A letter from Marseilles of the 3d inst. announces the arrival there, by the mail steamboat Mersey, of the P re Est ve, superior of the missionaries in Syria. He has come to France to give an account to the French Government of the massacres and plunder which have taken place in the Lebanon. He states that at Damascus alone more than 8,000 Christians have been put to death. The number of victims to Mahomedan fanaticism throughout Syria amounts to from 15,000 to 16,000.

A letter from ABD-EL-KADER himself gives us the most authentic account yet received of the massacres at Damascus. The Emir writes to the managers of the silk works at Krey:

DAMASCUS, 27th Zilhege, 1270 (July 18.)

"Dear and honored Friends, -- I greatly desire to see you, and pray Allah to preserve you. I have received your honored letter, dated July 13, inquiring what happened to the Christians at Damascus. In answer, you are informed that on Monday, July 9, at about 2 in the afternoon, the war broke out, in consequence of a punishment inflicted upon a few Mussulmans who had insulted the Christians. These Mussulmans, in a state of frenzy, rushed, armed to the teeth, to the Christian quarter, and began salying, burning and pillaging at the same time. The Turkish soldiers came to assist them, under the pretence of putting an end to the disturbance, but making common cause with the rioters, and killing, robbing, and plundering with them. A few old Mussulmans made efforts to stop the business, but the Turkish officers had no wish for peace, and, on the contrary, hounded on their soldiers against the unfortunate Christians, the soldiers being aided by hordes of plunderers belonging to every sect. Seeing matters were so desperate, I lost no time in taking under my protection these unfortunate Christians. I sallied forth, taking my Algerines with me, and we were able to save the lives of men, women and children, and bring them home with us. This state of things lasted Monday and Tuesday, during which the rioters did not cease to kill, burn and immolate the Christians, without the Governor affording them any help. I sent for M. LANUSSE, the French Consul, and other Frenchmen, to protect them from the fury of the mob. On the Wednesday, under the pretence of two Mussulmans having been found murdered, which was not the case, the war recommenced. Yet Damascus has a Governor; but it is the same thing as if it had not one. For me, I deplore the disaster which has befallen the Christians. The places where their houses stood cannot be recognized; all their dwellings are reduced to ashes. The number killed is not yet known, but it is estimated at 3,300. All the Europeans and Christians I have collected are in safety in my house. I provide them with all they want, and pray Allah to save the unfortunate Christians from those fanatics. ABD-EL-KADER-BEN MAHI-EDDIN."

The Moniteur says:

The Emperor, wishing to give ABD-EL-KADER a token of the sentiments which his noble conduct at Damascus has inspired, has conferred on him the Grand Cross of the Legion of Honor.