74 MISSOURI BOTANICAL GARDEN. 
* 
ination by his assistant, Mr. Brogan, shows it to possess a 
density of 0.207, water being taken as unity.* As is often 
the case with the roots of light trees, those of this species 
are appreciably lighter than the stem, and a similar deter- 
mination made by Mr. Timmerman at the request of Pro- 
fessor Nipher, gives for its root wood a density of 0.151, 
though as a cylinder of 3.79 cc. only could be used, it is 
probable that this determination is less accurate than that 
for the trunk. 
In his treatise on the forest trees of the United States, f 
Professor Sargent gives a tabulation of the specific gravity of 
the woods of all the North American trees recognized at that 
time, as determined at the Watertown Arsenal. From his 
tables it appears that the lightest known native wood (that 
of Ficus aurea of Florida), has a density of 0.2616, and 
the heaviest (also a Floridan species, Condalia ferrea), has 
a specific gravity of 1.302, while the density of the great 
majority of species lies between 0.400 and 0.800.t 
From a set of tables based on the experiments of 
Captain Fowke,§ on the woods exhibited at the Paris 
Exposition of 1855, and the London Exposition of 1867, it 
appears that an East Indian wood, ‘‘ Dedoaf Tha,’ has a 
specific gravity of 0.260, very nearly that of Ficus aurea 
* Professor Nipher informs me that in the determination, a cylinder 
was used, turned as accurately as possible, which was measured at a 
sufficient number of points to give average values, and the density was 
obtained by calculation from the dry weight of the cylinder, correction 
being made for absorption of water between the time of removal from 
the drying bath and the completion of the weighing, it having been found 
that the gain from the atmosphere was .007 gr. per minute, for the 
cylinder used. 
t Final Rept. Tenth Census, ix. 249, 
{ As a few examples may be mentioned the common hickories, ranging 
from 0.810 to 0.887, white oak, 0.747, tupelo, 0.519, the willows and pop- 
lars, usually considered very light woods, and lying between 0.363 and 
0.607, and white cedar, a favorite material for light boat construction, 
with a density of 0.332. 
§ Science and Art Department of the Committee of Council on Edu- 
cation, London, printed by George E. Eyre and William Spottiswoode, 
1867, p. 10. 
10 
