68 



FERGUSON'S LECTURES. 



LECT. 

 III. 



If the machine be made to move upon rollers or 

 friction-wheels, and the cylinder be supported upon the 

 plane C B by a line G parallel to the plane, a power 

 somewhat less than that which drew the cylinder up the 

 plane will draw the plane under the cylinder, provided 

 the pivots of the axes of the friction-wheels be small, 

 and the wheels themselves be pretty large. For, let the 

 machine ABC (equal in length and height to A EM, 



in the previous figure,) move upon four wheels, whereof 

 two appear at D and E, and the third under C, whilst the 

 fourth is hid from sight by the horizontal board a : let the 

 cylinder F be laid upon the lower end of the inclined plane 

 CB, and the line G be extended from the frame of the cylin- 

 der, about six feet parallel to the plane C B , and, in 

 that direction, fixed to a hook in the wall ; which will 

 support the cylinder, and keep it from rolling off the 

 plane : let one end of the line H be tied to a hook at 

 C in the machine, and the other end to a weight A, 

 somewhat less than that which drew the cylinder up 

 the plane before : if this line be put over the fixed 

 pulley /, the weight K will draw the machine along the 

 horizontal plane L, and under the cylinder F: and when 

 the machine has been drawn a little more than the whole 

 length C B, the cylinder will be raised to d, equal to 

 the perpendicular height A B above the horizontal part. 



