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From Almeria to Carthagena with an easterly wind always work up close in under the Cape, as the only danger is a sunken rock about a mile distant, and bearing south from that headland.*

Carthagena.—This port is so well known by its excellent Spanish surveys that I need say little about it, one or two remarks will suffice. As the wind at night or until eight and nine in the morning at this place comes always off the land blowing direct out of the har. bour, a large ship should never attempt to run in until nearly mid-day when the sea breeze sets in. Small vessels may go in at any time, as they can beat up to the anchorage; they may also where coming from the eastward and with the sea breeze run through the eastern passage between the Island of Escombrera and the main land. Water can be procured for ships of war, by application to the Dockyard, but of bad quality, being slightly brackish.

The roadstead of Valencia is represented as extremely dangerous by the Mediterranean Directory. It is there stated “that the ground is rocky and bad, and that it is highly dangerous to lay there during an easterly wind.” Now, on the contrary, the greater part of the anchorage is clear and excellent holding ground, being a stiff clay, so much so that it required some trouble to purchase our anchor, after lying there only two or three days; there may be some rocky spots, but not sufficient to prevent à ship getting a good berth. There certainly cannot be any doubt that during the winter months, Valencia must be any thing but a pleasant road to anchor in, as it is perfectly exposed to the north-east winds, but I should think except in a hard Levanter, a ship of war may lie there in perfect safety.

The Bay of Alicante, which is of considerable extent, is formed by Cape Santa Pola and Cape La Nuerta. The former is distinguished by the tower of Alcora ; from it extends a reef to the eastward, about half a mile, the latter at the water's edge is flat and low for a short distance, when the ground suddenly rises into a whitish rock or stone, on which is a tower. The anchorage although considerably exposed to the east and south-east winds, is nevertheless very safe for ships of all classes, even in winter, provided their ground tackle is good. The bottom is seaweed and sand. Large ships should moor north-east and south-west with the small bower to the south-west, about a mile from the land, in from 12 to 6 fathoms water. The Mole is very small, and only fit for faluchos and other coasting craft; it is, however, extending gradually, and if persevered in will be eventually a splendid work.

One of the best marks for knowing the Bay of Alicante at a long distance off, is the remarkable mountain, called the Archillada de Roldan, which rises up to the north-eastward of Alicante. This mountain is easily known by its towering height, and an extraordinary gap on its summit, which at a distance has the appearance of an embrasure. Water is scarce at Alicante. Our vessels of war generally procure that article at the small river Altea, near the town of the same name, which is about thirty miles to the northward and eastward of the Bay of Alicante.

* By doing this you will generally get favoured during the night by the land breeze.

During the summer, and even in the winter season, if the weather be fine, the wind generally draws off the land after sunset, and about 9 or 10 A.M. the sea breeze commonly sets in.*

In shaping a course from Cape Palos to Alicante, always keep well up to the northward, as the current sets here generally very strong to the eastward, so much so, that if you shape your course just to give the Isla Plana a good berth, you would find yourself a long way to leeward of the port by daylight, and have the pleasure of a good beat up.

Cape St. Antonio, coast of Valencia. Off this Cape vessels are often taken aback with the wind at north or north-east, when running with the wind at west or south-west. The northerly wind here frequently comes off very strong, therefore vessels should prepare and shorten sail in time, or they may endanger the masts.

Barcelona.-It is only lately that vessels drawing more than 12 to 15 feet water have been able to anchor inside the Mole, a deeper passage having been recently effected by the removal of vast quantities of mud; two vessels are still employed for the purpose, so that in the course of a few years, it is most probable that ships of any draft of water may be able to get in. The passage is, however, still so narrow, that it ought not to be attempted without a pilot.

ON TRIGONOMETRICAL SURVEYING, and its Application to correct the

Maps and Charts of the Hebrides.- By William Galbraith, M.A., F.R.A.S.

I HAVE occasionally drawn up a short paper on surveying connected with Scotland, suggested to me by the very glaring errors which I had discovered to prevail even in our best maps and charts +

From this and other causes hundreds of human lives and thousands of valuable property are annually lost, as the calendar of our shipwrecks daily testify. Though something continues to be done to improve the geography of our country, yet it appears to be very slowly felt. Indeed the extent of our foreign possessions makes a large demand upon the resources of the nation, which cannot with propriety be withheld ; but it appears somewhat strange, that so little attention is paid to the survey of our own shores. I have looked into the latest catalogue of charts published at the Hydrographic Office, and while I observe new surveys of almost every coast on the face of the earth have been executed, either wholly or in part, but by British naval and military officers, yet strange to say, since, comparatively speaking, the imperfect surveys of Mackenzie, nothing has been done for the Hebrides. I have searched catalogues in vain for anything recently published.

The shipping trade of the Clyde is certainly one of the most extensive

* The best anchorage at this port is a little to the westward of the Mole Head in about 8 or 10 fathoms water,

| The new map of Scotland, by Mr. A. K. Johnston, for his splendid Atlas, just published, has been greatly improved in many points,

in Scotland, and not the least in Britain, and I shall shortly prove, that, trusting to the charts and maps, now in existance, the master of a vessel, making for the Clyde, while passing from choice or necessity, near the shores of Islay, &c., in thick blowing weather, during the day, or not in view of a light-house at night, must almost with certainty be wrecked, if his reckoning be right. Is this a state of matters which ought longer to be tolerated ?

2. The mode in which maps may be engraved admits of considerable latitude. They may be, in a great degree, plain with a little hill shading to mark mountain ranges more distinctly. They may also, however, be enriched with much more important information than they commonly possess, by adopting peculiar modes of engraving. That mode of finishing maps by normal contours indicating the same level at different elevations, either by wave lines, or different bands of parallel lines, seems to be an excellent one for conveying correct information relative to different levels, each line or band designating a rise of a given number of feet. This method has been adopted by the French Engineers in their new surveys so long ago as 1818.* For the levelling of the sites of cities, such as Paris, each parallel marks a rise of two French metres, or a little more than 62 English feet.

For the level country ten metres, or 33 English feet, is chosen for the vertical distance or rise between the parallels. For our survey 10 feet would perhaps be a good vertical rise for cities, 30 to 50 feet for our carse and other superior lands, such as those of Gowrie, Stirling, many parts of the Lothians, &c., to be continued to a height of 300 or 500 feet. The pasture grounds above them might be taken at about 100 feet, between each band as far as 1000 feet, and those of the mountain ranges, above this, at 500 feet as far as the summit of our highest mountains. In this way the corresponding parallels throughout the whole country would all become known in a manner somewhat exemplified by the celebrated natural parallel roads of Glenroy in Lochaber.

A part of the Irish survey, since 1838, has been executed in this way, but from some remarks lately made at the meeting of the British Association this year at Cork, it appears now to be stopped. I shall endeavour to fortify the opinions I here advocate and which I have long entertained, by some important remarks by Captain Larcom on contoured maps, such as those I have attempted to describe.

3. It is important that maps constructed by the government should exhibit the levels of the country in the most intelligible manner; shewing heights, not merely on the tops of hills, but round their sides, and through the vallies, which traverse them. Such a system is offered by these contours. They are a series of horizontal lines, at a certain vertical distance asunder, and at a certain height above a fixed datum. The datum most commonly used is the level of the sea, doubtless from the shore line, being the limit of the land, and the point at which roads must cease, as well as from an idea that it is itself a level line, and therefore as a first contour, the most appropriate and natural zero from which to reckon the others.

The section of the Association on mathematical and physical science * It was previously adopted in the survey of the coast of Karamania, by Capt. Beaufort, in 1812.

was aware that it has been a point much discussed whether the high water, the low water, or the mean state of the tide offers the most level line. This is a point it would be out of place to discuss here, but it may be stated, that in order to determine it as far as Ireland is concerned, a series of lines has been very accurately levelled across the island in various directions, and permanent marks left in all the towns, and on numerous public buildings; and at the end of these lines on the coast, tidal observations have been made every five minutes during two complete lunations. These observations and the connecting lines of level are now in process of reduction. The degree of accuracy attained is such that a discrepancy of 0.2 (1) of an inch is immediately apparent, and from them we may expect many points of interest. The steeper the natural slope of the ground is, the closer together, of course, the contours will be, and the more oblique the road; where on the contrary, the ground slopes very gently, the contours are farther asunder and the road may be proportionally direct. By examining the maps of the Irish survey, on which contours have been drawn, it will be seen that they tell sad tales of the existing roads, every inch of which ascends and descends frequently instead of keeping on a gradual slope for its whole length.

In order to exhibit these lines, it is proposed, instead of adding them to the original copper-plate, which has a peculiar value as an official record of boundaries, to make a copy of the plate, by the electrotype, for the purpose of receiving these lines. Contour maps were thought of early in the progress of the survey, but means were wanting for their execution. At present however, the outline survey being complete, and the general map, or map of the surface being in progress, affords a convenient opportunity, which it is hoped will not be lost. Dr. Robinson of Armagh, an excellent mathematician and astronomer, enquired of Captain Larcom, whether the process of contouring the maps was proceeding, and how soon he supposed it would be completed for Ireland ? Captain Larcom replied, “ that for the present it had been suspended." Dr. Robinson observed that, “ whether he considered the value of this process in relation to the general interests of science, or the most important practical economics of the country at large, he could not but deeply deplore the suspension, temporary though he hoped it would be, of this great national undertaking, and he trusted, that, before the British Association closed its present sitting, the most energetic steps would be taken to make such an application to government as would induce them to resume this most valuable work. He begged to enquire from Captain Larcom what the expense would probably be ?" Captain Larcom replied that “ he should estimate it certainly at less than a farthing an acre.” Dr. Robinson,–"And the original price was probably sixpence or eightpence.” Captain Larcom said_" Perhaps seven pence to ninepence.” Dr. Robinson—" Then at a cost of about one thirtysecond part of the original expense this invaluable addition to that splendid work the trigonometrical survey of Ireland could be accomplished. If it was determined finally to suspend this work, he should say that it was very like what the homely adage characterised as penny wise and pound foolish.

4. Such being the opinion of this learned astronomer in reference to

Ireland, it might seem unnecessary to urge the same demand for Scotland, yet, strange to say, I am not aware that auy Scotchman, or Society connected with Scotland has had the patriotic boldness to claim for their country that invaluable appendage to our maps. Indeed, from what I can learn, they seem rather to discountenance the idea of making any similar claim. Seven hundred and fifty thousand pounds have already been spent on the survey of Ireland, and three hundred and fifty thousand pounds on that of the whole of Britain. Is this justice to Ireland ? It is more. Even of this three hundred and fifty thousand, how much has fallen to Scotland ? In giving these statements, it is clear I make uo charge against the excellent conductor of our survey, or any of the officers under him. They are, I know, ready to meet the orders of government, whatever these may be. I make no charge against the accuracy of their proceedings, except so far as the published volumes of the survey afford the means of testing them by a scientific examination of their results and methods of obtaining them, which, if conducted in a fair and candid manner, can give offence to no one. Iudeed from officers connected with the Ordnance Map Office, I have received various data, of which I have freely availed myself, in the present paper, and through Colonel Colby, by order of the MasterGeneral and the Honorable Board of Ordnance, I received about a year ago that valuable continuation of the survey, the Reduction of Zenith Sector Observations made at different stations in Britain, in which the computations are all made in the most approved manner. It would be ungrateful in me not to return my warmest thanks for these distinguished favors. It is not to cavil, therefore, I make the preceding statements, but to benefit the public at large, in which all will participate.

5. Again various colours might be fixed upon to designate different soils. A deep tint for dark loams, a sbade lighter for clays, another for gravels, a fourth for sands, a fifth for pastures, and a sixth for our heaths. By placing this, which might be called an Agricultural Map side by side with a Geological Map, there would be obtained every kind of knowledge required, both with regard to soils and minerals. It is impossible, however, in the present state of our knowledge of the geography of Scotland to form any such maps, and till a great advance in, or the conclusion of the ordnance survey, it must in a great degree re. main very imperfect; the few corrections made by private individuals being comparatively insignificant. I have occasionally remarked, that it would be of great consequence, if the results annually obtained by the Ordnance Surveyors were regularly published, so that private individuals might take advantage of them on the formation of plans of extensive landed proprietors, which as topographical information, might be embodied in county, or general maps of the country. The responsible officers would, perhaps, be unwilling to communicate their approximate results, yet requiring correction from combined operations; but still they might be given with that reservation, though the small errors or minute inconsistencies remained to be eliminated. These at least are my views on this important subject, in which I have had some little experience. When I began my enquiries I had no idea that the geoENLARGED SERIES. NO. 12.-VOL. FOR 1843.

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