542 



[Proc. B.N.F.O., 



Oxides .04 ; and Organic Matter .4. With regard to its physical 

 properties, the most remarkable is its porosity which, of course, 

 points towards its pseudomorphous character. A finely powdered 

 specimen after prolonged soaking in water had a density of 2.52 

 gms. per cc, but after prolonged boiling it rose to 2.6. Under 

 the microscope the exterior waved formation of beekite, with its 

 beautiful ridges of snow-white silica, makes a fine object for a 2 

 to 3 inch objective. From an examination of numerous thin 

 slices I found that the exterior whorls of a system bear no 

 crystalline relationship in disposition towards that of the nuclear 

 disc they enclose. The disc or nucleus invariably shows a 

 radiated structure, and black cross under polarised light. Slices 

 cut further down, below the ridged or furrowed exterior, also shew 

 the concentric structure, but this consists of alternate circles of 

 porous and more compact chalcedony. The compact circles 

 correspond to the exterior ridges or waves of the beekite, while 

 the more porous circles underlie the air-spaces between the ridges. 

 The porous nature of beekite makes it a difficult object to 

 slice, and it is almost impossible to get rid of air-bubbles in the 

 balsam. Mounting in oil is the remedy for the latter difficulty. 



ORIGIN OF BEEKITE. 



From a careful consideration of all the evidence available I 

 have arrived at the conclusion that three factors were at work in 

 the formation of this interesting form of silica : — 



(1) A calcareous ground-work such as a shell or coral. 



(2) The presence of organic matter in the shell-material and 



possibly around it. 



(3) A porous sediment containing freely circulating waters 



having silica, carbonic acid, and probably organic 



acids (such as lactic acid) in solution. 



In my opinion the time of formation is a very debatable 



point, but undoubtedly it may be referred to the period of the 



consolidation of the sediment, and was probably contemporaneous 



