A great deal of the power of machinery is transmitted through pulleys and belts; now I take it that this is much more similar to some of the drum and lever machines than to a simple crank. There is, however, a form of lever and crank combined, of which I have spoken elsewhere, that is really worse than any simple form of either, but we have just as much right to say the crank ought to make it good as to say the lever makes it bad; if the crank is such a great cure for all evils, as the maker quoted seems to imply, it ought not be so bad in any combination. There is no loss of power in pushing down a spring if it is only just strong enough to lift the leg, since the leg would otherwise have to be lifted by the expenditure of muscular energy. In using a spring we press down with a little more weight than is required to run the machine, so that a storage of power is the result which is given out in lifting the leg. In fact this is done to some extent in the crank machines; the rider not only puts enough power on each crank to turn the wheel, but also enough to lift the other leg; this is true at least when the rider is quite tired. Examples are known wherein a racer on long distances could no longer lift his legs, even with the aid of a spring, though at the same time, he still had strength enough left to propel the machine. In fine, this difference between the crank and spring lever is that in the former, a little extra power is exerted to lift the _other_ leg, while, in the latter, energy is stored to be used in raising the _same_ leg. In a perfectly fresh man I have found, by the registers of the cyclograph, that the rider lifts all weight from a returning crank, but this does not happen when he becomes tired. Evidently, if the spring is strong enough to more than lift the leg, a loss of power will result, since the rider would have to hold it in check even in coming up in order to keep it from stopping with a bang, as is sometimes noticed when he jumps from a treadle machine. The winding and unwinding of the spring involves no loss of power except in heat incident to motion and imperfect elasticity, which is quite small. This loss from heat within the molecular structure, I am constrained to think, is not what is popularly meant by loss of power in springs. Coming back to our quotation, true, in England levers have been tried and expunged. A prominent American, I believe, assisted some little in enlightening our too susceptible English brethren on the subject, yet some attempts have been made with them in this country which no fair person can call unsuccessful.