The result then is the same as though the periphery of E were formed into a fixed spurwheel, A, and another, a, of the same size, secured on a shaft, B, the two being connected by the three equal wheels, L, M, N. It need hardly be stated that instead of the eccentric, E, a stationary crank similar and equal to B G may be used, should it be found better suited to the circumstances of the case.
It is possible also to apply the planetary principle to mechanism composed partially of racks; in fact, a rack is merely a wheel of prodigious size—the limiting case, just as a right line is a circle of infinite radius. A very neat application of this principle is found in Villa's Pantograph, of which a full description and illustration was given in SCIENTIFIC AMERICAN SUPPLEMENT, No. 424; the racks, moving side by side, are the sun-wheels, and the planet-wheels are the pinions, carried by the traveling socket, by which the motion of one rack is transmitted to the other.
Thus far attention has been called only to combinations of circular wheels. In these the velocity ratios are constant, if we except the cases in which two independent trains converge, the two sun-wheels, or one of them and the train-arm, being driven separately—and even in those, a variable motion of the ultimate follower is obtained only by varying the speed of one or both drivers. It is not, however, necessary to employ circular wheels exclusively or even at all; wheels of other forms are capable of acting together in the relation of sun and planet, and in this way a varying velocity ratio may be produced even with a fixed sun-wheel and a single driver. We have not found, in the works of any previous writer, any intimation that noncircular wheels have ever been thus combined; and we propose in the following article to illustrate some curious results which may be thus obtained.
THE FALLACY OF THE PRESENT THEORY OF SOUND.
Dr. H.A. Mott recently delivered a lecture before the New York Academy of Sciences, in Columbia College, on the Fallacy of the Present Theory of Sound.
He commenced his lecture by stating that "the object of science was not to find out what we like or what we dislike; the object of science was truth." He then said that, as Galileo stated a hypothesis should be judged by the weight of facts and the force of mathematical deductions, he claimed the theory of sound should be so examined, and not allowed to exist as a true theory simply because it is sustained by a long line of scientific names; as too many theories had been overthrown to warrant the acceptance of any one authority unless they had been thoroughly tested. Dr. Mott stated that Dr. Wilford Hall was the first to attack the theory of sound and show its fallaciousness, and that many other scientists besides himself had agreed with Dr. Hall in his arguments and had advanced additional arguments and experiments to establish this fact. Dr. Mott first gave a very elaborate and still at the same time condensed statement of the current theory of sound as propounded by such men as Helmholtz, Tyndall, Lord Rayleigh, Mayer, Rood, Sir Wm. Thomson, and others, and closed this section of the paper with the remarks made by Tyndall: "Assuredly no question of science ever stood so much in need of revision as this of the transmission of sound through the atmosphere. Slowly but surely we mastered the question, and the further we advance, the more plainly it appeared that our reputed knowledge regarding it was erroneous from beginning to end."
Dr. Mott then took up the other side of the question, and treated the same under the following heads:
1. Agitation of the air. 2. Mobility of the atmosphere. 3. Resonance. 4. Heat and velocity of the supposed sound waves. 5. Decrease in loudness of sound. 6. The physical strength of the locust. 7. The barometric theory of Sir Wm. Thomson. 8. Elasticity and density of the air. 9. Interference and beats. 10. The membrana tympani and the corti arches.