But to return to the Green Cross Shell. These were used during the Somme Battle in enormous numbers, far surpassing anything we had had before in the extent of the bombardment. There were a great many new features about these shell quite apart from the altered nature of the gas. First of all there was the size. Until then we had had gas shell of only two sizes--150-millimetre howitzer shell and the 105-millimetre howitzer shell. The former contained from five to eight pints of liquid according to the construction of the shell, and the latter about three pints. To these longer shell were now added shell from the ordinary field gun, or 77-millimetre gun--quite a small affair compared with the others and containing only two-thirds of a pint of liquid poison. But then, though so small, it could be fired more rapidly and accurately and could bring off an initial surprise in a way that the bigger guns could not do. Shell of these three sizes were used then on nearly all occasions and in very large quantities. One thing that made large numbers possible was the simplicity of the shell compared with the old pattern. There was no separate lead container and the “gas” was filled straight into the body of the shell, as the new material was unacted on by iron or steel. The head of the shell was screwed in and kept in position and perfectly gas-tight by means of a special cement. As very little explosive was needed to open them up and spread the contents round the noise made by the burst of the Green Cross Shell was little more than a pop--at any rate when compared with the high-explosive shell or the old tear shell. The result was that at first men were apt to regard them as duds and to delay the putting on of respirators until it was too late. These gas shell are supposed to make a peculiar wobbling noise in the passage through the air because of the liquid inside them, and in this way to be recognisable beforehand. Personally I cannot tell any difference in the noise compared with H. E. or shrapnel of the same calibre, though I have heard thousands of both kinds; but I dare say some people can, as the belief is fairly widespread.