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Description of the Observatory at Cambridge, Massachusetts. 

 Br WILLIAM CRANCH BOND. 



(Communicated to the Academy, November 8th, 1848.) 



The Observatory is situated on an eminence elevated about fifty feet above the gen- 

 eral plain on which are the buildings of the University, and is seventy feet above the 

 tide-waters of Charles River. This height is found sufficient to give from the dome an 

 horizon almost uninterrupted, to within two or three degrees of altitude, in every direc- 

 tion. The grounds appropriated to it comprise six acres and a half. It is distant 

 three quarters of a mile northwest from University Hall, and three miles and a half 

 west-northwest from the State House in Boston. 



Plate I., Fig. 1, is a ground plan of the principal buildings and of those appropri- 

 ated to magnetic and meteorological purposes ; at 



A is the equatorial room and pier. 



B, The transit-circle room. 



C, The prime-vertical apartment. 

 In the smaller buildings, 



a, The situation of the four-foot meridian-transit instrument. 



b, The horizontal-force magnetometer. 



c, The declination magnetometer. 



V and c', The reading telescopes of the magnetometers. 



d, The small altitude and azimuth instrument. 



In the construction of the buildings which protect the magnetic instruments, iron has 

 been entirely excluded. 



The wires connecting with a system of magnetic-telegraph lines, extending to most 

 of the principal cities of the United States, are brought into the building containing the 

 four-foot transit instrument, at a. 



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