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To wind a chronometer, turn it over from right to left, and hold it firmly there by the left hand; turn the key slowly and steadily and more cautiously still, as the known last turn comes, until it butts; withdraw the key and turn the chronometer back with its face upwards.

The chronometer esteemed the best is usually selected as a standard, and with it, each of the others is compared at the time of winding daily, the comparisons entered in a book, the « chronometer journal ».

OLD NAVIGATION (1).

Up to the close of the last century, the navigator guessed as much as he calculated the place of his ship.

Chronometers now so accurate, were then an experiment.

The nautical ephemeris itself was faulty.

The instruments of navigation erred by degrees, for the rude cross-staff and back-staff, the sea-ring and mariner's bow, had not yet given place to the nicer sextant and circle of reflection of the present day.

Instances ares numerous of vessels navigating the Atlantic, in those times, being six, eight and even ten degrees of longitude out of their reckoning.

Such is now the degree of perfection to which nautical tables and instruments have been brought, that the

(1) Maury.

LE REMONTAGE.

Pour monter un chronomètre, renversez-le de droite à gauche et tenezle ferme dans cette position, avec la main gauche; tournez la clé lentement et régulièrement, et avec plus de précaution encore quand arrive le dernier tour connu à l'avance, jusqu'à ce qu'elle bute. Retirez la clef et retournez le chronomètre, face en dessus.

On choisit d'habitude, comme étalon, le chronomètre qu'on estime le meilleur; les autres lui sont comparés, chaque jour, au moment du remontage et ces comparaisons sont portées sur un registre « le journal des chronomètres ».

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Jusqu'à la fin du siècle dernier, le navigateur devinait, autant qu'il la calculait, la position de son navire.

Les chronomètres si répandus aujourd'hui étaient alors à l'essai.

Les éphémérides nautiques mêmes contenaient des fautes.

Les instruments de navigation avaient des degrés d'erreur, car ces grossiers arbalètes, astrolabes, cercles marins, arcs de navigation, n'avaient pas encore fait place aux bons sextants et aux excellents cercles de nos jours.

Les exemples ne manquent pas de navires qui, traversant l'Atlantique à cette époque, se trouvaient de six, huit et même dix degrés de longitude au delà de leur estime.

Tel est à présent le degré de perfection des tables et des instruments de navigation, que le marin peut au

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I should like to have my chronometers rated, but as one cannot rely on the longitude of this place, I wish you would kindly allow me to get a comparison from yours. It would be better, I think, than all the sights I could take with the artificial horizon.

Certainly, and I will give you with pleasure comparisons which you may rely upon, for I had my watches rated during our last stay in harbour no more than ten days ago, and my standard never alters.

Here is the error of the standard which is 1h3m04s slow of Paris mean time on the 12th of october; its rate is gaining 4,7 daily. Many thanks.

PRENDRE DES COMPARAISONS.

Je voudrais régler mes chronomètres, mais comme la longitude du lieu n'est pas encore bien déterminée, vous m'obligeriez en me laissant prendre des comparaisons avec les vôtres. Cela vaudrait mieux, je pense, que toutes les observations que je pourrais faire à l'horizon artificiel.

Certainement, monsieur, aussi je vais vous donner, avec plaisir, des comparaisons sur lesquelles vous pourrez compter, car mes montres ont été réglées dans notre dernière relâche, il n'y a pas plus de dix jours, et mon chronomètre-étalon ne bouge pas.

Voici l'état absolu de l'étalon qui est un retard de 1h03m04s sur midi moyen de Paris, le 12 octobre; la marche diurne est une avance de 4,7. Je vous remercie beaucoup.

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