248 



SCIENCE. 



[N. S. Vol. XXIV. No. 608. 



When a cyclone has once been inaugurated, 

 in whatever way this may be effected, it pre- 

 sents itself as a mountain of air with a tend- 

 ency to rise to a great height into the prevail- 

 ing over-current. If established before start- 

 ing on its journey, there was an inrush of air 

 from every direction, and to the extent of the 

 inomentum of this inrush the mountain was a 

 hollow one and its area a ' low.' At a variable 

 distance above the earth's surface the crest of 

 the cyclone is struck and carried away for- 

 ward by the prevailing over-current, which in 

 the tropics is the returning loop of the uplifted 

 trades as they' journey west, after that this 

 same loop becoming the antitrade as it takes 

 a brief turn poleward, and finally the prevail- 

 ing westerlies in the temperate regions. 



JSTow it is well known that the prevailing 

 westerlies, or any other steady winds blowing 

 across a mountain chain, draw up the air on 

 the leeward side of the mountain, condensing 

 its moisture into a constant cloud. There is 

 also a well-known instrument now widely used 

 by surgeons and painters, which consists of a 

 tube opening at right angles to the mouth of 

 another tube which dips into the fluid to be 

 sprayed. By blowing through the first tube a 

 liquid is made to rise up through the second 

 or perpendicular one. In both these instances 

 the horizontal current, by the momentum of 

 its trajectory, has to a greater or less extent 

 removed the pressure of the superincumbent 

 atmosphere and permitted the surrounding 

 pressure to farce the air or the liquid upward. 



Now in the case of the beheading of our 

 cyclonic mountain, the available energy is the 

 momentum of the horizontal trajectory of the 

 upper prevailing winds. Twenty-seven inches 

 of mercury is probably the extreme of ' low ' 

 for any cyclone, and this shading off to zero 

 at the edges, so that an average fall of one 

 inch over the entire area of a cyclone is the 

 highest probably ever attained if, indeed, it 

 goes nearly so high. This prevailing wind is 

 operative at from 2,000 feet to ten or more 

 miles high, while moving at a speed of from, 

 say, 50 to 2.50 miles an hour. But, whether it 

 embraces the entire operative force or not, 

 this prevailing overcurrent supplies a vast 



amount of the energy of motion to cyclones 

 and is to that extent a vera causa. Again, 

 the translatory energy, as well as the gyratory, 

 may be derived from the same source. While 

 the crest of the cyclonic mountain is being 

 dragged away forward, the body of the cyclone 

 itself is made to lean in the same direction. 

 In this case air, drawn into the cyclone from 

 in front, reaches its body at a given height in 

 less time than a like mass drawn in from the 

 rear, and this still more when the cyclone is 

 in motion. The result altogether will be that 

 the diameter of the base of the cyclone is 

 added to more rapidly in front than in the 

 rear. This of necessity results in a forward 

 movement of the center of gravity; and, since 

 the cyclone is rotating, it must continuously 

 advance in order to make its axis correspond 

 with its center of gravity. Indeed, so much 

 is this the case that the axis of a cyclone is 

 probably curved — advanced at the base and 

 at the top while lagging in the middle. 



D. T. Smith. 



SPECIAL ARTICLES. 



RECENT DISCOVERIES OP QUATERNARY MAMMALS 

 IN SOUTHERN CALIFORNIA. 



Several months ago Mr. F. M. Anderson 

 called my attention to a deposit of bones oc- 

 curring in asphalt beds near Rosemary Sta- 

 tion about nine miles west of Los Angeles. 

 In a small collection of specimens kindly pre- 

 sented to me by Mr. Anderson there were 

 represented a number of Quaternary mam-- 

 malian species which are either new to the 

 fauna of the Californian region or have been 

 very imperfectly known. 



Recently Mrs. Ida Hancock, the owjaer of 

 the property on which the asphalt deposits are 

 located, has very kindly given to the Univer- 

 sity of California permission to carry on ex- 

 cavation work in these beds, and a considerable 

 collection of valuable material has been ob- 

 tained. 



The beds in which the bones occur extend 

 over many acres. So far as I am aware the 

 bottom has not been reached in excavations 

 carried to the depth of at least fifteen feet in 

 quarrying the asphalt. Bones are scattered 



