128 MEMOIRSoftbe 
Tlhe 2)iff'erence of Timber in different Countries, and felled at 
different Seafons-^ by M. Leevvenhoeck. PhiJ. Tranl. N° 2 1 5. 
P«» -< /I. 
IT is the common opinion, that timber, which is ft-lled in 
winter, is ftronger and more lading, as being cloler and firmer 
than that which is felled in lummerj but M. L^eixenhoeck is of 
opinion, that there is no difference, except in the bark, and out- 
moll rinjT of the wood, which in the lummer is fofter, and {o 
more eaiily pierced by the worm j wood confifting of hollow pipes, 
which, both in fumraer and winter being full of moiflure, do not 
fhrink in winter, and therefore the wocd cannot be cloler at one 
time than another, for otherwife it would be full of cracks and 
clefts. The fudden and unexpefled rotting of Ibme timber, he 
conceives to proceed from lome inward decay in the tree, before 
it was felled ; having oblerved all trees to begin to decay at firft 
in the middle, or heart of the tree, tho' polTibly the tree may 
ftand and grow for near a hundred years afterwards, and increafe 
in bignefs kll along. He fays, he was once of opinion, that trees, 
growing in good ground, but increaling flowly, were the beft and 
ftrongeft timber ^' and that thole trees, which in few years grew 
large, were the Ibfteft and britlccft^ the contr ,ry to which, upon 
inquiry of experienced workmen, he found to be true, and he 
inftances in an elm of 80 years growth, which was 1 1 foot in cir- 
cumference, and proved excellent tough timber. The age of 
trees is to be known by the number of rin^s to be feen, when the 
tree is cut a-thwart, in each of which rings is one circle of large 
open pipes j now the fewer there are of* thefe large pipes, the 
flronger the timber isj wherefbre, by conlequence, thefe trees 
that make the largeft growth in a year, muft be the cloieft and 
flrongcH, and therefore thole trees, that grow in warm countries, 
grow faH-cfl:, and are the beft and toughclt timber^ which he con- 
firms by Riga and Dantzic oak, which is of a fiow growth, and 
proves Ipongy and brittle timber 5 whereas the C( irrary is obler- 
vable in En^lijh and French oak, which gruvvs falter, and is 
excellent timber. 
T'he "Polarity of Iron. Phil. Tranf. N° 214. p. 257 • 
IT is kiv:>wn, that a rod of iron held perpendicular to the 
horizon, Oi h-'clining, the lower end is its north pole, or arnacls 
the louth end of a maguetic; needle 5 and that the lame end held 
upwards, becomes a iouth pole, or attracts the north end of the 
needle, 
