168 
SECOND REPORT- 1832 , 
are others to which we may look as not far distant. The survey 
of Ireland that has lately been and is now going forward, is, I 
suppose, in accuracy and in excellence of arrangement, (I am 
not speaking of the minutiae of the map, but of the principal 
triangles, by which the great distances north and south or east 
and west are to be measured,) superior to every preceding sur¬ 
vey. Little is now wanting for the measure of an arc of meridian 
but the observation of zenith-distances of stars at its extremi¬ 
ties. The country is also favourable for the measuring an arc 
of parallel of considerable extent: and a new method of pro¬ 
ducing intense light, introduced into practice by one of the 
gentlemen employed on the survey, will probably give the 
means of determining the differences of longitude on a long 
arc without the errors produced by intermediate stations. It 
is also understood that our Government have long contemplated 
the repetition or extension of Lacaille’s measure at the Cape 
of Good Hope : and several circumstances lead me to hope 
that this undertaking, which would perhaps contribute more 
than any other to our knowledge of the earth’s figure, will ere 
long be seriously taken up. The extension of Struve’s arc is in 
contemplation. 
I may state here (though not immediately connected with the 
subject,) that a vast number of latitudes and longitudes have 
been determined, accounts of which are to be found in the 
Transactions and periodicals. Of the longitudes, one of the 
most important is that of Paris, determined by instantaneous 
signals as above described (see Phil. Trans . 1826 and 1827 ). 
The method of determining longitudes by transits of the moon 
has been pretty generally introduced (for which in this country 
we are indebted principally to the zeal of Mr. Baily) ; and the 
longitude of Paris has been determined by this means also 
{Conn, des Temps 1825). Surveys also, of different degrees of 
merit, have been going on in almost every part of the Continent. 
Of pendulum experiments, the most valuable series is that 
made by Captain Sabine in almost every practicable latitude. 
Invariable pendulums which had been observed in London (to 
ascertain the number of vibrations made per day,) were observed 
in the same manner at all the stations, and again in the same 
manner on returning to London. In this manner, without as¬ 
certaining the absolute force of gravity at any one place, the 
proportion at different places is found probably with greater 
accuracy than by any other method. This is the method com¬ 
monly adopted by the English experimenters. Experiments 
were previously made at several places in Britain by Captain 
Kater; and others have been made in different parts of the 
