On the effect of the gangetic alluvium on the plumb-line in northern India

From some years past, the Annual Reports of the Survey of India, and of the Indian Government Board of Scientific Advice, have contained references to the remarkable character of the deflections of the plumb-line at stations near the southern edge of the Himalayas. These facts, and the explanation which has been adopted by Colonel S. G. Burrard, Surveyour-General for India, have recently been brought into prominece by the publication of a memoir on "The Origin of the Himalayas," certain parts of which are in contraction with the conclusions, regarding the structure of the range, that had been drawn from geological observations. Briefly stated, the geodetic facts are as follows. Along the southern edge of the Himalayas very high very high northerly deflections, amounting to about 40" of are, are found, which rapidly decrease in a southerly direction by about 30" in as many miles, after which the decrease becomes much more gradual, and ultimately, a southerly deflection comes in. In a northerly direction, also, there is a decrease of deflection, though not so rapid as to the south, and there is a decrease of deflection, though not so rapid as to the south, and stations up to 30 miles from the edge of the hills, in spite of being nearer to the main range, show a decreasing northerly deflection, which may be as much as 20" less than that of the marginal stations.