OF THE UNITED STATES. 369 



across without taking; so much light from the telcscoi)c as to 

 produce any impediment. 



'I'iie easy motion of these shutter?;, and their close shut- 

 ting, against drifting snow [)articuluriy, is an object to be at- 

 tended to carefully, which cannot be described liere. 



The second instrument, for which a separate stand was to 

 be prepared in the observatory, wastlie /enith sector. 'I'his 

 was intended to i)e placed upon the conic pillars/, and to have 

 a large and suitable aperture in the roof, like that for the 

 transit. But as the zenith sector is not yet obtained, all ar- 

 rangements could be merely preparatory ; and they could 

 only be well adapted when tho, instrument sliould be at 

 hand. 



Wiien at any fulure time a mural circle should be added 

 to the o!)scrviitory, tliis was intended to take the place of 

 the sector, and tiie roof between tlie corresponding windows 

 to be opened as for the transit. 'I'he sector would then be 

 removed to tlie corresponding situation on the other side of 

 the transit,«wliere now the observer's and guard rooms were 

 placed, the partition being taken away, and an addition of one 

 or two windows breadth being made to the east of the build- 

 ing to provide these necessary rooms. 



The entry wouUl still remain the same, and it must be ob- 

 served, that all direct communication between the actual 

 observatory and any other room which may be heated in 

 winter, must be avoided. 



These rooms must be placed in the cast side of the build- 

 ing, and the fire place as much as jjossible towards the south- 

 east, because the north-east wind is in this country the rainy 

 wind, and therefore the smoke of the chimney, wliich woidd 

 obstruct the observations, can only be i)rought by the wiud 

 over the observatory, when the weather would otherwise 

 not allow the oiiservation to l)e made ; and with all other 

 winds which accompany fair wealher. it will be (bi\cii from 

 ihe observatory so as never to be incommoding. 



The floor of the observatory is su|)ported upon separate 

 pillars of masonry h. h. built in the cellar, and touches neither 



