A TREATISE ON THE PRINCIPAL MATHEMATICAL INSTRUMENTS EMPLOYED IN SURVEYING, LEVELLING, & ASTRONOMY, &c. &c. Late of the Royal Observatory, Greenwich, and formerly employed on the Ordnance Survey. SECOND AMERICAN EDITION, FROM THE SECOND (IMPROVED AND ENLARGED) LONDON EDITION. REVISED, AND WITH ADDITIONS, BY J. H. ALEXANDER. BALTIMORE: FIELDING LUCAS, JR. 170 MARKET STREET. 1844 ENTERED, according to the Act of Congress, in the year one thousand eight hundred and forty-four, by FIELDING LUCAS, JR. in the Clerk's office of the District Court of the United States. JOHN D. TOY, PRINTER. PREFACE TO THE FIRST EDITION. THE want of a work containing a concise and popular description of the principal Instruments used in Practical Astronomy and Surveying has long been felt, as the requisite information with respect to such instruments can only be obtained by consulting various expensive publications, which are not within the reach of many to whom such information is highly interesting and important. It was the original object of the writer of this little tract, to place at the disposal of the young surveyor a description of the instruments which are required in his profession, and such an account of the method of examining and rectifying their adjustments, as would enable him to obtain from them the most accurate results; but he found that, without greatly increasing the size of the book, he might materially add to its utility, by including in his plan the most approved Astronomical Instruments, that amateur astronomers as well as scientific travellers might have at hand a manual of instructions, which would enable them to use their instruments with the utmost advantage. Usefulness being the author's chief object, he has not scrupled to extract from the works of others whatever he found adapted to his own purpose; and to some kind literary and scientific friends he is under obligations, for which, if he had obtained their permission, he would be glad to thank them by name in this place. |
