Baron Humboldt on Rock Formations. 63 
Switzerland, of England, of Italy, of Poland, and of Spain. Du- 
ring these excursions, my attention was particularly directed to 
the relative position of formations, a phenomenon which I cal- 
culated upon discussing in ‘a special work. On my arrival in 
South America, and while at first traversing in different direc- 
tions the vast deposites which stretch from the maritime chain of 
Venezuela to the basin of the Amazon, 1 was singularly struck 
with the conformity of position which the two Continents present. 
(See my first sketch of a Geological Table of Equinoctial Ameri- 
ca, in the Journal de Phys.., vol. liii, p. 38.) Subsequent obser- 
vations, which included the Cordilleras of Mexico, of New Grena- 
da, of Quito, and of Peru^ from the 21st degree of north latitude 
to the 12th degree of south latitude, have confirmed these first 
perceptions. But in speaking of analogies which are observed 
in the relative position of rocks, and of the uniformity of those 
laws which reveal to us the order of Nature, I might adduce a tes- 
timony otherwise of more weight than mine, that of the great 
geognost whose works have thrown the greatest light upon the 
structure of our globe. M. Leopold de Buch has pushed his 
researches from the Archipelago of the Canary Isles to beyond 
the Polar Circle to the 71st degree of latitude. He has discovered 
new formations situated lietween others already known ; and, in 
the primitive as in the transition deposited in the secondary as well 
as in the volcanic, he has been struck with the great features by 
which the table of formations is characterized in the most distant 
regions. 
(To he continued.) 
Art. VII. — Description a simple.^ cheap ^ and accurate Me- 
thod of experimenting on small quantities of Gases-) hy means 
of Bent Tubes, By Mr William Kerr. 
The greatest obstacles to experimental research that have hi- 
therto presented themselves to young chemists, and even to pro- 
ficients in the science, are the expence of the requisite appara- 
tus, and the want of room to contain them. This has especially 
been the case with respect to apparatus for experimenting on 
