115 



and settle down in vessel number two. In this way " whiting" 

 is made and this, mixed with size, constitutes the white-wash used 

 for ceilings and for walls internal and external. A similar pro- 

 cess to that by which whiting is made gives, when carried out 

 with greater care, the " prepared chalk" of the druggist. This 

 finds application in medicine and as a cosmetic. 



Amongst minor uses of suitably prepared chalk may be men- 

 tioned the marking out of lawn tennis courts and the chalking of 

 billiard cues. The whiteness and softness also render it suitable 

 for writing on the blackboards of schools and colleges as well as 

 for chalking up scores behind the door of the village inn. It is, 

 however, the case that much of blackboard " chalk " is not 

 really chalk at all, but consists mainly of another calcium com- 

 pound, the sulphate already mentioned. The so-called French 

 chalk also, with which our tailors make little marks on our coats 

 when we are having them tried on, is not a true chalk, but a 

 variety of steatite or soapstone. Precipitated chalk, much used as 

 a dentifrice, either alone or with various additions, is an artificially 

 prepared calcium carbonate. 



Of the uses of chalk in agriculture our President treats in the 

 lecture which he contributes to this series. 



There are two other forms of naturally occurring calcium 

 carbonate to which I must refer before passing to the second 

 division of my subject. Coral is one of the forms of calcium car- 

 bonate of animal origin, and, like other varieties of this substance 

 may be used for making lime. The precious coral is, however, the 

 only kind that fairly comes within the scope of the present lecture. 

 This precious coral comes from the Mediterranean and has been 

 highly prized from the most remote times both for its beauty and 

 because various medicinal virtues were ascribed to it as well as 

 mysterious powers of preserving the wearer from danger, pro- 

 tecting from the evil eye and so on. The coral is found in shallow 

 water off the Algerian and Tunisian coasts as well as those of some 

 parts of Italy and of various Mediterranean islands. The Algerian 

 reefs are divided into ten regions, of which only one is " fished " 

 each year, so that ten years may be allowed for the renewal of the 

 crop. The collection of the coral and its manufacture are now 

 mainly in Italian hands. Coral of the very finest colour may be 

 worth as much as £100 per ounce, but, of course, such a price is 

 exceptional. There is a steady demand for it from China, India, 

 Central Asia, etc., the 1 European market varies according to 

 the incalculable caprices of fashion. 



The most highly valued of all forms of calcium carbonate is 

 the Pearl. This is found, as we all know, within the shell of the 

 pearl-oyster. The best are those perfectly spherical ones which 

 are loose in the soft tissues of the mollusc, those which are attached 

 to the interior of the shell are less symmetrical and usually less 

 valuable. According to Professor Cunningham the cause of pearl- 

 formation in most, if not all, cases is the dead body of a minute 

 parasite, so that it has been said that " the ornament that has in 



