Gas fired in shells was of two sorts, lethal and non-lethal. The former was a deadly poison. Unless taken in large quantities, the latter had no fatal, nor indeed serious, effects; designed to irritate the throat and eyes, it caused such sneezing and hiccoughing that whosoever breathed this sort of gas lost temporarily his self-control. Lethal and non-lethal gas were intermingled both by the Germans and ourselves with high explosive shells; the effect of each assisted the effect of the other. If one began to sneeze from the effect of non-lethal gas, one could not wear a gas-helmet to resist the lethal; the high-explosive shells disguised both types. Now it was planned by Wetherall to fire lethal gas against the enemy for several nights. On the night of the raid and during it, non-lethal only would be used. The two gases smelt alike and the presumption was that on the night of the raid the enemy would wear gas-helmets. [Illustration: IN A GERMAN GUN-PIT NEAR GAVRELLE] On the evening of November 17, only an hour before the raid was to take place, it was announced that the wrong type of shells had been delivered to the artillery. Barely in time to avert a fiasco, the affair was cancelled. Two nights afterwards, when the wind luckily was again from the right direction, the raid was carried out. The Germans, of whom some were found in gas-helmets, had no inkling of our plan. B Company, though they missed the gap through the enemy's wire, entered the trenches without opposition and captured a machine-gun which was pointing directly at their approach but never fired. Wallington, the officer in command of the storming party, killed several Germans. As often, there was difficulty in finding the way back to our lines; in fact, Moberly, the commander of the raid, after some wandering in No-Man's-Land, entered the trenches of a Scotch division upon our right. His appearance and comparative inability to speak their language made him a suspicious visitor to our kilted neighbours. Moberly rejoined his countrymen under escort. For a long time it seemed that no material results had been achieved in the raid. But the next morning Private Hatt, who for his exploit gained the D.C.M., crawled into our lines carrying the machine-gun which he had hugged all night between the German lines and ours. This raid took place the night preceding the great Cambrai offensive, and the success of Moberly and B Company formed part of the demonstration designed to attract enemy reserves away from the area of the operation mentioned.