344 Dow J- Rodriguez's Observations on the 
instruments with great delicacy, and was possessed of peculiar 
talents for this species of observation, has given us an instance 
of singular irregularity in the observations made at Montjui 
and at Barcelona. 
The latitude of Montjui, determined by a very long and 
regular series of zenith distances, is full 3", 24 less than 
that deduced from a similar series of observations made at 
Barcelona, with the very same instruments, and with equal 
care. Moreover, there is reason to think, from other obser- 
vations, that the latitude of Barcelona (which is supposed to 
be 45") ought to be diminished still one second, so that the 
difference between the observations at Montjui and at Barce- 
lona will probably amount to as much as 4". Local attractions 
are supposed to have been the cause of this irregularity ; but 
then the latitude, as deduced from observations made at Bar- 
celona, should have been less than it appeared by those made 
at Montjui itself; for the deviation of the plumb-line (or of 
the spirit contained in a level) could only be occasioned by the 
little chain of land elevated to 120 or 130 toises, which passes 
to the north of Barcelona in a north-easterly direction. Nov/ 
since the deviations arising from this source would be north- 
ward, the zenith distance of circumpolar stars would be aug- 
mented by that deviation, and consequently the latitude deduced 
therefrom would be diminished by just so much. But here 
the contrary occurs ; for the latitude of Montjui deduced from 
the observations at Barcelona is 48", 23, whilst that obtained 
by direct observations at Montjui is only 45". Hence it seems 
probable, that the cause of this irregularity must be sought 
elsewhere, and that it is not likely to be discovered without 
repeating over again the same observations. 
