HI THE HOT SPRINGS 23 



;. mile above Ndavutu. If the above statement of the natives is 

 correct, as I believe it is, then these thermal springs issue along a 

 1 ne quite four geographical miles in length extending inland from 

 the mouth of the Wainunu. 



All the springs are situated in the tidal part of the river-valley, 

 \'ith the exception of that of Thongea, which is just above this 

 1 mit. They are but little elevated above the sea-level, those ex- 

 josed being usually not more than ten feet above the river and 

 cften much less. This is a region of basalt, the valley of the 

 \Vainunu lying, as described on page 82, in the fold between two 

 great basaltic flows, and probably representing a line of weakness, 

 along which the hot springs issue either from among loose blocks, 

 cr from the soil, or from a tufaceous sandstone. They deposit 

 li ttle if any of the siliceous sinter which is often found in the ther- 

 mal waters of this island. This is due probably to their scanty 

 exposure and to their low temperature. The density of the water 

 15 near that of fresh water, being not over icxDi. The following 

 ti ;mperatures may be useful for comparison with future observations : 



T hongea, when not covered by the stream July, 1898, 127° F^ 



> davutu, bath-spring at Mr. Barratt's house Usually 100° „, 



„ on left bank of the creek near the landing place . June, 1898, 126° „. 



„ on left bank of creek near mouth Dec. „ 127° ,„ 



„ pool in foot-path on left bank J i , ' " „ '* 



' ^ I July 27, „ 111° „ 



at bottom of main river in depth of 3 feet, close 



to the left bank and just above the mouth xj , ^^^c 



^ , -KT 1 , ,,- • • ^- /July „ 122 



of the Ndavutu creek, self-registenng Six ' 



thermometer used 



}' 



2. The Hot Springs of Natoarau and its Vicinity. — This 

 tl ermal system lies in the lower valley of the Mbale-mbale branch 

 o: the river Ndreke-ni-wai. The principal springs are situated at 

 N atoarau, a village about half a mile in a direct line from Mbale- 

 n: bale, about three miles from the coast, and only about fifty feet 

 al >ove the sea. They bubble up in pools near brooks, and extend 

 a1 intervals over an area probably several hundred yards across. 

 F ve springs came under my notice ; but there are doubtless several 

 0I hers in the low-lying and often swampy land of this district. No 

 d« posits were noticed, but the mode of occurrence and low temper- 

 at ire of the springs serve to explain this fact. The following 

 te nperature observations were made by me in March, 1899 : — 



A. Pool 4 feet across, with sides of stone, close to village . . 126° F. 



B. Pool 10 feet wide, a few paces from pool A 114°)) 



