196 Transactions. 



It is best first to make a soap by boiling the castor-oil and the caustic- 

 soda solution. When an even yellow-green soap is formed the light oil may 

 be added. Constant stirring is, of course, necessary whichever formula is 

 used. 



As is well known, potash is generally more suitable than soda, but its 

 greater cost makes it unsuitable for this purpose. Owing to a shortage of 

 potash, soft-soap is becoming costly, and therefore other emulsionizing 

 agents are being experimented with. Up to the present good results have 

 been got with resin, neatsfoot-oil and whale-oil. The last-named is the 

 cheapest, and will be used for work in military camps. Unfortunately, it is 

 sometimes difficult to saponify it by the mean': always available. 



The castor-oil emulsion referred to above is a clear liquid emulsion, and 

 keeps well. 



Art. XX. — On the Age of the Waikouaiti Sandstone, Otago, New Zealand. 



By J. Allan Thomson, M.A., D.Sc, F.G.S., Director of the Dominion 



Museum, Wellington, New Zealand. 



[Received by Editors, 31st December, 1917 ; issued separately, 10th June, 1918.] 



Although contradictory opinions were held by Hutton and Haast on the 

 one hand, and Cox, McKay, and Hector on the other, as to the relative age 

 and relationships of the Notocene rocks of the north and south sides of the 

 Shag River, all these geologists were in agreement in correlating the Wai- 

 kouaiti sandstone on the one hand with the Caversham sandstone, and 

 on the other with the Ototara limestone. Both these correlations were 

 accepted also by Park (1910) ; but it is necessary to remember that at 

 that time he placed the Ototara stone as the uppermost member of the 

 Oamaruian. Marshall, in 1906, did not attempt a more detailed correlation 

 than that the Caversham sandstone belonged to the Oamaru system, but 

 in 1916 he referred to the foraminiferal limestone at Sandymount, which 

 he had previously correlated with the Caversham sandstone, as a repre- 

 sentative of the younger limestone of New Zealand— i.e., Ototaran. Thus 

 practically all geologists who have written on the subject have agreed that 

 the Caversham sandstone and Waikouaiti sandstone are the same horizon 

 and are Ototaran. 



The rightness or wrongness of this conclusion has more than a merely 

 local interest, for on it hang two other questions of a more general nature. 

 First, the age of the Dunedin volcanic series can only be limited as regard- 

 ing its commencement by reference to the Caversham sandstone — until 

 a detailed palaeobotanical investigation of the intervening Fraser's Gully 

 plant-beds is available. Secondly, the Miocene age of the Oamaruian is 

 based very largely upon Chapman's conclusions regarding the Foraminifera 

 collected by Park from the clays underlying the Waikouaiti sandstone, and 

 if the latter is Ototaran the clays are lower Ototaran, or more probably 

 Waiarekan, and the Middle, or more probably Lower Oamaruian, is Miocene. 

 Opinions to the contrary, however, have recently been independently ex- 

 pressed by Marshall and myself (1917). Discussing the Hampden beds, I 

 stated that " the percentage of Recent species in the Waiarekan is not 

 inconsistent with an older age than Miocene for this stage," while Marshall 

 concluded that " these Onekakara [i.e., Hampden] beds seem to be more 

 rightly classed with the Eocene than with any other European system." 



