Sketches of the Geology fyc. of Alabama. 77 



there be a loss of power, there must be a loss at some point 5 

 but there is not a loss at any point, and therefore there is no loss 

 of power: 1 ' certainly, "there must be a loss at some point, 1 ' 



the equation shows that loss; <f>R— Px, gives <f>=.LxP, x 



XV 



being less than R at all points except the extremities of the 

 horizontal diameter of the crank wheel, — must be a fraction 



XV 



at all other points of the revolution, showing clearly a loss 

 of power in transmitting it by the crank. By examining this 

 equation #R=Pa; it will be seen that from the dead points 

 where x=o and of course *=o, * goes on increasing until 

 #=R at the extremity of the horizontal diameter, which re- 

 sults correspond plainly with the case in practice. 



Mr. Doolittle, (see his letter in the last number of the 

 Journal,) will be convinced that his equation P X .6366 X semi- 

 circumference =$X diameter, does not apply to this ques- 

 tion, if he will consider that it has been proved that the case 

 in practice may be resolved into one in which the shackle-bar 

 shall remain vertical, and the power be applied to every point 

 of'the circumference of the wheel, giving the equation Px 

 .6366 X semi-circumference =$ X semi-circumference, or 

 *=P X-6366, the same given in my examination as showing 

 a loss of more than one third the power applied. 



Art. XIII. — Sketches of the Geology, fyc. of Alabama ; by 

 William S. Porter, in a letter to the Editor. 



The Alabama river is navigable for steam boats to the 

 junction of the Coosa and Tallapoosa. A few miles above 

 this junction the rapids commence on the Coosa, and con- 

 tinue at intervals for sixty miles. These rapids are all pas- 

 sable for boats during high water, and an engineer has re- 

 ported that by opening the river it may be made navigable 

 at all seasons of the year. Above these rapids, the river is 

 deep, smooth and perfectly navigable for two hundred miles, 

 to near its source in the valley of the Tennessee river, a nav- 

 igable branch of which, almost communicates with it. The 

 Coosa passes through an extensive valley, known by the 

 name of the Coosa valley. Whether this valley is interrupt- 

 ed at the rapids by mountains I am unable to say. If so, the 



