V. 



Phosphatic Chalk. 



NEARLY a year has elapsed since the occurrence of phosphatic 

 chalk in England was first announced (i). Though an exactly 

 similar rock had been extensively worked for some years in the north 

 of France and Belgium, with the result of an enormous increase in the 

 value of the land where it occurred, yet it had never been recognised 

 on our side of the Channel ; notwithstanding which it had lain open 

 to view for many years in an old chalk-pit hardly more than twenty 

 miles from London. This seems the more strange, in that the 

 appearance of the rock to the naked eye is sufficiently marked to attract 

 attention, while under the microscope its character is unmistakable ; 

 for the deposit consists almost entirely of phosphatised foraminifera in 

 beautiful preservation, together with fragmentary fish-bones, fish- 

 scales, and minute coprolites. These organisms are embedded in 

 chalky mud containing coccoliths and discoliths, and impart to the 

 rock a granular or sandy appearance, and a pale-brown tinge which 

 at once distinguish it from smooth white chalk of the ordinary type. 



New discoveries of phosphatic chalk are being made from time 

 to time on the Continent, yet an old chalk-pit at Taplow remains the 

 one known section of such a rock in England. That this is actually 

 its sole occurrence in this country seems scarcely probable. Yet our 

 Chalk, of late years especially, has received much attention from both 

 Foreign and English geologists, and the principal subdivisions into 

 which it can be separated are being traced throughout the country, 

 not only by the Geological Survey, but by men who have made its 

 study a speciality, and who are unlikely to overlook the least 

 variation in its lithological character. Many landowners, more- 

 over, keenly alive to the possibility of increasing the value of their 

 property, from time to time bring forward specimens which seem to 

 correspond to the description given of the Taplow Chalk. All this 

 notwithstanding, we cannot produce so much as a single phosphatised 

 foraminifer outside the limits of the old Taplow chalk-pit. Why this 

 should be, and what should be our guide in the search for fresh 

 deposits, are questions that await an answer. 



From the accounts given of the Continental deposits, we learn 

 that phosphatic beds are never continuous at any horizon in the 

 Chalk for more than a short distance. Thus, in one of the latest 



