Current Literature. 95 



•cent, of their immediate elastic limit, and deflections under such 

 load will gradually diminish to zero. Increase of dampness 

 lowers the elastic limit so that what was at first a safe load may 

 thereby become dangerous. 



5. After removal of a dead load, a beam's recovery from the 

 time effect is gradual and not always complete. 



6. A beam may be considered safe under a permanent load 

 when the deflections diminish during equal successive periods of 

 time. A continual increase in deflection indicates an unsafe load 

 which is almost certain to rupture the beam, S. J. R. 



The Silva of California. By W. L. Jepson. Memoirs of the 

 University of California, Volume II. Berkeley, California. 1910. 

 Pp. 283, plates 85, maps 3. 



The object of this memoir is "to bring together in one volume 

 an account of the timber trees of the state which shall as nearly 

 as possible represent our present knowledge of the taxonomy and 

 geographical distribution." It is the result of nineteen years of 

 field studies and collections on the part of the author, and the 

 volume throughout reflects that basis. 



The forests of California are characterized by the abundance of 

 conifers, both in species and individuals. The broad-leaved trees, 

 mainly evergreen, are rich in species but very poor in individuals. 

 Of these, most typically Californian and most abundant, are Live 

 Oak, Valley Oak, Blue Oak and Tan Oak, Laurel and Madrona 

 (Arbutus). A census of species indicates 92 in all, representing 

 22 families. Of this number, 49 species are typical of California 

 and 18 confined to that state. 



The state is divided by the author into five natural forest 

 provinces, according to the character of the forest, the composi- 

 tion and the species. 



The first of these, the great valley of the Sacramento and San 

 Joaquin rivers, is almost treeless, being characterized by scattered 

 groves of Live Oak and Interior Great Oak on the east side, and 

 in addition Willow. Cottonwood, Box Elder and Oregon Ash 

 along river banks. The present forestless condition is due largely 

 to the nature of the soil and climatic conditions, but also to the 

 earlier annual burnings by the Indians. Only fourteen species in 

 all are represented. 



