A Method for ascertaining Latitude and Time. 187 
this notable experiment, or they would have prevented Mr. 
M. from thus committing himself, and would have whis- 
pered him that most practicad tuners, if they do not actually 
count the beats while tuning, make use of their recollection 
from habit, of the frequency which they have in each 
concord to be tuned, for adjusting the same, according to 
the temperament they have been taught, or are used to, and 
never resort to the melody in tuning. I beg to subscribe 
myself _ 
London, No Friend to TuninG Ouacks. 
8th March, 1811. ~ 
XXXII. A Method for ascertaining Latitude and Time hy 
means of Two known Stars. By M. Detamere, 
Translated from the ** Connoissanee des Tems” by Mr, 
FIRMINGER, many Years Assistant Astronomer atthe 
Royal Observatory, Greenwich. 
{Concluded from p. 35.] 
dh sin A aed 
‘OS @ 
so that the case which appeared most unfavourable is on 
the contrary the easiest, and in which the error may be a 
minimum. 
Let us suppose, lastly, that A = A’= 90°, or that the two 
stars have been observed at the first vertical: in this case the 
error will be nought.—In fact, cot g = cot d cosa = cot? 
cos (A — ¢) = cot ® cos.§ cos A + cot & sin @ sin A; of 
tang &’ cot ¢ cos A = cos § cos A 4 sin 9 sin A tang 6’ cot ¢ 
: tang 0" cot 3 
= tang A sID tang aA = ee el 
cos § + tang a 9, g sing cot 9, 
Tue formula (5) is reduced to the term — 
and cot g = cot 2 cosa. 
It is evident that the errors dh and dh’ are nought, since 
hand fh’ need not be observed. i 
This case is, therefore, the truest of all, and the one that 
would be found most favourable, if it was easy to observe in 
the vertical. An znstrument des passages (transit instrument) . 
would be required for that purpose, directed east and west. 
Let us see, lastly, the case wherein A’, though not equal 
to it, differs from it a shght quantity: in this case x being 
equal to A—A’, 2 will be very small. 
; s —dh sin (A — dh’ si 
The formula (4) becomes —~2 0) —*) + di sin & 
mea Man ome bd 
dh' sin A—dh sin A+ Qdhsin Asin?4 w+dheosAsing _— (dh’— dh) sin A 
sin 7 sin wv 
+ dh sin A tang } 2 + dhcos A, dh cos 
