kOCKWORK. 



225 



circulation of air. In the one figured tliere is a bubbling 

 spring of water, giving rise to a lively rill which crosses 



Fig. 72.— GROUND OUTLINE OF ARTIFICIAL GROTTO — P, P, REPRESENT 



ROCK PILLARS. 



the floor, and an ample stone seat. There is a large field 

 for variety and for displaying taste and knowledge of 

 building in the construction of rockwork of this kind. 



Fig. 73.— CROSS-SECTION OP ARTIFICIAL FIs;. 74. — STAIRWAY IN ARTI- 

 GROTTO. FICIAL GKOTTO. 



In the Paris public gardens one may see that the con- 

 struction of Grottos may amount to quite an art. Great 



