away some of the whitewash where the letters were least legible and read:
AID
LTER.
ULANCE &
T AID.
This was evidently half an inscription which had been cut off exactly in the middle. To the left there was no sign of lettering. He puzzled the letters for a few moments before he came to an understanding.
"Air-raid shelter. Ambulance and first aid!" he read.
So that explained the new electric fittings. It was one of those underground cellars which had been ferreted out by the Municipality or the Government for the shelter of the people in the neighbourhood during air-raids in the Great War. Evidently there was extensive accommodation here, since this was also an ambulance post. Faintly discernible beneath the letters was a painted white hand which pointed downward. What had happened to the other half of the inscription? Obviously it had been painted on the door leading into the first-aid room and as obviously that door had been removed and had been bricked up. In the light of this discovery he made a more careful inspection of the wall to the left. For the space of four feet the brickwork was new. He tapped it. It sounded hollow. Pressing his back against the opposite wall to give him leverage he put his foot against the new brickwork and pushed.
He knew that the class of workmanship which was put into this kind of job was not of the best, that only one layer of brick was applied, and it was a mechanical fact that pressure applied to the centre of new work would produce a collapse.
At the first push he felt the wall sag. Releasing his pressure it came back. This time he put both feet against the wall and bracing his shoulders he put every ounce of
