278 ANNUAL OF SCIENTIFIC DISCOVERY. 



It follows, therefore, that if the earth's axis of rotation were at any 

 time stable, it would continue so forever. But, from the laws of fluid 

 equilibrium, the axis must have been stable from the epoch of the 

 first formation of the earth's crust ; consequently, it continued undis- 

 turbed, as the thickness of the crust increased during the several 

 geological formations. Thus it appears that the displacement of the 

 earth's interior strata, instead of having a tendency to change its axis 

 of rotation, tends to increase the stability of that axis. With reference 

 to inequalities arising from the friction of a resisting medium at the 

 earth's surface, the author observes that this could not exist, if, as in 

 the manner here shown, the axis of rotation coincided from the origin 

 with the axis of the figure. In conclusion, he remarks, that if we 

 could assume for the planets a similarity of physical constitution to 

 that of the earth, the theorem as to the greatest and least moments of 

 inertia of the earth would be applicable to all the planets ; and thus 

 we should be as well assured of the stability of our system, with 

 respect to the motion of rotation of its several members, as we are 

 already respecting their motion of translation. 



In reference to a third cause of disturbance in the place of the 

 earth's axis of rotation, namely, the effects of local elevations and 

 depressions at the earth's surface, the author says : If with Hum- 

 boldt, we regard the numbers expressing /the mean heights of the 

 several continents, as indicators of the plutonic forces by which they 

 have been upheaved, we shall readily see that these forces are of an 

 inferior order, to those affecting the general forms and structure of 

 the earth. If the second class of forces acted, so as not to influence 

 in any way the stability of the earth's axis of rotation, the former 

 class might, under certain conditions, produce a sensible change in the 

 position of the axis. But when the tendency of the second class offerees 

 is to increase the stability of the earth's axis, it would not be easy to 

 show the possibility of such conditions, as to render the operation of 

 the other forces, not only effective in counteracting that tendency, 

 but also producing a sensible change in the place of the axis of rota- 

 tion. Proc. Royal Society. 



SHOWERS OF SAND IN CHINA. 



THE following account of sand showers in China is given by Dr. 

 D. J. Macgowan, of Ningpo : 



The Phenomenon of falling sand is occasionally observed through a 

 great extent, if not the entire portion, of the vast Plain of China. It 

 is of such frequent occurrence that the Chinese regard it Avith no 

 more surprise than they do the flitting meteor. Probably no year 

 passes without several of these showers, though frequently so minute 

 as to escape general observation. Perhaps as often as once in three 

 years they are very heavy, but it is seldom that sand falls in such a 

 large quantity as during the last shower. The phenomenon was wit- 

 nessed three times during the present year, within a period of five 

 weeks ; the last and greatest commenced on the 26th of March, and 



