32 REPORT— 1860. 



General Abstract of the Results of Messrs. de Schlagintweit's Magnetic Sur- 

 vey of India, with three Charts. By M. H. von Schlagintweit. 



M. Hermann de Schlagintweit gave a general report on the results obtained 

 during MM. de Schlagintweit's magnetic survey of India and High Asia, from 1854 

 to 1857- 



He presented three charts, showing the lines of equal declination, dip, and inten- 

 sity, from Ceylon up to Turkistan. Also the details of their observations as con- 

 tained in the first volume of their work, ' Results of a Scientific Mission to India 

 and High Asia,' undertaken by order of the Hon. East India Company, was laid 

 upon the table. 



The magnetic results were preceded by a communication of those latitudes and 

 longitudes, particularly to the north of the Himalayas, which were either new as to 

 localities or found to differ from previous determinations. 



For the construction of their charts, they most carefully compared also the previous 

 observations ; such as, for the intensity in Northern India, Taylor's and Caldecott's, 

 and particularly those recently made by Mr. Broun ; for the declination along the 

 coasts, the determination of the Indian Navy ; but Capt. Elliot, their predecessor, 

 having died before he could extend his survey from the Indian Archipelago to India, 

 and the only detailed observations in the outer Himalaya (General Boileau's, at 

 Simla) being destroyed in the last mutiny, their observations must be considered as 

 made in a territory novel for this branch of science ; and a great part of them was 

 besides made under circumstances so difficult, that unhappily one of the three 

 brothers was killed in Turkistan. 



The following results are particularly to be mentioned : — 



I. Declination. — 1. A zone of too little easterly declination, of considerable ex- 

 tent, was found in Assam. 2. In the north-western part of India the declination was 

 found to vary more rapidly than in the surrounding territories. 3. In the region of 

 the Kuerluen the declination was found more easterly than given by the approximate 

 form of the isogonic lines as provisionally laid down till now for these regions. 



II. The Dip. — This was found, of the three elements, the most regular in its 

 general forms ; though local deviations are not unfrequent, they are small and very 

 limited. 



III. Total Intensity. — Two unexpected results presented themselves: — 1. A de- 

 cided inflection of the isodynamic lines in the central and southern parts of India. 

 2. A zone of depression all along the outer ranges and the base of the Himalaya. 



In reference to the first, M. de Schlagintweit pointed out, as particularly import- 

 ant, that the very careful observations of Mr. Broun all along the western coast of 

 India, made quite independent of, and subsequent to, their own, perfectly coincided 

 with the lines based on their observations. 



The magnetic influence of a large surface of soil exposed to the physical action of 

 a tropical insulation, and the non-existence of such an influence in the rainy and 

 much more clouded regions of the outer Himalayas, were named as perhaps not un- 

 connected with this phenomenon, so particularly characteristic in India. 



Outline of the Principles and Practice involved in dealing toith the Elec- 

 trical Conditions of Submarine Electric Telegraphs. By M. Werner 

 and C. W. Siemens. 



The authors, who have had very extensive experience in dealing with submarine 

 and other electric telegraphs, state that the failures of the more extensive submarine 

 lines commence generally by a gradual decrease of insulation. The cause of this 

 failure has been found, in repairing these lines, to consist in a disintegration of the 

 gutta percha by the electrolytical action of the currents employed in working the 

 line in such places where the insulating covering was much below the average thick- 

 ness, owing to excentricities, cavities, &c. In other places, where the gutta percha 

 had been of uniform and sufficient thickness, not the slightest destruction took place ; 

 but it might be laid down as an axiom, that " so long as there are any thin places 



