590 Transactions. — MiscellancoiLs. 



the tube D (PI. XLII.), leaving the tube C full of cool water. 

 By having the sponge nearlj' closing the tube down near the 

 bottom, so as to allow the mud in the funnel to be the point 

 of least resistance, the steam generated will, 

 when it acquires a certain force, escape 

 through that point of least resistance, and 

 the condensed steam about the mud will keep 

 it constantly soft; thus, after every steam- 

 bubble, the mud will refill the hole, and a 

 f} constantly boiling mud-volcano be illustrated. 



With this apparatus most of the phe- 

 nomena which excite the wonder of tourists to our district 

 can readily be explained. Thus, we are told that at Wairakei 

 a packhorse accidentally fell into a mud-volcano : this caused 

 the volcano to change itself into an intermittent geyser, which 

 lasted for six months, after which the mud-volcano resumed 

 its former quiescent normal action — the packhorse in this 

 case causing the same effect as the introduction of the sponge 

 into the tube. 



EXPLANATION OF PLATES XL.-XLII. 



Plate XL. 



Plan and section of geysers at Wliakareioaretva. 



Plate XLI. 

 Plan and section of Oruaw]iatua and Chameleon Springs. 



Plate XLII. 

 Apparatus designed to show geyser-action. 



A. Wooden stanci, 12in. by fin. by 4ft. high, fixed on a 12in. by fin. 



board, 1ft. 6in. long at bottom, with brackets to keep same in 

 position, and brackets at top supporting tray (B). 



B. Tray or tin vessel 14in. by 9in. by 2in., with hole in centre to 



admit of large cork through which the glass tubes are passed. 



C. D. Glass tubes, Jin. diameter and 2ft. Bin. long. 

 E. Glass retort or flask, to hold about a quart. 



P. Spirit-lamp. 



G. Iron tripod supporting flask. 



H, Maximum thermometer introduced through cork of flask. 



