Notes on the Management of Chronometers and the Measurement of Meridian Distances

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Page 16 - ... concussion. Frequently employing chronometers in boats, and in very small vessels, has strengthened my conviction that temperature is the chief, if not the only cause (generally speaking) of marked changes of rate. The balances of but few watches are so well compensated as to be proof against a long continuance of higher or lower temperature. It often happens that the air in port, or near the land, is at a temperature very different from that over the open sea — in the vicinity ; and hence...
Page 18 - ... two points. In other words, the compensation can only be exact for some two temperatures for which you may choose to adjust it. But...
Page 132 - The material and workmanship of all the chronometers is very good ; and amongst nearly all the chronometers there is very little difference indeed in this respect. In uniform circumstances of temperature, every one of the chronometers would go almost as well as an astronomical clock. " (B.) The great cause of failure is the want of compensation, or the too great compensation, for the effects of temperature. "(C.) Another very serious cause of error is brought out clearly in this trial ; namely, fault...
Page 16 - During eight years- observation of the movements of chronometers, I have become gradually convinced that the ordinary motions of a ship, such as pitching and rolling moderately, do not affect tolerably good timekeepers, which are fixed in one place, and defended from vibration as well as concussion. Frequently employing chronometers in boats, and in very small vessels, has strengthened my conviction that temperature is the chief, if not the only cause (generally speaking) of marked changes of rate....
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Page 18 - I have described cannot be made to decrease quite as fast as the heat increases ; and therefore its rate of variation can only be represented by a curve, and...
Page 134 - Bell does not pretend to say that this mode of operation will effect a permanent cure of cancerous cases, but he thinks that the plan presents various and considerable advantages over extirpation by the knife, as in producing much less shock to the system, in removing the...
Page 39 - ... glass lid of the wood box. II. Having closed the wooden chronometer box, it is to be placed in a wicker basket or hamper, or in a box of partially yielding character, and is to be packed therein with abundance of soft stuffing. If there is no wicker basket at hand, or nothing except a wooden box, this box must be surrounded with a large quantity of stuffing and inclosed in canvas, so that it can never receive a jarring blow. It is of the greatest importance that the outside of the...
Page 132 - ... fault in the oil, which is injured by heat. This is very different with the chronometers of different makers. For instance : the oil used by one chronometer maker (named in the Report) is not at all injured by heat ; while some of that used by another chronometer maker (also named) is so bad that, after going through the same heating as those of the first-mentioned maker, the rates of the chronometers are changed (on returning to ordinary temperature) by 80 seconds per week. '
Page 5 - ... Gentlemen, without going into details, you may rest assured that the residual errors of the lunar theory are reduced now to most insignificant limits; and certainly within the errors incidental to meridional observation with first-rate instruments, and very far within the limits of accuracy of observations with the sextant; — that Hansen's Tables are practically perfect for all the purposes of navigation, and that the great nautical problem of finding the longitude at sea is now completely...

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