The fact of the Danube forcing its way through the Carpathian chain in this remarkable manner is a very interesting problem to the geologists, and deserves more careful investigation at their hands than perhaps it has yet received.  They seem pretty well agreed in saying that there must have been a time when the waters were bayed back, and when the vast Hungarian plain was an inland sea or great lake.

Professor Hull, in a recent paper on the subject,[2] states the fact of the plains of Hungary being “overspread by sands, gravels, and a kind of mud called loess, or by alluvial deposits underlaid by fresh-water limestones, which may be considered as having been formed beneath an inland lake, during different periods of repletion or partial exhaustion, dating downwards from the Miocene period.”

The Professor goes on to say that “at intervals along the skirts of the Carpathians, and in more central detached situations, volcanoes seem to have been in active operation, vomiting forth masses of trachytic and basaltic lava, which were sometimes mingled with the deposits forming under the waters of the lakes.  The connection of these great sheets of water with these active volcanic eruptions in Hungary has been pointed out by the late Dr. Daubeny.  The gorge of Kasan, and the ridge about 700 feet above the present surface of the stream, appear to have once barred the passage of the river.  At this time the waters must have been pent up several hundred feet above the present surface, and thus have been thrown back on the plains of Hungary.  It was only necessary that the barrier should be cut through in order to lay dry these plains by draining the lakes.  This was probably effected by the ordinary process of river excavation, and partly by the formation of underground channels scooped out amongst the limestone rocks of the gorge.  These two modes of excavation acting together may have hastened the lowering of the channel and the drainage of the plains above considerably; nevertheless the time required for such a work must have been extended, and it would appear that while the great inland lakes were being drained, the volcanic fires were languishing, and ultimately became extinct.  Hungary thus presents us with phenomena analogous to those which are to be found in the volcanic district of Central France.”  It is a significant fact that even at the present day the waters of the Platten See and other lakes and swamps are diminishing, showing that the draining process is still going on.

The extent of the great lake of prehistoric times is forcibly brought before us by the fact that the Alfoeld, or great plain of Hungary, comprises an area of 37,400 square miles!  Here is found the Tiefland, or deep land, so wonderfully fertile that the cultivator need only scratch the soil to prepare it for his crop.