Considerations on the probable proportion which the number of known phænogamous plants bears to the entire number existing on the surface of the globe [119]-[125]
The different forms of plants successively noticed. Physiognomy of plants treated in a threefold manner; viz. as to the absolute diversity of forms, their local predominance in comparison with the entire number of species in different phænogamous Floras, and their geographical climatic distribution [126]-[200]
Greatest extension in height or of the longitudinal axis in arborescent vegetation: examples of 235 to 245 English feet in Pinus lambertiana and P. douglasii; of 266 English feet in P. strobus; of 298 and 300 English feet in Sequoia gigantea and Pinus trigona. All these examples are from the north-west part of the New Continent. Araucaria excelsa of Norfolk Island only attains, according to well-assured measurements, 203 to 223 English feet; and the Mountain Palm of the Cordilleras, Ceroxylon andicola, 192 English feet [165]-[168]
These gigantic vegetable forms contrasted with the stem of two inches high of a willow-tree stunted by cold of latitude or of mountain elevation; and still more remarkably with a phænogamous plant, Tristicha hypnoides, which, when fully developed in the plains of a tropical country, is only a quarter of an English inch in height [169]
Bursting forth of blossoms from the rough bark of the Crescentia cujete, the Gustavia augusta, and the roots of the Cacao tree. The largest flowers, Rafflesia arnoldi, Aristolochia cordata, Magnolia, Helianthus annuus, Victoria regina, Euryale amazonica, &c. [203], [240]
The different forms of plants determine the character of the landscape as dependent on vegetation in different zones. Physiognomic classification or division into groups according to external “facies” or aspect, entirely different in its principles from the classification according to the system of natural families. The study of the physiognomy of plants is based principally on what are called the vegetative organs, or those on which the preservation of the individual depends; systematic botany grounds the arrangement of natural families on a consideration of the reproductive organs, or those on which the preservation of the species depends [205]-[210]
On the Structure and Mode of Action of Volcanos in the different Parts of the Earth—p. [211] to p. [241].
Influence of journeys in distant countries on the generalisation of ideas, and the progress of physical geology. Influence of the form of the Mediterranean on the earliest ideas respecting volcanic phenomena. Comparative geology of volcanos. Periodical recurrence of certain natural changes or revolutions which have their origin in the interior of the globe. Relative proportion of the height of volcanos to that of their cones of ashes in Pichincha, the Peak of Teneriffe, and Vesuvius. Changes in the height of the summit of volcanos. Measurements of the height of the margins of the crater of Vesuvius from 1773 to 1822: the author’s measurements comprise the period from 1805 to 1822 [213]-[228]
Particular description of the eruption in the night of 23-24 October, 1822. Falling in of a cone of cinders 426 English feet in height, which previously stood in the interior of the crater. The eruption of ashes from the 24th to the 28th of October is the most remarkable of which we possess any certain knowledge since the death of the elder Pliny [228]-[235]
Difference between volcanos with permanent craters; and the phenomena (very rarely observed within historic times) in which trachytic mountains open suddenly, emit lava and ashes, and reclose again perhaps for ever. The latter class of phenomena are particularly instructive to the geologist, because they recall the earliest revolutions of the oscillating, upheaved, and fissured surface of the globe. They led, in classical antiquity, to the view of the Pyriphlegethon. Volcanos are intermitting earth springs, indicating a communication (permanent or transient) between the interior and the exterior of our planet; they are the result of a reaction of the still fluid interior against the crust of the earth; it is therefore needless to ask what chemical substance burns, or supplies materials for combustion, in volcanos [235]-[238]