NOTES. clxiii 



"Ces differences, quant a la richesse en silice, entrela pate et le feldspath," 

 adds Charles Deville, " paraitront plus frappantes encore, si 1'on fart attention 

 qu'en analysant une roche en masse, on analyse, avec la pate -proprement dite, 

 non seulement des fragments de feldspath semblables a ceux que Ton en a extruits, 

 mais encore des mineraux qui, comme 1'amphibole, la pyroxene, et surtout le 

 peridot, sont moins riches en silice que le felspath. Get execs de silice se mani- 

 feste quelquefois par des grains isoles de quartz, comme M. Abich les a signale's 

 dans les trachytes du Drachenfels, et comme moi-meme j'ai eu 1'occasion de les 

 observer avec quelque e'tonnement dans le dolerite trachytique de la Guade- 

 loupe." 



" If," says Gustav Rose, " we add to the remarkable table of the quantity of 

 silicic acid in the Chimborazo-rock the result of Rammelsberg's latest analysis 

 (May 1854), we find that Deville's result falls just intermediate between those 

 of Abich and Kammelsberg. We obtain : 



Chimborazo-rock. 



Silicic acid 65'09 Abich (specific gravity, 2'685). 

 63-19 Deville. 

 62-66 Deville. 

 59-12 Rammelsberg (specific gravity, 2'806) " 



In a newspaper appearing at San Francisco, in California, " 1'Echo d u Pa- 

 cifique," there is an account, on the 5th of January 1857, from a French tra- 

 veller, Monsieur Jules Remy, of his having succeeded, on the 3rd of November 

 1856, in company with an Englishman, Mr. Brenclday, m reaching the summit 

 of Chimborazo. He adds, " so wrapped in mist that as we mounted we were 

 not aware of it {sans nous en douter)." He observed the boiling point of 

 water at 77"5 cent., the temperature of the air being 1'7 cent., and on calcu- 

 lating the elevation from hence, " according to a hypsometric rule tested during 

 repeated journeys in the Sandwich Islands," he was surprised at the result he ob- 

 tained. He found that he had been at a height of 6543 metres (21,470 feet), 

 differing only forty French feet from that given for the top of Chimborazo by 

 my trigonometric measurement, taken in June 1803, from near Riobamba 

 Nuevo, in the high plain of Tapia. This agreement between a trigonometric 

 measurement, and one founded on the boiling point of water, is the more sur- 

 prising, because my result involved, as must always be the case in the Cordilleras, 

 a barometric portion (for the height of the plain of Tapia, 9484 feet), which for 

 want of corresponding observations on the sea-shore, could not have all the ac- 

 curacy that might be desired. (For details, see my Recueil d'Observ. astron. 

 vol. i. p. Ixxii. and Ixxiv.) Professor Poggendorff kindly undertook the trouble 



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