McKay. — On Diatomaceous Earth at PaJcaraka. 377 



to the south-east passed the southern base of Paeroa and 

 joined the eastern branch of the Waitangi "u-est of the 

 crater. 



But the lava-flows of later date choked this outlet also, 

 and in this manner formed the lake to the south-east of 

 Paeroa. This has no visible outlet, and Avithout question its 

 surplus waters for the most part escape through the barrier of 

 loose scoria-blocks and scoria-ash that lies to the north of the 

 lake and east and north-east of Paeroa itself. 



Several heavj' springs, e\'idently drainage from the lake, 

 appear at low levels among the scoria hills described. Of 

 these, that which most concerns us at the present time ap- 

 pears from a brecciated rocky face half a mile east of Pakaraka 

 House. It opens into a small nearly circular depression less 

 than an acre in extent. On the north side of this the waters 

 escape by a narrow passage, which has either been cut or 

 usiu-ped by the stream in its course north to join the larger 

 creek, which in that direction flows north-west along that 

 boundary of the Pakaraka Flat. In summer and during dry 

 weather the amount of water issuing from the underground 

 channel is very limited ; but after a continuance of wet 

 weather it is considerable, and not merely fills the narrow 

 channel cut through the little patch of level ground below the 

 outlet, but floods the whole basin to a depth of 3ft. or 4ft. 

 When dry weather again sets in the basin is draiued, and 

 then there is left on the grass, ferns, and stones which form 

 the bottom and sides of the basin, a white or greenish deposit 

 of what on examination proves to be mainly diatoms. What 

 of this falls on the bottom and level parts of the little gi'ass- 

 covered basin is soon washed tlii'ough the grass and indistin- 

 guishaoly added to a thick deposit of the same material 

 which has in this manner been accumulating since first the 

 underground waters filled the basin. 



On the stones and fern-fronds which are under water 

 when the basin is full, the green living diatoms are deposited, 

 forming a coating from ^in. to iin. thick, according to circum- 

 stances. This deposit round the margin of the basin soon 

 bleaches white on the surface, but is found to be green im- 

 mediately below the surface. According to Mr. Maskell it is 

 almost wholly composed of living forms of Diatomacea. 

 Verj' probably the same species would be found among the 

 gi'ass-roots, and for the first few inches into the deposit filling 

 the basin itself. Unfortunately, I did not bring samples to 

 prove that such is the case ; but it is so self-evident that this 

 must be so that no doubts need be ventured on the subject. 

 The deposit in the middle of the basin is 6ft. to 8ft. thick, and 

 was exposed by the cutting-down of a cattle-track crossing 

 the creek at this place. I took a sample from about 1ft. 



