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PROF. T. RUPERT JONES—CHALK AND FLINT. 
sometimes quartz crystals coating the interiors, which this Society 
possesses by the gift of the late Mrs. W. Stuart, who collected them 
at the digging of the Watford Tunnel on the London and North- 
Western Railway, ought to incite some of the Members of the 
Hertfordshire Natural History Society to the study of Flint. 
Conclusion .—I have now noted most of the features of the Chalk ; 
and, if I have not made them very clear, I have, at least, opened 
out lines of thought worth the study of those who have time 
to go into them. The formation of the Chalk geographically offers 
to you an interesting chapter in Geology, such as may be read in 
all the great systems of strata up to the present day. In the 
materials which form the Chalk you have an extensive and 
successional Natural History to look at. In it you have some of 
nearly every group of animals to study, except the high-class 
Vertebrata; but Birds must have existed even then, and also 
Mammals, because they lived before that time, though they could 
rarely be found in the deep sea. Leaving these matters for your 
further consideration, I may only remark that you have a very fine 
field of study in your own Chalk of Hertfordshire. 
