But the “Blutcher” was after all a very clumsy machine. The engine had no springs, and its movement was a series of jolts, that injured the rails and shook the machinery apart. The important parts of the machinery were huddled together, and caused friction, and the cog-wheels soon became badly worn. Moreover the engine moved scarcely faster than a horse’s walk, and the expense of running it was very little less than the cost of horse-power. Stephenson saw that he must in some way increase the power of his engine if he was to provide a new motive power for the mines. In this first engine the steam had been allowed to escape into the air with a loud, hissing noise, which frightened horses and cattle, and was generally regarded as a nuisance. Stephenson thought that if he could carry this steam, after it had done its work in the cylinders, into the chimney by means of a small pipe, and allow it to escape in a vertical direction, its velocity would be added to the smoke from the fire, or the rising current of air in the chimney, and would in that way increase the draught, and as a result the intensity of combustion in the furnace. He tried this experiment, and found his conjecture correct; the blast stimulated combustion, consequently the capability of the boiler to generate steam was greatly increased, and the power of the engine increased in the same proportion. No extra weight was added to the machine. The invention of this steam blast was almost the turning point in the history of the locomotive. Without it the engine would have been too clumsy and slow for practical use, but with it the greatest possibilities of use appeared. Encouraged by the success of his steam blast Stephenson started to build a second locomotive. In this he planned an entire change in mechanical construction, his principal objects being the use of as few parts as possible, and the most direct possible application of power to the wheels. He took out a patent for this engine on February 28, 1815. This locomotive had two vertical cylinders that communicated directly with each pair of the four wheels that supported the engine, by means of a cross-head and a pair of connecting-rods. “Ball and socket” joints were used to make the union between the ends of the cross-heads where they united with the connecting-rods, and between the rods and the crank-pins attached to each driving-wheel. The mechanical skill of his workmen was not equal to the forging of all the necessary parts as Stephenson had devised them, and he was obliged to make use of substitutes which did not always work smoothly, but he finally succeeded in completing a locomotive which was a vast improvement on all earlier ones, and that was notable for the simple and direct communication between the cylinders and the wheels, and the added power gained by using the waste steam in the steam blast. This second locomotive of Stephenson’s was in the main the model for all those built for a considerable time.