Notes on the Management of Chronometers and the Measurement of Meridian Distances |
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Common terms and phrases
Accumulated rate accurate adopted afford algebraic Amoy apparent noon applied approximate Arithmetic mean arithmetic series arrangement assistant-watch astronomical Cape Upstart Capt change of rate chro Chronometer Journal chronometers employed chronometric measurements comparison computation convenient correction corresponding Curaçoa daily rate determined difference of longitude Ditto equal altitudes equation Error of chron errors and rates Example exhibit favourable formula given Greenwich Greenwich mean Guayra Hardy's Islands Hence Hong Kong hydrographic La Guayra latitude Lizard Island local mean Maritime Geography mean epoch measurement of meridian meridian distance meters method minutes of arc Nautical Magazine navigation nometers number of chronometers Observatory obtained partial interval performances period place of observation Port Essington Porto Cabello position practice Raper recorded reduction remarks sextant Shanghai ship ship's shore spot of observation standard subsequently supposed taken temperature terminal stations Tiarks tion Trincomalee variation vations voyage Whence whole accumulation
Popular passages
Page 15 - ... 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. Hence the difference .sometimes found between harbour and sea rates.
Page 63 - ... details relative to the management of chronometers and to the determination of local time. In the fourth chapter the author explains the mode of ascertaining the rates of chronometers by two observations of a similar kind taken at a convenient interval. On this part of his subject he remarks : — "For the determination of the error on local mean time, it has formerly generally been the practice in the measurement of meridian distances, or on taking a departure from a port, to adopt as the starting-point...
Page 72 - ... interval for determining the rates of chronometers, the author justly remarks that if the stability of the rate could be relied upon, its value would be obtained with greater accuracy the longer the interval of time included between the observations for ascertaining the values of the error on mean time. " In practice, however, this theoretic view is limited in its application by the impossibility of depending confidently on the steadiness of the rate over long periods, and by the consequent necessity...
Page 20 - ... standard"* to which all observations for the determination of the time are in the first instance referred ; the indication of the other chronometers at the same moment being subsequently obtained by means of the comparisons. Distinction of Chronometers. — As the description of chronometers by means of their makers...
Page 16 - Some chronometrical measurements have erred, and caused much perplexity, in the following manner. The chronometers were rated in air whose average temperature was — let us suppose, for example, 70. They were then carried through air either considerably hotter, or considerably colder, and again rated in a temperature nearly equal to that specified. The rates were...
Page 55 - ... that under log B, is — when the polar distance is acute and increasing, or obtuse and decreasing, and + when the polar distance is obtuse and increasing, or acute and decreasing.' " A brief examination of these conditions will show that the following law prevails : — " The sign of the first part is positive from the summer to the winter solstice, and negative from the winter to the summer solstice. " And that of the second part, positive from the equinoxes to the solstices, and negative from...
Page 11 - The best mode of stowing them seems to be as follows : — A box, divided into as many partitions as there are chronometers to be stowed away, should be securely...
Page 12 - The shelves, on which the saw-dust and boxes were thus secured, were between decks, low down, and as near the vessel's centre of motion as could be contrived. Placed in this manner, neither the running of men upon deck, nor firing guns, (forward,) nor the running out of chain cables, caused the slightest vibration in the chronometers, as was often proved by scattering powder upon their glasses, and watching it with a magnifying glass, while the vessel herself was vibrating to some jar or shock. "...
Page 12 - ... and firmly bolted to the beams of the deck below. Each partition should in depth be about equal to that of the largest box of the chronometers to be stowed away, and in length and breadth about two inches longer than the sides of the box it is intended to secure ; the partitions, moreover, should be furnished with lids.