Hen­ry J. Lewis was a son of William Lewis, a pio­neer­ing pho­tog­ra­ph­er and sup­pli­er of daguer­reian mate­ri­als in New York. Hen­ry Lewis patent­ed a design that was a vari­ant of the Eng­lish Graphoscope.
The device has a large lens for con­ven­tion­al pho­tographs and two stereo lens­es. All three lens­es are mount­ed in a sin­gle pan­el, and the large lens can­not be fold­ed away, as is often the case in the Eng­lish Grapho­scope. The device folds up com­plete­ly into a rel­a­tive­ly com­pact box. The base­board is mount­ed on a mov­able sys­tem of struts that allows the view­er to be direct­ed. In a lat­er ver­sion, the struts were replaced by a sim­pler mechanism.
(from: Com­pendi­um of Stereoscopes)