186 KANSAS CITY REVIEW OF SCIENCE. 



results. Thev have a separate building with its own engine and a large amount 

 of valuable machinery. The complete success of this work would be of the- 

 greatest benefit to Kansas City, where fuel is one of the most important consid- 

 erations in developing manufactures. 



A special article on the theory and experiments with coal dust fuel will prob- 

 ably be furnished this Magazine before long. 



THE CENTER OF POPULATION. 



St. Louis is located almost exactly at the ultimate center of population of the 

 republic, and the progress of that center toward its final destination is a matter of 

 considerable interest to the intelligent people of the future great city. There is 

 probably a popular misapprehension as to what the center of population of the 

 country really is. It is often taken to mean that point which has an equal popu- 

 lation on opposite sides, but this conception of it is erroneous. The center of 

 population is that point on opposite sides of which the number of inhabitants 

 multiplied by the sum of their distances from it are equal. It is aptly defined as 

 the center of gravity of population, that is to say, the point from which if the 

 whole population of the country were suspended in place, it would exactly bal- 

 ance. This definition of course assumes that every person, large or small, con- 

 stitutes a unit of weight. If a line be drawn due east and west through the cen- 

 ter of population, and all the people on such a line travel to the center, the sum 

 of the distances traveled by those going east and west respectively will be equaL 

 If all parts of the country were covered by a population of equal density, the cen- 

 ter of population would be at the geographical center. The geographical center 

 of the country is in Northern Kansas, slightly nearer the western than the east- 

 ern boundary of that state, and not far from the thirty-ninth parallel of latitude. 

 Dividing the country by a meridian through this point, the western half is found 

 to be by far the most infertile, and consequently the least able to support popula- 

 tion. Multiplying area by fertility, it is discovered that the meridian which di- 

 vides the country into two parts of equal power to sustain population, passes very 

 near St. Louis. The two zones into which the thirty-ninth parallel divides the 

 country do not differ greatly in sustaining power, and the center of population 

 will eventually rest near that central parallel, which also passes near St. Louis. 



The progress of the center westward has been at the rate of about fifty miles, 

 during a decade. In 1790 it was east of Baltimore, being then, as it is now,, 

 near the thirty-ninth parallel. In 1840, fifty years afterwards, we find it twenty- 

 two miles south of Clarksville, in West Virginia, in latitude 39.02. From this 

 time it quickened its pace, and in 1850 it had reached a point twenty-five miles 

 southeast of Parkersburg, West Virginia, fifty-five miles west of the last position, 

 and in latitude 38.59. In i860 it was twenty miles south of Chillicothe, Ohio, 

 in latitude 39.03, having made eighty-two miles of westing during the decade. 



