^20 PHILOSOPHICAL TRANSACTIONS. [anNO 1683. 



a day to carry up 1 drop of water, and that 100 of these drops make one cubic 

 inch, there will be 200,000 cubic inches. These inches reduced to feet, amount 

 to full 115 cubic feet of Rhinland measure, of 12 inches to the foot; and one 

 cubic foot weighing 65 lb. of our Delpht water, the whole will amount to 7475 

 lb. or 14 Bordeaux hogsheads of water, which a tree of one foot diameter in 

 one day can bring up. Whereby it appears, that how small soever the quantity 

 of water is which a pipe or vessel may be supposed to carry up, yet if all the 

 vessels were employed to that use, how much the total would amount to. But 

 I conceive that several of these vessels convey of the same moisture downwards 

 again to the root, and so cause a circulation : as I have formerly said. 



These forementioned uprising vessels empty constantly their sap into an in- 

 credible number of vessels, which lie horizontally in the body of the tree, to 

 cause a continual growth in thickness. Fig. 2, GGG are a sort of vessels 

 which run horizontal, beginning from the pith of the tree, but afterwards in 

 great numbers taking their rise from the ascending vessels. These vessels ap- 

 peared like dark streaks running crooked, and winding for the most part along 

 the sides of the great vessels. To observe these vessels better, I caused the 

 wood to be cut in length in such manner that I came to divide the said vessel's 

 across very neatly. These vessels lie not above 5, 6, or 7, one above another, 

 as they are here drawn between the ascending vessels PQON, fig. 4. 



The second sort of horizontal vessels which lie in great numbers together, 

 but in some places much more than others, are described fig. 2, AB or CD : 

 but when we cut the wood in pieces longwise, and thereby cut across these 

 vessels, then they appear to our naked eye as RS, fig. 5. I have also drawn 

 the same in many places at their length, with crooked partitions, which I 

 judged to be valves* though I have not been able to see them always so clearly 

 as they are here expressed, but after I had found them sometimes, I concluded 

 them to be generally so, both because 1 have seen them in elm wood, as also 

 that I concluded without these valves it were impossible the tree should increase 

 in thickness, because of the force that is necessary not only to separate the 

 bark in the spring from the wood,-}- and keep it loose; but also to cleave and 

 open the bark all the time the tree is growing ; and thereby make room for its 

 increase in thickness. Now if there were none of these valves, then the sap 

 which was impelled by the heat of the sun against the bark, with the setting of 



• * Sig. Malpighi and Dr. Grew both make these partitions to be the terminations of the bladders 

 of which these radiated parts consist, and not valves. See the forementioned Anatomy of Tr. fig. 21, 

 p. 21, 22, and Anat of Roots, tab. 7. — Orig. 



+ Dr. Grew thinks that the bark is never separated from the wood. See Anat. of Tr. p. 52, ice. 

 —Orig. 



