Progress will undoubtedly be slow because the Germans have taken such tremendous pains to pave (in a literal sense) with concrete trenches the way of retreat. British airmen report line upon line of intrenchments where the Germans have defensively furrowed the land behind them for miles. As the Allies advance--and they indubitably will advance--these trenches will in turn be stubbornly defended. It is going to be, I am afraid, a long, weary, and bloody business. Those in England who sometimes complain at the absence of decisive victories may have to wait a long time yet before it can be said that the Germans are in full retreat; for full retreat is the very thing they have guarded against most carefully. In the semi-circle of slaughter around Ypres the trenches of the Allies and the Germans are at nearly all points extraordinarily close together. This means an immense strain on the men. They remain for hours together in cramped, unnatural positions, knowing from experience that an unwise move will bring a bullet from crack marksmen told off to snipe them. This close proximity of the rival forces confounds all the theories of the military writers of the past. According to the army textbooks this war is being conducted in a grossly unprofessional manner. For bringing his men so close to the enemy many a young company commander has received a severe dressing down on manoeuvres. Of course under such circumstances abuse and badinage is continually being bandied across the intervening spaces between the trenches, and the quick-witted Frenchmen generally get the better of it in the war of words. One of them, who came back from the Ypres neighborhood a few days ago, told me a delightful story of a practical joke played upon the Germans, who were entrenched only about thirty or forty yards away from his platoon. One bright spirit was lecturing the enemy and making dialectical rings round them. "Hola, bosches," he cried, "your Kaiser is very brave, isn't he? He wears the Iron Cross, but he doesn't come into your trenches. Tomorrow M. Poincare, our President, will visit us. He does not wear an Iron Cross, but he isn't afraid." On the morrow the Germans saw a top hat come bobbing and bowing along the French trench and heard loud cries of "Vive le President!" Time after time they riddled that top hat with bullets, and still it went bobbing along until the French took it off the spade handle, threw it into the air and howled in derision. Seeing Nieuport Under Shell Fire [Special Cable to THE NEW YORK TIMES.]