59 



the roof. The height from the ground to the top of the balustrade 

 surrounding the house is thirty-three feet, and to the top of the 

 dome is fifty-four feet. It has three wings : the eastern and the 

 western twenty-six feet three inches long, twenty-one wide, and 

 eighteen feet high ; the southern twenty feet long, and same width 

 and height as the others ; a passage-way ten feet square divides it 

 from the house. The masonry for the foundations of the walls and 

 piers is of the most massive and durable kind the greater portion 

 of that for the piers and circular wall being laid with the best hy- 

 draulic cement. The piers of granite were all erected in July, and 

 the brick-work completed early in October last; the roofs have 

 been sheathed, and the coppering will be finished in a few days; 

 a part of the floors has been laid, the furnace for heating the build- 

 ing put up, the cast iron work for the revolving dome fitted, and 

 plastering commenced. Mr. GILLISS expects to complete the work 

 during the month of May next. 



The magnetic observatory is ninety feet to the southwest of the 

 preceding, and is, with its entrance-way, entirely below the ground, 

 the roof of the former being rather more than four feet from the 

 surface ; the entrance to it is from the basement, through a subter- 

 ranean passage ninety-three feet long. This observatory is in the 

 foim of a cross; is seventy feet long in each direction, ten feet 

 wide, and ten feet high. It is built entirely of heavy North Caro- 

 lina heart pine, secured throughout with wood pins and copper 

 nails, on dry-powdered clay, rammed hard around the outer plank- 

 ing, and is so constructed that any piece may be taken out for 

 repair. An inside sheathing permits the air to circulate freely 

 around it, to prevent internal dampness ; and an octagonal dome 

 in the centre, fitted with double windows, admits sufficient light for 

 ordinary purposes, while the volume of air between the windows 

 is such as will prevent sudden changes of temperature. This 

 building was covered over early in August, and is completed, ex- 

 cept a little paint-work. The range of temperature within it, since 

 fitting the door and windows, as shown by self-registering ther- 

 mometers, has been from 55 to 58| Fahrenheit, equal 3^. 



The great telescope and the comet-searcher will be completed within 

 the specified time at Munich, viz. January 1st, 1844; the mural 

 circle will probably be shipped from London about the 1st of De- 

 cember ; the transit for prime vertical, made by PISTOR, at Berlin, 



