The chief effects of the mustard gas are on the eyes and lungs. The first thing you notice is the smell--which is slightly of garlic or mustard--and irritation of the nose and throat. Neither effect is enough to make you feel gassed, and the chief symptoms develop later on. When the gas is strong it is apt to cause sickness and sometimes actual vomiting. Later on the eyes inflame and get very sore, the lids swell and blister, but no permanent injury to the eyes takes place, though the victim may be temporarily blinded. The effects developed in the lungs are equally painful and consist of severe inflammation and bronchitis, which may take some time to get better and if not well looked after may develop into pneumonia. It will thus be seen that for a persistent gas, though not deadly poisonous, mustard gas is a nasty proposition. First the gas does not of itself force a man to protect himself. With the old lachrymators a man either put on his mask or his eyes would smart and water so badly that he could not keep them open. With the Green Cross and similar gases a man either protects himself or dies. But with the mustard gas, though the smell and irritation may be perfectly apparent, the effect is not such as to force a man to don his mask. Yet if he does not do so and continues to live in the vapour unprotected he will certainly become a casualty. It may take half an hour, it may take several hours to come on, but come on it will. Another particular disadvantage of the mustard gas is its persistence. It will hang about in shell holes for many hours and even for days. If it gets into a dugout it is very difficult to get rid of it, and as long as there is enough to produce the faintest smell or irritation of the nose there is enough to bring on serious symptoms eventually. This means that when it is used our fellows are forced to wear their masks for very long stretches of time. The mustard gas is known officially by the Germans as Yellow Cross gas, and the shells are marked on the sides with bright yellow crosses and bands. The paint used for these bands changes colour in contact with the mustard-gas liquid, so that if a shell should leak it at once becomes apparent and can be taken away and buried. The Yellow Cross gas was first used at Ypres and bombardments there were quickly followed by similar ones at Nieuport and Armentières. Enormous numbers of shell of all calibres were employed, including a new and larger size--the 8.3-inch howitzer shell, which holds nearly three gallons of the liquid and can be fired a distance of six miles. At Nieuport more than fifty thousand shell were fired in one night, and equally large numbers were used in deluging the other towns. Since then the numbers used have continually increased, especially when the boche was preparing for an attack or expecting one of ours.