By referring to the description of the inoperative features of the Hill machine (page 25) a parallel example of the time for the carry of the tens in the old Comptometer may be found, showing that but a ¹/₁₆₅ of a second was the allowance. The carrying means employed in the old Comptometer consisted of levers with dogs or pawls hinged on their free ends, which co-acted with the ten pins of the higher numeral wheels to ratchet them forward a step at a time. The power for supplying such ratcheting action, in the delivery of a carry, was produced in a spring attached to the carrying-lever to actuate it. [Sidenote: _Cam and lever carrying mechanism_] The means used to produce the power in the carrying-lever actuating springs, or best termed carrying springs, was through the turning of an envolute cam attached to the lower order numeral wheels, which, acting upon an arm of the carrying levers, forced them away from the wheels, and thus tensioned the carrying springs. The cam and lever is best shown in Fig. 7, page 130. The timing of the delivery of the carry, as the numeral wheel passed from nine to zero, was brought about by the high point of the cam passing from under the arm of the carrying lever, which, when released, allowed the carrying springs to act and ratchet the higher wheel forward a tenth of a revolution. This form of carrying action had a peculiarity of reaching a certain set tension when three wheels were employed, so that for all the wheels employed in greater numbers no higher tension was required and no lower tension could be attained. Another feature about this type of transfer device was the fact that to get the set tension as low as possible required that at least eight-tenths of the rotation of the lower wheel should be utilized in camming back the carrying lever or storing the power for the carry. A decrease in this timing meant an increase in the resistance offered in turning the lower wheel by the steeper incline of the cam, and when the wheel in turn received a carry, the increase of resistance increased the work of carrying, and so on by a geometric ratio. [Sidenote: _One-point carrying cam impossible_] In a recent patent suit, a physical test was made as high as three orders with a one-point cam; that is, a cam operating to store power during a one-tenth rotation of the lower wheel (not an uncommon combination as shown in patents that have been issued), and it was found that by the time the third carrying was reached the springs were so large and powerful that to turn the next wheel would require a railway-coach spring, and that under the same ratio a fifty-four ton hydraulic press would be required to depress the keys in the eighth order.