It was on a chilly day, amid falling hail, that he addressed a crowd of people in the castle-yard at York. They had listened already to several speakers, were weary, and about to separate, when Mr. Wilberforce appeared on the stand and began to speak. Silence was at once secured, and so perfectly were they swayed by his words that all signs of opposition or impatience disappeared. For more than an hour, notwithstanding unfavorable circumstances, he held their attention, winning them to harmony with his own political views. This was not all. Before the assembly dispersed, it was whispered from one to another, "We must have this man for our county member." The election of a member for Yorkshire was nigh at hand, and when its results were made known, he found himself in the influential position of "a representative of the tenth part of England." To this same member for Yorkshire, in conjunction with the Prime-Minister of England, we are indebted for the first Parliamentary agitation of a topic which has since been fruitful enough in discussion, --AFRICAN SLAVERY. The introduction of this subject into Parliament, during the administration of Pitt, was by no means the fruit of a sudden impulse, but was rather the matured expression of a series of preliminary efforts. In private circles, the Slave-Trade had been already denounced and protested against, as unworthy of a civilized, not to say a Christian people. In certain quarters, too, the press had become the exponent of these sentiments. Possibly, in their beginnings, no person did more in the exertion of those means which have wrought into the heart of the English people such undying hatred to Negro Slavery than the amiable recluse whose writings can never die so long as lovers of poetry continue to live. Who has not at times turned away from the best-loved of the living poets, to regale himself with the compact, polished, sweetly ringing numbers of Cowper? On the subject of Slavery he had already given expression to his thoughts in language which at the present day, in certain portions of the United States, must subject his works to a strict expurgatorial process. He had exposed to the world the injustice of the system, and had thrown around his words the magic of song.