The unfortunate Cass-Herran Treaty with New-Granada, after being shipwrecked twice, has at length reached Washington in charge of our Minister, Ex-Senator JONES of Iowa, who returned by the Ariel. It was first lost on its way to Bogota for ratification, on the Magdalena River, and subsequently, after ratification, on the passage from Carthagena. Even now, however, its benefits cannot be realized before the passage of a law by Congress providing for a commission for the settlement of claims under it, and making an appropriation to defray the necessary expenses. Gen. JONES, it is understood, is very popular at Bogota, and will soon return there.

Some additional European news by the City of Washington is telegraphed from St. Johns. Further accounts of the massacres in Syria show that the Turkish authorities are secretly instigating the Druses to the commission of these atrocities, or, at least, have refused to interfere to put a stop to the great sacrifice of life.

The Prince of Wales is expected to land at Halifax shortly before noon to-day. Great preparations have been made for his reception, and the Governor has proclaimed to-day and to-morrow holidays. The city is crowded with visitors.

A political excitement has for a short time past existed at a village in Virginia called Occoquan, growing out of the erection there of a liberty-pole, on which, was displayed a flag bearing the names of LINCOLN and HAMLIN as candidates for President and Vice-President. The chivalrous Virginians of the surrounding country, whose political proclivities are of that intense Pro-Slavery school which forbids the allowance of any exhibition of patriotism which does not fully accord with its own peculiar ideas regarding the "peculiar institution." determined that the pole should come down. On Friday last, accordingly, a party of forty men entered the village and demolished the offending article in the presence, and probably with the connivance, of a company of cavalry sent by Gov. LETCHER to prevent it. The Virginians, it seems, have not yet entirely come to their senses.

Particulars of the riot in St. Louis on Wednesday night last have reached us in the papers of that city. Between twenty and thirty houses of ill-fame were entirely cleared out, and the furniture was burned in the streets. The police were entirely taken by surprise, and the formidable numbers of the rioters prevented any effective demonstration for the prevention of the work of demolition until it had proceeded for upwards of an hour. Some disposition was shown to treat with indignity the women thus driven into the streets, but it was checked. The destruction of property in furniture and clothing must have been immense.

The exhibition of the Great Eastern in this City came to a close on Saturday. During the time she has been here the number of her visitors could not be less, and has possibly exceeded, 200,000. Yesterday, in the view of several thousands, she hauled into the stream, as easily and gracefully as a swan floats upon the water. Today she leaves for Cape May, and after her return, on Thursday she will start, at quite a moderate rate of fare, for Old Point Comfort, Annapolis Roads and Baltimore. She will return to this port on the 6th August, but what will be done with her until she takes her departure for Europe on the 16th is not yet fully decided. It is thought she may take an Eastern trip to Boston and Portland.

The Stock Market, on Saturday, continued active, and prices were generally higher than on Friday; closing firm. The export of Bullion by the Vanderbilt and City of Baltimore amounted to $2,520,000. The Money and Exchange markets closed steady.

Flour was in fair demand, and desirable lots were firm. Wheat and Corn were inactive. Provisions were lightly dealt in. Groceries were inquired for, at uniform quotations. Most other branches of trade exhibited no remarkable changes. There were 448 vessels in port.

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David Upton