282 IP s t e I s ia 



The majority of the smaller pools, as may 

 be seen in most of the photographs, are cir- 

 cular, but the larger ones are generally ellip- 

 tical, and give evidence of having been formed 

 by the union of two or more smaller pools, the 

 connecting rock ledges having been eroded. 

 Such pools are shown in Plate XXIII. fig. i. 



The pools vary in size from small depres- 

 sions a few inches in diameter, to those 30 feet 

 long, 20 feet wide, and 10 to 15 feet in depth. 

 Usually the largest are the most irregular in 

 outline, and contain the greatest diversity of 

 plant and animal life. 



The temperatures vary with the time of 

 day, the seasons, the depth, and the position 

 with regard to the tides, those lying highest 

 being warmest, since they are not subject to 

 a change of water with each incoming and 

 outgoing tide. One such pool was 30 feet long, 

 and 30 feet wide, and showed traces of several 

 connecting ridges. 



]\Iany pools, especially those in the region 

 of the "Devil's Billiard Table," contain boul- 

 ders, which appear to have the same composi- 



