160 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE. 



The Capstan. (Fig. 166.) One of the most efficient 

 forms of the wheel and axle is the capstan, used on board 

 of ships and in dock-yards. It consists of a vertical spindle 

 fixed firmly as in the deck of the vessel, but turning on its 

 axis, and supporting a drum, or solid cylinder connected 

 with it, and having its periphery pierced with holes directed 

 towards its centre. It is then worked by long levers, in- 

 serted in the holes, by men who walk in succession round 

 the capstan, and thus make it revolve ; a rope or cable 

 wound about the axle may act with force sufficient to weigh 

 a ponderous anchor, or warp a heavy laden vessel into 

 harbor. 



Small models made in mahogany, 6 inches high, serve to 

 illustrate the use of this instrument. Price, $2.50. 



Fig. 166. Fig. 1G7. 



Double Cone and Inclined Plane. (Fig. 167.) This is a 

 simple mechanical experiment, to show that although it is a 

 natural law that the centre of gravity of a body always 

 tends to, and endeavors to obtain the lowest station, yet 

 there may be cases in which it appears to roll upwards. 



The double cone rests upon the two sides of a sloping 

 railway ; if the cone be placed at the narrow end of this, it 

 will roll towards the other, and as the other is the higher 

 end, the cone appears to roll upwards ; though upon observ- 

 ing the height of the apex at each end, at the beginning 

 and end of its course, it will be seen that in reality it rolls 

 downwards ; the centre of gravity being situated in the axis. 

 Price, $1.00 to $2.00. 



" with screws, $3.00. 



The Whirling Table. A description of the whirling table, 

 or machine for exhibiting and demonstrating by experiments 

 the nature of central forces, or the principal laws of gravita- 

 tion of the planetary motions in their orbits : 



The whirling-table may be considered by a lecturer as an 

 essential part of his mechanical apparatus. 



