THE ANCESTORS OF THE BIG TREES. 473 



and four thousand years, what a tale they might unfold. Tradition 

 has it that Napoleon encouraged his soldiers hefore the battle of the 

 pyramids with the picturesque phrase ' forty centuries look down upon 

 you,' and yet the span of a single sequoia about equals what to the 

 biblical chronologies of Napoleon seemed the limit of time. Many of 

 the still vigorous and growing trees sprouted about the time that Christ 

 was born at Bethlehem in Judea. Most of those still standing had 

 commenced to grow at least before the fall of Eome. We can count 

 the annual layers in the wood of those which have been cut down, and 

 calculate with considerable accuracy their age and the varying rapidity 

 of their growth. For instance, the huge section on exhibition at the 

 American Museum of Natural History shows that the climate of Cali- 

 fornia was very propitious about the time that Charlemagne was 

 crowned by Pope Leo on Christmas clay, a.d. 800, as is evinced by 

 the rapid growth of the tree at that time shown by the comparatively 

 thick layer it added to its girth. 



It is not strictly correct to speak of these growth layers as ' annual.' 

 They are primarily the result of the varying rapidity of growth of the 

 cells ; thus in trees of temperate climes there is a gradual slowing down 

 of vital activity as the summer advances, followed by a prolonged rest- 

 ing period during the winter, and an accelerated resumption of activity 

 in the spring. These varying functions are recorded in the size and 

 nature of the cells formed. For example, in our oak or chestnut the 

 spring wood consists largely of pitted ducts of large size, which are 

 prominent and in marked contrast with the much smaller celled and 

 more solid additions formed by the slower growth later in the season. 

 In cone-bearing trees like the sequoia the differences are almost en- 

 tirely of size, the transition being abrupt from the very fine wood-cells 

 formed at the close of the season to the much larger cells of the vigor- 

 ous vernal growth. In the tropics the varying rapidity of growth is 

 not so marked, although here also there is usually a suspension of vital 

 activity during the hot dry season and a vigorous growth during the 

 humid season. This effectually records the alternation of seasons in 

 the rings of growth. It follows that under certain conditions a tree 

 might add more than one ring in a year, but for our purpose, and 

 generally speaking, it is proper to designate these rings as annual. 

 Year after year the sequoias have been adding layer after layer to their 

 girth in ever widening circles. The thousands of tons of bark shed 

 by each tree during its long career, the tens and hundreds of thousands 

 of tons of sap that have coursed through their venerable trunks, and 

 the innumerable progeny of a single tree in the older, more propitious 

 days — a contemplation of these facts assists us in realizing the true 

 proportions of these forest monarchs. Imagination, however, fails 



