190 J. C. BRANXER AGGRADED LIMESTONE PLAINS, BAHIA, BRAZIL 



that it is of vegetable origin, and, further, that it is most probably of an 

 algal nature." 



Specimens were also submitted to Professor A. Eothpletz, of Munich, 

 who writes as follows : 



"The one from America Dourada has a true oolitic structure. I do not know 

 of such a structure in fresh-water deposits, but it is very common in salt-watei 

 deposits of all ages. The roclv from Carahyba is also oolitic, but it is different 

 from the American Dourada rock. It is a particular kind of oolite, which I 

 should like to call a compound oolite. It is very common in marine limestones 

 deposited in seas undisturbed by sand and mud. Our Wettersteinkalk, Esino- 

 kalk, etcetera, of the Trias is usually full of it, but I know it from many other 

 places and formations." 



Mr. Edward B. Wethered, of Cheltenham, England, who has given 

 much attention to the microscopic study of oolitic limestones, writes me 

 as follows, under date of N'ovember 29, 1909, in regard to the Carahyba 

 rock : 



"I can find no evidence that the rock is of Jurassic age. Nor can I say to 

 what age it does belong. 



"There is no evidence of life other than in the granules, which are the chief 

 feature in the construction of the limestone. These granules I believe to be of 

 organic origin, but I know of nothing exactly like them. The concentric growth 

 of the granules is apparently due to low forms of life more allied to the cal- 

 careous algae than to anything of which we at present have knowledge. This 

 origin of the granules finds support in the quantity of carbonaceous matter left 

 after dissolving the limestone in acid. ... So far as I have yet been able 

 to come to a conclusion, I am disposed to think that the carbonate of lime con- 

 stituting the rock was secreted by the low forms of vegetable growth to which 

 I have referred." 



A chemical analysis was made of this oolitic limestone, with the follow- 

 ing results : 



Analysis of ooUtic Limestone from Carahyba 



L. R. Lenox, Analyst 



Silica (SiOa) 0.85 



Iron and alumina (FeaOg and AI0O3) 0.29 



Calcium carbonate ( CaCOg ) 97 . 14 



Magnesium carbonate (MgCOg) 1 .29 



Hygroscopic water . 08 



Very small amount of hydrogen sulphide (H2S) «nd 



organic matter 0.20 



Total 99 . 85 



