DOI Seite / Zitierlink:
https://doi.org/10.11588/diglit.20131#0481
SECTION VI.
GENERAL CONSIDERATIONS ON THE TERRESTRIAL MAGNETISM OF
INDIA AND THE SURROUNDING COUNTRIES.
A. MATERIALS OF OBSERVATIONS.
I. Stations of our magnetic survey, from 1854-7. II. Survey of the Indian Archipelago, from 1845-9, by Captain
C. M. Elliot. III. Determinations of the declination, from 1835-49, by the Indian Navy. IV. Observations in 1833
along the eastern coasts of India, by de Blosseville. V. Declination in Central India and Hindostan, from 1813-28,
by Major J. A. Hodgson. VI. Average declination in Rajvara, 1835, by Lieutenant A. H. E. Boileau. VII. Dip
and relative horizontal intensity from 1837-9, by F. G. Taylor and J. Caldecott. VIII. Declination and dip in
Kashmir and Ladak, by Major A. Cunningham. IX. Historical data for secular change, a. Declination, b. Dip.
B. CONSTRUCTION AND EXPLANATION OF THE MAGNETIC MAPS.
The systems of: 1. the isogonic lines; 2. the isoclinal lines; 3. the isodynamic lines.
C. RESULTS DEDUCED FROM THE ABSOLUTE DETERMINATION OF THE MAGNETIC ELEMENTS.
I. Declination: 1. Line of no declination; 2. Local disturbances; 3. Zones of greater deviations in Assam, in the
Bhutan Himalaya, in Berma, and in the Nilgiris; 4. Zone of most rapid change; 5. Karakorum and Kuenluen.
IF. Dip: 1. Tropical zone of rapid increase; 2. Regularity of isoclinal lines in general; 3. Zones of increase and
decrease; 4. Influence of height; 5. Local deviations.
III. Total Intensity, a. Modifications of the isodynamic lines in India: 1. Region of great increase in Central
India; 2. Depression along the foot of the Himalaya; 3. Physical condition of the surface of the soil, produced
by insolation and humidity; 4. Absolute minimum total intensity; 5. Average rate of increase with latitude.
p. Horizontal Intensity, y. Influence of height.
A. MATERIALS OF OBSERVATIONS.
For facilitating the general considerations on the magnetic conditions of India
and the surrounding countries, we present a tabular abstract of our magnetic and
geographical stations,1 together with a compendious enumeration of the materials
1 On the overland route we determined the following declination and dip, the results of which we add for the
completion of the series of our observations:
Declination. Dip.
O ./....:. o / o / o /
1857, May 13, Aden, Latitude North 12 4G Longitude East Green. 45 10 4 15 West 5 38-5 North
„ „ 20 Suez, „ 29 59 „ „ 32 3G 5 23 „ 41 10-35 „
. „ „ 25 Cairo „ 30 3 7 8 „ 41 24-38 „
(In 1836, Captain Haines found at Aden: Declination West. 5" 2'.)
GENERAL CONSIDERATIONS ON THE TERRESTRIAL MAGNETISM OF
INDIA AND THE SURROUNDING COUNTRIES.
A. MATERIALS OF OBSERVATIONS.
I. Stations of our magnetic survey, from 1854-7. II. Survey of the Indian Archipelago, from 1845-9, by Captain
C. M. Elliot. III. Determinations of the declination, from 1835-49, by the Indian Navy. IV. Observations in 1833
along the eastern coasts of India, by de Blosseville. V. Declination in Central India and Hindostan, from 1813-28,
by Major J. A. Hodgson. VI. Average declination in Rajvara, 1835, by Lieutenant A. H. E. Boileau. VII. Dip
and relative horizontal intensity from 1837-9, by F. G. Taylor and J. Caldecott. VIII. Declination and dip in
Kashmir and Ladak, by Major A. Cunningham. IX. Historical data for secular change, a. Declination, b. Dip.
B. CONSTRUCTION AND EXPLANATION OF THE MAGNETIC MAPS.
The systems of: 1. the isogonic lines; 2. the isoclinal lines; 3. the isodynamic lines.
C. RESULTS DEDUCED FROM THE ABSOLUTE DETERMINATION OF THE MAGNETIC ELEMENTS.
I. Declination: 1. Line of no declination; 2. Local disturbances; 3. Zones of greater deviations in Assam, in the
Bhutan Himalaya, in Berma, and in the Nilgiris; 4. Zone of most rapid change; 5. Karakorum and Kuenluen.
IF. Dip: 1. Tropical zone of rapid increase; 2. Regularity of isoclinal lines in general; 3. Zones of increase and
decrease; 4. Influence of height; 5. Local deviations.
III. Total Intensity, a. Modifications of the isodynamic lines in India: 1. Region of great increase in Central
India; 2. Depression along the foot of the Himalaya; 3. Physical condition of the surface of the soil, produced
by insolation and humidity; 4. Absolute minimum total intensity; 5. Average rate of increase with latitude.
p. Horizontal Intensity, y. Influence of height.
A. MATERIALS OF OBSERVATIONS.
For facilitating the general considerations on the magnetic conditions of India
and the surrounding countries, we present a tabular abstract of our magnetic and
geographical stations,1 together with a compendious enumeration of the materials
1 On the overland route we determined the following declination and dip, the results of which we add for the
completion of the series of our observations:
Declination. Dip.
O ./....:. o / o / o /
1857, May 13, Aden, Latitude North 12 4G Longitude East Green. 45 10 4 15 West 5 38-5 North
„ „ 20 Suez, „ 29 59 „ „ 32 3G 5 23 „ 41 10-35 „
. „ „ 25 Cairo „ 30 3 7 8 „ 41 24-38 „
(In 1836, Captain Haines found at Aden: Declination West. 5" 2'.)