172 



ME. J. MAETUST ON THE TEEEACES OF EO TO M AH AIT A , 



had been formed before the lateral slopes were cleared of vegetation, 

 as such masses could scarcely have been deposited by aqueous 

 agency if such a free outlet as the sloping sides had been open to 

 the escaping flood. 



The Eastern Wing of the Terrace, divided from the Middle Terrace 

 by a clump of stout manuka trees, formed a steep slope of sinter 

 deposit rippled into small wavy lines. Under the trees some very 

 nteresting features of new formation were observed, the prostrate 

 branches forming the foundation of ridges, and drifting twigs and 

 leaves collecting in the hollows became incrusted and cemented, 

 forming receptacles similar in character to those upon the Great 

 Terrace. 



The Western Wing was separated by a deep cleft and some 

 smaller clumps of bush. Its deposit was similar in character to 

 that of the east wing. Its lower portion was more extensive and 

 formed wide shallow areas, bounded by ridges of from one to three 

 inches in height ; these frequently contained beautiful tree-like 

 accretions, which rising on a stem, spread their branches on the 

 surface, the largest specimens extending over four inches. 



The Cold-water Basins formed the front extension of the lower 

 central portion of the Terrace. Viewed from above, they exhibited 

 an extraordinary combination of circular and crescented areas, 

 extending from five to twenty feet across, of pale, opalescent blue, 

 outlined by broad rims of grey and brown, with encroaching 

 margins of siliceous mud. 



Prom below they formed an ascending series of from one to four 

 feet in height, with rough perpendicular walls, in some instances 

 with a slightly projecting cornice, streaked with vertical lines of 

 white, grey, and brown, mingled with various stains. 



Their depth appeared to correspond to their height. The surface- 

 water was cloudy from suspended silica, and the basins full of a fine 

 siliceous ooze, gelatinous and cold. The contents of these receptacles 

 showed every stage of consolidation, and many had already become 

 compact tabular blocks. The conversion of the alkaline silicates 

 into carbonates by exposure to the atmosphere would precipitate 

 the silica in the forms observed in these basins. 



The outward trend of every curve in this wonderful series, and 

 the gradual descent from the apex or summit, seems to indicate their 

 origin from the great cauldron above. The theory of the formation 

 of the structure from siliceous deposition only fails to account for the 

 erection of such regular basins at such a distance from the source, 

 the cooled overflow leaving here so little surface-deposit ; and 

 further the excavation of the basin-hollows could scarcely have been 

 effected by the same agency as that by which they were now con- 

 solidating. 



The Lower Plateau skirting the Terrace on the lake-border marked 

 by its regular gradations the gradual lowering of the lake-level 

 through a distance of about four feet. Along the edge of the 

 Terrace it formed a sinter pavement, loose and fragmentary, readily 

 detached in surface-layers of about an inch in thickness. In many 



