This machine, first proposed by Lord Kelvin (William Thomson), performs integration with a wheel rolling on a rotating disk. Hartree visited Boston to learn about the workings of the differential analyzer, then returned to Cambridge and built his own.
Ang makina, unang iminungkahi ng Panginoon Kelvin (William Thomson), ay gumaganap ng integration sa isang gulong pagulong sa isang umiikot na disk. Hartree binisita Boston upang malaman ang tungkol sa workings ng kaugalian analyzer, pagkatapos ay bumalik sa Cambridge at nakapaloob sa kanyang sarili.