

PUEE MATHEMATICS, 



49. 



ACCOUNT OF SOME TRIGONOMETRICAL OPERATIONS TO ASCERTAIN 

 THE DIFFERENCE OF GEOGRAPHICAL POSITION BETWEEN THE 

 OBSERVATORY OF. ST JOHN'S COLLEGE AND THE CAMBRIDGE OB- 

 SERVATORY. 



[From the Cambridge Philosophical Society's Proceedings. Vol. I. (1852).] 



THE observations, especially those of eclipses and occupations, which 

 were made during many years by the late Mr Catton at the Observatory 

 of St John's College, and which have recently been reduced under the 

 superintendence of the Astronomer Royal, render it a matter of some 

 importance to determine the exact geographical position of that Observatory. 

 The simplest and most accurate means of doing this appeared to be, to 

 connect it trigonometrically with the Cambridge Observatory. For this 

 purpose, a base was measured along the ridge of the roof of King's College 

 Chapel, by means of two deal rods terminated by brass studs, the exact 

 lengths of which were determined by comparison with a standard belonging 

 to Professor Miller. The extremities of the base were then connected by 

 a triangle, with a station on the roof of the Observatory at St John's, 

 from which, as well as from the two former points, a signal post on the roof 

 of the Cambridge Observatory could be seen. The angles at the extremities 



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