The new establishments usually grew out of older shops of a less pretentious character, and were managed by men who had been trained by Watt, or who had had a still more awakening experience with those who vainly strove to make up, by their ingenuity and by great excellence of workmanship, the advantages possessed at Soho in a legal monopoly and greater experience in the business. It was exceedingly difficult to find expert and conscientious workmen, and machine-tools had not become as thoroughly perfected as had the steam-engine itself. These difficulties were gradually overcome, however, and thenceforward the growth of the business was increasingly rapid. Every important form of engine had now been invented. Watt had perfected, with the aid of Murdoch, both the pumping-engine and the rotative steam-engine for application to mills. He had invented the trunk engine, and Murdoch had devised the oscillating engine and the ordinary slide-valve, and had made a model locomotive-engine, while Hornblower had introduced the compound engine. The application of steam to navigation had been often proposed, and had sometimes been attempted, with sufficient success to indicate to the intelligent observer an ultimate triumph. It only remained to extend the use of steam as a motor into all known departments of industry, and to effect such improvements in details as experience should prove desirable. The engines of Hero, of Porta, and of Branca were, it will be remembered, non-condensing; but the first plan of a non-condensing engine that could be made of any really practical use is given in the "Theatrum Machinarum" of Leupold, published in 1720. This sketch is copied in Fig. 41. It is stated by Leupold that this plan was suggested by Papin. It consists of two single-acting cylinders, _r s_, receiving steam alternately from the same steam-pipe through a "four-way cock," _x_, and exhausting into the atmosphere. Steam is furnished by the boiler, _a_, and the pistons, _c d_, are alternately raised and depressed, depressing and raising the pump-rods, _k l_, to which they are attached by the beams, _h g_, vibrating on the centres, _i i_. The water from the pumps, _o p_, is forced up the stand-pipe, _q_, and discharged at its top. The alternate action of the steam-pistons is secured by turning the "four-way cock," _x_, first into the position shown, and then, at the completion of the stroke, into the reverse position, by which change the steam from the boiler is then led into the cylinder, _s_, and the steam in _r_ is discharged into the atmosphere.[44] [44] _Vide_ "Theatrum Machinarum," vol. iii., Tab. 30. [Illustration: FIG. 41.--Leupold's Engine, 1720.] Leupold states that he is indebted to Papin for the suggestion of the peculiar valve here used. He also proposed to use a Savery engine without condensation in raising water. We have no evidence that this engine was ever built.