wind during the night and generally early in the morning draws off the land; by so doing you will also get within the influence of the tides. Should it be ebb when you get up to Europa Point, it would be hopeless except with a very steady wind to attempt to beat round, which is very seldom the case when the wind blows strong from the west, for then the eastern side of the rock, like the western during easterly winds, is subject to violent squalls and puffs of wind, which completely frustrate any attempt to get round. Put the ship therefore under easy sail and lay to off and on until the flood tide makes, when you will get round with perfect ease, and soon gain the New Mole.

Whenever a large ship, particularly a line of battle ship anchors off the New Mole, she should take especial care to anchor as much abreast of the Dock-yard as possible, that is, to the north-east of the New Mole. A ship lying here ought always to be moored, and her best bower should be let go well to the northward; for if the wind suddenly shifts round to east, in a sudden squall as it generally commences, she is very apt to drive, before a second anchor can be let go.

One or two line of battle ships, and other vessels have been nearly lost by not attending to this precaution. Remark (particularly in winter) when you are close in under the land waiting for the breeze coming off shore, which you are generally sure of getting, do not be tempted to make much sail, particularly studding-sails, as at times the wind comes off so strong, and so sudden, that it oftentimes becomes requisite to close reef the top-sails; if this be not attended to, a ship will be very likely to lose her top-masts at the least.

The land and sea breezes on this coast are pretty regular during the summer months, but in winter the land breeze is seldom strong except after a fine day.

From Malaga to Almeria.-If you start with a fair and steady breeze, run down parallel to the shore keeping about five or six miles off the land or less during the day, as the coast is quite clear and bold until you arrive off Los Llaños or plains of Almeria, which in thick weather are dangerous being extremely low. On its south-west extremity is the Morro Point, where stands the Castle de Las Guardas Viejas or the Old Guard. From this Point the plains may be said to commence. Point Elena the eastern extremity is low and dangerous, and has a reef of rocks running out from it to the eastward. It ought not to be rounded nearer than a mile and a half, always taking care to keep the lead going, as the whole coast from it to Almeria is shoal.

The bay of Almeria is well protected from westerly winds by the high bluff points of Torrejon, on which is a small fort and a flagstaff. The best anchorage is in nine or ten fathoms close in under Torrejon, where you will lie as quiet as possible. The east wind throws in a

heavy swell, but there is no fear of a vessel, she having good anchors and cables. Water can be obtained here, but with considerable difficulty, as there is generally a surf on the beach. Almeria was once a celebrated sea-port, but nothing but its dilapidated castle remains to attest its former glories under the Moorish rule.*

*We have here a vice-consul. The best time for getting into Almeria is from 10 3 in the afternoon, as during the heat of the day, the wind generally draws from the southward.

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 harbour, 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 when 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 a 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 Ali

cante.

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 64 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 (3) of an inch is immediately appar ent, 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 sevenpence 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