Geographical Collections. 285 
ever impracticable, that when once broken up, they might, more especially in 
narrow straits as those of the Fury and Hecla, never unite again with such 
strength, but that the passage would, with the return of spring, be opened again 
at a much earlier season than when visited by the lirst navigators of these inhos- 
pitable seas. 

Results of the Geographical and Geognostical Labours of Mr. PENTLAND in 
Southern Peru; by Mr. ALEXANDER DE HumBotpT. (Hertna, T. 
XVIII. Cah. 1.) 
“¢ THE results which I communicate to geographers and to natural philosophers, 
(says Mr. de Humboldt,) may be ranked amongst the most remarkable with 
which science has been enriched for some time. Mr. Pentland, a traveller whose 
labours, though not numerous, are full of merit, and have "yearn published in the 
memoirs of the Geological Society of London, is personally known to me for se- 
-veral years back, and I look upon him as a distinguished naturalist. He has 
studied several years at Paris with Mr. Cuvier, and profited by all the instruc- 
tion which that excellent school can furnish. ‘To an extended knowledge of zoo- 
logy and comparative anatomy, he added, shortly before my departure for Ame- 
-rica, the practice ot geological research, which he put into exercise in a journey 
-to the south of France, and in parts of Italy. He was preparing himself for a 
scientific expedition to the East Indies, when he was joined to the British em- 
bassy to Peru. 
I immediately foresaw the excellent results of the mission, and I begged the 
illustrious minister of state, Mr. Canning, to send Mr. Pentland, provided with 
instruments, on the elevated and unknown plateau of Titicaca. Mr. Pentland 
. obtained all the astronomical and hyposometrical instruments that he desired. I 
_ do not know if he had occupied himself in Europe with geographical and astro- 
nomical observations ; but I can attest that he had made in Italy several very 
exact barometrical measurements for the outline of his geognostic profiles. It 
“must have been easy for him, in a long voyage round Cape Horn, to accustom 
himself to the use of chronometers, and of instruments of reflexion; and we may 
judge of the degree of exactness of his measurements, if, as we have every reason 
to hope, he publishes the details. 
If it is true, as Mr. Pentland assures us, that the limits of eternal snow are more 
elevated by 260 toises in the plateau which he has explored, than in the chain of 
the Andes of Quito, it is easily understood why to the eye the summits of the 
_ Tlimani and the Sorata do not appear to surpass the Chimborazo. 
» In the absence of direct measurements, the only means of judging are relative : 
they are, at the same.time, the elevation of the summits above the limits of eter- 
nal snow, and the distance at which this summit remains visible in the plain. 
- The mountains in the south-west of La Paz, and in the province of Larecaja, 
have always been considered as very lofty; but as they had never been measured, 
_ we had not even any idea of the height of the plateau which serves them as a 
basis. It had been hitherto impossible to establish any relation between the 
_ Chimborazo and the Sorata. 
In point of fact, the height of mountains is not a geological phenomenon of so 
much importance, that we must feel surprized if culminating points are discover- 
ed in an unexplored chain more elevated than those anteriorly known, and the 
number of summits measured from Cape Horn to the peak of Tolima, and to the 
Sierra Nevada of St. Marta, is very small.” 
This introduction of Mr. de Humboldt suffices to establish the degree of con- 
fidence which may be given to the observations of Mr. Pentland, one. already in- 
dicates the regions which he has explored. We shall now extract the positive 
documents, which he communicated to his illustrious predecessor in two letters, of 
