e. ie : Charles Whittlesey of Cleveland, on Natural Terraces, §c. 31 
_-» _ “This gives rise to a great many speculations, most interesting 
only element which is really well known, is the distance of the 
_ primary planets from the sun. Then there is the difficulty to 
_— which [ also alluded, in ascertaining the magnitude of spheres of 
attraction, that we catinot assume the nebulous matter to be 
equally dense; so that it cannot be demanded that the analogy 
should be very acéurately expressed by any given data. 
It is now extremely important that observations should be 
made upon the periods of the rotation of several planetary bodies, 
and it is much to be desired, as bearing upof this problem, that 
those who occupy themselves with what may be called the natu- 
ral history of astronomy should determine the times of rotation 
the position to which Mr. Kirkwood will be entitled, should his 
theory be found true. The Section seemed surprised at this re- 
mark. I do not wish to express myself strongly, but certainly 
when we look back upon the labors of Kepler, who strove so 
many years with results so unpromising, until he discovered the 
laws which underlie the whole fabric of our solar system, and 
then turn to Mr. Kirkwood, a teacher in the interior of Pennsyl- 
vania—who without the sympathies of kindred minds, or the 
use of any library of magnitude—without calling even upon the 
aid of strict mathematical analysis—has fixed his attention upon 
this one problem, and investigated it in all its bearings, until after 
_ ten years of patient thought and labor, he has arrived at such a 
result as this—we cannot but be struck with the similarity of the 
‘wo cases; nor can we consider it as very derogatory to the for- 
Mer to speak hereafter of Kepler and Kirkwood together as the 
Scoverers of great planetary harmonies. 
at 
Arr. V.—On the Natural Terraces and Ridges of the country 
_ bordering Lake Erie; by Cuartes Wurrttesey, of Cleve- 
10. 
land, Oh 
_ Turoven the assistance of the engineers, engaged at various 
times, in surveys for railroads and canals in Northern Ohio, I have 
been enabled to determine the elevation of our “ Lake ridges” a 
numerous points, between the Pennsylvania line and Sandus 
Bay, a distance of 130 miles. I am more particularly indebt 
for these levels to J. H. Sergeant, Esq., who has run several lin 
‘west Of Cleveland, and to Messrs. Harback and Smith, engineers 
for the Cleveland, Painesville and Ashtabula Railroad Company. 
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