260 A Talk of the Sim's Dcdbiafion, <5^'c. 



of matter in the sprine: and early part of the summer, to form 

 the leaves and voung shoots, which quantity could not have been 

 restored to it during the summer, oi] account of the descending 

 current of sap through the bark h;iving been wholly intercepted. 



Small blocks of equal weight of the alburnum of each tree were 

 divided by cleaving into thin pieces ; and these, after having be- 

 come perfectly dry, were suspended together during ten days, in 

 a somewhat damp room ; when 1000 grains of the alburnum of 

 the spring-felled tree were found to have gained 162 grains, 

 and an equal weight of that of the winter-felled tree 145 grains ; 

 and I found that each substance permanently retained moisture 

 nearly in the same proportion that it absorbed it. The albur- 

 num of the oakj as of other trees, therefore, undergoes some 

 change of properties in the spring; and I do not entertain any 

 doubt but that, in all cases in which it is expedient to give dura- 

 bility to that substance, much advantage may be obtained by 

 taking off the bark in spring, and suffering the trees to stand till 

 winter. The durability of the alburnum of large oak-trees of 

 British growth is not, however, generally an object of much con- 

 sequence; because it almost always lies wholly exterior to the 

 heart wood ; but in the oak timber, which is imported from the 

 North of Europe, the alburnum and heart wood are very often 

 intermixed, the grov/th of ten or a dozen years, or more, of al- 

 burnum and heart wood composing, in alternate layers of un- 

 equal depth, the whole body of tl>e tree ; and the value of the 

 timber of such trees is probably much affected by the season of 

 felling. 



Many experiments, similar to the preceding, were made U|)ou 

 the heart wood, in which I found the disposition to absorb mois- 

 ture, somewhat greater in that of the spring-felled, than in that 

 of the winter-felled tree; and I scarcely entertain any doubt but 

 that the winter-felled heart wood is the best and most durable ; 

 but I do not think any conclusion can safely be drawn till the 

 heart v/ood of many trees has been siihjected to exjieriment ; and 

 therefore, as I have no evidence to oflter which is in any degree 

 conclusive, I shall not at present trespass further n])on the atten- 

 tion of the Society. 



Dou-nton, March 29, 1820. 



XLT. A Tahleofthe Siw's DecUvalion to every Te?rMirmics()f 

 his Lnnsritude : with the Differences and Secular Varialion for 

 Jan. 1, ISOl. {Ohliq. of the EcVip. 2.3" 27' rj?", and Sec. Far. 

 .52"- 1.) CakvJ a ted from Taylor's Tables of Logarithms,. 

 By Mr. Jamks Utting, Lynn Regis. ^ 



[Continued from p. ISfi.] 



Argn- 



