De Lautouk. — Oil a Diatomaceous Deposit. 295 



Dr. ColquhoiTii, and also in some diatoms found in guano 

 given me by Dr. de Zouche. 



This discovery led to much inquiry, and many v/ere the 

 requests sent to various persons in Oamaru from all parts for 

 specimens of the earth ; and I am sorry to say that a great 

 deal of the wrong material has been sent away — perfectly use- 

 less. One parcel alone of nearly 2001b. weight contained only 

 one or two lumps of earth containing diatoms, and those were 

 by no means rich. 



To obviate this, and avoid disappointment for the future, I 

 have prepared a map of the district (PI. XVIII.) showing the 

 deposits as far as they have been hitherto found, and the roads 

 leading to them. The deposits are so extensive that there is no 

 fear of their becoming exhausted. One alone at Jackson's is 

 about a quarter of a mile long, and shows a face of some 60ft. 

 How far it goes back I have no means of ascertaining. I have 

 also prepared diagrammatic sketches showing the appearance of 

 the deposits as exposed, and the relation of the diatomaceous 

 ooze to the other earths. 



Plate XIX., fig. 1, shows a section of the railway-cutting 

 at Cormack's siding. Here the prominent feature is the vol- 

 canic dyke, h, cutting through it ; on each side is a hard white 

 earth very similar to the proper diatom ooze in appearance, 

 but heavier and much harder. This is the earth which has 

 been sent home, and which has led to so much vexation. It 

 is more easily collected. Between the volcanic dyke and this 

 hard material there is a distinct line of demarcation, but none 

 exists between the hard material and the true diatom earth ; 

 and as a matter of fact the further away from the dyke the 

 richer is the ooze in diatoms and other siliceous remains. 

 Hence I would infer that the intruding dyke has heated and 

 partly fused and compressed the diatom earth through which 

 it has burst. The same condition is found in various other 

 places where dykes exist or where there appears to be a 

 flow of lava, as under Jackson's paddock (Plate XIX., lig. 26) : 

 there, along the road-line, is a volcanic layer similar in its ap- 

 pearance to the dyke at Cormack's, and with the same hard 

 white stuff. At many points in Cave Valley, and in the Wai- 

 arekei Valley below Jackson's, Bain's, and Totara, does the 

 same condition exist ; and also, in the neighbourhood of these 

 places the plough turns up pure diatom ooze. The diatom 

 ooze, also, at Cormack's, as in the other sub-volcanic deposits, 

 is non-calcareous. Microscopically it is peculiar in the number 

 of a species of diatom called Stcphanopyxis present in it, and 

 which may be said to be characteristic of it. Also, this non- 

 calcareous ooze has a much smaller quantity of Radiolaria — i.e., 

 Polycijstince, &c. — and sponge-spicules in it than the calcareous 

 diatom ooze which is found above the volcanic remains. I have 



