372 The Commercial Products of the Sea. 



peting with us in the manufacture. France now works up 

 about 1500 tons of mother-of-pearl annually, while North 

 America and Austria also compete with us. We import 

 from 1 500 to 2000 tons of mother-of-pearl annually, worth 

 about 1 00,000. 



The quantity of mother-of-pearl and other nacreous 

 shells imported into France is thus given in the French 

 official returns : — 



Average Annual Imports. 



Kilogrammes. Value in francs. 

 In the ten years ending respectively 1856 ... 788,994 ... 730,308 



1866 ... 1,197,898 ... 1,331,884 



1876 ... 1,376,132 ••• 3,159,943 



Sea-ear shells {Haliotis) are also now imported into 

 France to the extent of 134,550 kilogrammes a year. 



Button-making is one of the largest uses to which 

 mother-of-pearl is turned. The blanks are cut out of the 

 shell with the annular or crown-saw fixed upon a lathe 

 mandril. They are split into two or more sections, accord- 

 ing to the thickness of the button required. They are then 

 ground down and cleaned, turned into a pattern, and after- 

 wards "fancied," or an ornament is worked on the face. 

 Next, the holes are drilled by which the button has to be 

 attached with thread to the garment, and lastly they are 

 polished. They are finally sorted and mounted on cards 

 of a gross each, which sell at from i^. 6d. to Zs. There are 

 some firms in Birmingham which turn out 500,000 gross 

 annually. Pearl buttons are made of all sizes, from the 

 Brobdignag ones as big as half a crown, for coats, costing 

 2s. or 3^". each, to the very tiny ones used for mere orna- 

 ment. 



This beautiful material has been as valuable to science, 

 by supplying confirmatory evidence of the truth of New- 

 ton's views respecting the origin of colour, as it has been 



