•20 



O N T H K C! O N S T E U C T I O N AND USE OF 



The niachiiip, Avliicli is a siiupliticatiuu of Ltud llossc's, was intended to give 

 spiral strokes. It differed from the original, however, in demanding a changeable 

 stroke, and in tlie absence of the lateral motion. In another most essential feature 

 it \ aried from l)otli tlnit and Mr. Lassell's, the. mirror urns alway/^ uppermost icliile 

 livUvliiiKj, and being nncounterpoised escajied to as great an extent as possible from 

 the eft'ects of irregular pressure. To any one wlio lias studied the deforniaticms of 

 a reflecting surface, and knows how troublesonu^ it is to support a mirror properly, 

 tlie advantage is ap])arent. 



Kig. 21. 



/ 



n 



r'/////////A'///////M'/i",yy.'-, t_L I J " I 



Folishiug Matliiiie. 



Tlie constrnetion is as follows: A stout vertical sjiaft. n. l'"ig. 'il. carries at its 

 top a circular table l>. upon ^vhi(•ll the ])()lislH'r <■ is screwed. 15i'lo\v a band-wheel (/ 

 is fixed. Al)(>\e the table, at a distance of four inches, a liori/ontal bar c is arranged, 

 so as to move back and forward in the direction of its length, and to carr}' with it 

 by means of a screw /. the uiirror ///. and its iron liack or chuck //. The bar is 

 mo\('d by a connecting rod /'. attached to it at one end. and at the other to a pin ;/ 



I-Mg. -l-l. 



Till- I'oot PowHi-. 



moving a slot. This slot is in a crank //, carried by a vertical shaft t, near the 

 former one a. The band-wheel h is connected with the foot power, Fig. 22. The 



