266 The Proposed Pendulum Operations for India. [No. 4, 



wards at Ualan, in the Caroline islands, Gi-uani, Bonin island (to the 

 south-east of Japan), at Sitka in Russian North America, at Petro- 

 paulowski, Valparaiso, St. Helena, and St. Petershurg. He deduced 

 an ellipticity of -^j from his ohservations. 



Schumacher, the celebrated astronomer of Altona, conducted in 

 1829-80, a series of experiments with Bessel's apparatus, at the castle 

 of Guldenstein, in order to determine the Danish standard, which was 

 to be a certain fractional part of the length of the seconds pendulum, 

 at the level of the sea, in latitude 45°. In order to estimate the in- 

 fluence of the air, he used, instead of a ball, a hollow cylinder of 

 platinum, made by Repsold, inside which a second solid cylinder, 

 also of platinum, fitted perfectly true. The outer cylinder was closed 

 by covers of the same diameter screwing on to it, which were both 

 perforated ; the clamp holding the wire was fastened on to the top, 

 and into the bottom was screwed a point with which the contact was 

 made in measuring the height of the cylinder by the micrometer 

 screw. 



The pendulum was swung under four different circumstances, viz. 

 the long pendulum, with and without the inner cylinder, and the short 

 pendulum, also with and without it ; and as exactly the same surface 

 was exposed to the air in each case, the influence of it could be 

 computed, which was done by a formula deduced by Bessel. The 

 reduction of the observations was made by Professor Peters. One 

 novelty was introduced, viz. that of computing out the attraction of 

 the ground on which the observations were taken. A square space 

 having a side of 600 toises (1279 yards), in the middle of which the 

 observatory was situated, was subdivided again into 36 squares of 100 

 toises (213 yards) a side ; in each of these borings were made, and 

 specimens of the earth removed and their specific gravities determined ; 

 as these were very nearly the same, a mean of the whole was taken. 

 The height of the floor of the pendulum room was 34J toises (220.6 

 feet) above the mean sea level, and the attraction of this plateau of 

 the earth's crust introduced a change in the length of the second's 

 pendulum of 0.000215 English inches. 



Carlini, whilst measuring the Piedmontese arc in 1821-23, took a 

 series of pendulum experiments at the Hospice on Mount Cenis, with 

 the view of determining the density of the earth. His pendulum was 



