312 Sfafe in uhich the true Sap of Trees 



being left on all, and all being placed in the same situation 

 to dry. 



In the beginning of August I cut off nearly equal por- 

 tions from a winter and summer -felled pole, which had 

 both grown on the same stool ; and both portions were 

 then put in a situation, where, during the seven succeeding 

 weeks, they were kept very warm by a fire. The summer- 

 felled wood was, when put to dry, the most heavy; but it 

 evidently contained much more water than the other, and, 

 partly at least, from this cause, it contracted much more in 

 drying. In the beginning of October both kinds appeared 

 to be perfectly dry, and 1 then ascertained the specific gra- 

 vity of the winter-felled wood to be 0.679, and that of the 

 summer-felled v,-ood to be 0.609 ; after each had been im- 

 mersed five minutes in water. 



This difference of ten per cent, was considerably more 

 than 1 had anticipated, and it was not till I had suspended 

 and taken off hom the balance each portion, at least ten 

 times, that I ceased to believe that some error had occurred 

 in the experiment : and ind;ed I was not at last satisfied till 

 I had ascertained by means of compasses adapted to the 

 measurement of solids, that the winter-felled pieces of 

 wood v.'ere much less than the others which they equalled 

 in weight. 



The pieces of wood, which had been the subjects of these 

 experiments, werL- again put to dry, with other pieces of the 

 same poles, and I yesterday ascertained the specific gravity 

 of both with scarcely any variation in the result. But when 

 I omitted the medulla, and parts adjacent to it, and used 

 the layers of wood uhich had been more recently formed, 

 I found the specific gravity of the winter-felled wood to be 

 only 0.583, and that of the suaimer-felled to be 0.533 ; and 

 trying the same experiment with similar pieces of wood, 

 but taken from poles which had grown on a different stool^ 

 the specific gravity of the winter-felled wood was 0.588, 

 and that of the summer-felled 0.534. 



It is evident that the whole of the preceding difference in 

 the specific gravity of the winter and summer-felled wood 

 might have arisen from a greater degree of contraction in 

 the former kind, whilst drying ; I therefore proceeded to 

 ascertain whether any given portion of it, by weight, would 

 afford a greater quantity of extractive matter, when steeped 

 in water. Having therefore reduced to small fragments 

 lOOO grains of each kind, I poured on each portion six 

 ounces of boilng water; and at the end of twenly-fcur 

 hours, when the temperature of the water had sunk to 60", 



I found 



