River is good. The bridge starts from tho hill itself, and crosses the part of the river liable to floating timber with seven 66 feet spans; the part beyond, being shallow-flooded ground, is crossed with 538 feet of low bridging of a cheaper character, having spans only 16^ feet. Beyond this again, in a low place, 132 feet of low bridging is allowed to act as a safeguard to the embankment in the event of unusually heavy floods. From the Silver Stream the line follows along one side of the trunk road until reaching a point where the hill abuts on the road, about one mile nearer town than Cruickshank's saw-mill. All along this portion, ballast can be procured at a low cost. The line now contours up the hill which divides the fiutt from the Mungaroa Valley, reaching the latter by a cutting through the crown of the hill behind Mr. Cruickshank's. This portion is full of curves, the sharpest being 200 feet radius. A gradient of lin 43, about a mile and a half long, brings us to the top, when the line runs over level forest for two miles straight. The soil is very stony, and will itself supply sufficient ballast when the ditches are thrown up. To the top of the Mungaroa Hill, which is crossed about 100 feet below the level of the present road, the curves are numerous, and the grades vary from lin4oto 1 in 41. The line now runs level for four miles, as far as the Pakuratahi. The hill slopes are light, and average about an angle of 20° with the horizon. We now commence the ascent in earnest —two miles of 1 in 49, and three of varying grades from 1 in 40 to 1 in 46, bring us to the main saddle, and here we get a rest of 15 chains of level. The saddle is 1,379 feet above the sea level, and 1,232 feet above Featherston by spirit level, which agrees very closely with height ascertained by aneroid observation on my preliminary survey, the difference being only a few feet. This shows how these instruments may be relied on in preparatory surveys. The side slopes average about 30° with the horizon ; there is not much rock out-cropping, but we may expect to find it a few feet below the surface whenever the inclination of the hills is over 35°. I have based my calculations on this assumption, and have reckoned on turning the rock to account in building up retaining walls to lessen the contents of the embankments. On the AVairarapa side of the range, the hill slopes are steeper, and several long viaducts over deep gullies will have to be made, otherwise the character of the line is similar—grades, nine miles, 1 in 41, and one mile and a half, 1 in 54, to the plains of the Wairarapa. There the country is easy, the only expensive works being the bridges. The line passes through Featherston along the side of Johnston Street, passing the large Government reserve on which the old Land Office stands. This reserve would be useful for station purposes. The crossing of the Tauherinikau was chosen directly behind Mr. Bunny's house, that being the most favourable spot outside the Gorges. The actual bridge has only three 66-feet spans, but low bridging of 330 feet is allowed to carry off flood waters. Ballast is plentiful all through the valley ; the plain intervening between the last river and the AVaiohine is nearly all covered with stones. The Waiohine is crossed between Cotter's and Revans' saw-mills, with a bridge having twelve 60-feet spans and one 52, besides 198 feet of low bridging, which is distributed over the flooded ground. This crossing was chosen partly because it was the narrowest between Greytown and the Gorge, and partly to avoid a large swamp which lies between the railway line and the road. The line now crosses the Matai-Rawa Plain, which is also very stony, and then goes through the bush known as " Three-Mile Bush." This bush is really about five miles through, and free from swamps along the line, and uniformly level; several clearings are passed through by the railway. Totara can be got in quantity in several places in this bush. On emerging on the Taratahi Plain, a swamp 18 chains over has to be crossed; then another stony plain to the Waingawa River, which is crossed one mile and a half west of the coach road with thirteen 66-feet spans and two short pieces of low bridging of 99 feet and 66 feet for flood opening. This crossing was chosen because it is the narrowest, and as offering a good site for a bridge, also as being the shortest line to the Gorge. The line will pass about two and a half miles to the west of Masterton, but the intervening country is open and level. I will now compare the line of railway just described—as to length, cost, &c.—with one in which the Rimutaka Range would be pierced with a tunnel, with the view of shortening the distance. At an early stage of my survey, I was called upon to report on the probable cost and length of a tunnel line, and accordingly did so, but with information at that time necessarily imperfect. Part of this I am now able to supply correctly, and the rest may be gathered, although not in full, from a published Report on a Tunnel Line by C. O'Neill, Esq.

FURTHER PAPERS RELATING TO CONSTRUCTION OF RAILWAYS.