Description: Print Specifics: Type of print: Steel engraving (Intaglio) - Original German antique printYear of printing: not indicated in the print - actual 1844 Publisher: Georg Heck Condition: 1-2 (1. Excellent - 2. Very good - 3. Good - 4. Fair). Generally commensurable with the age of print. Few very light brownish spots/smudges. Please examine the photos for extent. Dimensions: 9 x 11.5 inches (23 x 39 cm), including blank margins (borders) around the images.Paper weight: 2-3 (1. Thick - 2. Heavier - 3. Medium heavy - 4. Slightly heavier - 5. Thin)Reverse side: BlankNote: 1. Green color 'border' around the print in the photo is a contrasting background on which the print was photographed. 2. Print detail is much sharper than the photo of the print. Legend to the illustrations in the print: Fig. 1ab. Inclination charts, 2ab. Isodynamic charts, 3. [center] Chart of magnetic declination, 4ab. Barometrical wind rosettes, 5ab. Thermometrical wind rosettes. From the original narrative: The different values of the observed magnetic declination, inclination, and intensity, in different parts of the earth, are represented on charts by three systems of lines, called after Humboldt, isogonic, isoclinic. and isodynamic. Isogonic lines connect those parts of the earth possessing equal declinations. Charts on which they are delineated are called declination maps; they can, however, be relied on as accurate for a short time only, as the magnetic declination of a place is constantly changing. Nevertheless there are places on the earth where the declination does not sensibly change for a considerable period of time; among these are Spitzbergen and the western part of the Antilles. Among all the isogonic lines the line of no deviation is most remarkable, the line connecting all places where the needle points due north, or where the magnetic and astronomical meridians coincide. This passed through London in 1657, and through Paris in 1669. It divides the earth into two portions, of which the one has an eastern and the other a western deviation of the needle. The latter portion embraces all Europe, excepting a small part of Russia. Africa, and nearly all of the Atlantic Ocean. In north-eastern Asia the isogonic lines form a closed system of oval outline, this same condition being represented more regularly and of greater extent in the South Sea, between 20° N. and 45° S. latitude. In the Asiatic oval the deviation increases from without to within, while in that of the South Sea the reverse occurs. The chart occupying the middle of pi. 28 represents the observed values of the declination in the years 1827-30, in isogonic lines after Adolphe Erman. The figures accompanying the lines indicate the degree of declination, the western being taken as positive, the eastern as negative. Isoclinic lines connect those parts of the earth possessing the same magnetic inclination, and are represented on inclination charts. That one of these lines connecting those places where the needle is horizontal or has no inclination, is called the magnetic equator; to the north of this the north end of the needle will dip towards the earth, the reverse taking place to its south. In 1825 the one point of intersection of the magnetic and terrestrial equators was situated near the Island of St. Thomas, in the western coast of Africa, and distant 188J° from the node in the South Sea; from 1825 to 1837 the former node has moved 4° towards the west. On the coast of Brazil the magnetic equator is 15° south of the terrestrial. A great advantage in investigating and establishing the laws of terrestrial magnetism is found in the fact, that all but about one fifth of the magnetic equator falls in the ocean, and is therefore readily accessible. Those places on the earth where the dipping needle stands vertically are called the magnetic poles; of these there are two, one in the southern and one in the northern hemisphere. They are also characterized by the fact, that in all regions near one of these poles the horizontal needle is directed immediately towards it. PI. 28, figs. 1a and 1b, represent the isoclinic lines of the northern and southern hemisphere for the year 1825, after the chart of Admiral Duperrey, who crossed the magnetic equator six times between 1822 and 1825. Isodynamic lines connect those places which possess the same intensity of magnetism. Fig. 2 exhibits these lines for two hemispheres, likewise after Admiral Duperrey. In general the magnetic intensity increases from the terrestrial equator to either pole, but the isodynamic lines run parallel neither with the magnetic nor the terrestrial equator. An arbitrary unit has been made of the intensity observed at the magnetic equator in Peru by Humboldt, although this is by no means the minimum of observed intensity: this real minimum amounts to seven tenths of that assumed as the standard, and occurs on the coast of Brazil. By connecting those places in each meridian in which the intensity attains its minimum, we shall have a line, called by Duperrey the magnetic equator, which, however, by no means appears to coincide with the aclinic line, or line of no inclination. The maximum of known intensity amounts to a little over two, and occurs near the south magnetic pole; the observed maximum is thus about twice the minimum. Near the magnetic north pole in Melville Island it only amounts to 1.6. Martin2001 Satisfaction Guaranteed Policy! Any print purchased from me may be returned for any (or no) reason for a full refund including all postage. Internet seller since 1998.Five-star service.
Price: 21 USD
Location: Manassas, Virginia
End Time: 2024-09-19T20:03:10.000Z
Shipping Cost: 4.45 USD
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Item Specifics
Restocking Fee: No
Return shipping will be paid by: Seller
All returns accepted: Returns Accepted
Item must be returned within: 30 Days
Refund will be given as: Money Back
Style: Vintage
Listed By: Martin2001
Production Technique: Intaglio
Date of Creation: 1844
Print Type: Steel Engraving
Features: Not framed
Original/Reproduction: Original Print
Subject: Nature
Print Surface: Paper
Type: Print