Language /
Use of A/An/The ...... Articles [186]
Generally, I believe there are "hidden" reasons behind what we call exceptions in language. They are exceptions because language has changed, yet the old, logical and easily explicable forms survive, but are called "exceptions". (One example of this is that we say "we Wrocławiu", but we say "w Krakowie" in Polish, although both are masculine names of towns ending in -w.) Reasons for exceptions may be thus historical or may find their causes in our ancestors' "mentality", one that we don't share any longer. I believe that the ancestors of English people had perhaps their own reasons to put
the before names of rivers or mountain chains, while they did not do so with names of towns or individual mountains (I would very much like to discuss it some other time). An example of ancestors' mentality would be using names of countries or regions in Polish. If we go back to the 10th century, we discover that only the names of the then neighbours of Poland are used either with "na" or in plural or both together. Names of the rest are typically in singular and preceded by "w" in the locative case, as in "
w Anglii, we Francji, w Rosji". If we travel clockwise from the north-east, we would find names with the "na" preposition and in the singular : na Litwie (na £otwie
per analogiam), na Rusi, or na Ukrainie, na Słowacji; then the plural appears and the na is continued : na Węgrzech (a neighbour of Poland those days), na Morawach, then the na is abandoned : w Czechach, although na £użycach (!), w Niemczech, and w Prusach.
Interestingly enough, the "outer" regions of Poland are treated in the same way, as neighbours of Poland. In the language, Poland confines itself only to Wielkopolska and Małopolska (which was in fact quite true in the 10th century), so we have :
na Mazowszu, na Śląsku, na Pomorzu, na Kaszubach, na Kujawach.
[It is my own hypothesis, however, so it is subject to challenge.] 