﻿530 Pt^of. Liver sidge — Chalk in New Britain. 



microscope reveals tlie presence of tlie smallei' Foraminifera, of a few 

 sponge spicules, and minute grains of what are evidently siliceous and 

 igneous rock. 



The further examination showed that the material is limestone, 

 having a very close resemblance to chalk, both in chemical composition 

 and in physical properties ; in colour it is not the dazzling white of 

 some chalk, but bears a closer resemblance to the light grey varieties. 

 Although it is essentially composed of carbonate of lime, still it is 

 not perfectly pure ; there are certain impurities present in the form of 

 alumina, iron, silica, manganese, etc.; but reference will again be 

 made to this question later on. 



To ascertain whether my supposition that the rock might be regarded 

 as chalk and not merely as a soft, white friable recent limestone, or as 

 a deposit such as is now forming over parts of the beds of the Atlantic 

 and Pacific Oceans, I took an early opportunity, when writing, to 

 inclose a portion of the material to Mr. H. B. Brady, P.R.S., of 

 Newcastle-on-Tyne, who has devoted himself to the study of Foramini- 

 ferous deposits, and I have since received a reply from him, in which 

 he says : — 



"First, let me speak of your chalk from the New Britain Group. I 

 suppose you have ascertained that it is a Cretaceous chalk and not a 

 friable Tertiary limestone. All the Foraminifera, or nearly so, are 

 South Pacific recent pelagic and deep-sea species, GloMgerina huUoides, 

 Gl. inflata, Pulvinulina Menardii (a thick variety which I do not think 

 is yet named), P. Micheliniana, and probably P. Karsteni, PuUenia 

 sphceroideSj Nonionina umlilicatula, Bulimina Buchiana, fragments of 

 Pentalina, JJvigerina, etc. Also a characteristic Pulvinulina, with 

 thick shell and honeycombed surface, not yet described, of which I 

 have quantities in the ' Challenger ' material." 



In answer to a question as to the locality and mode of occurrence of 

 the material used for the carvings, the Eev. G. Brown wrote to me as 

 follows: — "The chalk of which the figures are formed is, I am in- 

 formed, only found on the beach after an earthquake, being cast up 

 there in large pieces by the tidal wave. It is only found, as far as we 

 know at present, in one district on the east side of New Ireland." 



We have now to consider its chemical composition in somewhat 

 closer detail, and to compare the results furnished by analysis with 

 those yielded by specimens of typical or true chalk. 



Chemical Composition of specimen from New Ireland. 



Hygroscopic moistvure, i.e. water driven off at 100° C. ... 1-202 



Carbonic anhydiide 3o'337 



Iron sesquioxide . 



Alumina 



Silica 



Phosphoric acid 



Manganese protoxide... 



Lime 



Magnesia 



Potash 



Soda ... 



Chlorine 



... 1-597 



... 3-131 



... 7-933 



Minute trace 



•623 



... 45-278 



•476 



•308 



•260 



•105 



Combined water and undetermined 3-750 



Specific gravity, 2-199 at 59° F. lQ(}-(iQO 



