Interpretation of elongated SP anomalies is usually accomplished by assigning two‐dimensional (2-D) shapes such as inclined sheets and horizontal cylinders to the source. However, since the shapes of the profiles are similar, it is extremely difficult to distinguish the source as cylindrical or sheet‐like from a given field profile. By defining two characteristic ratios from anomalies between the two extrema on the profile, we present a nomogram which not only helps identify the shape of the 2-D anomaly source, but also facilitates estimating all the parameters. Using this nomogram a field profile can be interpreted in a very short time with ease and accuracy. The method is demonstrated on two examples. Error response of the parameters estimated due to errors in data was studied through imposing ±5 percent to ±25 percent errors in the two characteristic ratios in two synthetic profiles due to a cylinder and a sheet. While the results on the cylinder showed negligible errors, the percent errors for the sheet model, in general, are less than the percent errors imposed.

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SATYANARAYANA MURTY, B.V., GHYASUDDIN, M. and VENKAT REDDY, P. 1982, Subsurface Gravity Measurements and Density Mapping in the Mailaram Copper Mines, Andhra Pradesh, India, Geophysical Prospecting 30, 444453.Gravity measurements were made in the Mailaram copper mines, Andhra Pradesh. The observations were distributed between the two shafts situated about 220 m apart and in the three levels up to a maximum depth of 100 m. Assuming a normal free-air gradient, average densities for the three layers were determined as 2.631, 2.604, and 2.823 g ~m -~, respectively. Upon incorporating the weighted mean density values from measurements on samples, the free-air gradients were found to be 0.315 mGal m-l for the second layer (i.e. between the first and second levels) and 0.2978 mGal mfor the third layer (i.e. between the second and third levels). The density variation map obtained from the gravity data, the deduced anomalies, the weighted mean density values from measurements on rock samples, and the varying free-air coefficients all suggest correspondence with the concentration of ore lodes.