OBSERVATORY. 
explicable by any caufe at prefent generally allowed. He 
has found a difference between the zenith 
8. 
rmagh Obfervatory —At Armagh, the metropolitan cit 
of a large 
hath Phos om RAK tat t 
this city, and it is faid that he thought this plan would be 
greatly promoted by previoufly erecting an obfervatory and 
mufeum here, which his lordfhip accom plifhed 
of about 15,000/. 
The obfervatory is erected on the fummit of a gently 
rifing hill, about go feet above the general level of the town, 
and furrounded by feveral undulating hills all nearly of the 
fame altitude. ‘This building is founded on a bafe of lime- 
ftone, and all the walls are of large hewn ftone, and of the moft 
firm and iubftantial workmanfhip. e tower, which joins 
the dwelling houfe, containsa very fine equatorial by Trough- 
ton, fixed upon a large pillar, which is raifed fo high that 
the inftrument in the dome can overlook all the buildings. 
To the eaft of the houfe ‘is a range of buildings for the 
tranfit room, and other aftronomical purpofes. he prin- 
cipal inftruments, befides the equatorial and tranfit, are 
fhaw of London, and Crofsthwaite of Dublin. 
i iberal income is allowed to the 
principal aftronomer, and a good fa It 
has b i 
church of St. 
Irifh Academy, chiefly o 
fervations, particularly on the fixed ftars, are confidered very 
accurate, and fome of his declinations have been tranferibed 
into the Philofophical Tranfaétions of the Royal Society 
of London in 1806. 
The regiftered obfervations here are thofe made with the 
tranfit inftrument and equatorial ; and alfo am account of the 
temperature and wei he atmofpl Of thefe, a feries 
of about eighteen years is preferved. The right afcenfions 
npared with the fixed ftars, are re- 
+t OT 
n kinds of good. He fpent a 
long life in a€ts of public and private beneficence, and his 
work was the obfervatory, which he began in his 84th 
year; and which he juft lived to fee finifhed, 
damps, which not only injure the inftruments, and 
—The defcriptions of the princi 
e fituation fhould be fufficiently elevated to command a 
view of the horizon, efpecially to the north and fouth ; but, 
very high places are not eligible, as they moftly attract 
clouds, and are in other refpeéts too much expofed to the 
feverities of weather. 
In choofing a fituation, it will be requifite to make pre- 
paration for a meridian mark, and for this purpofe it would 
be convenient if the obfervatory could be placed in the 
meridian line of fome building, or other permanent object,. 
upon which the mark may be made, and this is done as 
-foon as the tranfit inftrument is fet correétly in the meridian, 
by which it may be afterwards regulated. (See Transit 
Inflrument.) 1f two meridian marks can be fet up, one north, 
nd the other fouth, it will be defirable, and they fhould 
not be lefs than 500 yards diftant from the obfervatory : the 
farther the better, provided they are vifible. The obferver 
fhould have free accefs to them, as it may be neceflary fome- 
times to. illuminate them by night. Thefe marks ought to 
be nearly on the fame level, and not fubject to be ob{cured 
by grofs exhalations, as fuch are {uppofed to create horizon- 
tal refractions, and to make the marks appear out of the 
meridian. 
The foil fhould be naturally dry, which is generally the 
cafe when it is of a gravelly or ftony kind; but clay foils 
that do not foon abforb the rain caufe exhalations and 
ob{cure 
the atmofphere, but greatly increafe the irregularities of 
refraCtion. 
The foundation fhould be of the moft folid kind, and 
» 
or fuperftruGure. 
The building fhould therefore be of folid and fubftantial 
inftrument. 
With refpe& to the other apartments, their number muift 
depend on the number of inftruments to be ufed, whether 
at 
