小说搜索     点击排行榜   最新入库
首页 » 英文名人传记 » Life of Robert Stevenson » CHAPTER XV. MARINE SURVEYING.
选择底色: 选择字号:【大】【中】【小】
CHAPTER XV. MARINE SURVEYING.
Modern engineers who have practised only under the benign reign of Ordnance Surveys and Admiralty Charts, can have no idea of the toil their predecessors underwent in procuring data for their designs and reports; and I am safe in saying that Mr. Stevenson was of all others the engineer to whom in his sea coast practice, such useful aids would have been of the very highest value.

For example, before he could tell, with the exactness he desired, the distance between the Bell Rock Lighthouse and the shore, he had, in absence of any reliable information, to undertake a pretty extensive trigonometrical survey of the coast, involving the measurement of a base line upwards of two miles in length—a most “laborious operation,” he observes, in which his assistants were aided by six sailors from the lighthouse tender.

Again, to show the difficulty in determining the best site for a lighthouse in those early days, before an accurate Government survey of the coast line had been made, I give from Mr. Stevenson’s Journal the following notes of his observations to determine the best site for a lighthouse at Kinnairdhead in Aberdeenshire. I give them at length, as jotted down at the time, for they may197 perhaps lead young engineers of the present day to be thankful that, in most cases at least, they are not, from want of accurate coast surveys and soundings, left to resort altogether to their own resources in getting the information they require. But I think they are specially worthy of record as showing the extreme care bestowed by Mr. Stevenson in getting the data to enable him to determine the exact positions of the several lighthouses he designed. His Journal says:—

    “First.—I caused a mast to be erected upon the top of Kinnairdhead Castle or Lighthouse, making its extreme height from the ground 100 feet.

    “Got the yacht under weigh, and having a careful pilot on board, I sailed for Rattray Head, and there observed the mast over the land of Cairnbulg, it being then high water, or twenty minutes past 7 P.M. With the parapet of the lighthouse in view, have eight fathoms water off the head, which bore W.N.W. Run in upon the head with flag upon the mast seen over the land till seven fathoms water, when the flag disappeared. Then leave the vessel and sound from the boat, and have 6 fathoms, 5, 5, 4?, 3, 2, 1 fathom, and lastly 3? feet. Return to the ship in a more southerly direction, and have 3 feet, 1 fathom, 2, 2?, 2?, 3?, 4, 4?, 5, 5?, 6?, and 7 fathoms. All these soundings rocky bottom.

    “With the Windmill near Peterhead on with Stirling hill, and Monument hill on with the rounded Sandy Down of Rattray, and the parapet of Kinnairdhead Lighthouse seen over Cairnbulg land, you are in 8 fathoms water off Rattray Briggs, which lie about ? of a mile to the southward of the Sandy Down.

    “Wait off the Briggs till the light was seen, then stood in upon the Briggs till the light was shut in by the land of Cairnbulg, and at that moment had 8 fathoms water, so that at present the light forms an excellent direction for Rattray Briggs.

    198 “Find that the lightroom is seen fully from the yacht’s deck in 8 fathoms water off Rattray Briggs, that the flag upon the masthead is seen in 6 fathoms water—high water spring tides. Ship then bearing from the head E.S.E. and W.N.W., distant about one mile from the shore, where a man is distinctly observed at a boat in the twilight.

    “Secondly.—Remove the mast from the castle or lighthouse on the morning of the 15th to Cairnbulg, and elevate a flag to the height of 86 feet from the ground, or 97 feet from high water mark, at the distance of about 100 yards from the high water mark at the point connected with Cairnbulg Briggs.

    “The yacht lying off or to the westward of the Briggs, was got under weigh at 2 A.M. of the 16th, and beat up the north shore as far as Rosehearty, and there observed the flag over the land. Found off Rosehearty that the flag was just hid by the highest inequalities of the land to the southward of the Castle, and that it appeared at the lower or flat places sometimes in sight 20 feet above the land, and at other places intercepted by the land and houses of the town, amongst which it often appeared and disappeared. The range of the flag along the land was as far as Mr. Dalrymple’s house when it was time to put about, having there three fathoms at nearly low water.

    “After completing the observations in this direction, sailed along the shore southwards to Rattray Briggs. Find that Inverallochy head, south-eastward of the town of Cairnbulg, is the eastmost point on this coast, but, being at a distance from the foul ground of Cairnbulg, would make a less desirable point than Cairnbulg.

    “Off Rattray, in eight fathoms water, begin to lose sight of the lantern on Kinnairdhead Castle as before. See the mast and flag at Cairnbulg a considerable way up the country over the lands of Inverallochy. See the flag, standing in upon Rattray to five fathoms water at half tide, lose it, and then stand for Fraserburgh.

    199 “As the result of these trials, find that Inverallochy head or point is the most eastern or projecting point of land upon that coast, that Cairnbulg is the next projecting point. The former lies between the points of danger, viz., Rattray and Cairnbulg.

    “Find that if the light were to be moved to a more southern situation, it would be better on either of the above places than Rattray Head, which would entirely remove its usefulness from the Moray Firth.

    “Find that in the event of two lights for this coast, the one ought to be at Kinnairdhead, and the other upon the Cock Inch at Peterhead.

    “Under all the circumstances of the case, find that it would be most advisable to erect a new lighthouse at Kinnairdhead, about 100 yards more to the eastward than the Castle stands, and erect it about twenty or thirty feet higher than the Castle. This, with a better light, would perhaps answer the general purposes of the coast better than a single light placed on any of the other stations along this coast.”

After perusing this extract, the reader, I think, will not be surprised to find Mr. Stevenson making an urgent appeal on behalf of all interested—Seamen—Fishermen, and Engineers, for a Government Survey and “Sailing Directions” of the intricate navigation of the shores of Scotland, which he did in the following terms:—

    “The attention which Government has long paid to the improvement of the Highlands and Islands of Scotland, in connection with the British Fisheries, has been attended with the best effects in the country at large. It is much to be wished that these shores were rendered more accessible to the mariner.

    “The marine survey of the Highlands by Murdoch Mackenzie, undertaken by order of the Lords of the Admiralty, may be considered200 as the first grand step towards the improvement of the Highlands, and next to that the later institution of the Northern Lighthouses. By means of these the fisher may find his way from loch to loch, and the mariner bound over seas, instead as formerly of holding a course without the Lewis Islands, can now find his way through the Sounds, and in adverse winds take shelter in safe harbours, instead of being exposed to the boisterous seas of the Atlantic Ocean; these charts and lighthouses have in many points of view contributed to the improvement of the Highlands, and to the present flourishing trade carried on through these Sounds from Liverpool, etc., to the northern continent of Europe. However, from the extensive range of coast which these charts include, together with the prodigious number of extensive lochs and small islands, it was impossible that any first survey could be made so accurate as to supply the place of pilots, where there are neither landmarks to characterise the coast, nor beacons or buoys to point out the situation of sunk rocks; and although these charts have certainly contributed much to the facility and security of the navigation of the Highlands, yet no one will say that they are free from imperfections, and their incommodious size and high price are insurmountable bars to their general utility, thereby rendering them impracticable for the use of small vessels, so that they are only to be found in the cabins of large vessels, where large accommodation affords room to unfold them, but even here also the price forms an objection, as the charts are always found by the shipmaster.

    “Nothing therefore can be more necessary or essential to the improvement of the Highlands and Islands of Scotland, than an accurate survey of the fishing grounds, lochs, and harbours, upon a scale considerably larger than Mackenzie’s charts, given in the form of a book of the size of a large quarto, containing only the lochs, etc., interleaved with printed directions and descriptions of each chart or harbour, which book of charts, accompanied with a201 general chart would sufficiently guide the mariner and fisher in their several pursuits.

    “With regard to an accurate survey of the lochs and harbours in the Highlands published in the most commodious form for the use of small vessels, such an undertaking would require to be sanctioned in a manner similar to the survey undertaken by Murdoch Mackenzie, and though in process of time the sale of these charts might produce a considerable return to those concerned with it, yet the time and attention which such (with a laborious number of soundings) must occupy would certainly require that those concerned in the undertaking should be put in possession of certain sums of money to enable them to go on with that deliberation which is essential to accuracy, and this encouragement should be the more considerable that the charts might be procured to the public at a moderate price.”

This Memorial, written in 1803, was intended for and in some shape communicated to the Admiralty, and was followed by good results.

In “A Memoir of the Hydrographical Department of the Admiralty,” published in 1868,13 are the following remarks:—“It was about this time,” 1810, “that the Admiralty first conferred on the Hydrographer the privilege of selecting a surveyor for the home coasts. Singular as it may appear, the Hydrographer had at this time great difficulty in finding a naval officer competent to fill the position, or who was acquainted with anything beyond surveying by common compass. At length, however, about 1811, Mr. George Thomas, a master, was selected” for home service. The Memoir202 also states that at the same time the Hydrographer appointed to foreign service Mr. Beaufort, afterwards Sir Francis Beaufort, the eminent Hydrographer to the Admiralty, who was, all his life, Mr. Stevenson’s intimate friend and constant correspondent.

There is therefore, I believe, no reason to doubt that Mr. Stevenson’s original appeal and subsequent personal friendly and free intercourse with the officials of the Admiralty led to the establishment, on a systematic footing, of our Government “Admiralty Survey,” which, as all engineers know, indicates with marvellous accuracy and detail every shoal, sunken rock, and sounding on the coasts of Great Britain and Ireland; and from which the “Admiralty Sailing Directions” have been prepared with such discernment and care that the whole system of our coast survey may now be said to have attained perfection.

With Colonel Colby, also, of the Royal Engineers, who was Director of the Ordnance Survey, Mr. Stevenson regularly corresponded, being no less interested in the progress of the great national work so successfully carried on under his charge.


欢迎访问英文小说网http://novel.tingroom.com

©英文小说网 2005-2010

有任何问题,请给我们留言,管理员邮箱:tinglishi@gmail.com  站长QQ :点击发送消息和我们联系56065533

鲁ICP备05031204号