356 THE POPULAR SCIENCE MONTHLY. 



plant throughout life produces both forms, and on the same bough may 

 be seen phyllodes interspersed among ordinary pinnate leaves, the re- 

 spective advantages being, it would appear, so equally balanced that 

 sometimes the one, sometimes the other, secures the predominance. 



In the case of the eucalyptus, every one who has been in the south 

 of Europe must have noticed that the young trees have a totally dif- 

 ferent aspect from that which they acquire when older. The leaves of 

 the young trees (Fig. 18) are tongue-shaped, and horizontal. In older 

 ones, on the contrary (Fig. 19), they hang more or less vertically, with 

 one edge toward the tree, and are cimeter-shaped, with the convex 

 edge outward, perhaps for the same reason as that suggested in the 

 case of acacia. There are several other cases in which the same plant 

 bears two kinds of leaves. Thus, in some species of juniper the leaves 

 are long and pointed, in others rounded and scale-like. Juniperus 

 chinensis has both. 



In the common ivy the leaves on the creeping or climbing stems 

 are more or less triangular, while those of the flowering stems are 

 ovate-lanceolate, a difference the cause of which has not, I think, yet 

 been satisfactorily explained, but into which I will not now enter. 

 Contemporary Heview. 



-++*- 



EAETHQUAKE PHENOMENA. 



By EALPH S. TAEE. 



AT the present time the earth seems to be in a state of great seis- 

 mological action. Different parts of the world have recently 

 been disturbed by earthquakes which have caused wide-spread destruc- 

 tion. Those in Spain, which began December 24th, and have lasted, 

 with slight interruption, down to the time of writing, have been among 

 the most destructive of recent earthquakes. Over two thousand people 

 have been killed, many more wounded, and thousands of houses de- 

 stroyed. Such a state of affairs can not help arousing an interest in 

 this phenomenon. 



The earth is constantly quivering, some point on the surface being 

 the seat of a slight quake neaidy every moment of the day. By far 

 the larger number of these are of little intensity, being felt only by 

 delicate instruments, and the majority of cases come from volcanic re- 

 gions. So few facts are known, that we can neither draw deductions 

 nor even determine the causes. It is reported, however, that earth- 

 quakes more commonly occur at night, and that they are more abun- 

 dant in winter than in summer. 



The only settled facts about earthquakes are, that they are the re- 

 sult of some shock imparted to the rocks at a considerable distance be- 

 neath the surface, and that this shock reaches the surface in a series 



