MEMOIRS 
OF THE 
AMERICAN ACADEMY. 
III. 
On the Practice of Circummeridian Altitudes at Sea or on Shore. 
BY CAPTAIN W. F. W. OWEN, R. N., 
NAVAL SURVEYOR. 
1. Find the number of seconds that the sun has less altitude 
at (1™) one minute from the meridian than the meridian altitude; 
call this a’. It is found by this form, or, in some books, by a 
table. 
Ex. Latitude, 44 26 log. cosine, 9.854 
Declination, 20 6 log.cosine, 9.973 
Difference, = Mer. Zen. Distance, 24 20 log. cosecant, 0.385 
Constant log. 0.293 
all=3!1.20 log. 0.505 
2. Within a convenient time from the meridian take altitudes 
and the time by any common watch, noting seconds; generally 
it will be more convenient, and sufficiently precise, to note the 
times to tenths of a minute. 
3. If convenient, altitudes should be taken about one minute 
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