(802)
als, in regard there have been upon this account but very few Trees examin'd, comparatively to those, that are yet left unconsider'd and untry'd. The Publisher therefore, being lately discours'd with upon this subject, and told, how great an addition there might be made to this knowledge, and how beneficial that might prove both for the preservation and recovery of Mans health, (it being instanc'd to him, that one of the present Kings of Europe drinks much, and finds great benefit, of the juyce of Walnut-trees;) thought himself obliged to recommend the enlargement of the said knowledge, by further Experiments, to all Ingenious and Industrious Men; as also to request them, that they would please to impart unto him for publick use, what they either already know, or shall hereafter discover and learn of that nature.
A Note
About the small Empty Tubes, formerly described.
Ihave made shift to shuffle up for the Carrier the Patterns of our Optical Aydes. I had gotten the Tubes in Beaver, but they prov'd so slippery, that the Spectacle-bones would not hold theme. When those, which I send to you, are blackt with Ink, they will become stiffer and rougher, and hold firmer in any posture, as your occasion requires. At the first they should be drawn in the bone within the third part of an inch of the very top; and then, as by use you find them more agreeable.
I did redouble it upon you, that the greatest discouragement would arise from the difficulty of using them at first; and that I could-not expect, that any Man would have the patience to learn the right use of them, except he were constrain'd by necessity; and that my self, though I was fill'd with joy enough at the first discovery, could not endure the trouble above two hours at a time: But by the practise of a week or a fortnight, I found them an ease and pleasure to me for twelve at least of each 24 houres. And by all the tryals, which I have yet made upon others, whether pore-blind, or of faint-fight decay'd by Age, or however weaken'd, it proves a very great ayde. For the pore-blind, they must be made shorter: For the decay'd by age, they may be longer.
