To relate all their optic observations through the several sorts of their glasses, would be a tedious work, and tire even the most patient reader, wherefore I’ll pass them by; only this was very remarkable and worthy to be taken notice of, that notwithstanding their great skill, industry and ingenuity in experimental philosophy, they could yet by no means contrive such glasses, by the help of which they could spy out a vacuum, with all its dimensions, nor immaterial substances, non-beings, and mixed-beings, or such as are between something and nothing; which they were very much troubled at, hoping that yet, in time, by long study and practice, they might perhaps attain to it.