162 TIDAL OBSERVATIONS. 



from the south-west point of West Wallaby Island, 

 though it could only be traced by detached patches 

 of breakers. To the south-east of its commence- 

 ment lies Eveninof Reef. The observations were made 

 on the north end of the north-east Pigeon Island, 

 bearing W. by S. half a mile from our anchorage, in 

 lat. 32° 27' 21" S. and long. 2" 1' 10" W. of Swan 

 River, variation 4" 10' westerly. The temperature 

 of Houtman's Abrolhos is rendered equable by the 

 fact that they lie at the limit of the land breezes ; 

 during the month we were there the thermometer 

 averaged 71". 



Our protracted stay enabled us to get a tolerable 

 series of tidal observations, which present some singu- 

 lar results. The time of high water at the full and 

 change was six o'clock when the tide rose 30 inches. 

 It appeared that during the night there was a short 

 flood of six hours with a rise of seven inches, and an 

 ebb of two hours with a fall of only five inches ; but 

 that during the day the flow and ebb were nearly 

 equal, the former being eight hours and twenty 

 minutes, the latter eight hours and five minutes, and 

 the rise and fall in each being 25 and 26 inches 

 respectively. 



A diflference was also noticed between the day and 

 night tides at Rat Island, where the time of high- 

 water at the full and change of the moon was ten 

 o'clock, and the rise varied from 8 to 32 inches, from 

 the result of twenty-five observations ; by which I 

 found, moreover, that the tides ebbed five hours and 

 a half in the night, and six hours and a half during 



