(From our own Correspondent.)

London, July 21, 1848.

Dear Douglass,—Doubtless you have heard ere this, that the Archduke John, of Austria, has been elected Regent of Germany, (or Administrator of the United German Empire,) by the Parliament assembled at Frankfort. He is the uncle of the reigning Emperor, and has reached his sixty-sixth year. In his early career, and during the stormy times of the first French revolution, he was thrown into active life, and in 1800 he was placed in command of an Austrian army, and became extremely popular. When released from military duties, however, he preferred living the simple life of a mountaineer in the Styrian hills, to a residence in the capital. He served in the campaigns of 1813 and 1815: but when peace was restored and the arbitrary and oppressive ministry of Metternich commenced, which this noble man ever condemned, but had no means of actively opposing, he separated himself entirely from the court, became an exile from Vienna, and lived for many years in retirement at Gratz. Metternich fearing both his popularity and his opinions, kept a strict watch on his movements. He revisited the Tyrol in 1845, and was so enthusiastically received, that 'tis said the Viennese press were prohibited from publishing an account of his reception. One anecdote told of him is, that, at a public dinner held a few years since, he gave the toast—" No Austria—no Prussia, but a united Germany!" and it is added, that this has secured him much of his present popularity. When the recent revolution in Vienna broke out, he at once re-entered public life, and prevailed on Metternich to resign. Now, that once all-powerful minister is in exile, and the Archduke is regent of Austria, and chief of the German empire.

The latter event is, unquestionably one of immense importance in the history of Germany. In Berlin, of course, the feeling on the subject is of mixed character. The deputation from the German Parliament arrived in Vienna on the 4th inst., and was greeted enthusiastically by the citizens there. To their appeal the Archduke responded formally; and on the 11th inst. the newly appointed Regent entered the good old city of Frankfort in triumph—where, it is said, the joyous acclamations of the people were unprecedented. Since then the last sitting of the long famous German Diet has been held, and the President thereof has resigned all power into the hands of the Regent. A new ministry is formed, under the direction of Baron Gagem. Joyful demonstrations of every kind are taking place during this important visit of the Regent to Frankfort; and the enthusiasm seems to be universal. You can well imagine, that, throughout Europe, the future course and proceedings of this excellent Prince will be watched with exceeding interest.

In my last, I entered somewhat fully into the affairs of France, and the recent insurrection in Paris. The latest reports state, that all remains tranquil there, and a confidence is increasing. General Cavaignac has continued to prove himself equal to the emergency in which he was placed; and with all his confessed mildness and humanity has displayed great promptitude and firmness in repressing all attempts of a seditious character. Arrests are being hourly made of persons compromised in the conspiracy; large sums of money have been found on many of them; and at present the affair is shrouded in great mystery. A correspondent of the Daily News says, "Documents of the highest importance have been seized, which will show from whence proceeds the money distributed, and who were really the chiefs of the insurrection." Ere long the truth must be elicited.

That great and good man, Lamartine, has published an eloquent letter, in reply to the infamous suspicions propagated against him, in which he states, that to see himself "transformed into a professor of civil war, and a preparer of carnage, makes a cry of indignation rise from the inmost recesses of his soul." He is about to quit France and his fickle-minded countrymen, for the East.