Meanwhile, Vaugirard in his motor kept to the road and the staff on their motor cycles followed closely.
On both flanks the thunder of massed cannon was deepening, and now John, who used his glasses occasionally, was able to see wisps and tendrils of smoke on the eastern and northern horizons.

The tremor in the air was strong and continuous.

It played incessantly upon the drums of his ears, and he found that he could not hear the words of the other aides so well as before.

But there was no succession of crashes.

The sound was more like the roaring of a distant storm.
They advanced another mile, two hundred thousand men, afire with zeal, a whole vast army moved forward as the other French armies were by the hidden hand which they could not see, of which they knew nothing, but the touch of which they could feel.
John heard a whizzing sound, he caught a glimpse of a dark object, rushing forward at frightful velocity, and then he and his wheel reeled beneath the force of a tremendous explosion.