72 Scientific Intelligence. [Feb. 



the Irish survey : this was chiefly attributable to the number and experience of the 

 officers employed ; whose names we must be allowed to record, as we observed them 

 at their posts. 



At the boning' telescope, .. Lieut. Western, Engrs. with Lieut. Bridgman, Art. 



First microscope, Mr. J. Taylor, astronomer at Madras. 



/"Mr. Logan. 

 | Mr. T. Oliver. 

 Central microscopes, . . -^ Mr. J. Peyton. 

 | ;■ i. M. Torrick. 

 IJVIr. W. Rossenrode. 



Last microscope, Lieut. R. Wilcox, Surveyor of the Brahmaputra River. 



The length of the base between tower and tower was nearly 34,000 feet, or 

 6.4 miles, being 539 sets of bars. The whole of this extensive line came within 

 the limits of the Barrackpur road, falling about 30 feet to the eastward of its centre 

 at one place ; and the greatest deviation from horizontality in the road was at 

 about a mile from the south tower, to which point it sinks gradually about 5§ feet. 



At the north tower, it was found beforehand that there would be about 3 feet to 

 spare in excess of a certain number of bars. This, added to the possibility of the 

 dot on the centre stone moving during the settling of the tower, induced Captain 

 Everest to adopt the expedient of sinking a heavy stone of 3J feet cube, into the 

 ground, at the distance of one set of bars south of it : two brass plates were let into 

 this, one to receive a dot at the exact distance of a set of bars from the tower, and 

 one to receive the dot terminating the 538th set. By this arrangement the sur- 

 plus interval could be measured at leisure, with the same accuracy employed 

 throughout the remainder of the line. 



The difference found on remeasuring eleven sets of bars was. 026, or one-fortieth 

 of an inch on 700 feet — a surprisingly small quantity, and only one-third of what 

 was experienced in the previous trial at Lord's cricket ground. To form a tan- 

 gible idea of the error this might induce upon the result, it is sufficient to say, that 

 it would amount to about 12 feet between Calcutta and Delhi, or 125 feet in the 

 diameter of the great globe itself. 



This, it must be remembered, is without applying any correction for tempera- 

 ture, though the two measures were taken in November and January : and it is a 

 convincing proof how well the compensation had been adjusted in England. 



The southern tower was found to have moved one-thirteenth of an inch to the 

 south-east, which is not surprising, considering the light nature of the soil, and the 

 height, 80 feet, to which the building was forced to be raised to place the theodo- 

 lite within view of the other triangle stations. 



Upon the conclusion of the great work, the bars were brought to Calcutta, to 

 be recompared with the standard at the Surveyor General's office. But for the minute 

 particulars of this and all the other processes we must wait for the public account 

 that will doubtless be eventually given of the whole operation. 



We hear that Lieutenant Western is now deputed to carry a meridional series 

 of triangles southwards from the Parisnath meridian on the longitudinal arc, to 

 Cuttack. After which the same meridian is to be prolonged northwards to the 

 limits of our frontier. We presume, that the bars will shortly be transferred to the 

 neighbourhood of Agra, where another base will be necessary for the primary 

 meridian. Should an intermediate line be required, none could be found better 

 suited to the purpose than the military road between Benares and Allahabad, which 

 enjoys the same advantages of straightness, even level, and hard materials, with 

 that of Barrackpur, added to much greater openness of country. 



