THE SEAMAN'S ARITHMETIC, OR THE APPLICATION OF THE SEVERAL RULES OF THAT SCIENCE TO THE PURPOSES OF THE MARITIME PROFESSION; BEING INTENDED AS AN INTRODUCTION TO THE YOUNG MARINER PREPARATORY SUBSEQUENT GUIDANCE : IN WHICH ALSO ARE INSERTED SEVERAL EXAMPLES OF STATEMENTS AND ADJUSTMENTS OF GENERAL AND PARTICULAR AVERAGES, SUCH AS ARE GENERALLY PRACTISED AT LLOYD'S, AND BY OTHER THE WHOLE EXEMPLIFIED AND EXPLAINED IN A PLAIN AND SIMPLE MANNER, BY JOHN MARTIN, AGENT, KINCARDINE. EDINBURGH: ADAM & CHARLES BLACK, NORTH BRIDGE. MDCCCXLIII. PREFACE. CONSIDERING the number of Treatises already extant on Arithmetic, to some it may appear superfluous to trouble the public with any more; but it will be acknowledged that these, although excellent in their kind, are nevertheless for the most part adapted to general use; and the questions contained in them appear to the young seaman so foreign to his profession, that it is with a sort of reluctance that he performs the calculations. It is to obviate this difficulty as much as possible that the following Treatise has been compiled, wherein the questions given are selected from the common occurrences of a seafaring profession; and it being evident that a seaman requires as much knowledge of Foreign Money, Weights and Measures, as that of those in Britain, they are accordingly interspersed indiscriminately through the work. A question is often asked, "How much of Arithmetic is necessary to be acquired previous to learning Navigation ?" an acquisition which most of young seamen are anxious to obtain. To this it may be answered, that it is not altogether the great number of rules to be acquired that is needful, but the accuracy with which those that are requisite are performed, and therefore it is absolutely necessary to be well versed in the first four fundamental rules, namely, Addition, Subtraction, Multiplication, and Division: these, with Simple Proportion, and some knowledge of Decimals, particularly as much as that he can know at first sight nearly their value,-as, for instance, if 25 were presented to him, that it was only; if 5, that it was only ; and if .75, that it was only, and so of the rest: the reason for this is, that nearly all the tables in an epitome of Navigation are computed and expressed by Decimals. The above, if well acquired and judiciously applied, will enable the mariner to go through a system of Navigation in theory, and to apply it in practice, although it is doubtless preferable, if time will permit, to acquire as much of Arithmetic as possible, thereby enabling him to have a command of figures, in order to avoid or detect errors in calculation, an object very desirable in keeping a ship's reckoning, because an error of a single figure in this, or in misplacing those found, such as putting the difference of latitude for the departure, or the reverse, in the Traverse Table, will be the means of creating considerable error in the day's work, and causing much uneasiness when such is ascertained by an observation. It may be observed by some, that a number of the questions contained in this book belong rather to a Treatise on Navigation:-this is admitted; but it will also be allowed that, although they are so inserted in epitomes on Navigation, yet, before they are solved, recourse must be had to Arithmetic; indeed the most of modern books on that science commence at the very beginning with examples in Arithmetic, it being considered the most essential in point of priority. The insertion of the average statements, although not strictly belonging to a Treatise of this kind, as masters are not usually required to draw out such, yet it is advisable that they should have some notion of the method of doing so, in order that they may form some idea of what each party would have to contribute in the event of an accident happening to the vessel; at any rate, they are an exercise on figures, and, as such, it is hoped they will be found useful. KINCARDINE, Nov. 1842. b |