610 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



The speaker commenced his explanation by quoting from 01m- 

 stead's Philosophy : " The centrifugal force of bodies revolving in 

 a given circle, is proportional to their densities or specific gravities. 

 If quicksilver, water and cork be whirled together in a pail or 

 glass vessel, these bodies will arrange themselves in the order of 

 their specific gravities, so that the cork will be at the least, and 

 the quicksilver at the greatest distance from the center of motion." 



Let the earth represent this pail or glass vessel, or rather let 

 the northern hemisphere represent one basin containing water, and 

 the southern another. To save repetition, only the northern hemi- 

 sphere will be referred to. The equator would be the rim of the 

 basin and the North Pole the center. We have the revolving 

 motion in the diurnal motion of the earth. The light and heated 

 water represents the cork, and cold water the quicksilver. As 

 cold and heavy water is thrown from the North Pole to the 

 equator, that is, from the center of the whirling basin to its rim, 

 it becomes heated ; and as it moves from the equator to the pole, 

 or from the rim of the basin to its center, it becomes cooled. 

 These changes of temperature and specific gravities are constantly 

 taking place, consequently, these changes of position must also be 

 continuous, keeping up a constant exchange of water between 

 the pole and equator. The fact that these currents are concentra- 

 ted and more or less confined to localities, is owing to the conti* 

 nents, which break the surface of the water surrounding the earth. 

 The reason why their line of flow is not directly north and south, 

 is too well understood to dwell upon here. 



The American gulf stream rises in the Gulf of Mexico, and main- 

 tains a distinctive character as a river in the ocean for over 2,000 

 miles, and is not fully lost until it approaches the coast of NorAvay, 

 a distance of over 4,000 miles from its source. Its width in the 

 narrows of Bemina, or off the Florida capes, is 32 miles, and its 

 velocity four miles per hour ; its width off Cape Hatteras is 75 

 miles, and its velocity three miles per hour. This is a very 

 rcspcctalile velocity, and quite up to the average velocity of large 

 inland rivers. 



The navigable portion of the Mississippi is 2,700 miles in length, 

 and has a fall of 600 feet ; and its current is not swifter than that 

 of the Gulf stream. Now, that we have glanced at the propelling 

 power of one of the largest rivers in the world, and found its mov- 

 ing power to be a head of water 600 feet in height, let us inquire 

 into the propelling power of that "mighty riv^er in the ocean,'' 



