The engine should not have been submitted to such a test until after the differentiation had been equated, and perfect control in reversions established. And yet, so often has Keely made what seemed to be disasters an advantage in the end, it is possible that the interruption and delay may enable him to produce a perfect engine sooner than he would have done on this model. The world will never know how many mechanical difficulties Keely has conquered before attaining his present degree of success, in which he thinks he has mastered all that pertains to the principle of the force that he is dealing with, so far as necessary for commercial purposes, the difficulties that he still has to contend with being merely the minor ones of mechanical detail. The fact that so much of Mr. Keely's success, in conducting his experiments when giving exhibitions, depends upon the complete perfection of his instruments, is one of the strongest arguments that could be advanced in proof of the genuineness of his claims. Has any one ever heard of a performer in legerdemain who, after assembling an audience to witness his tricks, announced that something was wrong with his conjuring apparatus and that he was unable to exhibit his dexterity? Feats of legerdemain can be performed, night after night, year in and year out, without any hitch on the part of the operator; but all who are conversant with the failures attendant upon a certain order of experiments, as for instance in the liquefying of oxygen gas, will be able to appreciate the uncertainty which characterizes the action of Mr. Keely's instruments at times. It is only by progressive experimental research that knowledge of the laws governing Nature's operations can be gained, and a system evolved to perpetuate such knowledge. The hypothesis of to-day must be discarded to-morrow, if further research proves its fallacy. Is it not, then, another strong argument in favour of Keely's integrity that, confessing ignorance of the laws that govern the force he has discovered, he has plodded on through all these years, experimenting upon its nature, with instruments of his own invention, which from their delicate and imperfect construction are uncertain in their operations, until he has so improved the defective machine as to make it a stepping-stone, by which he ascends to perfection? Take the imperfect comparison of a ladder: no workman can attain the summit in one effort; he must mount step by step. To quote from Keely's writings, "The mathematics of vibratory etheric science, both pure and applied, require long and arduous research. It seems to me that no man's life is long enough to cover more than the introductory branch. The theory of elliptic functions, the calculus of probabilities, are but pygmies in comparison to a science which requires the utmost tension of the human mind to grasp. But let us wait patiently for the light that will come, that is even now dawning." [10]