Years ago—though not nearly so long ago as it seems—when artillery was still hauled into position by sweating gun-teams, a veteran ordnance officer, addressing a scientific society, told his hearers that the weight of artillery was governed by the limited power of the horse. As a horse has a sustained pulling power of only 650 pounds, he explained, it was obvious that a 6-horse gun-team could not pull a gun and limber weighing more than 3,900 pounds. “If Divine Providence had given the horse the speed of the deer and the power of an elephant,” he added, “we might have had a far wider and more effective range for our mobile artillery.” Could that officer have looked a few years into the future he would have been astonished to see that, thanks largely to the genius of a Californian named Holt, there would be substituted for the horse a curious contrivance known as the caterpillar tractor, which possesses many times the power of an elephant. Though the tractor cannot be claimed, by any stretch of the imagination, to have the speed of a deer, it nevertheless has sufficient speed to keep pace with the infantry, or, indeed, should it become necessary, with cavalry. Few people appear to realize how enormous were the savings in men, animals, feed, railway facilities, and ocean tonnage effected by the motorization of our artillery. The motorization of one 155-mm. howitzer regiment saved 1,440 horses. One tractor for this howitzer is the equivalent of sixteen heavy draft-horses and three riding-horses, yet it is so compact that it occupies in packing a space of but 360 cubic feet, and can be operated by two men. Tractors are not only easier to conceal from enemy observation than horses, but a shell-burst which would kill every horse in a battery, would leave an armored tractor uninjured. Not long ago, at the Aberdeen Proving-Ground, one of these tractors, on which was mounted an 8-inch howitzer, sent through a dense wood, ran squarely into a live locust-tree which was seventeen inches thick at the base. Before the onslaught of the tractor the tree went down as though it were made of cardboard, whereupon the amazing machine crawled over the fallen trunk, slid into and clambered out of a ravine, emerged from the wood and took up its firing position—all in scarcely more time than it takes to tell of it. Before the war ended virtually every piece of American medium and heavy artillery was either tractor-mounted or tractor-drawn, and we were on the road toward motorizing the field-artillery—the “seventy-fives”—as well. [Illustration: AN AMERICAN 75-MM. FIELD GUN. TRACTOR MOUNTED. Thanks largely to the genius of a Californian named Holt, there has been substituted for the horse a curious contrivance known us the caterpillar tractor which possesses many times the power of an elephant.] [Illustration: A 12-INCH RAILWAY GUN IN OPERATION. Note the shell in flight.]