366 SURVEY or THE COAST 



of these papers, and may at some future time become use- 

 ful. 



The present state of astronomy is averse to tliose vast and 

 splendid buildings formerly erected for observatories which 

 now stand near the smaller buildings forming the actual ob- 

 servatories, and obstruct their view. 



I therefore thought it my duty to propose a comparatively 

 small building, adapted to the instruments intended to be used 

 in it, but still so formed as readily to admit of enlargement, 

 if this should become necessary. 



The principal aim in an observatory building, besides pro- 

 per shelter for the instruments and convenience for tiieir use, 

 is the stability of the instruments them.selves, so that they 

 may be independent of the influence of any motion in the ob- 

 servatory itself, or in its neighbourhood. This object is ob- 

 tained by founding the parts intended to support any instru- 

 ment at some depth in the earth, insulating the building from 

 the surrounding ground by a ditch, and supporting the floor 

 of the observatory itself upon pillars separate from all other 

 parts of the building, and particularly from the pillars that 

 support the instruments. 



The instruments for which my plan was adapted were, — 

 a transit instrument of five feet, an astronomical clock, the 

 eighteen inch repeating circles, and the large telescopes, and 

 a zenith sector of six feet, ordered and yet expected of Mr. 

 Troughton. It was also intended to make this observatory 

 the place of deposit of the standards of weights and mea- 

 sures, the chronometers or any other instruments of the col- 

 lection when not in use, and of an appropriate library. 



Plate VIII. fig. 1, is the plan of the observatory, at the le- 

 vel of the floor ; fig. 3 the vertical section, in the direction 

 of the meridian, through the transit ; fig. 3 the northern front: 

 and fig. 4 the vertical section in the direction of the parallel, 

 through the transit. 



The whole building is forty-two feet in the direction of 

 the parallel, and twenty-eight feet in the direction of the me- 

 ridian. The walls are at least two feet and a half thick below 



