THE OPPORTUNITY OF THE AGRICULTURIST 685 



hand : using your eyes, you will sooner or later light upon shell 

 remains and Tennyson's lines will come home to you : 



There where the long street roars, hath been 

 The stillness of the central sea. 



Under the microscope, chalk bears most distinctly the impress 

 of a manufactured article ; far from being formless like clay and 

 sand, it consists for the most part of particles which are obviously 

 remains of organisms (Foraminifera). Within recent years the 

 origin of chalk has been disclosed by the discovery over vast 

 regions of the ocean floor, in the Atlantic and Pacific areas, of an 

 ooze or deposit precisely similar in appearance to chalk; the 

 formation of this ooze has been traced to the warm surface, 

 where the organisms themselves flourish : as they die, their 

 outer shelly casings sink slowly through the deeps and are 

 deposited, forming what is now called Globigerina ooze. Chalk, 

 therefore, is also a sedimentary deposit but of organic origin, 

 laid down in clear water in regions beyond those to which 

 clay is carried — in central seas, in fact. As chalk yields lime 

 when burnt, it is a form of limestone. But limestones occur in 

 all geological formations — of whatever age; the very earliest 

 contain animal remains which tell that they were formed in the 

 sea but their minute structure has suffered defacement at the 

 hand of time and we cannot always trace them to their origin. 



But what is limestone ; of what is it made ? Bred out of sea- 

 water by minute organisms, surely it is a material deserving our 

 careful study ; and it invites attention from so many points of 

 view. The farmer, guided by that shrewd power of observation 

 which he so often displays, has noted its agricultural value. 

 Walk, say, in the Isle of Wight along the chalk downs, and note 

 how frequently quarries occur abutting on the clay or sandy lands 

 bordering the ridge : to what end has so much chalk been dug 

 out — in the past, we must suppose, as the signs of recent removal 

 are few ? On inquiry we learn that it was once the custom 

 to spread chalk on such lands with great advantage to the 

 crops ; but of late years the practice is deemed too expensive 

 by most farmers. 



Here and there in all limestone districts kilns are to be 

 found in which the stone is burnt into lime — and lime confronts 

 us everywhere in admixture with sand, as mortar. Whitening, 

 which is simply very finely ground soft chalk washed free from 



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