It is very unaccountable how a person of Mr. Woolf's experience in the practical application of steam could be led into errors so gross as those involved in the averments of this patent; and it is still more unaccountable how the experiments could have been conducted which led him to conclusions not only incompatible with all the established properties of elastic fluids--properties which at that time were perfectly understood--but even involving in themselves palpable contradiction and absurdity. If it were admitted that every additional pound avoirdupois which should be placed upon the safety-valve would enable steam, by its expansion into a proportionally enlarged space, to attain a pressure equal to the atmosphere, the obvious consequence would be, that a physical relation would subsist between the atmospheric pressure and the pound avoirdupois! It is wonderful that it did not occur to Mr. Woolf, that, granting his principle to be true at any given place, it would necessarily be false at another place where the barometer would stand at a different height. Thus if the principle were true at the foot of a mountain, it would be false at the top of it; and if it were true in fair weather, it would be false in foul weather, since these circumstances would be attended by a change in the atmospheric pressure, without making any change in the pound avoirdupois.[23] [Footnote 23: It is strange that this absurdity has been repeatedly given as unquestionable fact in various encyclopædias on the article "Steam Engine," as well as in by far the greater number of treatises expressly on the subject.] The method by which Mr. Woolf proposed to apply the principle which he imagined himself to have discovered was by an arrangement of cylinders similar to those of Hornblower, but having their magnitudes proportioned to the greater extent of expansion which he proposed to use. Two cylinders, like those of Hornblower, were placed under the working beam, having their piston-rods at distances from the axis proportioned to the lengths of their respective strokes. The relative magnitudes of the cylinders A and B must be adjusted according to the extent to which the principle of expansion is intended to be used. The valves C C´ were placed at each end of the lesser cylinder in tubes communicating with the boiler, so as to admit steam on each side of the lesser piston, and cut it off at pleasure. A tube, D´, formed a communication between the upper end of the lesser and lower end of the greater cylinder, which communication is opened and closed at pleasure by the valve E´. In like manner, the tube D forms a communication between the lower end of the lesser cylinder and the upper end of the greater, which may be opened and closed by the valve E. The top and bottom of the greater cylinder communicated with the condenser by valves F´ F.