BULLETIN OF THE BUSSEY INSTITUTION, 33 
in pine sawdust, and 0.6% in spruce twigs picked out from the rak- 
ings of woodland. 
All of which goes to show that spent dye-woods are poor in nitrogen, 
and on that account peculiarly ill fitted for making compost. 
With regard to ash ingredients, it would naturally be expected that 
spent tan would retain a larger proportion of phosphoric acid, and pot- 
ash also, than could be held by leached logwood; since, during the 
growth of a tree, there is, ordinarily, a certain tendency to the 
accumulation in the bark of insoluble or difficultly soluble forms of 
inorganic matter.* But even with the barks, it is noteworthy how 
small a proportion of the fertilizing materials is left after the process 
of leaching. In respect to phosphoric acid, indeed, the ashes of spent 
tan are as rich as ordinary wood-ashes, but the proportion of potash 
contained in the ashes of spent tan (less than 5%) compares very 
unfavorably with the average amount (8}%) in wood-ashes from house 
fires. The remark of Berthier, cited on page 233 of the first volume 
of this Bulletin, that the ashes of fresh tan (oak-bark) contain a mere 
trace of phosphoric acid, is probably incorrect. Compare the result 
obtained by Eckert, as cited on the same page. 
From the analyses, it appears that ashes obtained by burning spent 
sumach would be but little better, as a manure, than leached wood- 
ashes, and that the ashes of spent logwood chips would hardly be as 
good as leached wood-ashes, were it not that they have the merit of 
being perfectly dry. As with leached wood-ashes, so with the ashes 
of the leached wood now in question, their fertilizing action is to be 
attributed, for the most part, to the carbonate of lime, of which they 
chiefly consist. 
The foregoing results agree with those of previous researches. It has 
been shown repeatedly by chemists that a large proportion of those ash 
ingredients of woods and herbaceous plants that are soluble in water, 
when in the form of ashes, may be removed by leaching the wood itself, 
or the herb. The experiments of Boerhaave and of Stahl exhibited this 
fact as long ago as the beginning of the eighteenth century; and the 
work of these chemists was carefully reviewed and confirmed by several 
of their followers, notably by Wiegleb,t who made many experiments 
on the subject. 
* Compare De Saussure, in his “ Recherches Chimiques sur la Végétation,” 
1804, p. 287; and Johnson’s “ How Crops Grow,” p. 190. 
T In his “Chemische Versuche iiber die alkalischen Salze,” Berlin, 1781, pp. 
79-84, 70. 
VOL. II. 3 
