< 8oi) 
als,in regard there have been upon this account but very few 
Trees examin'd, comparatively to thofe, that are yet left uncon* 
fider'd and untry'd. The Publifier therefore, being lately dif- 
cours'd with upon this fubje<3,and told, how great an addition 
there might be made to this knowledge, and how beneficial that 
might prove both for the prefervation and recovery of Mans 
health, (it being inftanifd to him, that one of theprefent Kings 
of Europe drinks much, and finds great benefit, of the juyc^ of 
Walnut -trees 5) thought himfelf obliged to recommend the en- 
largment of the faid knowledge, by further Experiments; to all 
Ingenious and Induftrious Men $ as alfo torequeft them, that 
they would pleafe to impart unto him for publick ufe, what 
they either already know, or (hall hereafter difcover and learn of 
that nature. 
A Note 
Abmt the fmaS Empty Tubes , formerly de[cribed. 
T have made ihift to fhuffle up for the Carrier the Patterns of 
\ our Optical Aydes. I had gotten the Tubes in Beaver, but 
they proved fo flippery, that the S pelade- bones would not 
hold them^ When thofe, which I fend to you, are black t with 
Ink, they will become ftiffer and rougher, and hold firmer in any 
pofture, as youroccafion requires. At the firft they fliould be 
drawn in the bone within the third part of an inch of the very 
tops and then, as by ufe you find them more agreeable. 
I did redouble it upon you, that the greateft difcouragement 
would arife from the difficulty of ufing them at firft 5 and that 
I could not exped , that any Man would have the patienceto 
learn the right ufe of them, except he were conftrain'd by necef- 
fity* and thatmyfelf, though I was filW with joy enough at 
the firft difco very, could not endure the trouble above two hours 
at a time : But by the pra6tifc of a week or a fortnight., I found 
them an eafe and pleafure to me for twelve at lean of each 24 
houres. And by ail the tiyals, which I have yet made upon 
others, whether pore-blind, or of faint-fight decay'd by Age, or 
however weakened, it proves a very great ayde. For the pore- 
blind, they muft be made fhorter : For the decay'd by age, they 
may be longer. 
An 
