42 



ON THE CONSTRUCTION AND USE OF 



surrounding country on the banks of the Nortli River is occupied by country seats, 

 on the slopes and summits of ridges of low hills, and no offensive manufactories 



Dr. Draper's Observatory. 



vitiate the atmosphere with smoke. Our grounds are sufficiently extensive to exclude 

 the near passages of vehicles, and to avoid tremor and other annoyances. 



An uninterrupted horizon is commanded in every direction, except where trees 

 near the dwelling house cut off a few degrees toward the southwest. The advantages 

 of the location are very great, and often when the valleys round arc filled with 

 foggy exhalations, there is a clear sky over the Observatory, the mist flowing down 

 like a great stream, and losing itself in the chasm through which the Hudson here 

 passes. 



The foundation and lower story of the building are excavated out of the solid 

 granite, which appears at the edge of the hill. This arrangement was intended to 

 keep the lower story cool, and avoid, in the case of the metal reflector, sudden 

 changes of temperature. The eastern side of the lower story, however, projects 

 over the brow of the hill, and is therefore freely exposed to the air, furnishing, when 

 desired, both access and thorough ventilation through the door. The second story 

 or superstructure is of wood, lined inside with boards like the story below. They 

 serve to inclose in both cases a non-conducting sheet of air. 



The inside dimensions of both stories taken together are 17| feet square, and 22 

 feet high, to the apex of the dome. This space is unnecessarily large for the tele: 



