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    Re: Lunars with a wooden octant in 1825
    From: Frank Reed
    Date: 2007 Nov 14, 22:19 -0500

    I wrote earlier:
    "Here's an article published in 1847 discussing the uses..." 
    
    And Alex, you asked:
    "Where, "here"?" 
    
    It was the body text of the message. Since it wasn't especially long, I'm 
    copying it into this message (apologies to anyone annoyed by seeing it 
    again):
    "By Capt. John S. Sleeper, Editor of the Mercantile Journal.
    Few instruments hove ever been invented, that are more ingenious or useful 
    than the chronometer, and the improvements introduced into its manufacture 
    within the last quarter of a century, are such as to make it an almost 
    perfect measurer of time. The difficulties caused by the expansion and 
    contraction of metals in different degrees of temperature, after a long 
    series of experiments, have been almost entirely overcome�and by means of 
    this little instrument, the longitude of a place may be determined with the 
    greatest ease and almost perfect accuracy. The advantages of this instrument 
    in navigation are of course immense, and begin to be generally appreciated 
    by the mercantile community. It must be evident that the safety of a ship, 
    and the time occupied in a passage, must in a very considerable degree 
    depend on the knowledge which the master may have of the position of his 
    ship from time to time. This, it is well known, cannot be determined with a 
    sufficient degree of accuracy by dead reckoning�and before chronometers were 
    introduced, no other means were ordinarily used at sea for this purpose than 
    lunar observations�the process of working which in those days was 
    exceedingly tedioue and laborious, and required much care to avoid error. 
    The process, however, which is now used, is much more simple, and requires 
    fewer figures than the former mode. 
    
    But the great advantage which the chronometer possesses over the sextant, in 
    determining the longitude at sea, is, that it may be used at all times when 
    the sky is so unclouded that an altitude of the sun in the morning or the 
    afternoon may be observed. It is not unfrequently the case that no 
    opportunity will occur during a long voyage to Europe, of measuring the 
    distance between the moon and the sun, or a star�while an altitude of the 
    sun in the forenoon or afternoon, may be obtained on almost every day during 
    the passage. Hence a chronometer on board our European traders, is not only 
    an article of great convenience, but should be regarded as an instrument 
    which cannot he dispensed with. 
    
    Some of our West India traders also find it of great value. With a 
    chronometer on board, a vessel with a perishable cargo can be navigated 
    directly towards the port to which it is bound, instead of proceeding so far 
    to the eastward that it will require several days to run down the latitude, 
    as is too often the case. When it ie considered that a few days' difference, 
    in a passage to the West Indies will sometimes make a difference of 
    thousands of dollars in the sale of a cargo, the great advantage of having a 
    chronometer on board will be at once perceived. We were once informed, by an 
    intelligent ship-master, that he was bound to a port, St. Pierre, in one of 
    the Windward Islands, and in the latitude of 28�, was steering due south, 
    having already arrived to the eastward of his destined port. At this time he 
    fell in with a lumber-loaded vessel from some port in Maine, bound to the 
    same place, which was steering S. E. by E., the captain of which was 
    exceedingly anxious to get far enough to windward. Our friend reached 
    Martinico in safety, after a very short passage.�discharged his cargo, 
    received another on board, and was in the act of leaving the harbor, when 
    the vessel which he had previously spoken arrived! 
    
    We conceive chronometers to be of much greater service in voyages to Europe 
    and the West Indies, than in voyages to the East Indies,-although in the 
    latter case it is well known that they are exceedingly useful. In East India 
    voyages, during a very considerable portion of the passage, the sky is 
    generally so unclouded that a sextant may be used, and the longitude 
    ascertained with great certainty by means of lunar observations. When a 
    sextant is not on board, or is out of order, a good quadrant will supply its 
    place. In the year 1825, while on a voyage from this port to Batavia, we 
    ascertained to our great regret that our sextant, a new one, and 
    high-priced, was a worthless instrument. There was no chronometer on board, 
    and we at first anticipated some difficulty in ascertaining the longitude, 
    but we soon found that by measuring distances of objects on each side of the 
    moon, with a quadrant, and by taking the mean of the observations, in this 
    way the longitude could be determined, as often as was necessary, with 
    almost perfect accuracy �this was proved in running for the Islands of Cape 
    de Verd, the Islands of Trinidad, St. Paul, and Java Head�and so far from 
    occupying unusual time in performing the voyage, as we apprehended might be 
    the case, when we first discovered the worthlessness of the sextant, the 
    whole voyage to Batavia and back to Boston, with full cargoes both ways, was 
    performed in a space of time unprecedentedly short�being only seven months 
    and eighteen days. 
    
    The greatest objection to the use of a chronometer is, that the instrument 
    being of delicate construction, is easily affected by injuries�and will 
    sometimes lose its rate, and may thus deceive the navigator, and lead him 
    into danger. This should be guarded against with the utmost care; and where 
    a vessel is furnished with only one chronometer, it should never be 
    implicitly relied on. Every opportunity should be seized to test its 
    correctness�particularly by lunar observations. 
    
    In European voyages, where, as we have before stated, an opportunity for 
    taking lunar observations seldom occurs, two chronometers, or a chronometer 
    and a well-regulated watch, will be found of incalculable value. So long as 
    there is no essential difference in the Greenwich time indicated by these 
    instruments, the navigator may run boldly, relying, with the aid of a good 
    look-out, upon the correctness of his longitude�but should a variation 
    occur, he will immediately perceive it, be upon his guard, and enabled to 
    escape dangers which might otherwise befall him. " 
    
    If you want a copy of the original, jus hit googlebooks and search for any 
    unique phrase. 
    
     -FER
    
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