There were horses in the column itself.

At first glance, it appeared as if there were nothing else, a riderless squadron tramping steadily over the upturned plough land of the ranch.

But it drew nearer.

The horses were in lines, six abreast, harnessed to machines.

The noise increased, defined itself.
There was a shout or two; occasionally a horse blew through his nostrils with a prolonged, vibrating snort.