If the register tonnage of a vessel denoted the actual capacity of the vessel in measurement tons of 40 cubic feet, or had any fixed proportion to that capacity, it would be easy to calculate the quantity of goods, of any specified kind, which the vessel would carry. But, as the present mode of measuring vessels is defective, the register tonnage is not a certain guide to ascertain the quantity of cargo which a vessel can carry, as much depends on the peculiar build of the vessel.

A good carrying vessel will carry one-half more tons than her register tonnage; and on this principal the quantity of cargo may be ascertained, as in Article 59.

The only correct mode of ascertaining the quantity of cargo which a vessel can carry, is to ascertain practically the quantity of dead weight which the vessel can take as a complete cargo: say the number of tons of coals. Also, ascertain practically the number of measurement goods the vessel can stow; which will give the contents of the vessel in tons of 40 cubic feet. With these data, the quantity of any specified kind of goods which a vessel can take as a complete cargo may be calculated as in Articles 60, 61, 62, and 63.

The mode of making these calculations by means of Logarithms is given in Article 64.

In chartering vessels, it is often the case that a certain rate of freight is stated for a specified kind of goods; and should the vessel be loaded with any other kind of goods, the Charterparty stipulates that a proportionate rate of freight will be paid. It is, therefore, of the utmost importance to the shipowner or shipmaster to know what the exact proportionate rates of freight of different kinds of goods should be, in order that he may be certain that he will earn the amount of freight which he expects. This is found by means of Tables 1, 2, or 3. See Articles 67 and 87.

The usual mode, however, of chartering vessels, is to stipulate for a proportionate rate of freight according to the London printed Rates. And this often causes loss and disappointment to the shipowner. Thus, a vessel may be chartered at 80s. per ton of tallow, and at proportionate rates for other goods. The shipowner is contented with the specified rate of tallow, as he calculates on receiving a certain amount of freight; but, if the charterer's agent loads with wheat instead of tallow, the amount of freight earned by the vessel, if the London printed Rates are used, will be 11 per cent. less than the shipowner expected. See Article 90. Again, if instead of loading with tallow, the vessel is loaded with deals, the amount of freight will be 244 per cent., being a loss of nearly one-fourth to the shipowner. See Article 91.

The Tables in the present work will, therefore, enable shipowners and shipmasters to guard against the loss which they may incur by signing open Charterparties, as it gives them the exact proportionate rates of goods, which, if adopted, will make the amount of freight carned the same, whatever goods are taken as cargo.

Consequently when a vessel is chartered to load at a certain port, as it is well known what kind of cargoes are usually procured there, an open Charterparty should never be signed unless the rate of freights for all kinds of goods usually loaded at the port be practically specified in the Charterparty.

Besides all the necessary Tables for ascertaining Freights correctly, the present work contains extensive Tables of Foreign Weights, Measures, and Moneys, to enable the shipmaster to understand the accounts he may receive in foreign countries. And in the Appendix the Passenger's Act is given, thus rendering the work as complete a guide to shipbrokers, shipowners, and shipmasters in chartering vessels.

Captain Sumner's Method of finding a Ship's Position at Sea,

Improved and simplified, containing the solution of the double altitude problem by projection; and a new method of finding the Time at Sea, which is conceived to be the shortest and easiest of any yet published. Bound in Cloth 78. 6d.

THE EXAMINER FOR THE NATIONAL MARINE BOARDS.

This work is intended for the use of Commanders and Mates of Vessels, who are desirous of obtaining a Certificate of Qualifications from any of the Marine Boards now established in the United Kingdom, in accordance with the Regulations of the Lords of the Committee of the Privy Council for Trade.

An Appendix is annexed. The First Part contains Rules for finding the various quantities used in Nautical Astronomy, from the Nautical Almanack, with the requisite degree of accuracy. The Second Part contains a very extensive collection of Nautical and Astronomical Definitions. These are generally given very briefly in Treatises on Navigation; but as the London Marine Board required a thorough knowledge of them, they are here given very fully, and with copious notes in explanation; as it is probable they will be again introduced into the Examination. "Bound in Cloth

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The author flatters himself that this little work will enable any one who studies it carefully to acquit himself creditably at his Examination before any of the Marine Boards.

THE EXTRA EXAMINER FOR THE NATIONAL MARINE BOARDS:

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WORKS BY WILLIAM TURNBULL.

NAVIGATION AND NAUTICAL ASTRONOMY.

A plain and popular Treatise containing all the Sailings; Plain and Spherical Trigonometry; various methods of ascertaining the Latitude by Meridian, Single, and Double Altitudes; the Longitude by Chronometer and Lunar Observations; and the Variation of the Compass by Amplitudes and Azimuths, and also a Journal of a Voyage from London to Madeira. The whole being illustrated by practical Rules, ! and a sufficient number of appropriate Examples, for rendering the Student proficient in the necessary computations of Navigation and Nautical Astronomy. Accompanied by a Set of requisite Tables, with their explanation and use in resolving the various Astronomical and other Problems, given in the course of the work. With an Appendix containing the Principles of Great Circle Sailing, and twenty additional methods of finding the latitude and longitude. By JAMES GRIFFIN, but revised and considerably improved and enlarged by WM. TURNBULL 12s. Od.

KEY to the Exercises of the above work, in which every Question is worked

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In this edition several alterations have been made in the plan of the work, in as far, at least, as the nature of the observations would allow, introducing, at the same time, such discoveries as have been long anxiously desired by the Maritime world.

For the better arrangement of the subject, it has been judged advisable, in composing the work, to commence with such technical terms as are required to be perfectly understood in the doctrines of Navigation and Nautical Astronomy; and in order that those terms may be the more easily comprehended, they are given under the head of "Definitions;" first, those that are peculiar to the elements of Navigation in its several divisions; and in their proper place, those that are peculiar to the different branches of Nautical Astronomy, these being considered as two distinct branches of the subject, and treated accordingly.

The definitions peculiar to the part of Navigation are followed, in their order, by brief and comprehensive directions for resolving the different kinds of Sailing; and those peculiar to Nautical Astronomy are in like manner followed by rules for adjusting the angular instruments, such as the quadrant and sextant, and also by rules for taking the observations that are necessary for ascertaining the ship's place by means of the heavenly bodies; but this latter part of the subject may be better acquired through the assistance of a practical observer, than by means of any written instructions that can be given.

In the next place, there are given very concise and simple methods of finding the latitude by means of the meridian altitude of the sun, the moon, the planets, and the stars, and also by the altitude of the pole star, observed at any particular time.

This method of finding the latitude is well adapted to the practice of Seamen, and is particularly applicable when the latitude is required to be found with great accuracy.

Besides this method of finding the latitude, which is common and well known, being treated on in almost every book on the subject of Navigation, another new and concise method is given; it consists in taking the altitude of a heavenly body at any distance from the meridian, or by the altitudes of any two objects taken at the same time. This is a very useful method to the Mariner, and is next in value to the preceding mode of finding the latitude by a meridian altitude; for by this method, the disadvantage of frequently losing the latter by the intervention of clouds is obviated.

Following the preceding methods, is a new and concise process of finding the latitude by two altitudes of the same body, which process is founded on the principles of approximation, and is equally as correct as either of the preceding methods, provided that the observations are taken in the manner directed; the observations being of the utmost consequence for the success of the method and the accuracy of the results.

The method of computing the time at any given meridian is next considered; and following this, is the use of the Chronometer, a subject so generally understood by nautical men of the present day as to render it unnecessary, in this place, to say any thing respecting its management at sea; it has, therefore, been considered sufficient to point out the practical methods of discovering its rate and error; and here the Author has effected such improvements in the mode of rating it by equal altitudes, as to render it the simplest that has yet been offered to the public.

A method is also given of finding the longitude by the Chronometer, without the assistance of an ephemeris: this is a point of the utmost importance to the Navigator, but more especially in foreign countries, and other places where the Nautical Almanac cannot at all times be procured.

In the next place is given a new and concise method of finding the longitude at sea by Lunar Observations, independently of the moon's horizontal parallax; this method is adapted to the distances as now given in the Nautical Almanac. It is, however, intended for another set of distances to be hereafter computed; namely, the distance between's the moon's bright limb and the nearest limb of the other object; by which means the solution of this very important problem is rendered the most simple that has ever yet been brought into use; for in the application of it, parallaxes and semidiameters are dispensed with, these being the elements that render this part of the computation so very troublesome and perplexing to a beginner, and even those of larger experience.

Following this, is given a very useful and convenient method for ascertaining the altitude of the heavenly bodies, at any proposed time, with a description of the Compass, and a method of correcting it by astronomical observations. After this comes a method of keeping a Journal at sea, in which is given every circumstance that can be met with by a ship running on a long voyage; the whole being illustrated by a sufficient number of rules and examples for every purpose to which attention may be directed.

With reference to the Tables it may be stated, that those which are common, and have been previously in the hands of the public, are reprinted from the most correct copies; but the Tables from 14 to 38, both inclusive, are all new, and calculated by the author himself; and in as far as regards their accuracy, it may be mentioned that they have all been examined by differences, the proofs of which were compared with the originals, first by four different readers, and afterwards by the Author and another skilful individual, so that it is presumed that few, if any, errors of any consequence have escaped.

Upon the whole, it is presumed that the work as it now appears, with the Appendix containing the principles and practice of Great Circle Sailing, together with twenty additional methods of determining the latitude and the longitude by Lunar Observations, will meet the Mariner's approbation, and prove conducive to his intimate and extensive acquaintance with the subject of navigation in all its bearings.

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SPHERICAL ASTRONOMY.

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THE DAILY ASSISTANT.

Containing the application of Plane and Spherical Trigonometry to Practical Naviga tion and Nautical Astronomy; with a method of finding the Latitude by Meridian Altitudes; and a Journal of a Voyage from London towards Madras; the whole fully illustrated by simple Rules and Examples, to complete the young Student: an Appendix, containing an extensive Set of Requisite Tables, with a copious Explanation of their use in the computation of the different Cases in Practical Navigation, and in the solution of other Problems in Nautical Astronomy. Demy 8vo., neatly bound in sheep 5s. Od.

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THE CATECHISM OF NAVIGATION.

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Memoir of the North and South Atlantic Oceans. Containing Sailing Directions for Navigating the Coasts of France, Spain, and Portugal, the West Coast of Africa, the Azores, Madeira, Cape Verdes, and all known Islands, Rocks, Shoals, and Dangers, in this Navigation; together with the East Coast of South America, the Strait of Magelhaen, the Falkland and Shetland Islands, Tierra del Fuego, &c., &c, General Description of Winds, Tides, and Currents, Tracks to and from England to the Cape of Good Hope, Coast of Brazil, West Indies, North America, &c., &c., and a Copious Table of Latitudes and Longitudes. By M. Blachford, Hydrographer. Demy Svo. 12s. Od

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