cio Uf roc. B.JX.l'.c, 



In examining the local deposits (Co. Antrim) I was much 

 struck by the fact that beekite is practically absent from the 

 Chalk, abundant in the Chloride Sands and Yellow Sands, but 

 practically absent again in the Glauconitic Sands, although the 

 same and similar shells persist through all the strata. Its absence 

 from the Chalk and abundant presence in the English Carbon- 

 iferous limestones may be accounted for by the fact that the 

 former is comparatively free from organic matter which is most 

 certainly a factor in the formation of beekite. The Chloritic and 

 Yellow Sands of Co. Antrim are highly fossiliferous, and at the 

 time of their deposition probably contained much organic matter, 

 which would account for the formation of beekite. 



In the Glauconitic Sands of Co. Antrim beekite appears to 

 be absent, but here again at the time of its deposition another 

 factor made itself felt. Iron oxide and iron silicate have even a 

 greater attraction for organic matter than silica ; and the large 

 quantities of iron in these beds fully accounts for the neutralisation 

 of the organic matter as a factor in the possible formation of 

 beekite. As the iron compounds disappear beekite appears to 

 increase. Silicified shells without beekite are found in the 

 Glauconitic Sands, however, but a microscopic examination of 

 these specimens (for example, Exogyra cornea), reveals the fact 

 that the crystals of replacing chalcedony are much larger than 

 those of beekite, suggesting that they were of much slower 

 formation. 



All of the fossils in one bed are not beekised, and the fact 

 that two fossils are found side by side one coated with beekite and 

 the other untouched, is in many cases due, I believe, to the fact 

 that aragonite yields more rapidly to dissolving solutions con- 

 taining carbonic acid gas (and organic acids) than calcite. 

 Although calcite shells are found coated with beekite, and taking 

 the latest researches on the subject of the nature of shell-layers 

 into account, I am of the opinion that aragonite is more frequently 

 beekised than calcite, and more heavily than the latter. 



