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



Fig. 129. 



The structure of the instrument is very simple : it consists 

 of two or more hoops of thin tin, or brass. These are 

 fastened below to a spindle, so that they must turn with it, 

 but move easily up and down that spindle when put in mo- 

 tion. The spindle has a pulley below, and is supported at 

 top by a cross arm. The pulley is turned by a string pass- 

 ing over a multiplying wheel. Upon turning this wheel, the 

 hoops being put in motion will endeavor to fly out by cen- 

 trifugal force, and assume the shape represented by the 

 dotted line ; that is, will become an oblate spheroid, or a 

 globular body flattened towards either pole. 



Price, $4.50. 



Fig. 129, as above, represents a cheaper construction of 

 this instrument, having a three inch globe in the centre. 

 The motion is given by turning it rapidly with the finger. 



Price, $2.50. 



Astronomic Telescope on Brass Stand. No invention in 

 the mechanic arts has ever proved more useful and enter- 

 taining than the production of the telescope ; its utility, 

 both by sea and land, is well known ; in respect to the 

 heavenly bodies, much of our knowledge is due to the 

 invention of the telescope. 



