470 SIR RODERICK I. MURCHISON'S ADDRESS. [May 25, 1857. 



FitzRoy, sliowing that tlie difference of longitude in time between 

 Valparaiso and Paris is 10"-4 in excess. Callao, therefore, would be 

 only 5h. 18' 4" -6 to the west of Paris. The passage of Mercury, how- 

 ever, over the solar disc, which was observed on the 4th of May, 1832, 

 at Lima by Mr. Scholz, again gives for Callao 5h. 18' 13"* 7 west of 

 Paris — supposing the chronometrical differences between Lima and 

 Callao, which I published in the second volume of my Astronomical 

 Observations, to be correct. The electric telegraph, established in 

 May, 1855, has given Oh. 3' 56"* 5 for the difference of longitude 

 between Valparaiso and Santiago. M. Moesta, therefore, places 

 Valparaiso in 4h. 55' 49"-5 ; and I and FitzEoy 4h. 56' 6"'6:' 



After this clear and succinct analysis of so valuable a geographical 

 datum, obtained through an expedition of the United States, the 

 veteran philosopher concludes in these words : " And thus this long 

 endurance of life (cette patience de vivre) has enabled me to 

 witness all these rectifications." * 



In looking to the general configuration of South America, I am 

 further reminded by Baron Humboldt, that the trachytic regions 

 form insulated bands in the Cordillera, such as the volcanic Sangai, 

 to the S.E. of Quito, which is constantly throwing out incandescent 

 scoriae, like those of Stromboli. This insulated trachytic mass, 

 which has a diameter of 45 English miles only, rises out of a granitic 

 and gneissose plateau 16,070 French feet above the sea, thus present- 

 ing an analogy to the structure of the Thian Chan in Central Asia. 



* Having been made acquainted by my friend Mr. Pentland with data 

 respecting Admiral Beechey of which 1 was ignorant, it is due to the memory 

 of my lamented predecessor to state, that in a letter to Admiral Krusenstern, 

 he fixed the longitude of Valparaiso by independent astronomical observations 

 at 4h, 46' 37" 6'", only diflFering 8"'6 from that deduced by Moesta's observations ; 

 and as the latter are probably 3" '7 in error, it follows that there may be little 

 more than one mile between his result and that of Admiral Beechey.* 



The position adopted on the Admiralty Charts, and in Lieut. Eaper's elaborate 

 Tables of Positions, has been deduced solely by means of chronometers during 

 Admiral FitzRoy's surveys ; the latter officer having made few absolute astro- 

 nomical observations ; whilst his chronometrical data are entitled to the greatest 

 degree of confidence. 



I am also informed by Mr. Pentland, that he having made independent observa- 

 tions, similar to those of Admiral Beechey (moon culminating stars) at stations 

 referred trigonometrically and chronometrically to places on the coast, he found 

 for the latter, longitudes agreeing with those deduced from the position of Val- 

 paraiso, as determined by my distinguished predecessor. Thus the position of 

 Arica deduced by Mr. Pentland from observations made at La Paz, and carried 

 on by a series of triangles and chronometers to that place, is identical with that 

 deduced from Beechey's longitude of Valparaiso cariied on by FitzRoy's chrono- 

 metrical chain to the Peruvian port. — R. I. M. — 1st Aug. 1857. 



* See Journal R. G. S., vol. ix. p. 502 ; also Daussy's Positions Ge'ographiquGS, 

 1842, p. 67, &c.— Ed. 



