1879. ] Distribution of the North American Flora. 169 
trunk thirty annular rings to the inch. This,if the rings were of uni- 
form diameter in the rest of the trunk, would give the incredible 
age of 6400 years; but as the interior rings of such trees are 
much broader than the outer, half that number to the inch is a 
more conceivable estimate, which would give an age of 3200 
years. The only other instance of careful counting of rings 
which I can find is that of the felled tree in the Calaveras grove, 
which measured seventy feet girth inside the bark at six feet 
above the ground, and which at forty feet above the ground had 
1255 rings. In this case the rings next the bark were thirty-three 
to the inch, a number which at five feet inward had diminished 
one-half. The result of many measurements, chiefly by Prof. 
Whitney, gives, as the average height of full-grown trees, 275 
feet, and a maximum a little over 320; a girth outside the bark, 
at six feet above the ground, of seventy, with a maximum of 
120; whilst the maximum age possibly attained may be 4000 
years, though this is very improbable. 
The duration of the dead wood in the forest is very great. I 
rarely observed signs of rot in the fallen trees I examined, whilst 
in similar forests in North California I saw gigantic trunks of 
silver firs forming mounds of rotten dééris without an atom of 
sound wood, and this in two years after their fall, as I was 
assured, I had no data for ascertaining the length of time during 
which any of the prostrate Sequoia trunks which I saw may have 
lain on the ground, but Mr. Muir has supplied me with a very 
crucial case. It is that of a prostrate trunk with no signs of 
decay in any part of it, which had been burnt in two by a forest 
fire, and in the trench between the severed portions of which a 
silver fir grew. This fir was felled, and had 380 annual rings ; 
therefore, to estimate the time during which the Sequoia trunk 
had lain uninjured, we must add to the 380 years, first the time it 
lay before the forest fire burnt it in two, and then the unknown 
interval between that time and the arrival of the silver fir seed. 
_ The millenia during which these Sequoia trees must have 
remained čz statuo quo, proving the long duration of existing con- 
ditions of climate, are but as minutes compared with the time 
occupied by the migration of this very species, or its ancestors, 
1 Very careful measurements of the trees in = Calaveras and Mariposa groves 
ar 
given by Prof. Whitney (State Geol ogist) in the Yosemite Guide-Book, a 
under the tampa of the Geological Survey p California (1874). 
