In the year 1828, when the greatest portion of his literary labor had been
accomplished, he undertook a scientific journey to Siberia, under the
special protection of the Russian government. In this journey -- a journey
for which he had prepared himself by a course of study unparalleled in the
history of travel -- he was accompanied by two companions hardly less
distinguished than himself, Ehrenberg and Gustav Rose, and
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the results obtained during their expedition are recorded by our author in
his 'Fragments Asiatiques', and in his 'Asie Centrale', and by Rose in his
'Reise nach dem Oural'. If the 'Asie Centrale' had been his only work,
constituting, as it does, an epitome of all the knowledge acquired by
himself and by former travelers on the physical geography of Northern and
Central Asia, that work alone would have sufficed to form a reputation of
the highest order.

I proceed to offer a few remarks on the work of which I now present a new
translation to the English public, a work intended by its author "to embrace
a summary of physical knowledge, as connected with a delineation of the
material universe."

The idea of such a physical description of the universe had, it appears,
been present to his mind from a very early epoch. It was a work which he
felt he must accomplish, and he devoted almost a lifetime to the
accumulation of materials for it. For almost half a century it had occupied
his thoughts; and at length, in the evening of life, he felt himself rich
enough in the accumulation of thought, travel, reading, and experimental
research, to reduce into form and reality the undefined vision that has so
long floated before him. The work, when completed, will form three volumes.
The 'first' volume comprises a sketch of all that is at present known of