described above, the quantitative results obtained were shown to possess great accuracy. The determinations were found to be capable of being made with considerable rapidity. Only one final reading was all that was necessary for the determination of the absolute index. With a finely graduated circle, a true cylinder, and a perfectly parallel air-film, there is no reason why the method described above should not give results possessing the highest degree of accuracy.
(From unpublished Paper, 1895.)