The carry of the tens transfer device is of the same order as that described in the Pascal and Hill machines; that is, a one-step ratchet-motion actuated by a cam lug or pin from the lower wheel. The carry transfer device consists of the lever F, and pawl f⁴, acting on the ratchet of the upper wheel which is operated by the cam lugs b⁵ of the lower wheel acting on the arms f¹ and f³ of the lever F.
From the Robjohn Patent Drawings
Inoperativeness of Stark machine
The machine shown in the Stark patent was provided with but one set of keys, but the arrangement for shifting the driving ratchet pawl E², from one order to another, so that the action of the keys may rotate any one of the numeral wheels, gave the machine greater capacity than the single digit adders; but as with the Chapin machine, of what use was the increase in capacity if the machine would not add correctly. That is about all that may be said of the Stark machine, for since there was no means provided by which the rotation of numeral wheels could be controlled, it was merely a device for rotating numeral wheels and was therefore lacking in the features that would give it a right to the title of an adding machine.
Nine keys common to a plurality of orders
The nine-key scheme of the Stark invention, connectable to the different orders, was old, and was first disclosed in the U. S. Patent to O. L. Castle in 1857 (a machine operated by a clock-spring wound by hand), but its use in either of these machines should not be construed as holding anything in common with that found in some of the modern recording adders. The Castle machine has not been illustrated because it does not enter into the evolution of the modern machine.
The ancient Art, or the Art prior to the invention of Parmelee, consisted of mechanism which could be controlled by friction devices, or Geneva gear-lock devices, that were suitable to the slow-acting type of manipulative means.
The first attempt at a positive control for a key-driven adding device is found in a patent issued to W. Robjohn in 1872 ([see illustration]). As will be noted, this machine was referred to in the foregoing discussion as merely a single-digit adding machine, having the capacity for adding but one column of digits at a time.