Correspondence.

Lyttelton Times, Volume VIII, Issue 511, 26 September 1857, Page 4

Correspondence.

To the Editor of the ' Jjyttelton Times' \ Sir, —Although I am not an engineer worthy of the name, I will reply to " Traveller's " letter. The gentleman thinks that the costs of monster blasts are confined to the cost of the powder, and that 160,000 tons of rock could be moved for the sum of £525. He would move rock in his path by sprinkling powder on it, as he formerly, under his nurse's advice, caught sparrows by sprinkling salt on their tails. I will try. not to.think this too silly to reply to. "Monster blasts" are made by driving driftways or tunnels into the face of thY rock to be moved, then crossing the ends with.shafts or horizontal headings, and in them constructing cham* bers hewn out of the rock, in whichJ the powder is placed. The whole is then built up again with solid masonry to- the face, or ramn'ied-with stone. There are usually several of these'Vchambers. At Dover .there were three; at Holyhead there were five,- and they are simultaneously fired by electric sparks sent from an electric battery. The whole operation is difficult and costly. The preparations for the "monster blast" at Holyhead took nine months. The account before us does not say how many men were employed, but as there were upwards of a thousand on the works it was probably not very few. The cost must have been considerable.

The lowest saddle at the back of Lyttelton is the bridle-path ; that is also, I believe, the narrowest. Lingard's Gulley runs up to a saddle which may be as narrow, but is much higher. There is no accurate sectional survey of the two. Now, the

shortest distance through the bridle-path saddle, at about 400 feet below the summit, has been measured ; it is 1,800 feet. Suppose so much of that summit to be removed by a "monster blast." Suppose the sides of the cutting to stand at a half to one (we cannot say leas, but I am trying to do with as little as possible), and the bottom of the cutting for the road to be 30 feet wide, the quantity to be removed will in this case amount to upwards of eightytwo millions of cubical feet, or nearly seven million tons of rock. Now the quantity moved at Holy head was 160,000 tons, or about a forty-fourth part of the quantity in our case. In order, therefore, to lower the bridle-path summit to the height of Evans Pass we should have to make forty-four '• monster blasts," which, with all the appliances at our disposal which are in use at the Holy head works, probably the greatest in the world, would occupy fortyfour times nine months, or thirty-three years. And this, after all, to construct a road passing over a height as great as that of Capt. Thomas's old road. But the Sumner tunnel passes through the hill at a distance of 300 feet below that again. To lower the Tiridle-path saddle to that height, that is from 1,000 feet to 350 feet, would involve a removal of at least sixty millions of tons of matter, which could perhaps be effected by about four hundred " monster '% blasts." And the road would have then to be made over a hill the same height as the prespnt proposed tunnel, and over country of very much the same description. The cost is incalculable. So is the time. So is the amount of labour. In addition, I wish to observe that " monster blasts" have hitherto been used solely for blasting down overhanging or perpendicular faces of rock. ■ The blast only blows out a small ledge of rock at the base of the intended cutting, when the face of the cliff, deprived of its support, falls of its own weight. This was the case at Holyhead; but, in addition, there was a natural fissure or dyke parallel to the face of, the cliff, which induced Mr. Rigby to attempt the separation of the outside slice. But I believe *he. attempt to blow out a large quantity of eaTth or rock from a solid bed has never been attempted or even dreamt of for engineering purposes; it is effected in military engineering by what is called a mine, but on a comparatively speaking very small scale, and where, the object being merely destruction, the cost and labour are unlimited. Any one who will refer to tbe proper books or will take the trouble to check my calculations can satisfy himself of the truth of these facts and arguments. When the Sumner Road is attacked by science it -will fall to the ground; but the attack of "Traveller " is, like those which have preceded it, one of ignorance. I am, Sir, .PACTS.. To the Editor of the JLyitelton Times. Sir, —Allow me through the columns of your , -valuable Journal to direct the attention of the public ■to the great disadvantage, as well as loss of time and money, which we of Akaroa suffer by the Government holding the sales of Akaroa Town Land in Christchurch. • In the other settlements parties are not forced to leave their homes and business (for an indefinite period) when they wish to purchase a section of land. The land at the Bluff is sold at the Bluff. The Ahuriri lauds are sold at Napier. The Akaroa lands at Christclvurch. The Government seem to be extremely gracious in electioneering matters, as they appoint additional polling places (doubtless because the inhabitants should not lose their valuable time). Why not then, for It is more desirable, sell the land where the land is, and not subject the hona fide Akaroa settlers by a journey to Christchurch to great inconvenience and actual loss? I remain your's, &c, Akaroa, Sept. 15. - x CUT. To the Editor of the Lyttelton Times. Sir, —Mr. Ollivier is about coming before his constituency for the purpose of his re-election to the Provincial Council. Before I venture to record my vote in that gentleman's favour, I should wish to be well informed on one subject. A rumour is afloat that he will not proceed to Auckland when summoned. " I shall feel obliged to Mr. Ollivier by stating whether this rumour is correct or incorrect. I remain, Sir, your very obedient servant, , AN ELECTOR, j