(862)
Fiat Experimentum, Since we are now in that very season, to see whether that early ascent is to be imputed to the forwardness of the year, or not? Let it also be observed, whether the Sap ascends in Oak and Elme, at any time in this month of January; and likewise, which of these three, the Maple, Sally, or Willows, be the most early in yielding of Sap?
And to obtain an Universal and Accurate knowledg of the nature of Sap in Trees, its properties and accidents; Observations and tryals must be made by a Number of men, that have leisure to attend that business daily which are to examine concerning every Tree;
1. Its Age, Soyle, Situation, &c. the variety of the Ascent of the Sap depending thereon, as on the nature of the Tree it self.
2. The different time of Ascent in Branches, Body, Roots; and of its distilling from cut branches; from roots, not from branches.
3. The Seasons and differences of the time of the year, month and day, in which these accidents happen or cease; whereby it may appear, what to determine concerning them: And particularly, whether that conjecture be well-grounded, which supposes, That Sap does not descend from Trees otherwise than by jellying so as to fail above, whilst there is yet plenty below; as seems to be manifest by the running in the Roots, when it ceases in the Branches.
It were also not amiss to observe, Whether in any Trees, the Sap as to its ascending, keeps time with the Suns entrance into this or that Sign?
To the 11th. The same. The best time of the day for Tapping, is about Noon. In the latter season, when Sap is not very plenteous in Trees, they will neither run morning, not evening, nor probably at any time of the night; but when they are very full of Sap, and emptied but by small vents, the Sap may run night and day, till exhausted; but never in large vents.
Quere, Whether this Observation may not give light to that Opinion, which holds, that the Ascending of the Sap depends upon the Pressure or Pulsion of Heat, striking the Earth, and thereby driving the moisture of the Earth into the Root?
To the 12th. The same. Trees afford no juice at all (that has been observ'd) in Autumne.
To the 13th. The same. Rain being fearce, the juice will be fearcer. Plenty of Rain can onely give such plenty of Sap, as the pores will admit.
The Answers to the rest of the Queries we reserve for another Month, least these Paper be altogether filled with one subject. Those that have been deliver'd here from Dr. Tonge were for the rnost part taken out of his Letters to Sir R. Moray, in January, February, March, Aprill, 1666; at which time he had newly made Experiments about Saps; and are now, after conference with him, accommodated to the Queries formerly made publick.
