THE SEQUOIA 
represent periods of interrupted growth, a trec carries its biog- 
raphy within itself. During more favorable seasons, the circles 
are wider, and the intensity of the winter intensifies the outlines 
of the rings. 
“Mark Twain”’ upholds the reputation of the Big Tree for 
longevity. The rings show that it was 1341 years old when cut 
down in the fall of 1891. Thus it must have begun its life in 
A.D. 550, or only seventy-four years after the Fall of Rome. 
Practically all of medieval history, as well as modern, must be 
included in this period, while Natural Science or Biology may be 
said to have developed during its old age. 
The small black cards which have been placed on the tree 
mark the successive centuries and give the growth of the tree 
during each hundred years. The uppermost row of white cards 
1619 
HARVEY 
Discovers circulation 
of the blood 
indicates political events and discoveries which have had influence 
on the progress of civilization since the year 550. The remain- 
der show the progress in biology. The group immediately above 
the black cards represents the change in thought in philosophical 
biology, while those below give a history of biology proper.* 
When the tree was a mere sapling, Europe was overrun by 
the Goths, Vandals and Franks, and a state of almost universal 
war prevailed. About twenty years later Mahomet was born, 
* Each card is mounted on a pin which is stuck into the ring of growth 
corresponding to the date on the card. For example, in the accompanying 
sketch: 1619 is the year that William Harvey announced his discovery of 
the circulation of the blood. The pin attached to the card is inserted into 
the ring of wood which represents the growth of the tree during the year 1619. 
In some instances it has been necessary to put two dates on acard. In these 
cases the pin has been stuck into the ring of growth of the earlier date. 
It 
