This was one of the ways in which the Saracens employed the celebrated "Greek fire"--an inflammable compound that is understood to have been a mixture of petroleum, saltpeter and pitch. The chief horror of it, from the Crusaders' point of view, was that it was unquenchable. Mere water had no effect upon it. Hence they were sure that it must be of diabolical origin. But the up-to-date incendiary bomb is a great improvement on its original of the Middle Ages. The modern contrivance is thoroughly scientific, and it does its destructive business with certainty and dispatch. No less effective are the gas bombs which were introduced by the German soldiers at Rheims, and which when exploding near the trenches occupied by the French and English threw off vapors and poisonous gases which killed or overwhelmed thousands of brave men. These devices used in violation of all rules of civilized warfare sent hundreds to the hospitals. Seventy-five victims were taken at one time from the trenches to the hospital at Zuydcoote, north of Dunkirk, where it was found that some of those who had inhaled the fumes turned a violet tinge. Altogether it was estimated that from 3000 to 5000 men were affected by the gas fumes in this first onslaught and at least 10 per cent of those who were overcome succumbed to the deadly fumes. Many of those who inhaled the poisons expectorated blood and for days afterward were racked by terrible coughing. In many cases fever developed in a few days ending with pneumonia. When the men were not sufficiently poisoned to cause death they were so affected that their usefulness as soldiers was ended for all time. The poison made them confirmed invalids. INTRODUCTION OF GAS MASK. Naturally human ingenuity was called into play to protect men against the poisons and the gas mask came into being. These were of many types. The early creations consisted primarily of a nose and mouth covering with a receptacle for inclosing a sponge or gauze soaked with a chemical which possessed the power to neutralize the gas fumes. Such devices have been used by fire fighters in large cities the world over where the men battling to save buildings have been compelled to enter smoke-filled rooms and cellars. Other types which have proven more effective are designed after the fashion of the diving apparatus, and having a small tank of compressed oxygen with feeding tubes running to the mask. The oxygen combines with the contaminated air breathed through absorbent cotton or sponge and provides the wearer with the proportion of oxygen necessary to existence. And even the horses have been provided with such masks.