After an appetizing supper eaten in the cellar with the officers of the field ambulance, we medical officers took turns attending to the many wounded who were arriving. All went well till eleven o'clock that night, when we heard the whirr of gas shells coming in our direction. As they burst close to us, we soon smelt their penetrating, pineapple odor. The Huns continued to pour them in large numbers in our direction, and, as the town of Vimy is in a hollow at the foot of Vimy Ridge, the atmosphere soon became laden with the poison gas which, being heavier than air, sinks to the bottom of any hollows. The air in our cellars became saturated with the filthy, death-dealing gases in spite of the wet blanket which we hung over the entrance to prevent their entering. Had we been able to stay in the cellar and keep the blanket tightly placed over the entrance, our misery would have been much less, but wounded were coming in from all directions and we had to keep going in and out, in turns, to the cellar in which we did our dressings. The gas kept thickening every minute. To add to the discomfort these gas shells contained two gases. One entered the lungs, causing congestion of their tissues followed by inflammation, suffocation, and death if a sufficient amount were inhaled; the other, lachrymatory gas--called tear shell gas by the soldiers--which not only inflames temporarily the conjunctiva of the eyes, but is cursedly irritating while it lasts. Naturally we quickly adjusted our gas masks. But, as it was fifty feet from one cellar to the other, and we dared not flash lights to pass over the stone and mortar of the fallen walls, we found it necessary to remove our masks for moving, as well as for the purpose of tying up the wounds in an acceptable manner. Thus, by midnight, our eyes were as red as uncooked beefsteak and they felt as if they had been sandpapered. Our lungs on each respiration felt as though they were gripped in a closing vise. The gas masks act by filtering the inhaled air through a chemical, which neutralizes the poisonous materials in the gases. When we removed them we had severe attacks of coughing which were relieved only by breathing through the mouthpiece of the masks. Hours dragged slowly by. Still the whirr of approaching shells and the soft thud of their bursting continued. Misery? Never elsewhere had we experienced anything akin to it--the inflamed eyes; the suffocation in our lungs; the knowledge that inhalation of sufficient of the gas would put us into Kingdom Come. We knew that we could easily get out of this poisonous atmosphere by climbing to the top of Vimy Ridge, only a few hundred yards behind us. But we did not, for that would be deserting our posts.