THE 



SCIENTIFIC PROCEEDINGS 



OF THE 



EOYAL DUBLIN SOCIETY. 



A CONTEIBUTION TO THE HISTOKY OF FLINTS. By 

 Professor W. J. SOLLAS, D. So., LL.D. 



[Read December 14, 1887.] 



THAT the material of Flints has been derived from the silicious 

 remains of Sponges can no longer be regarded as a mere 

 hypothesis; it is a suggestive fact, and affords a basis for further 

 investigations. In the present Paper I propose first to give the 

 results of some investigations which I have lately made to deter- 

 mine the ratio between the weight of the silica (Si0 2 ) forming the 

 skeleton of a given sponge and that of the whole sponge, including 

 all internal cavities, supposing it to be converted into a solid mass 

 of flint ; and next to offer an estimate as to the length of time 

 which would be required for the secretion of such a mass of flint. 



The total volume of the sponge was first determined as 

 follows: — A spirit specimen was transferred from alcohol to 

 distilled water, which was repeatedly changed till all traces of 

 alcohol were removed. It was then totally immersed in well- 

 boiled distilled water contained in a weighing bottle, and the 

 bottle and its contents were weighed : the sponge was then removed, 

 and a second weighing of the bottle gave, by difference, the weight 

 of the sponge and of the water contained within it and coating its 



SCIEN. PliOC, lt.D.S. VOL. VI., PT. I. B 



